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Doc. No. A1-RAD-IF-03-v2-DRAFT

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RADMON Experiment Interface Document-Part B Date:17.03.2014

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Aalto-1

Aalto-1

RADMON Experiment Interface Document-Part B

Name Signature Date

Prepared by J. Peltonen 14.03.2014

17.03.2014

Checked by R. Vainio 15.03.2015

Approved by

DISTRIBUTION

Name Organisation

Aalto-1 Team

CHANGE LOG

Date Issue Rev. Pages Reason for change

29.10.2013 03 v1-Draft New document for CDR replacing all earlier EID-B versions

14.03.2014 (JP)

15.03.2014 (RV)

17.03.2014 (JP)

03

03

03

v2-Draft

v2-Draft

v2-Draft

1-27

Corrections related to RIDs before the CDR

Added operational modes

Clarifications to the communication section

Resolution/clarity of some images

Scientific part corrections. General document check

Added table of content. Changed some heading levels for

readability. Further clarifications to the text.


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Contents

1 Introduction .............................................................................................................................................. 3

1.1 Scope ................................................................................................................................................. 3

1.2 Applicable Documents ....................................................................................................................... 3

1.3 Reference Documents ....................................................................................................................... 3

1.4 Abbreviations and Acronyms............................................................................................................. 3

2 Mechanical Interface ................................................................................................................................ 4

2.1 Coordinate System and Mechanical Structure .................................................................................. 4

2.2 Mass Budget ...................................................................................................................................... 5

2.3 Center of Mass and Moments of Inertia ........................................................................................... 6

2.4 Mechanical Interface to the Spacecraft ............................................................................................ 6

3 Electrical Interface .................................................................................................................................... 9

3.1 General Description of RADMON Electronics .................................................................................... 9

3.2 Subunits Interfacing (RADMON Bus) ................................................................................................. 9

3.3 Aalto-1 Bus Interfacing .................................................................................................................... 11

3.4 Grounding ........................................................................................................................................ 12

3.5 Communication Interfaces .............................................................................................................. 12

3.5.1 Interfacing, Bits and Bytes ....................................................................................................... 13

3.6 Power Interface ............................................................................................................................... 14

3.6.1 Power Modes and Currents ..................................................................................................... 15

3.7 Electromagnetic Interface ............................................................................................................... 15

4 Software Interface, Data Transfers and Commands ............................................................................... 17

4.1 Data Protocols ................................................................................................................................. 17

4.2 RADMON Commanding ................................................................................................................... 17

4.3 Data and Housekeeping Read Rates ................................................................................................ 20

4.4 Data/Housekeeping Content ........................................................................................................... 20

4.5 Housekeeping Measurements ......................................................................................................... 20

5 RADMON Operational Modes ................................................................................................................. 22

6 Thermal Interface ................................................................................................................................... 23

6.1 Expected Dynamical Thermal Load over Experiment Operation Cycle ........................................... 23

6.2 Acceptable Operational and Stand-by Temperature Ranges .......................................................... 23

6.3 Expected Components for Cooling/Heating .................................................................................... 23

7 Ground Segment ..................................................................................................................................... 24

7.1 Ground support equipment ............................................................................................................ 24

7.2 Communication and Data Delivery .................................................................................................. 24

8 Scientific Experiment .............................................................................................................................. 25

8.1 Observed Data and Mission Objectives ........................................................................................... 25

8.2 Experiment Cycle Description.......................................................................................................... 25

8.3 Dynamic Power Budget ................................................................................................................... 27

8.4 Dynamic Data Budget ...................................................................................................................... 27

8.5 Attitude Control and Determination Requirements ....................................................................... 27

8.6 Positioning Requirements ............................................................................................................... 27


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1 Introduction

1.1 Scope

This document provides the Part B of the Experiment Interface Document for RADMON, the radiation

monitor for the Aalto-1 satellite. A new document version IF-03 was created for the Critical Design Review.

1.2 Applicable Documents

Ref. Document Name Document Reference Issue

A1 Experiment Interface Document (Part A) A1-SYS-EID-01 v7

1.3 Reference Documents

Ref. Document Name Document Reference Issue

R1 Mechanical Drawings for RADMON A1-RAD-DW-01 Draft

R2 Aalto-1 OBC –

Payload Communication Protocol Definitions

and Details

A1-OBH-DS-03-v3 10.7.2013

1.4 Abbreviations and Acronyms

EMC Electro Magnetic Cleanliness

HK House Keeping (measurements)

I2C Inter- IC bus

LVDS Low Voltage Differential Signaling

PCB Printed circuit board

PSU Power Supply Unit

RADMON Radiation Monitor for Aalto-1 satellite


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2 Mechanical Interface

2.1 Coordinate System and Mechanical Structure

The S/C coordinate system is defined in [A1] and depicted in Fig. 1. RADMON is placed so that its field-of-

view is through the –Z panel. The figure gives a sketch of the RADMON Unit and its main parts. A

summary of the mechanical structure is given below. For a more detailed description of the mechanical

design, see [R1].

RADMON has a mechanical structure consisting of five subunits (Figure 1):

• Detector Unit: quasi-cubical, 30×30×27.2 mm³ (TBC) with two extruding Board-to-Wire connectors

• Power Supply Unit (PSU) Board: one-sided CubeSat-kit-compliant PCB (90.17×95.89 mm²) with

PC104 bus connector (1×SAMTEC ESQ-126-39-G-D) and another stack-through-connector

SAMTEC ESQ-126-37-G-D to the Digital Electronics Board

• Digital Electronics Board: two-sided CubeSat-kit-compliant PCB (90.17×95.89 mm²) with a stack-

through-connector SAMTEC SSQ-126-22-G-D to the PSU Board and to the Analog Electronics

Board

• Analog Electronics Board: two-sided CubeSat-kit-compliant PCB (90.17×95.89 mm²) with a stack-

through-connector SAMTEC SSQ-126-22-G-D to the Digital Electronics Board

• Top Frame: Al structure providing support for the detector and the upper mechanical interface to the

spacecraft.

The main outer dimensions of RADMON are:

Figure 1. Radmon mechanical structure


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o width (X-direction) 90.17 mm

o height (Y-direction) 40.00 mm

o depth (Z-direction) 95.89 mm

The Detector Unit extrudes outside this envelope by 7 mm (TBC) towards the –Z-direction, providing it with

a view to space. The cross-section of the extruding part (in XY plane) is 30×30 mm² and positioned 1 mm

(TBC) below the upper plane of the unit in the Y direction and centered in the X direction.

The RADMON will be attached to the Aalto-1 short-stack with four 3 mm crews at the corners.

The detector of RADMON will be also attached from below with two 3 mm screws and spacers to the Al-

support on the PSU board. And from above with two 3mm screws to the support frame and with two 3 mm

(TBC) screws to the short stack support plate.

Note that the screw heads will be extruding the main envelope below and possibly from the detector top side

at the frame and short stack connection (TBC). In addition, the 52 pins of the Board-to-Board through

connector between the PSU Board and the Digital Board will extrude the bottom plane by ~1 mm (TBC).

Thus, Plasma Brake should not assume a completely flat lower surface of RADMON.

The boards will be stacked using the 52-pin stack-through connectors. In addition, they will be mated by

(M3) male-female stainless steel standoffs in the corners (see http://www.unicorpinc.

com/metric_3.2mm_maletofemale.htm ). If needed, a thin PTFE (teflon) insulator will be added between the

standoffs and the PCB boards (TBC).

The distances between the PCB boards are

• PSU Board -Digital Board 14.6 mm (bottom to bottom)

• Digital Board – Analog Board 12.1 mm (bottom to bottom)

• Analog Board – Upper Frame 13.3 mm (bottom to top)

The positions of the screw holes are determined by the CubeSat-kit PCB dimensions. The Top Frame has

screw holes with 3-mm thread at correct positions for the male end of the standoffs between the Analog

Electronics Board and the Digital Electronics Board.

2.2 Mass Budget

The mass breakdown of RADMON at subunit level is presented in Table 1. The mass of the PCBs is

estimated using the thickness 0.16 cm, the outer dimensions 9.017×9.589 cm² and FR-4 mass density of 1.85

g cm⁻³. This gives a base mass of 23.6/25.6 g for cards with/without the (2.1×3.2 cm²) cutout for the

Detector Unit. PC-104 style connectors are assumed to weigh 8 g / 52 pins. The Detector Unit mass is

estimated as follows: 135 g for the outer brass parts (assuming density 8.7 g cm⁻³), 5 g for the CsI crystal and

10 g for the rest (consisting mainly of plastic).

Currently the mass budget includes some reserve for addition of copper between the PCB boards and for

changing TBD plastic parts to ceramic. The first proto model PCB boards weighted ~150 g (measured

17.10.2013: PSU1 56g, Dig 44g, Ana 44g and Det 144g,). The weight will increase some for the next models

but the total weight will stay in the given limits.

A more detailed breakdown of RADMON mass is presented in [R1].


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Table 1. Mass breakdown for RADMON. All numbers TBC. Margin is 20% of the estimated

mass.

Subunit Mass (g) Margin (g) Mass with margin (g)

Detector Unit 150 30 180

PSU Board + Connectors 80 16 96

Digital Electronics Board + Connector 70 14 84

Analog Electronics Board + Connector 60 12 72

Top Frame 25 5 30

Standoffs, screws, spacers 30 6 24

Total 415 83 498

2.3 Center of Mass and Moments of Inertia

Will be determined by measurement (CM) and using the CAD model.

2.4 Mechanical Interface to the Spacecraft

The mechanical interface to the spacecraft and the outer dimensions of RADMON are compliant with [A1].

The mechanical interface between the RADMON stack and the spacecraft is achieved from above through

the screw holes with 3-mm thread through the corners of the Top Frame (see Fig. 2). Their positions are

determined according to the standard hole positions of a CubeSat-kit PCB, as required in [A1].

The orientation of the male-female connectors is such that RADMON has male interfaces towards the

Plasma Brake.


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Figure 2. RADMON Top Frame


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The protruding part of the Detector Unit has two M3 (TBC) screw holes in TBD positions facing the short-

stack support plate (see [A1]) on top of RADMON, to allow further support to the heavy detector unit. Using

these holes, the Detector Unit shall be fixed to the short stack support plate.

Figure 3. RADMON PSU Board viewed from above (top) and from the +X side

(bottom).


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3 Electrical Interface

3.1 General Description of RADMON Electronics

Electrically, RADMON consists of four subunits:

• Detector Unit

• Analog Electronics Board

• Digital Electronics Board

• PSU Board

An overview of the electrical interfaces between the four subunits and the S/C is depicted in Fig. 4. The

spacecraft PC-104 bus (sBus) shall be implemented as in [A1]. Inside RADMON, the sBus extends only to

the PSU Board. From there on, the power lines and inter-board communication are handled via the 52-pin

(TBC) RADMON bus. See [R2] for more information.

3.2 Subunits Interfacing (RADMON Bus)

The Aalto-1 Short Stack communication signals go from the RADMON Power board the Digital board via

the RADMON internal bus. RADMON internal bus connections are therefore summarized also here.

The Detector Unit is connected to the Analog Board via two harnesses, one for each detector. Signals carried

by the harnesses are bias (about –50 V) and ground. The Si detector has a guard ring, which has to be biased

as well. The harness for the Si detector needs three signal wires and the one for the photodiode needs two.

Figure 4. Overview of RADMON electrical interfaces. Spacecraft Bus is terminated at the

PSU Board. All signal and power lines between the RADMON Boards are via the RADMON

bus consisting of a 52-pin (TBC) stack-through connector. The Detector Unit is connected to

the Analog Board via two harnesses, one for each detector.


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Internally RADMON communicates through 52-pin bus. The internal bus pin layout and

signals are shown in Figure 5.

Figure 5. RADMON internal bus pin order

Remarks From-To Bus Signal Bus Signal From-To Remarks

Scintillator Ana-Dig SCINT_B11 1 2 SCINT_B10 Ana-Dig Scintillator






Semicond Ana-Dig SEMI_B11 13 14 SEMI_B10 Ana-Dig Semicond






GND 25 26 ANA_CS Dig-Bus Ana FF-Chip sel

CLK to Ana Dig-Ana ANA_CLOCK 27 28 HK_CLOCK Dig-Bus HK-Clock to all

GND 29 30 HK_DIN Bus-Dig

HK-DataIn to

FPGA

HK-Data Out Dig-Bus HK_DOUT 31 32 HK_CS1 Dig-Bus HK-Circuit CS

HK-Circuit CS Dig-Bus HK_CS2 33 34 HK_CS3 Dig-Bus HK-Circuit CS

LVDS

Communication

Dig-(PSU)-

Aalto LVDS_MISO_POS 35 36 LVDS_MISO_NEG

Dig-(PSU)-

Aalto

LVDS

Communication

LVDS

Communication

Aalto-(PSU)-

Dig LVDS_MOSI_POS 37 38 LVDS_MOSI_NEG

Aalto-(PSU)-

Dig

LVDS

Communication

I2C

Communication Aalto-PSU-Dig I2C_CLK_A 39 40 I”C_DATA_A

Bidirectional

Aalto-(PSU)-

I2C

Communication

NC 41 42 VREF Dig-Ana Ref 4.1 V

Power PSU-Dig +1.2V 43 44 +2.5V PSU-Dig Power

Power PSU-Dig +1.8V 45 46 -6V PSU-Ana Power

Power PSU-Dig/Ana +3.3V 47 48 +6V PSU-Ana Power

Bias on/off

Clock Dig-Ana BIAS_CLOCK 49 50 +12V PSU-Ana Power

GND 51 52 GND

HeaderRadmon Bus Signal Radmon Bus Signal


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3.3 Aalto-1 Bus Interfacing

The Aalto-1 short stack signals used by RADMON (and the corresponding RADMON/PSU signals) are

shown in Fig 6.

Figure 6. RADMON short stack bus signals and pins

Remarks In/Out PSU Signal PSU Signal In/Out Remarks

Radmon LVDS Master

out, slave in+ In

LVDS_MOSI_PO

S RAD_LVDS_MOSI+ 1 2 RAD_LVDS_MOSI-

LVDS_MOSI_NE

G In

Radmon

LVDS

Master out,

Radmon LVDS Master

in, slave out+ Out

LVDS_MISO_PO

S RAD_LVDS_MISO+ 3 4 RAD_LVDS_MISO-

LVDS_MISO_NE

G Out

Radmon

LVDS

Master in,

Ground connection GND GND_1-5 5 6 GND_1-6 GND

Ground

connection

NC Reserved Aalto 7 8 Reserved Aalto NC





Radmon +12V power

line +12V_ABUS +12V RAD 17 18 +5V RAD +5V_ABUS

Radmon

+5V power

line




Ground connection GND GND_1-25 25 26 Reserved Aalto NC





Ground

connection




Ground

connection

I2C data In/Out I2C_DATA_A I2C_PRI DATA 41 42 I2C_PRI DATA I2C_DATA_A In/Out I2C data

I2C clock In I2C_CLK_A I2C_PRI CLK 43 44 I2C_PRI CLK I2C_CLK_A In I2C clock





Communication

Power

Radmon Signal Aalto Radmon Signal

Short Stack Header 2: Outer Header


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3.4 Grounding

The RADMON detector unit enclosure or detector box is grounded directly to the spacecraft hull by

conductive screws. Sensor ground is connected to the signal ground near the amplifiers of the analog board

and further to the RADMON power/digital ground. A single common digital/power ground is used at the

digital card. The power ground origin is at the PSU board, near the power converters. At PSU, there is a

possibility to connect the chassis to the common RADMON ground at the PSU. Filtering is used at the

chassis connections to isolate the PCBs from noise sources of chassis. The details of this filter are TBD. A

reservation for a resistor in parallel with a capacitor has been made to the layout of PSU board in the

engineering model. Note that the Short Stack bus ground wires all connect at the RADMON interface. If

these grounds do not connect to common plane there is a loop possibility. At least two of these ground pins

should be in use at RADMON for connection reliability. The principle of RADMON grounding is shown in

Figure 7.

Figure 7. Principle of the electrical grounding of RADMON instrument (TBC).

3.5 Communication Interfaces

RADMON communicates with the S/C using

• Asynchronous Low Voltage Differential Signaling (LVDS) and

• Synchronous I2C-bus (Inter-IC) communication.

There is dedicated serial LVDS interface for RADMON, differential inputs terminated with 100 Ohm

resistor. The I2C bus is shared between other payloads and sensors. The pull-up resistors of I2C (2K2 Ohm)

and the serial resistors (47 Ohm) can be implemented or left out (TBC).

The physical interfaces are shown in Figure 8. .


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Figure 8. I2C and LVDS interfaces

3.5.1 Interfacing, Bits and Bytes

Both data interfaces use bytewise communication and data/command packets. Each communication

operation will be in the form of request and response. OBC will be acting as the master of communication

and every request will come from that end. After receiving the command, RADMON will form an

appropriate response. In the case of checksum error or faulty command, RADMON will respond with an

error reply asking for retry.

LVDS channel transmission is typical serial UART converted to LVDS. Transmission speed is 115 200 bit/s.

Actual transfer speeds will be lower than this because of the stop and start bits. Standard LVDS signals

(swing 350 mV around 1.25V) are acceptable.

I2C communication is very much the same as the LVDS communication though the transfer follows the I2C-

standard. Transmission link clock is 400 kHz and the actual transmission speed depends on the packet length

(~315 kbps at lowest). RADMON slave address is 0x15. The physical level of the I2C signals is 3.3 V.

The bit level signaling of the interfaces is shown in Figures 9a and 9b.

Figure 9a. LVDS data transmission. Note that the LSB comes first. Bytewise the

communication is big-endian, MS-byte first. The clock shown is only for elucidation

(asynchronous communication).


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Figure 9b. I2C data transmission. Note that MSB comes first in contrary to the LVDS

transmission.

The details of the packet formats are given in document [R2]. A shortened description of packets and

commanding is given also in Section 4.

3.6 Power Interface

RADMON uses S/C the +12V and +5V lines of the S/C power bus. The principle of the power connections

is shown in Fig. 10.

The power pins of Aalto-1 short stack were given in Figure 6.

Figure 10. Principle of the RADMON power connections, triggering the killswitch located at

the Aalto PSU cuts the RADMON +5V line. The RADMON +5V line then triggers an

internal switch of RADMON PSU cutting the +12V line. RADMON can tolerate any

switching order, however is preferred that the +12V input is ready when +5V is switched on.


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3.6.1 Powers and Inrush Currents

RADMON has two power modes: on and off. The power consumption of RADMON is given in

Table 2.

Table 2 Power consumption and inrush currents of RADMON (TBC)

NODE Off

On

(Measurement

and Calibration

modes similar)

Inrush currents when

switched on REMARKS

+12VRAD 0 0.03A

~1 A peak, duration

~100 us. Less than 0.5A

averaged over 2 ms.

94 uF tantalum+

small ceramic at

input.

1.5 Ohm resistor

in series and then

overload

protection circuits.

+5VRAD 0 0.22 A

~0.6 A, duration ~1 ms

FPGA logic is

unfinished and this

power inrush value is

preliminary. We don’t

expect significant

change

94 uF tantalum +

small ceramic

at input

1 Ohm resistor in

series and then

overload

protection circuits.

3.7 Electromagnetic Interface

RADMON shall comply with the EMC-requirements of Aalto as given in [TBD] document. RAD-

MON uses only low power and low voltage electronics so it is believed it will not generate consid-

erable EM-noise.

The foreseen sources of electromagnetic radiation in Radmon are summarized in Table 3.


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Table 3. EM noise sources of Radmon

Power supplies: ~500 kHz (+6.8V/60 mA peak)

~500 kHz (-6.8V/60 mA peak)

2.25 MHz fixed (digital voltages/0.8 A peak at start)

200 kHz fixed (+-6.8 V/50 mA peak)

FPGA and other logic:

Oscillator frequency 40 MHz

FPGA clock frequency 10 MHz

ADC conversion 10 MHZ

Communication I2C CLOCK 400 kHz

LVDS 111.5 kHz

The results of the following instrument EM tests will be made available:

• Emission measurements (radiation caused by RADMON)

o Conductive 150 kHz - 30 MHz

o Radiative 30 MHz - 1 GHz

• Behavior in RF radiation field (RADMON influenced by the field)

o Radiated RF field 80 MHz - 1 GHz

o Conductive RF field 0.15 - 80 MHz

The tests will be carried out at the EMC tests laboratory of Turku University of Applied Sciences.


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4 Software Interface, Data Transfers and Commands

4.1 Data Protocols

The commands used in the protocol are 4-257 bytes wide. This range comes from the length field being one

byte that determines the packet length excluding checksum portion. The commands are designated to each

payload from the range of different commands. 8-bit command identifier gives us a range of 256 commands,

some of which are same for all payloads. Command structure is presented Figure 9. Communication between

RADMON and the OBC happens with this protocol. In addition to RADMON, other payloads will use the

same scheme as well.

Figure 9. Payload command packet according to the protocol

4.2 RADMON Commanding

Overview of the RADMON commanding is presented in Table 3. More details of the communica-

tion are given in [R2].


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Table 4. RADMON commanding. Radmon will response sending the above specified data

package to OBS. The response ACK/ERR in the table refers to the content of the status field:

0x00= ACK, 0x01-0xFF error codes (TBD). On powering RADMON will automatically go to

the measurement mode.

Generic commands

Command name Function

Command pre-

requisite Hex value Response

Status Ask for house-

keeping data

Response possible

1 second from the

power switching

0x01 Housekeep-

ing data

On Turns payload

ON. Not used

by RADMON

Response possible

1 second from the

power switching

0x02 ACK/ERR

Off Command not

used. For

shutdown,

switch powers

OFF

0x03 ACK/ERR

Standby Same as ON.

Not used by

RADMON.

Response possible

1 second after the

power switching

0x04 ACK/ERR

Reset Resets payload

internal state

Further com-

mands possible 1

second from the

Reset command

0x05 ACK/ERR

RADMON specific commands 0x51 - 0x79

Command name Function Command pre-

requisite

Hex value Data accom-

panied

Response

Calibration The collection

of the science

data is inter-

rupted. Sci-

ence counters

are zeroed.

Then payload

collects a sam-

ple of 1 k raw

data, and sends

the data values

and associated

counters to

OBC.

0x51 Pulse/coun

ter data.

Typically

13 ~max

length data

packets


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Measurement Payload will

end calibration

mode and will

go back to

normal meas-

uring. Science

counters are

zeroed.

0x52 ACK/ERR

Sanity check Asks payload

for sanity

check

0x53 Sanity check

challenge

Correct

challenge

response

Read memory ad-

dress

Reads specific

memory slot.

Not used.

0x54

Memory

address

ACK/ERR

Read status regis-

ters

32 Byte status

registers are

read

0x55

Data portion

to be read

Data/ERR

Write status regis-

ters

32 Byte status

registers are

written

0x56

Data portion

to be written

ACK/ERR

Scientific data

Reads scien-

tific data.

Nominal inter-

val 15 seconds

(TBC).

0x57

Scientific

data, 64

Bytes

(Note the

increased

number of

bytes!)

Change configura-

tion points Sets new val-

ues for every

configuration

point for the

data analyzer

0x58 New values

(21 values

12bits each

total 42 bytes

with pad-

ding)

ACK/ERR

Readback configu-

ration points Reads the con-

figuration

point values

0x59 Config

values.

Data 42

Bytes


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4.3 Data and Housekeeping Read Rates

In the normal Measurement-mode the science data should be read in ~15 seconds intervals. The

simplest operation scenario is that Housekeeping data is read in similar intervals, at the same time.

The resulting raw data rate is (TBC)

106 bytes/15 seconds or 424 bytes/min.

The Calibration-mode will be used only in the start of the mission and as an exception.

4.4 Data/Housekeeping Content

The housekeeping monitoring of RADMON will be done from the ground. The task of the Aalto-1

OBC is just to store and transfer RADMON science and housekeeping data, and to label the data

with additional information. The minimum is that each data and HK packet to ground should in-

clude the date and time stamps of the packets received from RADMON. If available, the spacecraft

position, the orientation of the RADMON and the components of the local magnetic field should be

added to the scientific data.

• The scientific data, normal data giving the particle energy channels out, consists of series of

32-bit counter values. The Aalto-1 OBC should store and transmit these values to ground as

they are. Data stamping as above. 64 bytes.

• The calibration/raw data values are series of 12 bits ADC values, one event requiring 3

bytes. The Aalto-1 OBC should store and transmit these values to ground as they are. On

one calibration command RADMON will send out 13 data packets (TBC). (An alternative

possibility is that OBC requests each of the 13 packets separately). Date and time stamps are

needed.

• Housekeeping data will be 25 values (TBC) of 12bits, each value occupying two bytes and

padded with 4bits of zeroes. So the whole response will be 50 bytes long. The packet should

be send as-is to the ground station. Data stamping preferably as for the science data.

• Readback configuration data should be sent to ground similarly as the housekeeping data.

4.5 Housekeeping Measurements

Radmon will monitor most of its internal voltages, currents and temperatures and will keep record

of the data collection time by specific livetime counter. The tiny (pA range) detector leakage cur-

rents are not currently been measured (TBC). The HK data is summarized in Table 5. In addition to

these there will be logic status information (TBD). In all, Housekeeping will include 50 data bytes.


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Table 5 Housekeeping measurements HK0-20. Measurements HK21-24 are TBD.

Board- HK

Data

Measured Value/Signal Range or calibration Explanation

PSU -HK0 U_MEAS+12V /U11-IN0 3.0 V @ Vin = 12.0 V Voltage +12V


PSU -HK2 I_MEAS+12V /U11-IN2 1.0 V @ I = 20 mA Current +12V

PSU -HK3 I_MEAS+5V /U11-IN3 1.0 V @ I = 124 mA Current +5V


PSU -HK5 U_MEAS-6V /U11-IN5 3.0 V @ Vin = - 6.0 V Voltage -6V

PSU -HK6 TEMP_PSU /U11-IN6 1.574 V @ +25 C PSU board tem-

perature

PSU -HK7 I_MEAS+3.3V /U11-IN7 1.0V@I(R85)=124 mA Current +3.3V

DIGIT -HK8 MEAS 1.2 V /U3-IN0 Direct Voltage +1.2V




DIGIT -HK13 DIGI_TEMP /U3-IN4 1.574 V @ +25 C

DIGIT -HK14 GND /U3-IN5 Direct



DIGIT -HK17 Internal FPGA TBD Internal Temp of

FPGA

DIGI -HK18 Internal FPGA LiveCount Livetime Counter

ANA -HK19 BIAS_MEASUREMENT_2/

IN0

Scintillator bias

voltage

ANA -HK20 BIAS_MEASUREMENT_1/

IN1

Si detector bias

voltage


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5 RADMON Operational Modes

There are three modes:

• Off (powers off)

• Measurement- or the basic On-mode. After Reset command or power up RADMON enters

this mode. This is the standard mode of RADMON. All commands.

• Calibration-mode. RADMON enters this mode after receiving the Calibration command.

Can be ended with the Measurement or Reset commands. Normal scientific data collection

is prohibited and raw pulse data with science counters and parameters will be sent out. All

commands accepted but science data not valid.


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6 Thermal Interface

6.1 Expected Dynamical Thermal Load over Experiment Operation Cycle

The instrument dissipates TBD W (~1 W) while switched on. No specific thermal hardware for cooling the

device is foreseen.

RADMON has a small surface area directly visible to space. It consists mainly of aluminum. It is assumed

that practically the whole dissipated power is conducted/radiated to the spacecraft structures.

6.2 Acceptable Operational and Stand-by Temperature Ranges

RADMON has only two power modes (ON/OFF). Spacecraft temperature sensor reading shall be used to

determine whether the experiment can be switched on. The operational temperature range is from –30ºC to

+40ºC (TBC).

RADMON has internal sensors, which monitor the instrument temperature. OBC decides based on this

information whether it is safe continue the operation of the instrument.

6.3 Expected Components for Cooling/Heating

N/A.


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7 Ground Segment

7.1 Ground support equipment

RADMON will have dedicated electrical ground support equipment, which will be procured and tested

before the integration of the protoflight model. This consists of a laptop computer (TBC) with a

communication card that can emulate the interface to the spacecraft. In the development phase, both groups

have their own ground support equipment, which are standard laboratory equipment and ad-hoc

communication/data collection boards for analyzing the software and hardware performance.

RADMON will flight model will have also some mechanical ground support equipment: a custom briefcase

for transportation and some jigs to support the device in various tests.

Note that we do not intend to apply nitrogen purging to the protoflight model despite the fact that CsI(Tl) is

slightly hygroscopic. Instead, the RADMON briefcase shall contain some silica aerogel to absorb the

moisture.

After launch, RADMON data can be analyzed using standard data analysis software (matlab, IDL). Thus, no

dedicated ground support equipment at this phase is needed.

7.2 Communication and Data Delivery

TBD.


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8 Scientific Experiment

8.1 Observed Data and Mission Objectives

The main science objective is to provide mapping of the inner-belt proton (electron) spectra in the

energy range >10 MeV (>700 keV) as a function of geographic coordinates, especially in the SAA

region. The observations are performed in logarithmically spaced energy channels at 15-second

time resolution, corresponding to ~1° latitude resolution on a ~90-min polar orbit. The energy reso-

lution of the observations is ∆E/E ~ 40% (~70%).

In addition to trapped particles, as the mission is going to occur during the solar maximum activity,

the experiment will provide valuable data on outer-belt dynamics in response to geomagnetic activi-

ty driven by solar eruptions. Also solar energetic particle events are likely to occur during the mis-

sion, and the data – when combined with observations outside the magnetosphere (e.g., by another

Finnish instrument, SOHO/ERNE, that observes fluxes at Lagrangian point L1 of the Sun–Earth

system) – will provide new information on the penetration of SEPs into to the geomagnetic field.

The most important technology demonstration objective is to operate in space a novel readout elec-

tronics concept, where the amount of analog electronics is minimized and the identification of parti-

cle-generated pulses, determination of the energy losses in the detector elements and counting in the

spectral channels is all done digitally using a single FPGA. The analog electronics is minimized to a

pre-amplified detector signal, which is digitized at high rate to the input of the signal processor. To

our knowledge, this is the first time such a concept is flown in space.

The minimal goals for a successful RADMON mission are:

• Successful operation of the device and successful continuous observation of electron and

proton fluxes, while powered on for at least one month in orbit.

• Mapping of the trapped particle environment at the flight altitude at 3-by-3-degree latitude-

longitude-resolution.

• Successful observation of at least one solar energetic particle event occurring over the

mission (if applicable).

8.2 Experiment Cycle Description

RADMON experiment is continuously operated in a single observation mode, ideally during the whole

science mission. The radiation environment consists of the low cosmic-ray background, quasi-static intense

regions of trapped particles (Figure 10 and Figure 11) and occasional solar energetic particle events.

Due to power limitations, the spacecraft may have to switch RADMON off. However, during the science

phase, RADMON shall be switched on for at least 80 % (TBC) of the time. The best regions for observation

are those with high particle fluxes, i.e., close to and inside the South Atlantic Anomaly region, the outer

radiation belt region and the polar caps above the radiation belt latitudes, which are accessible to solar

energetic particles. The boundaries of the best observing regions can be translated to latitude and longitude

ranges as

λ>44º+10ºsin(φ–20º)

λ < –44º + 10º sin φ + 60º exp{–[(φ + 45º)/90º]⁶},

where λ and φ are the latitude and longitude, respectively, and the sign convention follows that of Figure 10

and Figure 11, i.e., positive values denote northern latitudes and eastern longitudes. The two boundaries are

marked in Figure 11 as black curves. The low-latitude band between these limits is a region, where we do not

expect strong flux enhancements to be observed.


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Figure 10 Trapped >10 MeV proton flux at 700 km altitude according to the AP-8 model, as

plotted from SPENVIS (spenvis.oma.be).

Figure 11 Trapped >700-keV electron flux at 700-km altitude according to the AE-8 model, as

plotted from SPENVIS (spenvis.oma.be). The thick black curves give the boundaries of the

low-latitude region, which is unlikely to exhibit high fluxes.


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Due to data download and, thus, the operation of the S-band transmitter, RADMON will have to be switched

off while Aalto-1 is visible to the ground station. As the ground station will be placed in Otaniemi (TBC), the

orbits that pass over Northern Europe will have a break in RADMON measurements. Geographic

distribution of fluxes, however, can be reconstructed from measurements outside this region, as it is

organized by the magnetic field.

8.3 Dynamic Power Budget

The power consumption of RADMON, while switched on, is TBD. Power consumption in the OFF-mode is

negligible (TBC).

8.4 Dynamic Data Budget

The average data rate of RADMON is 100 bit/s (TBC), and it is accumulated quasi-continuously in TBD

packet format, when the experiment is ON. In this budget, an 80% duty cycle is assumed.

8.5 Attitude Control and Determination Requirements

RADMON shall be pointed mainly within 10 degrees (TBC) to the east-west direction to ensure that the

trapped particle populations (pitch angles around 90 degrees) are visible to the instrument window. The

actual attitude and the orientation of the detector with respect to the local magnetic field need to be known

within 1 degree. The magnetic field direction has to be either measured locally (by the attitude control

system) or computed from a model using a known spacecraft position.

8.6 Positioning Requirements

The spacecraft position along the orbit needs to be known within 10 km, so that it does not introduce

inaccuracies in the construction of the maps of the radiation environment. This accuracy is also enough for

the determination of the local magnetic field from models.