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D2.1 - REQUIREMENTS BASELINE - UV
Version 1.0
31.05.2018
Status: Released
ESBO DS Requirements Baseline - UV Version: 1.0
Page 1 of 20
Deliverable
H2020 INFRADEV-01-2017 project "European
Stratospheric Balloon Observatory Design Study"
Topic: INFRADEV-01-2017 Design Studies
Project Title: European Stratospheric Balloon Observatory Design Study –
ESBO DS
Proposal No: 777516 – ESBO DS
Duration: Mar 1, 2018 - Feb 28, 2021
WP WP 2 Del. No D2.1 Part 1 Title Requirements Baseline - UV Lead Beneficiary “MPG”
Nature “Report”
Short Description This document contains the top-level user requirements that
shall be fulfilled by the infrastructure.
Dissemination Level “Public”
Est. Del. Date 31/05/2018
Version 1.0
Date 31.05.2018
Status Released
Authors T. Müller, tmueller@mpe.mpg.de, MPG-MPE
P. Maier, pmaier@irs.uni-stuttgart.de, USTUTT
B. Stelzer, stelzer@astro.uni-tuebingen.de, EKUT
K. Werner, werner@astro.uni-tuebingen.de, EKUT
L. Hanke, hanke@astro.uni-tuebingen.de, EKUT
Approved by P. Maier, pmaier@irs.uni-stuttgart.de, USTUTT
ESBO DS Requirements Baseline - UV Version: 1.0
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TABLE OF CONTENTS
LIST OF ABBREVIATIONS AND DEFINITIONS ................................................................. 3
REFERENCE DOCUMENTS ..................................................................................................... 3
1 INTRODUCTION .................................................................................................................... 5
2 SCOPE ...................................................................................................................................... 5
2.1 Scope of the Requirements Baseline ......................................................................... 5
2.2 Scope of this Document ............................................................................................ 6
3 NEEDS AND REQUIREMENTS LOGIC ............................................................................ 6
3.1 General Needs and Requirements Logic ................................................................... 6
3.2 Needs and Requirements Levels covered in this document ...................................... 8
4 SCIENCE CASES AND NEEDS ............................................................................................ 8
4.1 Science Goals / Objectives ........................................................................................ 8
4.1.1 Search for variable hot compact stars .................................................................. 8
4.1.2 Detection of flares from cool dwarf stars ............................................................ 9
4.2 STUDIO Mission Statement ................................................................................... 10
4.3 Scientific Needs ....................................................................................................... 10
5 STUDIO REQUIREMENTS ................................................................................................ 10
5.1 Terms and Categories .............................................................................................. 10
5.2 STUDIO Scientific Requirements ........................................................................... 12
5.3 STUDIO Functional Requirements ......................................................................... 13
5.4 STUDIO Operational Requirements ....................................................................... 14
5.5 Studio Interface Requirements ................................................................................ 15
5.6 Studio Environmental Requirements ...................................................................... 16
5.7 STUDIO Physical Requirements ............................................................................ 17
6 ADD-ON SCIENCE NEEDS AND REQUIREMENTS ..................................................... 17
6.1 Add-On Mission Statement ..................................................................................... 18
6.2 Add-On Instruments Requirements ......................................................................... 18
7 PRELIMINARY TECHNOLOGY DEMONSTRATION PROTOTYPE NEEDS ......... 18
7.1 Precise Image Stabilisation System ......................................................................... 19
7.2 Soft Landing Technology ........................................................................................ 19
7.3 Modular and Scalable Gondola and Subsystems .................................................... 20
ESBO DS Requirements Baseline - UV Version: 1.0
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LIST OF ABBREVIATIONS AND DEFINITIONS
Abbreviation Definition
AO Adaptive optics
BLAST Balloon-borne Large Aperture Submillimeter
Telescope
CBE Current Best Estimate
DH Detector Head
DLR German Aerospace Center
ESA European Space Agency
ESBO DS European Stratospheric Balloon Observatory
Design Study
FEE Front-End-Electronics
FIR Far-Infrared
FWHM Full Width Half Maximum
HV / HVPS High-Voltage Power Supply
(Hochspannungsversorgung)
PDR Preliminary Design Review
NASA National Aeronautics and Space Administration
NIR Near Infrared
SOFIA Stratospheric Observatory for Infrared
Astronomy
STUDIO Stratospheric Ultraviolet Demonstrator of an
Imaging Observatory
TBC To be confirmed
TBD To be determined
TDR Telescope Design Review
UV Ultraviolet
WD White Dwarf
REFERENCE DOCUMENTS
[RD1] ORISON - innOvative Research Infrastructure based on Stratospheric
balloONs. Technical and Functional Report. 30 November 2016.
[RD2] ORISON - innOvative Research Infrastructure based on Stratospheric
balloONs. State of the Art and Market Offer Report. Version 1.2. 29
January 2018.
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[RD3] Fuhrmeister et al. (2011). Multi-wavelength observations of Proxima
Centauri. Astronomy & Astrophysics, Volume 534, id. A133.
[RD4] Berkefeld, T. et al. (2011). The Wave-Front Correction System for the
Sunrise Balloon-Borne Solar Observatory. Solar Phys, 268, 103-123.
[RD5] Shariff, J.A. et al. (2014). Pointing control for the SPIDER balloon-borne
telescope. Proc. SPIE, 9145, id. 91450U.
[RD6] Pascale,E. et al. (2008). The Balloon-borne Large Aperture Submillimeter
Telescope: BLAST. Astrophys. J. 681 400.
ESBO DS Requirements Baseline - UV Version: 1.0
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1 INTRODUCTION
The Requirements Baseline contains the top-level user needs and requirements as defined
for the infrastructure to be developed, upon which all subsequent development within ESBO
DS will be based. It thereby summarizes and documents the work performed under WP2,
“Detailed Science Case Analysis”.
2 SCOPE
2.1 SCOPE OF THE REQUIREMENTS BASELINE
The purpose of the Requirements Baseline is to document the needs and requirements of
scientific users with regard to the ESBO infrastructure, i.e. the first / second level of the
requirements hierarchy as also further described in chapter 3 of this document. Detailed
technical requirements on the system level and below are foreseen to be documented in
further Technical Requirements Specification documents.
User needs and requirements have been defined with regard to four aspects of the ESBO
DS project, and mirroring the four tasks within WP2:
o User needs and requirements for UV science, i.e. already relevant for the prototype
development within ESBO DS;
o User needs and requirements for near infrared (NIR) science, including exoplanet
science, i.e. relevant for the mid-term platform of ESBO;
o User needs and requirements for far infrared (FIR) science, i.e. relevant for the long-
term platform of ESBO;
o User needs in terms of operation.
The structure of the Requirements Baseline follows these four categories of needs and
requirements. As there are significant differences in the degrees of detail to which needs and
requirements of these four categories are known at this time (e.g. for UV science, system
level technical requirements have been identified already), the requirements baseline is
implemented as a series of three documents:
o D2.1-1 Requirements Baseline – UV
Contains detailed scientific user requirements as well as system level technical
requirements already identified and relevant for the prototype development within
ESBO DS;
o D2.1-2 Requirements Baseline – NIR & FIR
Contains descriptions of the driving science and scientific needs as well as
requirements to the degree known at this point for the two mid- and long-term
platforms currently envisioned for ESBO;
o D2.1-3 Requirements Baseline – Common Operational Needs
Contains user needs of the scientific community regarding the infrastructure’s
operational concept beyond the scientific needs of each science case and applicable
to all three scientific areas / envisioned flight platforms.
Particularly parts 2 and 3 of the Requirements Baseline are, to large extents, based on
findings of the ORISON H2020 project.
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2.2 SCOPE OF THIS DOCUMENT
This document – the Requirements Baseline – UV – covers the user needs and requirements
for UV science, which will be relevant for the prototype development within ESBO DS. As
the UV science cases are already well defined, the document includes
o A description of the UV science cases and their scientific needs;
o The detailed scientific user requirements of the UV science cases;
o The technical requirements on system level.
In addition to the requirements related to the UV science cases, this document also includes
other user requirements relevant to the prototype development, particularly those derived
from the concept of add-on platform science opportunities and those for the proof-of-concept
function of the prototype as far as they have already been identified.
A further description of the different hierarchical levels of needs / requirements covered in
this document is included in chapter 3.
The prototype mission was assigned the mission name “STUDIO” (Stratospheric Ultraviolet
Demonstrator of an Imaging Observatory) so that the mission name will be used
synonymously throughout the rest of this document.
3 NEEDS AND REQUIREMENTS LOGIC
3.1 GENERAL NEEDS AND REQUIREMENTS LOGIC
Figure 1 shows the general flowdown of needs and requirements within the ESBO
DS project, limited to the highest levels as relevant for this report. For further details on the
requirements flowdown, please consult the System Engineering Plan (D1.4).
Definition of “user”
As ESBO is envisioned as an infrastructure primarily for astronomical (and via the add-on
platform instruments also others) scientific observations, the “user” in the case of ESBO /
ESBO DS is always the scientist who will exploit the infrastructure for scientific research.
As ESBO foresees different kinds of usage, however, a distinction of different types of
scientific users needs to be made as they are understood within this document:
o The most general interpretation of “user”, mostly relevant to parts 1 and 2 of the
Requirements Baseline is the astronomical community (or parts thereof) that requires
or desires certain observational capabilities / means to further scientific research.
This interpretation of “user” underlies the identification of the driving science;
o More specifically and particular to the kinds of usage foreseen for ESBO, the user
can be a scientist / scientific group that wants to fly an own instrument on ESBO, or,
o A scientist / scientific group that wants to use an existing instrument on ESBO for
an observation.
General Needs and Requirements Logic
The following graph and paragraphs describe the general hierarchical logic of needs and
requirements. The general description is followed by an indication as to which elements of
the hierarchy are covered in this particular part of the Requirements Baseline. This indication
is included in each part of the Requirements Baseline.
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Figure 1: General flowdown of needs and requirements
User Needs
The User Needs describe in general terms what is needed or desired by the user. In the scope
of parts 1 (UV) and 2 (NIR and FIR) of this document, scientific user needs are described as
science cases / scientific applications to be coverable. In Part 3 (Common Operational
Needs), they are represented as general descriptions of operational concepts and details that
are important for the usability and suitability of an observatory infrastructure for the
scientific user.
The User Needs answer the question “What does the user need?” with a general, verbal
description, including the necessary context.
User Requirements
The User Requirements are a specification of the User Needs into concrete, preferably
quantified pieces of information.
They answer the question “What does the user need?” with concrete, quantified
requirements.
Technical Requirements
The technical requirements on the system level are derived from the User Requirements and
describe the top-level technical (functional, operational,…) requirements that the
infrastructure needs to meet in order to fulfill the user requirements. The answer the question
“What is needed form the infrastructure perspective to fulfill the User Needs and User
Requirements?
User Needs
User Requirements
Technical Requirements (System Level)
Lower Level Technical Requirements
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Lower Level Technical Requirements
The lower level requirements are requirements on subsystems or components, derived from
the technical requirements on the next higher level. The Technical Requirements on System
Level represent the highest level.
3.2 NEEDS AND REQUIREMENTS LEVELS COVERED IN THIS DOCUMENT
Figure 2: Elements of the needs and requirements hierarchy covered in this part of the Requirements
Baseline
4 SCIENCE CASES AND NEEDS
4.1 SCIENCE GOALS / OBJECTIVES
4.1.1 Search for variable hot compact stars
Hot and compact stars are the rather short-lived
end stages of stellar evolution. They comprise the
hottest white dwarfs (WDs) and hot subdwarfs. A
significant fraction of them show light variations
with periods ranging from seconds to hours.
Among them are diverse types of pulsators, which
are important to improve asteroseismic models.
Others are members of ultracompact binaries (e.g.,
WD+WD pairs) and are strong sources of
gravitational wave radiation and crucial calibrators
for the future space mission eLISA. They are also
User Needs
User Requirements
Technical Requirements (System Level)
Lower Level Technical Requirements
Figure 3: Left: The globular cluster 47 Tuc as
seen by the Hubble Space Telescope. Right:
Faint, hot white dwarfs in this dense field are
identified by comparing visible light and UV
images (image credit: NASA).
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ESBO DS Requirements Baseline - UV Version: 1.0
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regarded as good candidates for the progenitors of thermonuclear supernovae. Furthermore,
compact binaries are formed via common envelope evolution and are important to study this
poorly understood phase of binary evolution.
Hot compact stars have so far been studied predominantly at high Galactic latitudes. Due to
their very blue colours they stick out in old stellar populations like the Galactic halo.
However, the density of stars at high Galactic latitudes is rather small and those objects
therefore very rare. Due to the 1000-times higher stellar density, the disc should contain
many more of those objects. Searches in the Galactic plane are desirable but the
identification of these faint stars is hampered by the dense, crowded fields. But not so in the
UV band. The hot stars are much easier to detect there, because their emitted flux is
increasing towards the UV, while the flux of the majority of other stars decreases because
of their lower temperatures. Surveying the Galactic plane with a UV imaging telescope will
uncover many new variable hot stars.
4.1.2 Detection of flares from cool dwarf stars
Red dwarf stars (spectral type M) are hydrogen-
burning main sequence stars like our Sun, but less
massive, cooler and less luminous. The large
majority of the stars in our Milky Way belong to
this group. Red dwarfs emit most of their radiation
in the visible and near-infrared wavelength
regions. Their UV and X-ray emission, despite
being energetically a minor contribution to the
overall radiation budget, ionizes material
surrounding the stars and is, therefore, of central
interest for the evolution of planets and other
circumstellar matter. This high-energy emission of red dwarf stars is highly dynamic.
One characteristic phenomenon are flares that
are stochastic brightness outbursts resulting
from reconfigura-tions of the stellar magnetic
field. During such flares, these normally faint
stars become much brighter for the duration of
minutes. A strong emission line of ionized
magnesium (Mg II) at 280 nm, covered by the
STUDIO instrument, can carry up to 50% of
the near-UV flux during flares. Up to now, no
systematic monitoring of “flare stars” exists.
Consequently, the flare occurrence rate is
unknown as well as the flare energy number
distribution. Particularly interesting for the
study of the physics of flares is their multi-wavelength behaviour (time lags, relative energy
in different bands). However, only a few simultaneous UV and optical observations of flares
exist. STUDIO enables such observations by monitoring (continuous over hours or multi-
epoch) of stars across the field or of individual prominent objects.
Figure 4: Relative size of a low-mass flare
star (image credit: NASA).
Figure 5: A flare observed from our nearest-
neighbour star Proxima Centauri. Green: optical
light, red: X-rays (from Fuhrmeister et al. 2011;
A&A 534, A133 [RD3]).
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4.2 STUDIO MISSION STATEMENT
The ESBO DS prototype mission, whose scientific component will be to study the
abovementioned science cases, will have the mission name STUDIO (Stratospheric
Ultraviolet Demonstrator of an Imaging Observatory). Its scientific mission statement is as
follows:
We will study the brightness variability of low-mass stars in two different stages of their
evolution. We aim to understand (i) their interior structure during the final evolutionary
stage (hot white dwarfs and subdwarfs) as well as their interaction with binary companions,
and (ii) the atmospheric dynamics driven by magnetic fields during the main-sequence stage
(M dwarf stars).
4.3 SCIENTIFIC NEEDS
We aim to detect variability of hot compact stars (white dwarfs and subdwarfs) as well as of
cool main-sequence stars in the ultraviolet band. We need a moderate field-of-view (30'x30'),
large enough to achieve a useful detection probability but not too large in order to avoid
source confusion. A number of about 15 fields shall be observed for ~2 hours each. We
estimate to find about 20 variable hot stars. About 1000 M dwarf stars out to 300pc are
located in 15 fields but their flare rate is rather uncertain and subject of the proposed study.
5 STUDIO REQUIREMENTS
5.1 TERMS AND CATEGORIES
Numbering of Requirements
The requirements are named according to the following scheme:
R-UV-SCI-XX
Where the first element indicates the type of requirement, the second element indicates the
science case it refers to, the third element indicates the topical area covered, and XX is a
running number. Tables 1 to 3 list the applied implementations of the first three elements.
Table 1: Abbreviations used for types of requirements
Abbreviation Meaning
R Scientific Requirement
RF Functional Requirement
RO Operational Requirement
RI Interface Requirement
RE Environmental Requirement
RP Physical Requirement
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Table 2: Abbreviations used for the originating science case
Abbreviation Meaning
UV Original (variable hot compact stars) UV science case
FL Additional requirements from the flare-stars UV science case
Table 3: Abbreviations used for the topical area
Abbreviation Meaning
SCI Scientific
POI Pointing
TEL Telescope
FLI Flight conditions
COM Communication
POW Power supply
DH Detector head
FEE Front-end-electronics
HV High-voltage power supply
Requirements and Goals
Requirements that will not be treated as design drivers are indicated as “Goals”, with the
first letter “R” in their designation being replaced by “G”.
Distinction of image acquisition modes
Additionally, in some cases a distinction is made between Mode 1 and Mode 2, referring to
different image acquisition modes of the UV instrument. These are:
o Mode 1
Events are integrated to images in the front-end electronics and sent to the payload
computer as complete images.
o Mode 2
Single photons are registered with a time stamp, integration to images is performed
on the ground.
Status and time of definition of requirements
The requirements table also indicates the current status of each requirement and, if
applicable, the time of final / next definition for the requirement (abbreviated as “Def.”).
The status indicators used are:
o Final
o TBC – to be confirmed
o TBD – to be determined
o CBE – current best estimate of an underlying property, i.e. final value TBD
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The time of definition either quotes a specific time or one of the following reviews:
o TDR – Telescope Design Review (August 2018)
o PDR – Preliminary Design Review (November 2018)
5.2 STUDIO SCIENTIFIC REQUIREMENTS
Wavelength and Colour Status Def.
R-UV-
SCI-01
Wavelength coverage
The primary UV payload shall provide imaging capabilities in the
wavelength band 180 to 330 nm
Final -
R-UV-
SCI-02
UV Filters
3 Filters required: Sloan u, GALEX NUV filter, fail safe hole;
filter changer to be provided by USTUTT (filter details to be
provided by EKUT; Filters procured by EKUT)
Final -
R-UV-
SCI-03
Visible channel complement
The payload shall allow complementary simultaneous imaging
capabilities in a visible channel. These shall offer the choice of
the following filter bands: Sloan g, r, i, z?, block, open
TBC PDR
Sky Coverage
R-UV-
SCI-04
The mission shall allow coverage of regions within the galactic
plane. (specific regions TBD)
TBD in observation plan
TBD PDR
R-FL-
SCI-05
The mission shall allow coverage of regions within the galactic
plane. (specific regions TBD)
TBD in observation plan
TBD PDR
Field of View and Resolution
R-UV-
SCI-06
UV payload field of view
The primary UV payload shall have a field of view of at least 30
x 30 arcmin
Final -
R-UV-
SCI-07
UV payload pixel size
The primary UV payload shall have a pixel size on the sky of not
more than 1.1 arcsec
Final -
G-UV-
SCI-08
Visible channel complement (Goal)
The visible camera shall provide complementary images with a
field of view of at least 8 x 8 arcmin
TBC PDR
G-UV-
SCI-09
Visible channel complement (Goal)
The visible camera shall provide complementary images with a
pixel size on the sky of not more than 1.1 arcsec
TBC PDR
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5.3 STUDIO FUNCTIONAL REQUIREMENTS
Pointing System Status
RF-UV-
TEL-01
Telescope elevation
The primary telescope shall be able to observe at elevation angles
between TBD deg (flexibility, determined by technical limitation)
and TBD deg (determined by reasonable length of flight train)
TBD TDR
GF-UV-
TEL-
02a
Image Stabilisation (Goal) – Mode 1
The PSF center on the UV detector shall be positionally stable to
less than 0.5 arcsec over the integration time of TBD s
(Await Modtran calculations; will be the longer one of the
flare/hot compact science integration time requirements)
TBD TDR
GF-UV-
TEL-
02b
Image Stabilisation (Goal) – Mode 2
The PSF center on the UV detector shall be positionally stable to
less than 40 arcsec.
Final -
GF-UV-
TEL-03
Pointing Accuracy
The pointing of the telescope line of sight shall be accurate to +/-
40 arcsec in both elevation and azimuth (uncritical)
Final -
RF-UV-
TEL-04
Pointing Knowledge
The sky position of the image center shall be reconstructable
without information from the UV instrument to within +/- 0.5
arcsec in both elevation and azimuth at a time resolution of 2 kHz
Final -
RF-UV-
TEL-05
Tracking velocity
The pointing system shall allow sidereal tracking.
Final -
RF-FL-
TEL-06
Integration time
The observation system shall allow for a maximum observation
time of 60 s for flare observations
TBC TDR
RF-FL-
TEL-07
Time resolution
The observation system shall allow for a minimum time
resolution of 60 s for flare observations matching time resolution
with visible instrument
TBC TDR
Telescope
RF-UV-
TEL-08
Instrument contamination
The telescope and optical bench shall be sealable to allow
protection of the optical elements against dust and other
contaminants during ground handling, launch, ascent and descent.
Final -
RF-UV-
TEL-09
Outgassing
Outgassing of the carbon composite telescope tube or other parts
within the optical system during launch or flight shall be avoided.
Final -
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RF-UV-
TEL-10
Mirror coatings
Standard aluminium mirror coatings are sufficient for the UV
instrument. Overcoating with SiO2 is allowed.
(TBC)
TBC TDR
5.4 STUDIO OPERATIONAL REQUIREMENTS
Balloon Flight Status Def.
RO-UV-
FLI-01
Transmission altitude
The observational pressure altitude of the balloon shall be at least
TBD km / shall allow at least access to transmission windows in
between 180 to 220 nm & 280 to 330 nm
TBD after Modtran simulations and THISBE measurement
crosscheck
TBD PDR
RO-UV-
FLI-02
Pressure measurement
Precise pressure measurement shall be taken during the flight to
allow precise reconstruction of the pressure altitude at the time of
observations.
Final -
RO-UV-
FLI-03
Telescope elevation
Observations for the hot compact stars science case shall take
place at elevation angles between TBD deg and TBD deg.
TBD after sky brightness Modtran simulations
TBD PDR
RO-FL-
FLI-04
Telescope elevation
Observations for the flares science case shall take place at
elevation angles between TBD deg and TBD deg to ensure
observability of the Mg II line.
TBD after sky brightness Modtran simulations
TBD PDR
Communication
RO-UV-
COM-
01
Scientific data downlink
The system shall be capable of downlinking at least one full frame
per instrument at each new field acquisition.
Everything else TBD in operation plan
Final
/TBD
- /PDR
RO-UV-
COM-
02
Payload operations and manual control
The baseline operational concept of the flight system shall rely
upon pre-scripted, pre-programmed observations that are executed
automatically with minimal external interference.
The system shall, however, allow full manual command at all
times.
Final -
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5.5 STUDIO INTERFACE REQUIREMENTS
Communication interface Status Def.
RI-UV-
COM-
01a
Data Rate – Mode 1
The communication interface shall allow science data to be sent
from the FEE to the payload OBC of up to 3.4 Mbit/s (t_int = 10s;
2k x 2k, 8 bit) (compression TBC)
Final -
RI-UV-
COM-
01b
Data Rate – Mode 2
The communication interface shall allow science data to be sent
from the FEE to the payload OBC of up to 12.6 Mbit/s (X & Y
coordinates, 12 bit each; time stamp, 20 bit; up to 300,000
events/s)
Final -
RI-UV-
COM-
02
Time support signal
The UV payload OBC shall receive an external support time
signal (preferably global GPS time) at least every 1 min.
Final -
RI-UV-
COM-
03
Data storage
The payload data storage shall be able to record the scientific data
produced during up to 30 h.
Final -
Power supply
RI-UV-
POW-
01
Voltage
The UV instrument (single power supply line) shall be supplied
by a DC voltage between 24 and 36 V.
Final
RI-UV-
POW-
02
Voltage stability
The voltage supply to the UV instrument shall be stable to within
24 & 36 V during operation.
Final
RI-UV-
POW-
03
Average power
The power supply shall be able to provide, via one single
interface, an average power of 25 W to the detector head, front-
end-electronics, and the high-voltage power supply (1 W DH, 21
W FEE, 3 W HVPS).
Numbers are CBE for the worst case, driven by the RAM. To be
measured with the integrated hardware.
CBE
Next
est.:
end
2018
RI-UV-
POW-
04
Peak current
The power supply shall be able to provide peak current of up to
TBD A to the detector head & front-end-electronics and of up to
TBD A to the high-voltage power supply.
(CBE: 2 A)
CBE Est.
end
2018
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5.6 STUDIO ENVIRONMENTAL REQUIREMENTS
MCP Detector Head Status Def.
RE-UV-
DH-01
Temperature Range
The temperature of the detector head shall not exceed the
following limits:
Operating: min.: TBD; max.: 60 °C
Inactive: min.: -40 °C; max.: 60 °C
TBC End of
May
2018
RE-UV-
DH-02
Temperature Stability
Temperature stability and temporal gradient of the detector head
are not critical.
Final -
RE-UV-
DH-03
Radiation shielding
No radiation shielding of the detector head shall be necessary.
Final -
Front-End-Electronics
RE-UV-
FEE-01
Temperature Range
The temperature of the front-end-electronics shall not exceed the
following limits:
Operating: min.: -44 °C; max.: 75 °C
Inactive: min.: -44 °C; max.: 75 °C (not separately tested)
(the critical element is the beetle chip; everything else is MIL
grade, with an operating range of -60 °C to 125 °C)
Final -
RE-UV-
FEE-02
Temperature Stability
Temperature stability and temporal gradient of the front-end-
electronics are not critical.
Final -
RE-UV-
FEE-03
Radiation shielding
No radiation shielding of the front-end-electronics shall be
necessary.
Final -
High-Voltage Power Supply
RE-UV-
HV-01
Temperature Range
The temperature of the high-voltage power supply shall not
exceed the following limits:
Operating: -20 to +60 °C (Tested)
Inactive: not supplied
Final -
RE-UV-
HV-02
Temperature Stability
Temperature stability and temporal gradient of the high-voltage
power supply are not critical.
Final
RE-UV-
HV-03
Radiation shielding
No radiation shielding of the high-voltage power supply shall be
necessary.
Final
ESBO DS Requirements Baseline - UV Version: 1.0
Page 17 of 20
RE-UV-
HV-04
Condensation/water protection
The high voltage power supply shall, under all operation
conditions and circumstances, be protected against the intrusion
of water and against internal condensation.
Final -
5.7 STUDIO PHYSICAL REQUIREMENTS
Status Def.
RP-UV-
01
Mass
The payload structure shall foresee the accommodation of the
detector head & FEE with a mass of 3.75 kg (2.5 kg CBE+20%
conting.+25% sys. Margin, including cables) on the optical bench.
The gondola shall foresee the accommodation of the HV with a
mass of 1.375 kg (1 kg CBE + 10% conting. + 25% sys. Margin)
RP-UV-
02
Physical size (HV)
The gondola shall foresee the accommodation of the HV as
specified by the technical drawing in document STU-EKU-
DWG-1243-00.0000-vx.xx.
Final -
RP-UV-
03
Physical size (FEE)
The telescope assembly shall foresee the accommodation of the
FEE as specified by the technical drawing in document STU-
EKU-DWG-1242-00.0000-vx.xx.
(Current version is CBE, but no large changes are expected)
CBE PDR
RP-UV-
04
Detector assembly
The telescope assembly shall foresee the accommodation of the
detector assembly as specified by the technical drawing in
document STU-EKU-DWG-1241-00.0000-vx.xx.
(Current version is CBE, major changes, particularly of the
interfaces, are still expected)
CBE PDR
6 ADD-ON SCIENCE NEEDS AND REQUIREMENTS
In addition to the telescope instruments, the ESBO flight platforms will provide space and
support for add-on platform instruments. Those instruments could be nadir-viewing, side-
viewing, or not requiring a view at all. They can potentially cover a wide range of interesting
applications, from Earth observation and atmospheric research to research and tests under
analogue conditions for space or combined stress.
Providing these flight opportunities will allow a significant benefit to additional scientific
and technical communities at a small additional effort for ESBO flights.
ESBO DS Requirements Baseline - UV Version: 1.0
Page 18 of 20
6.1 ADD-ON MISSION STATEMENT
The ESBO flight platforms will provide flight opportunities for add-on platform instruments,
not utilizing the main telescope, to cover a wide range of scientific and technical
applications.
6.2 ADD-ON INSTRUMENTS REQUIREMENTS
The following requirements were identified during the ORISON project to allow an effective
use of add-on platform instruments [RD1]. As the add-on instruments are not regarded as
design drivers, their requirements are expressed as goals.
Functional Requirements
GF-
ADD-
01
Pointing stability
The ESBO platforms shall provide pointing stability of +/- 100 arcsec or better
in azimuth for add-on instruments
GF-
ADD-
02
Single instrument mass
The ESBO platforms shall allow the installation of add-on instruments with a
mass of at least 4 kg for an individual instrument
GF-
ADD-
03
Total instruments mass
The ESBO platforms shall allow the installation of add-on instruments up to a
total mass of at least 20 kg.
GF-
ADD-
04
Telemetry
The ESBO platforms shall provide a limited downlink capability to add-on
instruments during flight.
GF-
ADD-
05
Power supply
The ESBO platforms shall provide limited power supply to add-on instruments.
Operational Requirements
GO-
ADD-
01
Exchange of instruments
The ESBO system shall allow the exchange of add-on platform instruments in
between flights.
7 PRELIMINARY TECHNOLOGY DEMONSTRATION
PROTOTYPE NEEDS
In addition to the scientific mission aspect, the ESBO prototype will also need to serve a
technology demonstration function, particularly for the following technologies:
o A highly precise and reliable astronomical image stabilization system for flying
platforms on different scales;
o Soft landing systems for scientific balloon payloads;
o Modular and scalable scientific balloon gondolas and subsystems.
ESBO DS Requirements Baseline - UV Version: 1.0
Page 19 of 20
In the following, the background for each technology is shortly described, along with the
associated needs with regard to the prototype.
7.1 PRECISE IMAGE STABILISATION SYSTEM
In order to access the full potential of a balloon-borne stratospheric observatory it is
necessary to consider pointing control systems that enable stable performance close to the
diffraction limit. This is definitely a challenge on a moving platform that causes disturbances
in terms of structural deformation and vibrations. In addition, aerodynamic forces and the
rigid-body movement of the gondola itself have to be considered and possibly compensated
to achieve precise pointing. Other airborne platforms, e.g. SOFIA, aim for high image
quality to achieve its scientific goals, translating in a pointing requirement of 0.4 arcsec rms
image stability. The overall excitation level on a balloon-borne telescope at cruise altitude
(>20 km) is considerably lower than on a plane like SOFIA, however wind gusts and
pendulum motion of the gondola could pose possible challenges [RD4],[RD5]. Different
balloon missions have already shown that precise pointing is possible. The SUNRISE
mission mostly managed pointing stability of less than 0.04 arcsec rms [RD4] over a rather
long time window. However, the sun is a very specific bright source for tracking and
pointing, which is usually not the case other than in solar astronomy. Other astronomical
balloons aim at a pointing level of several arcseconds or arcminutes, e.g. BLAST [RD6] or
SPIDER [RD5], a balloon-borne polarimeter.
Ultimately, ESBO shall work with a large, 5-meter-class telescope in the far-infrared, e.g. at
the wavelength of the interstellar cooling line of singly ionized carbon (CII), λ = 158 µm.
Critical sampling of the diffraction limited point spread function λ/D = 6.5 arcsec requires
pixels of 3.3 x 3.3 arcsec2. As a rule of thumb, the pointing stability should be about 1/10 of
the pixel size, i.e. ~ 0.3 arcsec. The STUDIO pre-cursor mission in the UV requires a
pointing stability of 1 arcsec, which will be a good preparation for the final FIR mission and
for potential intermediately sized missions.
Similar to other airborne astronomy platforms, such precise attitude control will only be
achievable with a multi-stage design. STUDIO therefore foresees a two-stage
Needs
Demonstrate highly precise image stabilization for astronomical observations based on a
scalable and extendable two-step pointing system using a closed-loop inner stage with a
tip/tilt mirror and a tracking sensor.
7.2 SOFT LANDING TECHNOLOGY
All flight systems of ESBO will be designed to allow safe payload recovery and re-flight
with minimum turnaround efforts. This is a key element of the ESBO DS D2.1 Requirements
Baseline - UV concept that is crucial in making the operation as an accessible observatory
economically feasible. Safe recovery with minimal damage to the gondola and payload will
be achieved by the use of steerable parafoils instead of the typical round parachutes. The
adaptability of this technology has been demonstrated for lower-flying balloon payloads
from 30 km altitude by the U.S.-based company World View, with highly accurate flights
to the landing zone and structural landing loads on the payload considerably lower than the
structural loads during parachute opening. Similar developments are also under way in
Europe.
ESBO DS Requirements Baseline - UV Version: 1.0
Page 20 of 20
Needs
Steered parafoil solutions can be procured as stand-alone systems, including the deployable
parafoil and an aerial guidance unit [RD2]. These systems can be installed on or above the
payload. The approach within ESBO DS is to procure such a system, to integrate it with the
prototype flight system and to demonstrate it with one of the first flights following the ESBO
DS project period. The prototype platform therefore needs to foresee:
o Ways to integrate the steered parafoil system into the flight train;
o Ways to potentially integrate parts of the steered parafoil system into the gondola;
o Potential structural implications for the gondola;
o Means to add “landing hear” and protection specific to landings with a steered
parafoil system.
7.3 MODULAR AND SCALABLE GONDOLA AND SUBSYSTEMS
Balloon gondolas are currently built specifically for single missions or mission sequences.
While some subsystems are available separately, they are not necessarily easily compatible.
This includes flight control and piloting systems, power systems, communication systems,
and the balloons themselves.
Needs
Demonstrate ways to provide standardized systems and interfaces, particularly including
systems vital for astronomical observatories (but also beneficial for other applications) such
as attitude stabilization.
D2.1 - REQUIREMENTS BASELINE – NIR & FIR
Version 1.0
31.05.2018
Status: Released
ESBO DS Requirements Baseline – NIR & FIR Version: 1.0
Page 1 of 21
Deliverable
H2020 INFRADEV-01-2017 project "European
Stratospheric Balloon Observatory Design Study"
Topic: INFRADEV-01-2017 Design Studies
Project Title: European Stratospheric Balloon Observatory Design Study –
ESBO DS
Proposal No: 777516 – ESBO DS
Duration: Mar 1, 2018 - Feb 28, 2021
WP WP 2 Del. No D2.1 Part 2 Title Requirements Baseline – NIR & FIR Lead Beneficiary “MPG”
Nature “Report”
Short Description This document contains the top-level user requirements that
shall be fulfilled by the infrastructure.
Dissemination Level “Public”
Est. Del. Date 31/05/2018
Version 1.0
Date 31.05.2018
Status Released
Authors P. Maier, pmaier@irs.uni-stuttgart.de, USTUTT
B. Stelzer, stelzer@astro.uni-tuebingen.de, EKUT
D. Angerhausen, daniel.angerhausen@csh.unibe.ch1
A. Krabbe, krabbe@dsi.uni-stuttgart.de, USTUTT
L. Venuti, venuti@astro.uni-tuebingen.de2
J., Alcala, alcala@oacn.inaf.i3
1 External collaborator, Center for Space and Habitability, Universität Bern 2 External collaborator, Institut für Astronomie und Astrophysik, Universität Tübingen 3 External collaborator, INAF - Osservatorio Astronomico di Capodimon
ESBO DS Requirements Baseline – NIR & FIR Version: 1.0
Page 2 of 21
TABLE OF CONTENTS
LIST OF ABBREVIATIONS AND DEFINITIONS ................................................................. 3
REFERENCE DOCUMENTS ..................................................................................................... 3
1 INTRODUCTION .................................................................................................................... 9
2 SCOPE ...................................................................................................................................... 9
2.1 Scope of the Requirements Baseline ......................................................................... 9
2.2 Scope of this Document ............................................................................................ 9
2.3 Coverage of the Needs/Requirements Logic ........................................................... 10
3 NEAR INFRARED SCIENCE NEEDS AND REQUIREMENTS .................................... 11
3.1 Exoplanet Atmospheres Transit Observations ........................................................ 12
3.2 Accretion in Young Stellar Objects ........................................................................ 13
3.3 Small Bodies ........................................................................................................... 15
4 FIR SCIENCE NEEDS .......................................................................................................... 17
4.1 Overview of the Current Situation .......................................................................... 17
4.2 FIR Science Areas and their Needs ......................................................................... 18
4.2.1 Surveys ............................................................................................................... 18
4.2.2 Discrete Sources................................................................................................. 18
4.2.3 Solar System ...................................................................................................... 21
ESBO DS Requirements Baseline – NIR & FIR Version: 1.0
Page 3 of 21
LIST OF ABBREVIATIONS AND DEFINITIONS
Abbreviation Definition
AO Adaptive optics
BLAST Balloon-borne Large Aperture Submillimeter
Telescope
DLR German Aerospace Center
EChO Exoplanet Characterisation Observatory
ESA European Space Agency
FIR Far-Infrared
FWHM Full Width Half Maximum
HST Hubble Space Telescope
IRAS Infrared Astronomical Satellite
ISM Interstellar Medium
ISO Infrared Space Observatory
JAXA Japanese Aerospace Exploration Agency-
JWST James Webb Space Telescope
KAO Kuiper Airborne Observatory
MIR Mid Infrared
NASA National Aeronautics and Space Administration
NIR Near Infrared
PACS Photodetector Array Camera & Spectrometer
PMS Pre-Main Sequence
SOFIA Stratospheric Observatory for Infrared
Astronomy
STO Stratospheric Terahertz Observatory
TBC To be confirmed
TESS Transiting Exoplanet Survey Satellite
UV Ultraviolet
YSO Young Stellar Object
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[RD51] De Luca, M.; Gupta, H.; Neufeld, D.; Gerin, M.; Teyssier, D.; Drouin, B. J.;
Pearson, J. C.; Lis, D. C.; Monje, R.; Phillips, T. G.; Goicoechea, J. R.;
Godard, B.; Falgarone, E.; Coutens, A.; Bell, T. A., Herschel/HIFI
Discovery of HCl+ in the Interstellar Medium, ApJ, 751 (2), L37, 2012.
[RD52] Caselli, P., and Ceccarelli, C., Our astrochemical heritage, Astron. &
Astrophy. Rev., 20, 56, 2012.
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[RD53] McClure, M.K., Espaillat, C., Calvet, N., Bergin, E., D’Alessio, P., Watson,
D.M., Manoj, P., Sargent, B., Cleeves, L.I., Detections of trans-neptunian ice
in protoplanetary disks, The Astrophysical Journal, 799, 162, 2015.
[RD54] Giuliano, B.M., Esribano, R.M., Martín-Doménech, R., Dartois, E., Muñoz
Caro, G.M., Interstellar ice analogs: band strengths of H2O, CO2, CH3,
CH3OH, and NH3 in the far-infrared region, A&A, 565, A108, 2014.
[RD55] Devlin, M.J., Ade, P.A.R., Aretxaga, I., Bock, J.J., Chapin, E.L., Griffin, M.,
Gundersen, J.O., Halpern, M., Hargrave, P.C., Hughes, D.H., Klein, J.,
Marsden, G., Martin, P.G., Mauskopf, P., Moncelsi, L., Netterfield, C.B.,
Ngo, H., Olmi, L., Pascale, E., Patanchon, G., Rex, M., Scott, D., Semisch,
C., Thomas, N., Truch, M.D.P., Tucker, C., Tucker, G.S., Viero, M.P.,
Wiebe, D.V., Over half of the far-infrared background light comes from
galaxies at z ≥ 1.2, Nature, 458, 737-739, 2009.
[RD56] Küppers, M., O’Rourke, L., Bockelée-Morvan, D., Zakharov, V., Lee, S.,
von Allmen, P., Carry, B., Teyssier, D., Marston, A., Müller, T., Crovisier,
J., Barucci, M.A., Moreno, R., Localized sources of water vapour on the
dwarf planet (1) Ceres, Nature, 505, 525-527, 2014.
[RD57] Hartogh, P., Lis, D. C., Bockelée-Morvan, D., de Val-Borro, M., Biver, N.,
Küppers, M., et al., Ocean-like water in the Jupiter-family comet
103P/Hartley 2. Nature, 478, 218-220, 2011.
[RD58] Hartogh, P., Lellouch, E., Moreno, R., Bockelée-Morvan, D., Biver, N.,
Cassidy, T., et al., Direct detection of the Enceladus water torus with
Herschel. Astronomy and Astrophysics, 532: L2, 2011.
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1 INTRODUCTION
The Requirements Baseline contains the top-level user needs and requirements as defined for the
infrastructure to be developed, upon which all subsequent development within ESBO DS will be
based. It thereby summarizes and documents the work performed under WP2, “Detailed Science
Case Analysis”.
2 SCOPE
2.1 SCOPE OF THE REQUIREMENTS BASELINE
The purpose of the Requirements Baseline is to document the needs and requirements of scientific
users with regard to the ESBO infrastructure, i.e. the first / second level of the requirements
hierarchy as also further described in chapter 3 of part 1 of this document. Detailed technical
requirements on the system level and below are foreseen to be documented in further Technical
Requirements Specification documents.
User needs and requirements have been defined with regard to four aspects of the ESBO
DS project, and mirroring the four tasks within WP2:
o User needs and requirements for UV (ultraviolet) science, i.e. already relevant for the
prototype development within ESBO DS;
o User needs and requirements for near infrared (NIR) science, including exoplanet science,
i.e. relevant for the mid-term platform of ESBO;
o User needs and requirements for far infrared (FIR) science, i.e. relevant for the long-term
platform of ESBO;
o User needs in terms of operation.
The structure of the Requirements Baseline follows these four categories of needs and
requirements. As there are significant differences in the degrees of detail to which needs and
requirements of these four categories are known at this time (e.g. for UV science, system level
technical requirements have been identified already), the requirements baseline is implemented as
a series of three documents:
o D2.1-1 Requirements Baseline – UV
Contains detailed scientific user requirements as well as system level technical
requirements already identified and relevant for the prototype development within ESBO
DS;
o D2.1-2 Requirements Baseline – NIR & FIR
Contains descriptions of the driving science and scientific needs as well as requirements to
the degree known at this point for the two mid- and long-term platforms currently
envisioned for ESBO;
o D2.1-3 Requirements Baseline – Common Operational Needs
Contains user needs of the scientific community regarding the infrastructure’s operational
concept beyond the scientific needs of each science case and applicable to all three
scientific areas / envisioned flight platforms.
Particularly parts 2 and 3 of the Requirements Baseline are, to large extents, based on findings of
the ORISON H2020 project.
2.2 SCOPE OF THIS DOCUMENT
This document – the Requirements Baseline - NIR & FIR – covers the currently foreseen driving
science in the near and far infrared, the derived scientific needs, and partly the associated scientific
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requirements for the mid- and long-term platforms envisioned for ESBO. For both platforms, no
concrete instruments are known yet, so that this part of the Requirements Baseline rather serves to
collect and document potential driving science, based on which instruments (and platforms) will
be studied. It may thus well turn out that different instruments will be necessary / make sense to
study the different science cases.
For the NIR platform, a timeframe until a potential flight at the order of 5 years is currently
considered realistic. Within this timeframe, the development of technology is somewhat
foreseeable, so that it is sensible to already define more concrete requirements for the instruments.
For the FIR platform, a more likely timeframe is expected in the range of around 15 years. In this
case, it is more sensible to more generally assess the scientific needs & science areas of interest
within the FIR community. This will, particularly in WP 3 Infrastructure Analysis and WP 5
Conceptual Design, then be used as a basis for the exploration of different instrument options.
2.3 COVERAGE OF THE NEEDS/REQUIREMENTS LOGIC
As figure 1 illustrates, the content of this document focuses on the scientific needs from the user
perspective. Where possible, it also goes into the associated user requirements. Particularly for the
FIR part, these will be derived and documented in the subsequent work packages mentioned in
section 2.2, also following D3.1 (Concept presentation to scientific audience). Technical
requirements for the near infrared part of the infrastructure will also be derived and documented
within these following work packages. For the far infrared infrastructure, a set of general technical
requirements will be derived and different concept options explored within the abovementioned
work packages.
For a general description of the high-level flowdown of needs and requirements within ESBO
DS and a description of the different elements, please refer to Part 1 of the Requirements Baseline
[RD1].
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Figure 1: Elements of the needs and requirements hierarchy covered in this part 2 of the Requirements
Baseline
3 NEAR INFRARED SCIENCE NEEDS AND REQUIREMENTS
For the mid-term platform, we list three scientific areas that have been identified to be of particular
interest. While they all benefit from the mostly unobscured access to the NIR region in the high
stratosphere, it should be pointed out that the instrumental focus of the areas described in sections
3.1 and 3.2 is quite different to that of the scientific area described in section 3.3 (small bodies).
While most of the “small bodies” science cases require a very high spectral resolution (at the order
of R ~ 20,000 to 40,000), for the Exoplanets Atmospheres case (section 3.1) and the Young Stellar
Objects (YSOs) Accretion case (section 3.2), a spectral resolution below R = 1000 suffices. The
Exoplanets Atmospheres case furthermore has quite unique requirements to the instrument,
telescope, and platform with regard to photometric stability. While from the current point of view,
the Exoplanets Atmospheres case and the YSO Accretion case seem to be approachable by one
instrument, this will require confirmation during further in-depth study. This analysis will also
consider whether some of the spectrally less demanding “Small Bodies” cases might be coverable
by the same instrument.
It should furthermore be noted that while the focus of the ESBO mid-term platform so far has been
on science in the NIR, the analysis of the science cases below showed that for all of the science
areas considered, simultaneous observations in the UV would add considerable value to the
scientific yield. As adding UV capabilities to the same telescope might pose considerable
challenges (additional detector technology required, wide-band reflectance of mirrors from UV to
NIR required, UV requirements on optical surface quality might drive the mirror design), this
option will need to be considered carefully.
User Needs
User Requirements
Technical Requirements (System Level)
Lower Level Technical Requirements
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3.1 EXOPLANET ATMOSPHERES TRANSIT OBSERVATIONS
Science Description:
Little more than 20 years after the discovery of the first exoplanet, more than 3500 planets in more
than 2600 planetary systems are known today. The study of exoplanets has become the most
rapidly growing field in modern astronomy; holding the promise of finding an Earth-like planet in
a potentially habitable zone, and potentially, signatures of life. Evidence for a terrestrial planet at
our closest neighboring star, Proxima Centauri [RD2] or the detection of a multiplanet system
around the near-by late type star TRAPPIST-1 [RD3] have caught attention by the public world-
wide.
The field has moved from detecting and analyzing individual systems to an era of “comparative
exoplanetology”. A particular priority in exoplanet science will be spectroscopy of exo-
atmospheres of edge-on planetary systems in transit, eclipse, or throughout their orbits as a
continuous time series to create phase curves. A variety of questions exists that are potentially of
interest for a balloon borne mission:
Clouds and Hazes in Exoplanet atmospheres: multicolor transit depth observations,
preferably reaching from the UV to the NIR, act as low resolution transmission spectroscopy
of exoplanet atmospheres (see references in Narita et al., [RD4]); providing e.g. clues on
presence of haze or clouds. Wide spectral band observations of atmospheres were conducted
for a few 10s of exoplanets, implying the existence of aerosols. Balloon based observations
can be designed to characterize clouds over a range of planet sizes and effective temperatures.
Understanding Exoplanet Formation and Evolution Pathways: The proposed balloon
platform would provide measurements of elemental abundances of exoplanets that will place
chemical constraints on their formation and migration mechanisms.
Vetting Candidates for JWST observations: in the context of the aforementioned science
cases, the proposed observations can be used to vet candidates for the James Webb Space
Telescope (JWST). E.g. “cloud-free” planets or planets with particular impact on formation
theories can be identified in order to use JWST time most efficiently.
Spectroscopic Phase Curves: a balloon platform will complement JWST by providing long
time baselines to map the spectral variation of planets over their full orbits.
Understanding stellar contributions: It should be noted that simultaneous multiband
photometry of a transit are one way to mitigate systematic effects, as stellar activity (e.g.
flares, sun spots) can affect luminosity and hence transit depth. (details in White Paper by
Apai, et al, 2018 [RD5] or SOFIA science case in [RD6]).
Challenges:
Spectroscopy at long wavelengths (up to ~16 µm) would be desirable, but presents major
challenges (availability of detectors, characteristics of detectors, warm telescope) and has been
discarded for the envelope of a balloon mission, given that the wavelength range of 1-5 µm already
contains most key molecular signatures of interest. Particularly above 2 µm, where some of the
interesting molecules have vibration-rotation bands, strong signatures can be found already.
A balloon borne mission for low resolution exoplanet spectroscopy in the 1-5 µm band based on a
~0.5 m telescope has been discussed by Pascale et al. [RD9],[RD10]. Being limited to relatively
small telescope diameters, such a mission would focus on characterizing hot Jupiters and warm
Neptunes, but would potentially allow to study a significant sample of this population. Again, this
science case is unique to a balloon-borne platform as it provides unobscured access to wavelengths
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that are affected by telluric bands for ground based observations. Observations would potentially
be even possible during daytime [RD9].
Science Needs:
Two different instrumentation approaches can be used to cater the abovementioned science cases.
Approach 1: high precision multichannel imager for absolute transit photometry (compare also
the NIMBUS instrument proposal for the Stratospheric Observatory for Infrared Astronomy
(SOFIA) [RD11]).
Spectral region: visible, NIR, preferably supported by UV.
Spectral resolution: standard filters, e.g. Sloan g,r,z, or JHK, R~10 to 20.
Type of observation: absolute photometry.
Required sensitivity: for atmospheric characteristics: 0.01% (per spectral element).
Better suited for phase curve observations and vetting of JWST candidates.
Approach 2: slit-less (TBC) spectrometer (compare also the proposed instrumentation for the
Exoplanet Characterisation Observatory (EChO) [RD12]).
Spectral region: NIR (1-5µm), preferably supported by UV and optical (especially for
clouds and hazes).
Spectral resolution: ca. 30-50 for chemical census; ca. 200-300 for first insights into
atmospheric processes (with spectral oversampling and binning as an option).
Type of observation: transit spectroscopy.
Slit size: sufficiently large to minimize slit losses & photometric variations due to slit
losses caused by pointing instability. Preferably slit-less.
Better suited for the study of clouds and hazes, required for the detailed measurement of
elemental abundances.
Perhaps more importantly, both approached share the following needs that are very specific for
exoplanet transit observations:
Long-term photometric stability: over 3-6 h for 1-3 h transits.
Photometric precision: at ppm-level.
Addendum:
In addition to the abovementioned transit science cases, balloons might offer an opportunity for a
coronographic exoplanet imaging mission that leverages the low seeing in the upper atmosphere
(see the similarly equipped PICTURE-C mission to directly image debris disks around nearby stars
from a balloon [RD13],[RD14]).
3.2 ACCRETION IN YOUNG STELLAR OBJECTS
Science Description:
Mass accretion is among the prime physical processes governing the evolution of accretion disks
around young low-mass stars (< 2 Msun). The mass accretion rate is an important parameter in disk
evolution models [RD15] and disk clearing mechanisms [RD16], and references therein), and is a
key quantity for the studies of pre-Main Sequence (PMS) stellar evolution and planet formation.
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Matter accretes from the disk onto the star channeled by the magnetic field [RD17]. This leads to
the formation of accretion columns along the field lines and hot spots at the point of impact on the
stellar surface. The additional luminosity produced by accretion in YSOs is a consequence of the
conversion of kinetic energy of the accreted matter into radiation. The mass accretion rate can,
therefore, directly be obtained from the observed accretion luminosity, Lacc. This accretion
luminosity can be measured as an excess above the photospheric luminosity of the star visible at
UV wavelengths. In addition, emission lines are produced in the heated gas of the accretion
streams. Considerable effort has been put in calibrating the empirical relation between the UV
luminosity excess and the optical and near-IR emission line fluxes of YSOs (e.g. [RD18]).
As low-mass stars are faint in the UV, line emission is generally a more easily accessible diagnostic
of accretion. The different excitation conditions of various sets of lines, e.g. lines from different
elements, different ionization stages and different line series, probe distinct regions in the accretion
flow. As a result of the large abundance of hydrogen, the optical line spectra of accreting YSOs
are dominated by Balmer lines. Individual lines of the Paschen and Brackett series have been
detected in near-IR spectra of YSOs. However, the strongest line of the Paschen series (Pa α @
1.875 μm) and the higher-n lines of the Brackett series (e.g. Br δ @ 1.944 μm, Br ε @ 1.817 μm)
have remained unobserved in YSOs because they are located in wavelength regions with strong
atmospheric telluric lines. Moreover, the strongest transitions of the Brackett series (Br α @ 4.015
μm) and the whole Pfund series have wavelengths longward of the K-band where few
spectroscopic observations are available. These important diagnostics have, therefore, been elusive
in previous studies. Spectroscopic observations from locations above (most of) the Earth’s
atmosphere and at wavelengths > 2μm are, therefore, required to assess the accretion physics
associated with the higher-n series of hydrogen.
A spectroscopic balloon mission will enable establishing empirical relations between the fluxes of
the above-mentioned, so far unexplored, emission lines and the accretion luminosity Lacc obtained
from previously measured UV excess of the same stars. Calibrating such relations for bright YSOs
is an essential step for subsequent studies of embedded protostars for which the UV and optical
spectra are not accessible and the near-IR lines represent the only ways to probe and to quantify
mass accretion.
Science Needs:
Spectral resolution: R >= 800, absolute minimum: R = 500 to 600;
Accurate pointing and limited field of view preferable to avoid source confusion;
Sensitivity / targets: number of bright targets in northern sky is limited, observations from
the Southern hemisphere might provide access to more targets at a given sensitivity.
As per the current knowledge, the science needs of the YSO Accretion case may also be coverable
by an instrument designed for medium spectral resolution transit spectroscopy of exoplanet
atmospheres (“Exoplanet Atmospheres” Approach 2). The required spectral resolution to study
YSO Accretion is higher, but spectral binning could be applied for exoplanet observations to reach
the required signal to noise ratio with an instrument that offers higher spectral resolution than
absolutely required. Secondly, the limited field of view requirement might be reachable by adding
an exchangeable narrow slit to the instrument, depending on the instrument design.
Careful considerations during further iteration steps taking into account the needs of both science
cases will need to show whether a reasonable instrument design can cover both.
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3.3 SMALL BODIES
Science Description:
Small solar system bodies are remnants and direct witnesses of our solar system’s formation
process, whose material is thought to have only been slightly altered since the formation of the
planets. Their study thus can reveal a wealth of information about many aspects of the solar system
formation process, among others about the distribution mechanisms of water, the local distribution
of processes during the formation, their
timescales, and even about the formation
routes to complex organic molecules.
Small bodies have received considerable
attention over the last years, particularly
through in-situ missions to comets and
asteroids, such as NASA’s Deep Impact
mission, JAXA’s Hayabusa mission, or
most recently ESA’s Rosetta mission, but
also through highly-sensitive space-based
observations and high-dispersion ground
based observations. However, many
important questions remain to be answered.
Comet volatiles. The abundance and
precise composition of volatiles on comets
provides a good record of their past and
their potential origin. A good
understanding of the current account of
volatiles in different groups of comets,
particularly in Oort cloud comets and
Kuiper Belt objects would provide an
important test of current models of solar
system formation [RD21], in particular the
“Nice Model” which predicts a
considerable mixing between the abovementioned dynamic populations [RD19],[RD20].
Particular volatiles whose abundances and mixing ratios are of interest (and which have already
been detected through gas state emissions on comets) are CO2 [RD23], CO [RD23], OH [RD22],
HCN [RD24], H2O [RD23], and organics such as CH4 [RD22], C2H6 [RD24], and CH3OH [RD24].
Among these, the organics are additionally interesting in respect to the question where and how
complex organic molecules first started to form. Another measurand of particular interest is the
abundance of deuterated water (HDO) on comets, since it allows (in combination with the easier
measurable abundance of H2O) the comparison of D/H ratios in cometary and terrestrial water and
thus might provide a clue towards the origin of Earth’s water [RD25]. The difficulty to measure
these species during the perihelion passage of a comet differs considerably. All of them show
emission lines in the NIR and very short MIR between 2.7 µm and 5.6 µm, however at considerably
different line widths and line strengths. Many of them are very present in the Earth’s atmosphere
and thus can only be measured if either the telluric contribution is precisely known and subtracted
or if telluric and cometary lines are separated due to Doppler shift (and can be discriminated by
very high spectral resolution measurements) [RD24]. These telluric lines are weaker, but still
present at altitudes reachable by airplane. Balloon-borne observations at altitudes around 40 km
would allow the measurement of some of these volatile species and other undetected ones around
Species Wavelength [µm] Line strength
[W/m2]
H2O 2.7 [RD23] 1.6E-16 [RD23]
CO2 4.25 [RD23] 1.3E-16 [RD23]
CO 4.65 [RD23] 7.6E-17 [RD23]
CH4 3.3 [RD22] 1E-17 [RD22]
OH 3.28 [RD22] 3E-18 [RD22]
HCN 3.02 [RD24] 1.5E-19 [RD24]
C2H6 3.35 [RD24] 1.5E-18 [RD24]
CH3OH 5.52 [RD24] 1E-18 [RD24]
HDO 3.7 [RD25] < 1.5E-19 [RD25]
Table 1: Emission wavelengths and measured emission
line strengths of confirmed gaseous species in comet
comas. Some line strengths were calculated from flux
densities, some converted to an assumed 5 mag comet.
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cometary perihelion passage without the restrictions and the considerable effort (e.g. use of
adaptive optics (AO) systems) applicable to ground-based or airborne observations and cheaper
than with space-based instruments.
Small bodies compositions. Another diagnostic tool to probe the formation of the solar system and
the applicability of the current formation models is the mineral/solid state composition of asteroids.
Findings about their composition help to trace their origin, their thermal origins, but can also
provide views into the interior of once-larger parent bodies [RD26]. In a first step, asteroids are
routinely grouped into spectral classes. Closer investigation of smaller and weaker features in the
spectrum of reflected sunlight however
also allow the detection of certain species
or classes thereof. Such detectable
species are water ice [RD28], frozen
methanol or photolytic products of
methanol [RD29], hydrated minerals
through the detection of OH [RD27], but
also mineral classes through e.g. the
detection of different iron ions (Fe2+,
Fe3+) [RD30],[RD32] (for band
positions, see table 2). Traces of water
and iron-rich minerals (which can also be
used as a potential indicator of dissolved
platinum group metals [RD31]) in main
belt or near-Earth asteroids are
additionally interesting to pre-filter
potential targets for asteroid mining.
Observations of these absorption features from the ground are partly possible, but severely
complicated by strong telluric absorption bands and night-sky emission lines. UV features (details
of the absorption edge below 400 nm [RD33], absorption features around 300 nm [RD34] and
200 nm [RD29]) are not accessible from the ground at all.
Science objectives:
Case 1: Study the potential local distribution of evaporation and condensation of solids from hot
gas by determining volatile abundances on different small solar system bodies.
Case 2: Test the solar system formation models by determining potential differences in volatile
abundances of Oort cloud and Kuiper belt comets.
Case 3: Determine the chemical paths to complex organic molecules by studying the distribution
of precursor molecules in Kuiper belt objects, Oort cloud objects, and asteroids.
Case 4: Determine the source of terrestrial water and other volatiles.
Case 5: Constrain the effect of space weathering on small body surfaces by studying the
reflectance slope at the boundary between NUV and visible.
Case 6: Study the surface composition of asteroids (particularly near-Earth asteroids) and comets.
Science needs:
Case 1: Measure molecular emission lines of volatiles (H2O, CO2, CO, CH4, OH, HCN, C2H6,
CH3OH, see table 1) in cometary comas around perihelion passage with a sensitivity of at least
4 Most prominent and unambiguous indicator [RD35].
Species Wavelength [µm] Band depth [%]
OH 2.8 [RD27] < 4 [RD27]
H2O 3.14 [RD28]
2.04 [RD29]
10 [RD28]
12 [RD29]
CH4 2.27 [RD29] 9 [RD29]
Fe ions 0.2 [RD30]
~1 [RD30]
~0.5 [RD30]
0.43 [RD32]
n.a.
n.a.
n.a.
3-4 [RD32]
Table 2: Measured absorption features of selected species
on asteroids.
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1E-18 W/m2. Spectral region: 2.7-5.6 µm. Type of observation: spectroscopy. Required spectral
resolution: R~20,000. Required angular resolution: > 3 arcseconds.
Case 2: Measure molecular emission lines of volatiles (H2O, CO2, CO, CH4, OH, HCN, C2H6,
CH3OH, see table 1) in cometary comas around perihelion passage with a sensitivity of at least
1E-18 W/m2. Spectral region: 2.7-5.6 µm. Type of observation: spectroscopy. Required spectral
resolution: R~20,000. Required angular resolution: > 3 arcseconds.
Case 3: Measure molecular emission lines of volatiles (H2O, CO2, CO, CH4, OH, HCN, C2H6,
CH3OH, see table 1) in cometary comas around perihelion passage with a sensitivity of at least
1E-18 W/m2. Spectral region: 2.7-5.6 µm. Type of observation: spectroscopy. Required spectral
resolution: R~20,000. Required angular resolution: > 3 arcseconds.
Case 4: Measure molecular emission lines of volatiles, including HDO (H2O, CO2, CO, CH4, OH,
HCN, C2H6, CH3OH, see table 1) in cometary comas around perihelion passage with a sensitivity
of at least 1E-19 W/m2. Spectral region: 2.7-5.6 µm. Type of observation: spectroscopy. Required
spectral resolution: R~40,000. Required angular resolution: > 3 arcseconds.
Case 5: Measure the UV-vis reflectance slope of asteroids in different parts of the solar system.
Spectral region: 0.2-0.4 µm. Type of observation: medium-resolution spectroscopy. Required
spectral resolution: > 1 nm, i.e. R~200 to 400. Required angular resolution: > 1 arcsecond.
Case 6: Measurand: absorption features in the reflectance spectrum. Spectral region: NUV to IR
(0.2 - 3.1 µm). Type of observation: spectroscopy. Required spectral resolution: down to 2 nm
preferable to detect features of metallic species as well, i.e. R~100 to 1500. Required sensitivity:
< 1%.
4 FIR SCIENCE NEEDS
4.1 OVERVIEW OF THE CURRENT SITUATION
The Far Infrared (FIR) spectral range is very important for astronomy. About half of the radiation
from evolving galaxies in the early Universe reaches us in the FIR and submillimeter wavelength
ranges [RD36], also cosmic dust has its maximum emission in this wavelength range. As the FIR
range is not accessible from the ground, the FIR astronomy community only slowly started to
develop (and is still developing) thanks to a series of space-based and airborne observatories. Most
of them, however, have been spacecraft with a limited lifetime or instruments with limited spectral
range or resolution. As such, after the end of the Herschel mission, the community is currently left
with one active FIR observatory, SOFIA, and sporadically flying balloon missions (such as
BLAST [RD39], STO [RD38], or PILOT [RD37]).
Astronomers, especially astrochemists are still waiting for new FIR telescopes. It is thus the time
to plan the next mission that will cover the gap in the FIR sky.
Next steps of FIR science will, as expressed e.g. by the European Far-Infrared Space Roadmap
[RD40], further investigate the origins of water on planets in our and distant solar systems, study
mechanisms and details of star and planet formation by investigating chemical evolution and
cooling processes throughout the universe, and further investigate the Interstellar Medium (ISM),
its interaction with stellar environments, and its energy cycle, by observations of dust and gas.
Taking these scientific steps forward will require telescopes with better angular resolution, more
observational capacity (in terms of spectral coverage and observation time), and higher sensitivity.
Balloon-borne telescopes are particularly well suited to address the first two needs, while offering
the possibility to regularly use the most up-to-date instrumentation.
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The following sections list a number of outstanding scientific areas in need of further observational
infrastructure for which balloon-borne observatories would offer particular advantages. As they
are collected from an infrastructure provider’s point of view, they are grouped by types of
observation required: surveys / mapping; (pointed) observations of extrasolar discrete sources;
(pointed) observations within our solar system.
4.2 FIR SCIENCE AREAS AND THEIR NEEDS
4.2.1 Surveys
100 µm continuum map of our galaxy after IRAS
While the 0.3 m-Infrared Astronomical Satellite (IRAS) surveyed the whole sky at 12 µm, 25 µm,
60 µm, and 100 µm, follow up missions like the Infrared Space Observatory (ISO), Spitzer, and
Herschel were observatories executing mostly dedicated and pointed observations. The same is
true for the Kuiper Airborne Observatory (KAO) and for SOFIA. The only complete continuum
sky survey at 100 µm existing today is therefore by IRAS at an angular resolution of 1.5
arcminutes. The Photodetector Array Camera & Spectrometer (PACS) FIR instrument on board
Herschel has at least mapped the central part of our galaxy and other galaxies. A dedicated far-
infrared camera for mapping out dedicated regions in our own galaxy as well as in other galaxies
at an angular resolution of 5 arcsec is an indispensable tool in the post-Herschel and post-SOFIA
era in order to be at least somewhat compatible with the arcsec and subarcsec angular resolution
of ALMA (sub-mm) and the upcoming JWST (mid-IR).
Spectral line maps of our galaxy
Even more important are dedicated spectral line surveys. Far-infrared fine structure spectral lines,
in particular the 157.7 µm (CII) line and the 63.18 µm (OI) lines are very important galactic
emission lines, which by themselves may radiate up to several percent of the entire galaxy’s energy
output. As such they serve as very important cooling lines not only for our galaxy but for many
galaxies, in particular the active ones. While these lines are important features of the energetics of
our own galaxy, very little is still known about their spatial distribution across our galaxy. Maps
of a representative number of large molecular clouds within the Galaxy do not exist. These lines,
due to their far-infrared wavelengths, do suffer only very little from foreground extinction making
them ideal tools for a galactic inventory of such cooling processes. Mapping out these and other
important far-infrared spectral lines (such as the 128 µm HD line) across a major fraction of our
own galaxy as well as of other galaxies with a high signal to noise ratio will boost our
understanding of the chemical evolution of our galaxy and of galactic evolution in general.
A balloon observatory can achieve about 1000 hours of observing time during a 6-weeks mission
with one instrument attached. Such a set-up is very much suited for executing large surveys.
4.2.2 Discrete Sources
Spectroscopy of light hydrides
Light hydrides (molecules with a single heavy element atom and one or more hydrogen atoms,
such as OH, NH, CH, or SH) were discovered thanks to their electronic transitions in the visible
range. However, due to the nature of molecular lines, they can be best seen in the infrared spectral
range. Light hydrides belong to the first molecules to form in atomic gas and are thus at the starting
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point of astrochemistry and the building blocks of larger molecules [RD44]. Their study allows
fundamental insight into the first building steps towards interstellar molecules. As their chemical
formation process only involves a few steps, the interpretation of their abundances is comparably
straightforward and they can provide key information about their environments, including on
dynamical processes (shocks, turbulence, large scale winds), cosmic ray ionization rate, and
presence of molecular hydrogen [RD44].
The observation of light hydrides thus promises to provide a valuable tool to understand planet
and star formation, and, through the measurement of isotopic ratios, also to understand the origin
of volatiles in our own solar system. ALMA and NOEMA are already enabling highly sensitive
and spatially highly resolved observations of light hydrides in distant galaxies, for which the
ground state transition lines are sufficiently redshifted to fall into the sub-mm / mm spectral
regions. For observations in the ISM in our own galaxy, or neighboring galaxies, however, the
lines have to be observed at (or close to) their original wavelengths in the FIR.
Affected species particularly include H2, CH2, CH+, OH, H2O, H3O+, HF, SH, HCl+ and their
isotopologues [RD44], which all have a multitude of emission and absorption lines in the FIR.
Picking out single most attractive lines for observation is difficult, as different lines often trace
different physical and chemical conditions. For known H2 lines, see e.g. [RD41], for CH2 lines
[RD42], for CH+ lines [RD43], for OH lines [RD45], for H3O+ lines [RD46], for HF lines [RD47],
for SH lines [RD48] ([RD49] for the detection with SOFIA/GREAT), for HCl+ lines [RD50]
([RD51] for the detection with Herschel/HIFI).
Science Needs:
High spectral resolution and high sensitivity observations at the wavelengths of light hydrides
ground states in many targets across the Galaxy.
Ice features in the FIR
For years, dust annoyed astronomers by covering their favourite stars. With the development of
infrared observatories, however, cold dust and ices became a hot topic. Among other things, their
study now allows important insights into the process of star and planet formation and the migration
of water through evolving planetary systems.
Both in dark clouds and protoplanetary disks, atoms and molecules freeze out onto the cold surface
of dust grains, forming icy mantles. In dark clouds, this process is accompanied by hydrogenation,
forming small molecules such as CO, CO2, H2O, H2CO, CH3OH, CH4, HCOOH, OCN- and other
hydrogenated species [RD52]. Within protoplanetary disks, particularly more complex molecules
formed during the protostellar phase freeze out onto grain mantles, where ice from the pre-stellar
phase may still be present, in cold regions of the disk.
So far, mainly features in the near- and mid-infrared have been used to detect and characterize
these molecular ices. As their FIR emission features are attributed to intermolecular vibration
modes, however, observing them makes it furthermore possible to determine the structure and
transitions between phases of the observed medium (e.g. amorphous vs. crystalline). In particular,
the FIR band positions and widths are, in addition to the abundance of the emitting species,
sensitive to the grain geometry and size distribution, the environment temperature and density
structure. Combined with modelling of protoplanetary disk emissions, the analysis of the FIR
features thus allows to infer the abundance and location of ices within the disk, making it, with
sufficient data, possible to constrain the location of the snow line [RD53].
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So far, only water ice features have been detected in the FIR in a few disks, while the band strengths
of other ices are thought to be not strong enough to have been detected. Giuliano et al. [RD54]
provide band locations and band strengths of several ices from laboratory measurements as
summarized in table 3, providing an indication of which observations offer the most information
(and which might be feasible in terms of sensitivity). In terms of feature width, McClure et al.
[RD53] find, e.g., the equivalent band width of the 63 µm water feature to be in between 1 and 4
µm for different disks.
Table 3: Molecular ice emission features in the FIR, from [RD54]
Species
(ice)
Wavelength of
feature [µm]
Ice structure
H2O 44.1 Crystalline
45.7 Amorphous
62.55 Crystalline
CO26 85.5 Amorphous
144.9 Amorphous
CH3OH 28.8 Crystalline
33.0 Amorphous
56.5 Crystalline
CH4O7 33
CO / CH4 No features in FIR
Science Needs:
Medium spectral resolution and high sensitivity observations at the wavelengths of ice features in
many targets across the Galaxy.
Other science fields
Several other topics that partly overlap with the ones discussed before but are important enough to
separately point them out would equally benefit from high-stratospheric observations in the far
infrared. They will not be discussed in detail in this document, but will still find consideration in
the following design study:
- Study of the 70 µm CO2 feature in protoplanetary disks at medium spectral resolution;
- Spectroscopy of water in the FIR in different regions;
- Observation of hyperfine transitions in dark clouds at high spectral resolution;
5 Presence / absence of feature may be an indication of cubic or hexagonal ice 6 Bands only narrow in the transition from amorphous to crystalline 7 Band shows frequency shift at state conversion
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4.2.3 Solar System
Science Description:
Observations in the submillimetre domain provide a unique window for the study of atomic and
molecular gas. The very high achievable spectral resolution allows not only to study molecular
abundances, but also to determine the shapes of absorption lines. In a solar system context, this
allows e.g. conclusions about vertical distributions of molecules in atmospheres of planets and
satellites or in comae.
Submillimetre and FIR observations are severely limited from the ground. Particularly in between
30 µm and 300 µm, atmospheric absorption makes observations from the ground practically
impossible. Conditions at SOFIA altitudes are better, but telluric absorption lines are still
considerably pressure broadened in the remaining atmosphere. At 30 to 40 km altitude, the line
width of telluric absorption lines is narrow enough to allow discrimination between the telluric
lines and Doppler shifted absorption features on solar system objects.
Recent flights of the Stratospheric Terahertz Observatory (STO) [RD38] and the Balloon-borne
Large Aperture Submillimetre Telescope (BLAST) [RD39],[RD55] have strikingly demonstrated
the feasibility of carrying out submillimetre / FIR observations on interstellar and galactic targets
from balloons. In the solar system, space based observations have been carried out with e.g.
Herschel, which, among others, lead to the detection of water vapour around the dwarf planet
(1) Ceres [RD56], the first detection of the D/H ratio in a Jupiter family comet [RD57], and the
first detection of the Enceladus water torus [RD58]. With the required cryogen supplies on
Herschel, Spitzer, and Akari having depleted, however, no space-based capabilities in this region
are currently available, while many questions regarding gas atmospheres on the planets, their
moons, and small bodies remain to be answered.
Science Objectives:
Measure the abundance and vertical distribution of gases (O2, H2O, HCl,…) and their
isotopologues in the atmospheres of solar system comets, planets, and their moons. Measure the
abundance, local distribution, and temporal variation (rotational, seasonal, orbital) of gases around
small bodies.
Science Needs:
Measurable: absorption bands at high spectral resolution with a sensitivity of at least 1 Jy. Spectral
region: submillimetre / FIR. Type of observation: spectroscopy. Observation of small bodies and
planetary moons at different points on their orbit and the orbit of their host planet.
Science Requirements:
Wavelength coverage Absorption bands at 750, 1100, 1250, 1650 GHz
Required sensitivity At least 1 Jy
Required spectral resolution TBD
Required spatial resolution Better than 1 arcmin
D2.1 - REQUIREMENTS BASELINE – COMMON
OPERATIONAL NEEDS
Version 1.0
31.05.2018
Status: Released
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Deliverable
H2020 INFRADEV-01-2017 project "European
Stratospheric Balloon Observatory Design Study"
Topic: INFRADEV-01-2017 Design Studies
Project Title: European Stratospheric Balloon Observatory Design Study –
ESBO DS
Proposal No: 777516 – ESBO DS
Duration: Mar 1, 2018 - Feb 28, 2021
WP WP 2 Del. No D2.1 Title Requirements Baseline – Common
Operational Needs Lead Beneficiary “MPG”
Nature “Report”
Short Description This document contains the top-level user requirements that
shall be fulfilled by the infrastructure.
Dissemination Level “Public”
Est. Del. Date 31/05/2018
Version 1.0
Date 31.05.2018
Status Released
Authors T. Müller, tmueller@mpe.mpg.de, MPG
P. Maier, pmaier@irs.uni-stuttgart.de, USTUTT
Approved by P. Maier, pmaier@irs.uni-stuttgart.de, USTUTT
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TABLE OF CONTENTS
LIST OF ABBREVIATIONS AND DEFINITIONS ................................................................. 3
REFERENCE DOCUMENTS ..................................................................................................... 3
1 INTRODUCTION .................................................................................................................... 4
2 SCOPE ...................................................................................................................................... 4
2.1 Scope of the Requirements Baseline ......................................................................... 4
2.2 Scope of this Document ............................................................................................ 5
2.3 Coverage of the Needs/Requirements Logic ............................................................. 5
3 APPLICABILITY OF OPERATIONAL REQUIREMENTS ............................................. 6
3.1 Scope of “Infrastructure” .......................................................................................... 6
3.2 Possible Perspective / Development Sequence ......................................................... 7
4 GENERAL OPERATIONS & INFRASTRUCTURE CONCEPT ..................................... 8
4.1 Constraints Imposed by Balloon Operations ............................................................. 8
4.2 Consequences for Observations ................................................................................ 9
4.2.1 Constraints ........................................................................................................... 9
4.2.2 Advantages ........................................................................................................... 9
5 COMMON OPERATIONAL NEEDS & REQUIREMENTS ........................................... 10
5.1 User Needs for Efficient Scientific Exploitation ..................................................... 10
5.1.1 General User Needs for operation...................................................................... 10
5.1.2 Needs for the operation of PI instruments (also in shared-time) ....................... 11
5.1.3 Needs for the operation of facility instruments .................................................. 11
5.1.4 Services and support for instrument developers ................................................ 12
5.1.5 Need for reliable operation and derived needs from the operator’s perspective 12
5.2 Operational User Requirements .............................................................................. 12
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LIST OF ABBREVIATIONS AND DEFINITIONS
Abbreviation Definition
AO Adaptive optics
BLAST Balloon-borne Large Aperture Submillimeter
Telescope
DLR German Aerospace Center
ESA European Space Agency
ESBO European Stratospheric Balloon Observatory
ESBO DS European Stratospheric Balloon Observatory
Design Study
FIR Far-Infrared
FWHM Full Width Half Maximum
GPS Global Positioning System
HK Housekeeping
PI Principal Investigator
TAC Time Allocation Committee
TBD To be determined
TC Telecommand
TM Telemetry
REFERENCE DOCUMENTS
[RD1] ESBO DS – European Stratospheric Balloon Observatory – Design Study,
Requirements Baseline – UV. 31 May 2018.
[RD2] ESBO DS – European Stratospheric Balloon Observatory – Design Study,
Requirements Baseline – NIR and FIR. 31 May 2018.
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1 INTRODUCTION
The Requirements Baseline contains the top-level user needs and requirements as defined
for the infrastructure to be developed, upon which all subsequent development within ESBO
DS will be based. It thereby summarizes and documents the work performed under WP2,
“Detailed Science Case Analysis”.
The foremost focus of ESBO DS lays on developing an infrastructure that provides easy
access to stratospheric observations to the broad scientific community. In practice, it shall
provide operations and accessibility comparable to current ground-based astronomical
facilities. The operational concept and the system layout thus need to focus on this primary
infrastructure goal, providing a system that is sufficiently flexible to accommodate the needs
of different researchers and research communities, and at the same time affordable enough
to allow regular operation.
This part of the Requirements Baseline summarizes these user needs in terms of
infrastructure operation and services.
2 SCOPE
2.1 SCOPE OF THE REQUIREMENTS BASELINE
The purpose of the Requirements Baseline is to document the needs and requirements of
scientific users with regard to the ESBO infrastructure, i.e. the first / second level of the
requirements hierarchy as also further described in chapter 3 of part 1 of this document.
Detailed technical requirements on the system level and below are foreseen to be
documented in further Technical Requirements Specification documents.
User needs and requirements have been defined with regard to four aspects of the ESBO
DS project, and mirroring the four tasks within WP2:
o User needs and requirements for UV science, i.e. already relevant for the prototype
development within ESBO DS;
o User needs and requirements for near infrared (NIR) science, including exoplanet
science, i.e. relevant for the mid-term platform of ESBO;
o User needs and requirements for far infrared (FIR) science, i.e. relevant for the long-
term platform of ESBO;
o User needs in terms of operation.
The structure of the Requirements Baseline follows these four categories of needs and
requirements. As there are significant differences in the degrees of detail to which needs and
requirements of these four categories are known at this time (e.g. for UV science, system
level technical requirements have been identified already), the requirements baseline is
implemented as a series of three documents:
o D2.1-1 Requirements Baseline – UV
Contains detailed scientific user requirements as well as system level technical
requirements already identified and relevant for the prototype development within
ESBO DS;
o D2.1-2 Requirements Baseline – NIR & FIR
Contains descriptions of the driving science and scientific needs as well as
requirements to the degree known at this point for the two mid- and long-term platforms
currently envisioned for ESBO;
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o D2.1-3 Requirements Baseline – Common Operational Needs
Contains user needs of the scientific community regarding the infrastructure’s
operational concept beyond the scientific needs of each science case and applicable to
all three scientific areas / envisioned flight platforms.
Particularly parts 2 and 3 of the Requirements Baseline are to large extents based on findings
of the ORISON H2020 project.
2.2 SCOPE OF THIS DOCUMENT
This document, the Requirements Baseline - Common Operational Needs – covers the user
needs of the scientific community regarding the infrastructure’s operational concept beyond
the direct requirements of each science case. Topics addressed in this document include,
inter alia, exchangeability of instruments, frequency of flights/observation opportunities
from the perspective of continuity, real-time access to observation data and instrument
command, methods of observation time allocation, provision of observer tools, provision of
data processing tools, and provision of further support.
The needs and requirements as documented in this document will be passed on to WP3
(Infrastructure Analysis), WP5 (Conceptual Design), and WP6 (Observatory Operations and
Governance Concept) to be taken into account for the mid- and long-term development of
the infrastructure.
The needs and requirements compatible with the constraints of the prototype development
will also be passed down to the prototype requirements (mostly WPs 8, 10, and 11).
While it will need to be decided during the further course of the prototype definition and
development, which of the operational requirements from this document can already be
taken into account for the prototype, the association of the requirements to the likely
operational development phases as described in section 3.2 provides a first indication.
2.3 COVERAGE OF THE NEEDS/REQUIREMENTS LOGIC
As figure 1 illustrates, the content of this document focuses on needs and requirements from
the user perspective, namely the User Needs and the User Requirements. Detailed technical
requirements for the infrastructure will be derived and documented in the subsequent work
packages mentioned in section 2.2 as the way of fulfilling the operational user requirements
(and to some extent also the exact user requirements applicable in each development phase
of the project) will heavily depend upon the operations and governance concept eventually
applied.
For a general description of the high-level flowdown of needs and requirements within
ESBO DS and a description of the different elements, please refer to Part 1 of the
Requirements Baseline [RD1].
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Figure 1: Elements of the needs and requirements hierarchy covered in this part 3 of the Requirements
Baseline
3 APPLICABILITY OF OPERATIONAL REQUIREMENTS
3.1 SCOPE OF “INFRASTRUCTURE”
The term “infrastructure” in the context of ESBO and ESBO DS does not only refer to the
flight infrastructure / flight systems carrying telescopes and instruments. It rather refers to
the entire observatory infrastructure including everything required to operate ESBO as a
stratospheric balloon observatory and to provide the foreseen services. As figure 2
User Needs
User Requirements
Technical Requirements (System Level)
Lower Level Technical Requirements
0.5 m telescope
FS
1.5 m telescope
FS
5 m telescope
FS
Ground Systems
Pro
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sal T
oo
ls
Dat
a P
ipel
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ESBO Infrastructure
Governance Structure
Use
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ersp
ecti
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“Wh
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Infr
astr
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Dev
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“What
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Figure 2: Illustration of ESBO infrastructure elements
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illustrates, this includes the flight systems (dark blue), the ground systems (light blue),
proposal and other observer tools as well as data pipelines and processing tools (red) and the
governance structure / organisation (orange).
The operational needs and requirements covered within this document refer to this full
infrastructure.
3.2 POSSIBLE PERSPECTIVE / DEVELOPMENT SEQUENCE
As already described in more detail in part 1 of this requirements baseline, the ESBO concept
foresees different kinds of users with different degrees of involvement in the infrastructure,
namely scientific users / groups that provide an own instrument (“PI instrument”) and users
/ groups that use observation time on instruments provided by the observatory operators
(“Facility instruments”), or on PI instruments via open time access.
Which type of instruments (and users) will be used (or dominate) at a certain implementation
phase of ESBO will be highly dependent upon the eventual governance structure, the
financing, and the backers of each specific phase.
It appears likely, however, that the implementation of ESBO firstly will be dominated by PI-
instruments, before facility instruments are deployed on a larger scale. In order to also duly
take into account the prototype phase, which will have particular constraints on operations,
the following potential development phases are used to indicate which operational needs and
requirements will be relevant for which operational setup (these phases should not be
misunderstood as a hard plan for the sequential development of ESBO, but rather as a way
to associate the needs and requirements with different operational setups).
The envisioned general strategy, reflected in the phases, is to, during the early development
of ESBO, have the data calibration, processing, and related tools be taken care of by the
instrument teams. Centralized processing tools, calibration procedures, observation modes,
etc. may be defined and developed during the further process of including instruments into
the ESBO facility itself.
1. Prototype Phase (within ESBO DS)
- The Prototype Phase refers to the development and the first flights of the
prototype platform with one UV instrument (EKUT), which is being designed
and manufactured within ESBO DS and one supportive visible light instrument
(USTUTT)
- All responsibility for the instrument, for calibration plans, for commissioning
plans, science verification plans, etc. in this phase resides with the scientific PI
(i.e. EKUT for the UV instrument, USTUTT for the visible light instrument)
- All responsibility for data processing, calibration, archiving, etc. also resides with
the respective PI
- Responsibility for housekeeping & technical data (pointing, stability,
environment conditions, altitude, telemetry, other atmospheric data, timestamps
(reliability & accuracy), etc.) as well as general performance verification
measurements reside with the observatory operator (entire consortium)
2. PI-driven Phase
- The subsequent development and operation of ESBO after the prototype flight(s)
will likely be dominated by scientific groups with an interest to fly their own
instruments. While this does not necessarily exclude the option of providing
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observation time to other groups, operations in this phase would be driven by the
interests of the PI.
- Responsibility for data processing, calibration plans, instrument operations, etc.
in this scenario would be mostly the responsibility of the PI, with comparably
little involvement of the observatory operator.
3. Open Observatory Phase
- This phase describes the scenario in which ESBO operates own facility
instruments with open access to observation time, or PI instruments with a large
portion of observation time open to the community.
- In this case, likely a large part of the responsibility for data processing,
calibration, archiving, data delivery, but also for proposal selection and time
allocation will need to be taken care of by the observatory operator.
The requirements table in section 5.2 includes an indication for each requirement during
which phase it will likely be relevant.
4 GENERAL OPERATIONS & INFRASTRUCTURE CONCEPT
4.1 CONSTRAINTS IMPOSED BY BALLOON OPERATIONS
Launch locations and flight trajectories
Ground handling and launch of large balloons with payload masses of several hundred kg
and respective balloon sizes of several 100.000 m3 pose significant challenges to ground
infrastructure and launch conditions. On the technical side, this includes the necessity to
have large launching areas, provide sufficient amounts of helium, and ground handling
equipment for the balloon, flight service equipment, and the payload. On the side of
environmental conditions the constraints mostly include suitable wind conditions in order to
avoid damage to the balloon during ground/launch operations or during ascend due to sheer
winds.
Several launch providers are working towards making it possible to choose flexible launch
locations and part of the effort within ESBO DS is to study different options to ease the
operation of large balloon launches and to ensure regular and predictable flights. For flights
in the short- and mid-term, it needs to be assumed, however, that launch locations would be
used that offer existing ground facilities, comparably easy access, and cost-efficient
operation. In addition to the suitability of launch locations, stratospheric wind patterns and
overflight regulations constrain possible flight trajectories.
Depending on the desired flight duration, established launch locations with respective
trajectory options include e.g. Esrange in northern Sweden (offering 10-40 hour flights
above the base during “turnaround conditions”, or up to ca. 14 day flights on transatlantic
trajectories), or the McMurdo base in Antarctica (offering the opportunity of circumpolar
flights of typically 30 to 40 days duration). Experience at both locations (and all others)
shows that weather conditions may force the shift of launch dates by days or weeks.
Flight altitude and atmospheric conditions
While balloon flights aim at reaching specific altitude intervals during flight, the altitude
cannot be expected to be constant during a flight. The reasons for this can be
- That altitude changes are required for navigational purposes to reach different wind
layers (e.g. very relevant for flights during “turn-around” conditions over Esrange);
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- That altitude changes occur due to the heating and cooling of the lifting and
surrounding gas over day/night cycles. This oscillation can be minimized by
dropping ballast and venting lifting gas, however, a more stable altitude consequently
requires more ballast, which reduces the available payload mass, reachable altitude,
or possible flight duration.
These changes in altitude also cause changes in the surrounding atmospheric conditions in
terms of air density and of column density of telluric species.
4.2 CONSEQUENCES FOR OBSERVATIONS
4.2.1 Constraints
The abovementioned constraints of balloon flights consequentially lead to a difficulty to
precisely predict and pre-plan observation conditions. This concerns details in the visibility
of targets, which depends on the time of flight, and also the detailed quality of observation
conditions that depends on the flight altitude / the composition of the remaining atmosphere
along the line of sight.
These consequences need to be taken into account carefully when designing the operations
concept, as a well-planned operations concept can compensate parts of the difficulties caused
by the flight constraints.
4.2.2 Advantages
On the other hand, the unique operations conditions of balloons bring about a number of
advantages for the scientific operation:
- Regular access to instruments in between flights
Depending on the flight duration, instruments can be accessed after several days or
weeks of flight time and, at that occasion, can be refurbished, serviced, or updated.
- Return of data storage hardware
In contrast to space missions, the data storage hardware can be retrieved after each
flight, making it unnecessary to downlink all scientific data during flight. On the one
hand, the light and cheap availability of data storage makes it possible to generally
collect more data (the capabilities of space missions, including instrument size and
duty cycle, are frequently limited by their data downlink capacity). On the other
hand, it makes it unnecessary to put as much effort into on-board data compression
and on-board data processing as typically done for space missions. This means that
raw data can be saved and accessed without losing any potentially valuable
information, while at the same time the complexity of on-board data processing units
can decrease significantly.
- Design for reliability of hardware
Two aspects distinguish the requirements for hardware design of space missions to
those of balloon missions: the environmental conditions at balloon flight altitudes,
particularly in terms of radiation, are less challenging, and hardware does not have
to be designed for an uninterrupted service life of 5 to 15 years, as typical for space
missions.
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5 COMMON OPERATIONAL NEEDS & REQUIREMENTS
5.1 USER NEEDS FOR EFFICIENT SCIENTIFIC EXPLOITATION
As mentioned above, ESBO will cater different types of users. The definition of each “user”
type is given in 3.1 in the first part of D2.1 (Requirements Baseline – UV), distinguishing
between the general community desiring a certain observational capability, a group or
scientist with an own instrument, and a scientist who wants to use an existing astronomical
facility.
Each user group will have different dominance during each of the likely development phases
(“Prototype Phase”, “PI-driven phase”, “open observatory phase”) so that it makes sense to
examine the needs separately.
Instrumentation concept
As mentioned above, ESBO will, at least during the early development, rely on instruments
provided by scientific groups (“PI instruments”). This provides the advantage that one can
rely upon the expertise of research groups specialized in instrument development and that
the instruments at the same time will certainly cater the scientific needs of the developing
and or associated research groups. In addition, PI instruments create (as compared to “facility
instruments” owned and operated by the observatory institution) relatively little overhead on
the side of the observatory institution, as calibration, data processing, instrument servicing,
etc. would mostly be taken care of by the PI institution.
Facility instruments, on the other hand, allow an observatory institution to very freely
manage observation time and to provide a maximum of openly available observation time
to parts of the community that do not develop their own instruments. It is not decided at this
point whether ESBO shall aim at operating true facility instruments at some point or rather
aim at PI instruments with a shared time approach for the “open observatory” phase, within
which access to observation time, calibration tools, pipelines, etc. is also provided to external
observers.
5.1.1 General User Needs for operation
One important prerequisite for all scientific users of balloon telescopes is a basic summary
of the conditions during the observation phase. It is essential to know the environmental
temperatures, atmospheric conditions, water vapor, altitudes, flight geometries, sky
brightness, and also the expected timescales for changes in these parameters. This
information will need to allow an observer to judge which observations are possible and at
what quality. This includes the need to have tools to calculate the visibility of a given object,
to do exposure time calculations, and to have observing sequences and observation templates
available.
The second block of general needs is directly related to the operations: pre-scheduled
observations can be executed in an autonomous fashion (as baseline), but the possibilities
for data downlink and interventions have to be stated clearly. Many instruments will also
require intermediate data or control frames of the cameras or instruments to judge the
instrument performance and health of the instrument (e.g. the first frame of every
observation). It might also be required to change the observing plan or sequence, depending
on the outcome of the control frames or the auxiliary HK values.
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5.1.2 Needs for the operation of PI instruments (also in shared-time)
All the above needs for the general operations also apply for the operation of PI instruments.
In addition to information about the observation phase (nominal altitude phase), providers
of PI instruments also need to be informed in detail about conditions on ground, during
takeoff, ascending phase, descending phase, landing phase, and during the time until the
gondola is recovered. The description should include relevant aspects of the expected ground
weather, temperatures, winds, humidity, etc. during preparation and launching phase, as well
as for landing and recovery phases. For takeoff and landing it is important to know the
maximum accelerations and the potential risks for the gondola and the payload. For the
operation phase it is necessary to also know the environmental conditions in more detail than
for general observers.
In addition, the PI instrument operations requires detailed information about the telescope
operation and performance, about the telescope and subsystem HK and frequency, details
on the time referencing (central clock vs. instrument clock), GPS information, power
interfaces, the data storage procedure, including data format, exchange protocols, data rates,
amount of data, the necessary steps for accepting commands from ground, procedures for
downlinking information and so on. PI instruments are very useful for the early development
phases to test and consolidate operational aspects. When the instrument operations,
calibration and data handling is established, one should consider options to include part of
the astronomical community to broaden the scientific outcome. Part of the PI instrument
observing time can then be made available in an open time call, but always in close
collaboration with the PI instrument team. Here, it is important to document the instrument,
the observing modes, the performance characteristics, sensitivities, calibration, data
reduction schemes, data formats, and to have a selection of conducted observations available
in a database. At this stage, also data reduction software (including documentation) and
worked-out examples are important.
5.1.3 Needs for the operation of facility instruments
The needs for the operation of facility instruments include all the general needs and also the
above-mentioned aspects for PI instruments. It addition, the policy for observing time has to
be defined: regular (open) observing time, large programmes, instrument/observatory teams
guaranteed time, director’s discretionary time, observing time for targets of opportunity,
technical/calibration time. The procedures for nominal calls for observing time have to be
established: frequency of calls, total amount of observing time, ranking of proposals,
procedures for implementing observations, sorting by priorities and sky availability,
efficiency of the observatory, availability of instruments, restrictions from observing
conditions, etc. This “nominal” operation phase also requires proper storage of data (science
data, calibration data, supplementary data), availability of pipelines, interactive analysis and
calibration tools, means to do quality assessment for each observation, and proper
documentation of all steps involved.
The scheduling of observations is also different from the way it is done for ground-based
observatories: balloon flights have some uncertainties in the flight times, directions, and
durations. Therefore, there is a need to keep some flexibility in handling observations
(visibilities might become more important than priorities for a given programme). In order
to avoid time-consuming adjustment of observation requests due to changes in observation
ESBO DS Requirements Baseline – Common Operational Needs Version: 1.0
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conditions, observations should be defined in observation blocks which can be picked up by
an automatic scheduler.
5.1.4 Services and support for instrument developers
In order to facilitate the deployment of PI instruments, ESBO will need to provide support
to the developing scientific groups. This concerns technical topics related to the connection
of instruments to the gondola and telescope, including support systems, but also support for
the development of hardware to operate under stratospheric conditions.
ESBO will need to offer support systems for instruments, including the observatory control
computer, telemetry and telecommand (TM/TC), and data downlink through the service
system, but also thermal control to a certain degree. Besides providing these systems
themselves in a way in which they can support different instruments, the observatory
organisation will also need to provide support to the teams developing instruments on
interfacing with the gondola, telescope, and support systems. This may include the need to
provide adjustments to the support systems based on the particular needs of instruments.
Given the aspired long flight times and comparably low, but non-negligible launch and flight
costs, ESBO will need to operate with a high reliability. This holds true for the flight
platforms, but also for the instruments. As most groups that may provide instruments will
likely not have experience with building hardware for the high stratosphere, ESBO will need
to provide support on designing for reliability under flight conditions in the high
stratosphere. Providing good design guidelines will not only be important in order to ensure
reliability, but also to avoid significant increases in development effort due to over-
engineering, e.g. for space conditions. One way to provide these guidelines and to ensure
reliability may be to offer flight worthiness certification from the side of ESBO.
5.1.5 Need for reliable operation and derived needs from the operator’s perspective
In order to provide meaningful scientific output, it is imperative to assure reliable technical
functioning of the instruments, which implies that the gondola itself needs to function
reliably and provide the necessary conditions to the instruments.
This requires, besides correspondingly careful design, permanent access to critical
housekeeping (HK) parameters of the gondola, the telescope, the instrument(s) and the
control units. There should be also means to verify the pointing performance of the telescope,
the functioning of auxiliary systems or instruments (e.g., water vapor monitoring,
temperature sensors, radiation sensors, clocks, etc.), and to have the necessary access to GPS
information. It is also important to document the needs for activation, initialization,
calibration, switch-off, standby, and safe modes of the telescope, the instruments and the
relevant subsystems.
5.2 OPERATIONAL USER REQUIREMENTS
The following table lists the preliminary operational user requirements derived from the user
needs in terms of observation described above. This list is represents the first iteration to
serve as a basis of more detailed analysis particularly in WP 6, where they will be reviewed
and adjusted if necessary depending on the operations concepts studied. In particular, the
current list of requirements is not to be considered as complete. The requirements are
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Page 13 of 15
grouped into categories for better orientation, but follow one single numbering scheme (R-
OPS-SCI-XX, where XX is a running number). In addition, an indicator in the last column
shows for which of the likely development phases each requirement will likely be relevant.
The following nomenclature applies:
- 1 – Prototype phase
- 2 – PI instruments driven phase
- 3 – Open observatory phase
Flight Systems – Instruments Phase
R-
OPS-
SCI-
01
Exchange of instruments
The ESBO flight systems shall allow the exchange of instruments and/or
telescopes in between flights.
2 & 3
R-
OPS-
SCI-
02
Update of instruments
The design of the ESBO flight systems shall facilitate the
update/manipulation of instruments and/or telescopes in between flights
2 & 3
R-
OPS-
SCI-
03
Exchange of platform instruments
The ESBO flight system shall allow the exchange of add-on platform
instruments in between flights
all
R-
OPS-
SCI-
04
Community-developed instruments
The ESBO flight systems shall allow the installation of community
developed instruments (PI instruments) of both telescope and platform
instruments
all
Flight Systems – Operation
R-
OPS-
SCI-
05
Automated operation
The baseline operation of ESBO flight systems shall be automatic operation
of the scientific payload following scheduled observations / procedures.
All
R-
OPS-
SCI-
06
Manual interference
ESBO flight systems shall allow the manual control of the telescope and
instruments. Frequency/responsivity and degree of interference TBD.
All
R-
OPS-
SCI-
07
Access to data during observations
During baseline operation it is required to have access to the necessary HK
of the gondola, the telescope, the science instrument(s) and auxiliary
systems. In addition, it shall be possible to downlink snapshots of the
science data in regular intervals, e.g. the initial frame of each observing
block or a calibration image.
All
R-
OPS-
Regularity of flights 2 & 3
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SCI-
08
ESBO flights shall be organized at a regular and preferably long-term
(years) predictable basis to facilitate planning, development, and
deployment of instruments.
Observation Time Policy
R-
OPS-
SCI-
09
Time allocation policy
ESBO observation time allocation policy shall foresee different types of
observations requests/proposals and associated types of observation time,
among them at least:
a) During nominal PI instrument operation phase: part of the
observing time will be opened up to the general community, but
always in close contact with the PI team, the remaining time is
guaranteed for the PI team, in close collaboration with the
observatory lead, and fulfilling also the needs for technical and
calibration time.
b) During nominal facility instrument operations: there shall be
regular calls for observing time, including options for nominal
open-time observations and large programmes. There shall also be
options for director’s discretionary time and programmes with
targets of opportunity.
(2 &)
3
R-
OPS-
SCI-
10
Community access to observation time
ESBO flights shall generally provide at least TBD % of the observation time
as proposal-based open time to the community.
3
R-
OPS-
SCI-
11
Time allocation
Open time shall be allocated in a transparent manner by a time-allocation
committee (TAC)
3
Data Policy
R-
OPS-
SCI-
12
Data access (via data catalogue or science publications)
Reduced & calibrated data underlying scientific publications shall be
available from the PI upon request after a reasonable proprietary period.
Details TBD.
2 & 3
R-
OPS-
SCI-
12
Data access (all data)
The ESBO data policy shall, as a baseline, foresee public availability after
a maximum of 1 year after data delivery, at least for measurements taken in
validated observing modes (in a form suitable for scientific analysis).
2? &
3
R-
OPS-
SCI-
13
Data protection
The ESBO data policy shall foresee a proprietary period with exclusive
access by observation PIs after the data delivery, at least for measurements
taken in validated observing modes (in a form suitable for scientific
analysis). The baseline duration of this period shall be 1 year.
2 & 3
Provision of Tools and Services to Observers
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R-
OPS-
SCI-
14
Data pipelines
ESBO shall provide validated data pipelines for facility instruments / ensure
access to validated data pipelines for shared-time on PI instruments.
3
R-
OPS-
SCI-
15
Calibration services
ESBO shall provide calibration procedures and tools for facility instruments
/ ensure access to calibration procedures and tools for shared-time on PI
instruments.
3
R-
OPS-
SCI-
16
Data processing tools
ESBO shall provide validated data processing tools for facility instruments
/ ensure access to validated data processing tools for shared-time on PI
instruments, including TBD.
3
R-
OPS-
SCI-
17
Data archiving and provision
ESBO shall ensure structured data provision to the scientific community,
including an accessible, searchable data archive. This shall apply at least for
facility instruments and shared-time on PI instruments. (TBC)
3
R-
OPS-
SCI-
18
Other observer tools & services
ESBO shall provide access to visibility calculation tools, tools to prepare
observations, exposure time calculators, tools to calculate the influence of
varying parameters, like the water vapour content, on the instrument
sensitivity, etc.
2 & 3
R-
OPS-
SCI-
19
Documentation
ESBO shall provide detailed documentation on the platform, environmental
conditions, observation conditions, and the accessible instruments.
2 & 3
Provision of Services to Instrument PIs/Developers
R-
OPS-
SCI-
20
Instrument support systems
The ESBO flight and ground systems shall provide support systems for PI
instruments, including functions of observatory computer, commanding and
power switching of instruments and components, TM, TC, and data up- and
downlink capabilities, and 1st-level thermal control of the instrument.
2
R-
OPS-
SCI-
21
Interfaces to instrument support systems
ESBO shall provide clear options to interface with the instrument support
systems, suitable to support a range of instruments. In addition, ESBO shall
offer the option to adjust support systems to the needs of instruments within
a reasonable range.
2
R-
OPS-
SCI-
22
Design guidelines / flight worthiness certification for instruments
ESBO shall provide support to instrument teams to design their instruments
and hardware efficiently to operate with high reliability under flight
conditions.
2
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