eess (passive): impact of interference examined through agenda items 1.2 and 1.20 of itu-r wrc-07

1WMO Workshop, Geneva - March 20-21, 2006 J. PLA - CNES

EESS (PASSIVE): IMPACT OF INTERFERENCE EXAMINED THROUGH AGENDA ITEMS 1.2 AND 1.20

OF ITU-R WRC-07

EESS (PASSIVE): IMPACT OF INTERFERENCE EXAMINED THROUGH AGENDA ITEMS 1.2 AND 1.20

OF ITU-R WRC-07

Jean PLA

CNES, Toulouse, France


Introduction to the passive bands under examination for agendas 1.2 and 1.20

Description of the agenda items

Proposed methods, future work

Summary


Review of the passive bands under examination for agendas 1.2 and 1.20

• The Earth Exploration Satellite Service (EESS) (passive): name used by the International Telecommunications Union (ITU) for passive microwave remote sensing of the Earth, operates passive sensors that are designed to receive and to measure natural emissions produced by the Earth’s surface and its atmosphere. The frequency and strength of these natural emissions characterize the type and status of many important geophysical, which describe the status of the Earth/Atmosphere/Oceans System:

– Earth surface parameters such as soil moisture, sea surface temperature, ocean wind stress, ice extension and age, snow cover;

– Three-dimensional atmospheric parameters (low, medium, and upper atmosphere) such as temperature profiles, water vapour content.

• Microwave observations at frequencies below 100 GHz enable studies of the Earth’s surface and its atmosphere from space-borne instruments even in the presence of clouds, because clouds are almost transparent at these frequencies.

• « All-weather" observing capability in spaceborne observations : repetitive global coverage mandatory for meteorological, climatological, and environmental monitoring and surveying.


Review of the passive bands under examination for agendas 1.2 and 1.20

ATMOSPHERIC OPACITY IN FREQUENCY RANGE 1-275 GHz

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1 26 51 76 101 126 151 176 201 226 251

Frequency (GHz)

Ver

tica

l op

acit

y (d

B)

Minor constituents

OxygenWater vapour tropical

Water vapour sub-arctic


Objective of the passive bands: Sensitivity of brightness temperature to geophysical parameters over ocean surface

010 20 30 40

WIND SPEEDSALINITY

LIQUID CLOUDS

WATER VAPOUR

SEA SURFACETEMPERATURE

Frequency (GHz)TbPi

+

_


Objective of the passive bands: Sensitivity of brightness temperature to geophysical parameters over land surface

5 10 15 20 25 30 35 40Frequency (GHz)

Soil moisture

Vegetation biomassSurface roughness

Integrated water vapour

Cloud liquid water

Tb Pi


Characteristics of the passive bands: technical(1/2)

• Increase of the noise in passive bands: particular concern to highly sensitive passive service receivers that measure very low energy levels for purposes such as weather prediction and scientific research.

• Passive services usually have instrumentation that is significantly more sensitive than that used by other radiocommunication services.

• Operations of the radio astronomy service (RAS), Earth exploration-satellite service (EESS) (passive) and space research service (SRS) (passive): measurement of naturally-occurring radiations, of very low power levels. Contain essential information on the physical process under investigation.


Characteristics of the passive bands: technical(2/2)

• The relevant frequency bands are mainly determined by fixed physical properties (e.g. molecular resonance) that cannot be changed. Those properties support scientific activities including weather forecasting, as well as water and climate modelling. These frequency bands are, therefore, an important natural resource. Even low levels of interference received at the input of the passive sensors may have a degrading effect on passive service band usage.

• EESS (passive) monitors the Earth and its atmosphere worldwide. Corrupted measurements from one or more areas may affect the ability to make reliable weather forecasts for the entire world, which may have significant economic and public safety impact.


Characteristics of the passive bands: regulatory

Two kinds of passive bands

P= primary exclusive 5.340 « All emissions are prohibited in the following bands … »

The passive sensors are unable to discriminate between these natural radiations and man-made radiations. Article 5.340 of the RR enables the passive services to deploy and operate their systems

p = primary passive bands shared with other active services, in general terrestrial services (FS, MS), not space services (MSS, FSS)


Objective of the passive bands

1400-1427 MHz: salinity (ocean), soil moisture (ground)10.6-10.7 MHz: rain, snow, ice, sea state, ocean wind23.6-24 GHz: total content of water vapour 31.3-31.5 GHz: the lowest cumulated effects due to oxygen and water vapour in the vicinity of the 50 GHz band. Optimum window channel to see the Earth’s surface: reference for the other channels. 36-37 GHz: cloud liquid water, vegetation structure, surface roughness50.2-50.4 GHz: temperature profile


OXYGEN BANDS AT 50-60 GHz

• Two atmospheric gases , CO2 and O2, are playing a predominant role, because their concentration and pressure in the atmosphere are almost constant and known all around the globe.

• It is therefore possible to retrieve atmospheric temperature profiles from radiometric measurements at various frequencies in the appropriate absorption bands (typically around 15mm for CO2, and around 57GHz for O2).

• Vertical atmospheric sounding from space, the radiometer measures at various frequencies the total contribution of the atmosphere from the surface to the top.

• Each layer (characterized by its altitude) radiates energy proportionally to its local temperature and absorption ratio. Integration of the radiative transfer equation along the path from earth's surface to the satellite reflects this mechanism, and results in a weighting function which describes the relative contribution of each atmospheric layer, depending on its altitude.


Absorption spectrum along a vertical path around 60 GHz

55.22 GHz

50 55 60 65 70

Frequency (GHz)

200

100

0

PASSIVE SENSORS REQUIREMENTS IN O2 ABSORPTION SPECTRUM AROUND 60 GHz(U.S. standard atmosphère - Absorption model: Liebe 1993)

Tot

al o

xyg

en a

bso

rptio

n al

ong

a v

ert

ical

pa

th (

dB)

55.78 GHz

RESONANCE FREQUENCIES (GHz)

51.503452.021452.542453.066953.595754.130054.671255.221455.783856.264856.363456.968257.612558.323958.446659.164259.591060.306160.434861.150661.800262.411262.486362.998063.568564.127864.678965.224165.764866.302166.836867.369667.9009

52.6 GHz

50.2-50.4 GHz

Excl.

Excl.

Shared

59.3 GHz


Objective of the passive bands: ITU-R SA. Recommendations

SA. 1028 Performance criteria

SA.1029 Permissible interference criteria levels for frequency bands P and p

1400-1427P MHz: -174 dBW, 27 MHz, 99.9%

10.6-10.68p,10.68-10.7P MHz:-156,-166 dBW, 100 MHz, 99.9%

23.6-24P GHz: -166 dBW, 200 MHz, 99.99%

31.3-31.5P GHz: -166 dBW, 200 MHz, 99.99%

36-37p GHz: -166 dBW, 100 MHz, 99.9%

50.2-50.4P GHz: -166 dBW, 200 MHz, 99.99%


Objective of the passive bands: Data availability

Data availability is the percentage of area or time for which accurate data is available for a specified sensor measurement area or sensor measurement time.

For a 99.99% data availability, the measurement area is a square on the Earth of 2,000,000 km2, unless otherwise justified.

For a 99.9% data availability, the measurement area is a square on the Earth of 10,000,000 km2 unless otherwise justified.

For a 99% data availability the measurement time is 24 hours, unless otherwise justified.


Agenda item 1.2 of WRC-07

• to invite ITU-R to conduct sharing analyses between the EESS (passive) and the SRS (passive) on one hand and the fixed and mobile services on the other hand in the band 10.6-10.68 GHz to determine appropriate sharing criteria

• to invite ITU‑R to conduct sharing studies between the passive services and the fixed and mobile services in the band 36-37 GHz in order to define appropriate sharing criteria



• For the bands 10.6-10.68 GHz and 36-37 GHz, the corresponding radiometers are all conical scan (rotating).

Useful scan-angle

Usefulswath

IFOV

Conical scanaround

nadir direction

Incidence

Satellite subtrack

Geometry of conically scanned microwave radiometer

Pixel



• For both bands 10.6-10.68 GHz and 36-37 GHz, dynamic simulations are conducted for specific passive sensors (AMSR-E, AMSR, CMIS, MEGHA-TROPIQUES) and for typical deployments of terrestrial systems.

• Example of a dynamic simulation

-220 -210 -200 -190 -180 -170 -160 -15010

-3

10-2

10-1

100

101

102

Received power at the radiometer

Cor

resp

ondi

ng c

umul

ativ

e %



• The received power are compared to the thresholds contained in Recommendation SA.1029-2 according to a cumulative corresponding % of 0.1 for a limited area of 10000000 km2

• Proposed methodology in the Conference preparatory text: development of sharing criteria based on single entry emission limits to be included in a footnote of Article 5 of the Radio Regulations. Those limits are suggested to be non-retroactive for terrestrial active systems brought into use before WRC-07.



• to consider the results of studies, and proposal for regulatory measures, if appropriate, regarding the protection of the Earth exploration-satellite service (passive) from unwanted emissions of active services in accordance with Resolution 738 (WRC-03)



Bande attribuée au SETS (passive) Bande attribuée à un service actif Service actif

1 400-1 427 MHz 1 350-1 400 MHz Service fixe (SF), service mobile (SM) et service de

radiolocalisation (RL)

1 400-1 427 MHz 1 427-1 429 MHz SF, SM (sauf mobile aéronautique) et service de

recherche spatiale (Terre vers espace)

1 400-1 427 MHz 1 429-1 452 MHz SF et SM

23,6-24 GHz 22,55-23,55 GHz Service inter-satellites

31,3-31,5 GHz 30-31 GHz SFS (Terre vers espace)

50,2-50,4 GHz1 50,4-51,4 GHz1 SFS (Terre vers espace)1

50,2-50,4 GHz1 47,2-50,2 GHz (Régions 2 et 3)

49,44-50,2 GHz1 (Région 1)

SFS1

1 LES ÉTUDES RELATIVES À CETTE BANDE DOIVENT TENIR COMPTE DU NUMÉRO 5.340.1 DU RÈGLEMENT DES RADIOCOMMUNICATIONS.


Agenda item 1.20 of WRC-07: unwanted emission problem

• The boundary between the out-of-band and spurious domains occurs at frequencies that are indicated in Figure 1: in general, the boundary, on either side of the centre frequency of the emission, occurs at a separation of 250% of the necessary bandwidth, or at 2.5 BN.

FIGURE 1 Out-of-band and spurious domains

Unwanted emissions Unwanted emissions

Spurious domain Spurious domain Out-of-band domain

Out-of-band domain

Necessary bandwidth

Frequency of the emission

Boundary of the spurious domain Limits of the necessary bandwidth


SATELLITES FOR THE BAND 1400-1427 MHZ ESA, CNES are jointly developing an interferometric

radiometer at L band, named SMOS, for a launch planned in 2007. This mission aims at retrieving soil moisture and sea surface salinity.

• SMOS is based on an innovative concept as it images at each integration time a large scene (typically 1000 x 1000 km) with various incidence angles at ground level (ranging from 0 to 55°). SMOS uses interferometric techniques in order to improve spatial resolution: SMOS will use a fixed array of small antennas instead of large scanning antennas

NASA/JPL is currently developing two instruments for measuring Soil Moisture and Sea Salinity (the HYDROS and AQUARIUS). For the HYDROS project, the antenna is an offset fed parabolic


SATELLITES FOR THE BANDS 24, 31, 50 GHZ

IFOV: 1.1° 83° re.nadir

Cold calibration:83° re.nadir90° re.orbit plane

Field of view:Cross-track,+/- 50° re.nadir 50°50°

EESS orbit850 km alt.

Nadir direction

ORBITAL CONFIGURATION OF PUSH-BROOM PASSIVE SOUNDER

Sub-orbital track

Swath width2300 km


Agenda item 1.20 of WRC-07: representation of unwanted emission spectra

• Use of RR No. 1.153 the unwanted emission power in the passive band to be no greater than 0.5% of the total mean power of the emission (23 dB attenuation).

• Recommendation ITU-R SM.1541 provides a worst-case analysis in which the OOB emissions from the active service are overstated.

• Usage of more realistic methodologies– Modulation filtering: DVB-S standard (40 dB attenuation) or usage of

more traditional waveforms (20 dB attenuation) such as

– Post-modulation filtering in most cases: between 25 and 40 dB attenuation

• Total expected attenuation (depending on bandwidth of the active service) within the adjacent passive band: between 23 and 80 dB.

2sin

fT

fT


Agenda item 1.20 of WRC-07: dynamic simulations, methodologies

Like agenda item 1.2, dynamic simulations are conducted in a co-frequency mode.

How much is the interference threshold exceeded according to ITU-R Recommendations?

The bandwidth scaling factor compares the necessary bandwidth Bn of the active service to the EESS (passive) bandwidth Bp.

Attenuation provided by Recommendation ITU-R SM.1541 or other modulation/ post-modulation filtering (see before).


Method to solve the agenda item 1.20 of WRC-07

Proposed methodology in the Conference preparatory text: development of a single entry emission limit for each corresponding active service within the EESS (passive) band to be included in a footnote of Article 5 of the Radio Regulations. Those limits are suggested to be non-retroactive for active systems brought into use before WRC-07.


Agenda item 1.20 of WRC-07: future work

• Refinement of compatibility analysis to establish the list of the proposed limits (still two ITU-R meetings).

• One question is: examine the potential impact of interference to remote sensing. Two options.– Limits in the RR in accordance with the results of the

aggregate simulations: worldwide protection.– If those limits are higher than those expected or if another

method is retained which provides less protection, what are the consequences from a meteorological point of view: total loss of pixels, total corrupted data? Scientific rationale is needed in this area as a future work.

eess (passive): impact of interference examined through agenda items 1.2 and 1.20 of itu-r wrc-07

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