1. European Perspectives on Geostationary Microwave Sounding
Bizzarro Bizzarri
CNR Istituto di Scienze dell’Atmosfera e del Clima, Roma, Italy
Phone , Fax ,
Content
European undertaking in the geostationary orbit
Principle of MW precipitation & sounding from geostationary orbit
GOMAS (Geostationary Observatory for MW Atmospheric Sounding)
2nd GOES Users Conference, Boulder CO, USA, 1-3 October 2002

2. European undertaking in the geostationary orbit
Meteosat 1 was launched on 23 November 1977, first of a pre-operational series (Meteosat 1, 2 and 3).
Meteosat 4 was launched on 6 March 1989, first of an operational series (Meteosat 4, 5, 6 and 7) to be used until 2005.
All these are spinning satellites, equipped with a 3-channel VIS/IR imager.
MSG 1 was launched on 28 August 2002, first of a Meteosat Second Generation series (Meteosat 8, 9, 10 and 11) to be used until 2020.
These are still spinning satellites, equipped with a 12-channel VIS/IR imager (SEVIRI) and an Earth Radiation Budget radiometer (GERB).
Mission definition of post-MSG, or Meteosat Third Generation, has started, in view of a first launch in A 1st User Consultation Workshop was held on November 2001.

3. Temperature and humidity profile
PARAMETER
OBSERVABLE FROM
GEO
OBSERVABLE
  FROM LEO
Temperature and humidity profile
IR emission from different atmospheric layers by spectroscopy.
Emission from different layers by MW/Sub-mm radiometry.
IR/MW emission from different atmospheric layers by spectroscopy.
 Occultation of signals from GPS received by a LEO satellite.
Wind
profile
Motion of water vapour patches by IR imaging spectrometers with frequent observing cycle.
Tracers motion (clouds, water vapour and ozone patches)
Tracers motion (clouds, water vapour and ozone patches) measured by
Backscattered light from aerosol eddies or
Derived by 4-D assimilation of frequent temperature / humidity profiles.
measured by VIS/IR image sequences..
overlapping VIS/IR images at high latitudes.
molecules by Doppler lidar.
Cloud pattern,
type, and evolution; water vapour growth
Frequent measurement of scattered and emitted radiation in several VIS/IR channels covering atmospheric windows and water vapour absorption bands.
Scattered and emitted radiation in several VIS/IR channels covering atmospheric windows and water vapour absorption bands.
Precipitation rate
Derived by 4-D assimilation of frequent temperature /
Correlation with cloud top ice as observed by VIS/IR
MW/Sub-mm radiation in absorption bands
Correlation with lightning intensity and
MW backscattering from raindrops by radar - Profile provided.
humidity profiles.
radiometry.
- Gross profile possible.
flashes/time in a given area.
MW radiation in atmospheric windows.
INSTRUMENT
IR sounding spectrometer.
VIS/IR imaging radiometer.
MW/Sub-mm radiometer.
Lightning mapper.
LEO technique also applicable to GEO.
LEO instruments not applicable to GEO.
FEASIBILITY
Demonstration mission being developed in US.
Current practise. Improvements feasible.
To be demonstrated.
Demonstrated in LEO.
Current or demonstrated.
Demonstrated or planned.
COLOUR CODE
Marginal compliance
Poor compliance
Fair compliance
Good compliance
Excellent compliance

4. (WMO representative of current or near-future, EUM of > 2015)
WMO and EUMETSAT requirements for precipitation observation
(WMO representative of current or near-future, EUM of > 2015)
Requi-
G l o
b a l
N W P
Reg
Ional
N o
w c a s
t i n g
rement
Unit
W M O
E U M
Target
Threshold x km 50
100 5 10 3 1
r.m.s.
mm/h
0.1 t h 12
0.5 6
0.08
0.03
0.3
delay 4 2

5. The problem of measuring precipitation
The most long-standing practise makes use of VIS/IR image sequences from GEO:
The observing frequency is suitable (15 min with MSG)
The measurement is strongly indirect (VIS/IR only “sees” the cloud top)
The applicability is mostly addressing convective precipitation.
From LEO, MW images are used (from SSM/I, TRMM, in the near future GPM):
The measurement is direct for low frequencies (10 GHz), less for high frequencies (90 GHz)
The applicability is better for convective precipitation, but extends to all precipitation types
The frequency, with GPM, will be around 3 hours
Global scale will be served optimally, regional scale to a fair extent
For the mesoscale, fusion between LEO MW images and GEO VIS/IR images will be attempted.
The ideal would be to extend the MW imagery technique to the geostationary orbit, but:
The antenna diameter for a 10-km resolution is 15 m at 90 GHz, 35 m at 37 GHz, 70 m at 19 GHz
Polarisation diversity is not practical from the geostationary orbit (large and variable z-angle).
GEO requires using higher frequencies and exploiting a different physical principle.

6. The physical principle for measuring precipitation from GEO
MW observation from LEO makes use of “atmospheric windows”:
Most common frequencies: 6 GHz, 10 GHz, 19 GHz, 23 GHz, 37 GHz, 90 GHz, 150 GHz
Dual polarisation for roughness effects (over the sea) and scattering from ice (over land).
The proposed principle for GEO exploits absorption bands:
Profiles of temperature and humidity are measured by more bands at different frequencies
Profiles observed exploiting bands of different frequencies are differently sensitive to clouds
Absorption bands at very high frequencies enable using antennas of affordable size
It is not necessary to differentiate polarisations
In absorption bands the measurement is equally effective over sea and land.
The precipitation measurement passes through the sounding one, therefore:
Many more channels are needed, very narrow (< 1 ‰), with SNR > 100
In exchange, one simultaneously gets:
- the temperature vertical profile (also inside clouds)
- the humidity vertical profile (also inside clouds)
- the columnar content (or gross profile) of liquid water in the cloud
- the columnar content (or gross profile) of ice water in the cloud
- the precipitation.

7. Multi-channel image from an airborne radiometer (Gasiewski et al, 1994). Note:
In absorption bands (183 and 325 GHz) increasing cloud impact moving from the peak to the window (from 183  1 to 183  3 and 183  7; and from 325  1 to 325  3 and 325  9);
In windows (89, 150, 183  7, 220 e 325  9) increasing cloud impact with increasing frequency.

8. Precipitation images from a cold front on October 7, 1998: NEXRAD precipitation map smoothed to 15 km resolution (left image), and NOAA/AMSU precipitation map obtained using a neural net retrieval technique (right image) (Staelin and Chen, 2000).

9. NOAA-15 AMSU-B 183+/-7 GHz 15-km resolution imagery of small rain cells over the Eastern U.S on August 2, 2000 (from Staelin and Chen, 2000).

10. Comparison between the 118/54 GHz profile ratio from the NAST-M microwave radiometer being flown on the NASA ER-2 aircraft and simultaneous EDOP Doppler radar reflectivity observation. Hurricane Bonnie at 17 GMT on August 26, 1998 (Tsou et al, 2001). The ratio 118/54 is unit in the absence of precipitation or above the precipitation cell, and reduces in the presence of precipitation because of higher attenuation from drops and impact from ice scattering at the higher frequency. The agreement between the two vertical cross-sections is striking. Horizontal maps of this information from GEO at 15 min intervals, will resemble a proxy rain radar operating over continental field of view, particularly over oceans and mountainous terrain.

11. Atmospheric spectrum in the MW/Sub-mm range (Klein and Gasiewski, 2000).
Preferred bands - for O2 (temperature): 54 GHz, 118 GHz, 425 GHz; for H2O: 183 GHz, 380 GHz.

12. Incremental Weighting Functions (IWF) for the selected channels in the bands of oxygen (54, 118 and 425 GHz) and of water vapour (183 and 380 GHz). Note that the sensitivity of 380 and 425 GHz drastically drops in lower troposphere (Klein and Gasiewski, 2000).

13. Retrieval errors for bands 118, 183, 380 e 425 GHz, stand-alone or associated to an IR sounder of the IASI or AIRS class (“GAIRS”). Temperature on the left hand, humidity on the right. On the left hand, GAIRS is compared to GAIRS alone and to alone. For reference, the EOS/Aqua AIRS + AMSU/A + AMSU/B complex also is shown (Blackwell and Staelin, 1996).

14. Initiatives for MW/Sub-mm sounding from GEO
Early proposals:
Staelin D.H. and P.W. Rosenkranz, editors, 1978: "Applications Review Panel: High resolution passive microwave satellites". A report to NASA.
Chedin A., D. Pick and R. Rizzi, 1985: "Definition study and impact analysis of a microwave radiometer on a geostationary spacecraft". A report to ESA.
Fresh start:
Staelin D.H., J.P. Kerekes and F.J. Solman III, 1997: "Final Report of the Geosynchronous Microwave Sounder Working Group". A report to NOAA/NESDIS.
Staelin D.H., A.J. Gasiewski, J.P. Kerekes, M.W. Shields and F.J. Solman III, 1998: "Concept proposal for a Geostationary Microwave (GEM) Observatory". A proposal to NASA and NOAA.
Bizzarri B., 2000: "MW/Sub-mm sounding from geostationary orbit". A report to EUMETSAT.
Current projects:
GEM (Geostationary Microwave observatory).
GOMAS (Geostationary Observatory for Microwave Atmospheric Sounding).

15. Horizontal resolution Resolution v/s frequency and antenna diameter
Reference user requirements adopted for GOMAS
Geophysical
parameter
Horizontal resolution
Vertical resolution
Accuracy (r.m.s.)
Observing cycle
Delay of availability
Temperature profile
30 km
2.0 km
1.5 K
1 h
15 min
Humidity profile
20 km
20 %
Cloud liquid/ice water
5.0 km
50 %
5 min
Precipitation rate
10 km -
5 mm/h
Resolution v/s frequency and antenna diameter
Antenna Ø
54 GHz
118 GHz
183 GHz
380 GHz
425 GHz
1 m
242 km
112 km
73 km
35 km
31 km
2 m
121 km
56 km
36 km
18 km
16 km
3 m
81 km
37 km
24 km
12 km
10 km
4 m
60 km
28 km
8.8 km
7.8 km

16. GOMAS (Geostationary Observatory for MW Atmospheric Sounding)
European sector (1/12 of disk) scanned each 15 minutes.
The sector can be moved everywhere inside the visible Earth disk.
The satellite can be shifted to serve from USA to India.
Simultaneous retrieval of temperature/humidity profiles, cloud liquid/ice water and precipitation.

17. Radiometric performance assessment for 15 min observing cycle
NEDT compliance code
Compliant
Nearly compliant
Compliant on 2 x or 1 h
Candidate to be dropped 
(GHz) 
(MHz)
Product resolution
IFOV
s.s.p.
Required NET (K)
Expected
NET (K)
Peak of IWF
(s.s.p.)
NE T (K)
56.325 50
0.6
0.15
27 km
 0.300
300
0.45
10 km
56.215
0.5
23 km
 0.900
500
0.35
8.5 km
56.025
250
0.07
17 km
 1.650
700
2 x 2 pixels
0.29
7 km
55.520
180
0.4
0.08
13 km
 3.000
1000
(20 km)
24 km
0.3
0.24
6 km
54.950
6 x 6 pixels
0.06
 5.000
2000
0.17
5 km
54.400
220
(60 km)
81 km
8 km
 7.000
4 km
53.845
190 
4000
0.18
surface
53.290
360
3 km
 0.045 30
2.36
15 km
52.825
0.2
2 km
 0.400
200
0.91
51.760
400
0.1
0.05
1 km
 1.500
0.58
11 km
50.300
 4.000
900
12 km
0.43
9 km
 0.018 6
1.32
34 km
 9.000
 0.035 12
0.93
29 km 
0.36
 0.080 20
0.72
 0.030 10
3.40
 0.200
100
0.32
19 km
 0.070
2.41
28 km
 0.400
3 x 3 pixels
0.23
 0.150 60
1.39
 0.700
(30 km)
37 km
0.16
 0.300
1.08
18 km
 1.100
 0.600
0.76
 1.500
 1.000
0.54
 2.100
800
0.11
 1.500
600
0.44
 3.000
0.10
 4.000
0.34
 5.000
1 pixel
1.0
(10 km)
1.02

18. Space Calibration Tube 3” Thick Composite Reflector
Azimuth Motor
& Compensator
Elevation Motor
Nodding / Morphing
Subreflector
Thin Struts
Space Calibration Tube
Backup
Structure
3” Thick Composite Reflector
GHz Feeds
Receiver Package
The GOMAS instrument with its 3-m antenna

19. Space Calibration Tube S-Band Antenna for TT&C
The GOMAS
satellite
NORTH DIRECTION
Space Calibration Tube
NADIR
Solar Wing
3 -meter
Antenna
Star Sensors
S-band Antenna
for TT&C
Mass: 860 kg (“dry": 430 kg)
Electrical power: 500 W
Volume: 3.0 x 3.0 x 3.0 m3
Data rate: 128 kbps (S-band, compatible with MSG LRIT).
S-Band Antenna for TT&C
S-band antenna
for LRIT

20. List of Proponents of GOMAS (undertaking to implement the scientific programme)
P.I.: Bizzarro BIZZARRI, for the CNR Istituto Scienze dell'Atmosfera e del Clima, Roma, Italy
Team leader
Institute
Umberto AMATO
CNR Istituto Applicazioni della Matematica, Napoli, Italy
Paul MENZEL
NOAA/NESDIS Office of Research and Application, Madison Wis., USA
John BATES
NOAA/NESDIS, National Climatic Data Center, Asheville NC, USA
Jungang MIAO
Institute of Environmental Physics, University of Bremen, Germany
Wolfgang BENESCH
Deutscher Wetterdienst, Offenbach, Germany
Alberto MUGNAI
CNR Istituto Scienze dell'Atmosfera e del Clima, Roma, Italy
Stefan BÜHLER
Paolo PAGANO
Servizio Meteorologico dell'Aeronautica, Roma, Italy
Massimo CAPALDO
Jean PAILLEUX
Météo France, Toulouse, France
Marco CERVINO
CNR Istituto Science dell'Atmosfera e del Clima, Bologna, Italy
Juan PARDO
Instituto de Estructura de la Materia, Madrid, Spain
Vincenzo CUOMO
CNR Istituto Metodologie Avanzate di Analisi Ambientale, Potenza, Italy
Federico PORCU'
Department of Physics, University of Ferrara, Italy
Luigi De LEONIBUS
Catherine PRIGENT
Dep.nt de Radioastronomie Millimetrique, Observatoire de Paris, France
Michel DESBOIS
CNRS Laboratoire de Météorologie Dynamique, Palaiseau, France
Franco PRODI
Stefano DIETRICH
CNR Istituto Science dell'Atmosfera e del Clima, Roma, Italy
Rolando RIZZI
Department of Physics, University of Bologna, Italy
Frank EVANS
University of Colorado, Atmospheric & Oceanic Sciences, Boulder Co., USA
Guy ROCHARD
MétéoFrance, Centre de Météorologie Spatiale, Lannion, France
Laurence EYMARD
CNRS Centre études Environnement Terrestres et Planétaires, Vélizy, France
Hans Peter ROESLI
MétéoSuisse, Locarno-Monti, Switzerland
Albin GASIEWSKI
NOAA Environmental Technology Laboratory, Boulder Co., USA
Carmine SERIO
Dip.nto Ingegneria e Fisica Ambiente, University of Basilicata, Potenza, Italy
Nils GUSTAFSSON
Swedish Meteorological and Hydrological Institute, Norrköping, Sweden
William SMITH
NASA Langley Research Center, Hampton VA., USA
Georg HEYGSTER
Antonio SPERANZA
Hydrographic and Mareographic Service, Roma, Italy
Marian KLEIN
David STAELIN
MIT Research Laboratory of Electronics, Cambridge MA., USA
Klaus KÜNZI
Alfonso SUTERA
Department of Physics, University of Roma, Italy
Vincenzo LEVIZZANI
Jung-Jung TSOU
Gian Luigi LIBERTI
Chris VELDEN
Cooperative Institute for Meteorological Satellite Studies, Madison Wis.,USA
Ernesto LOPEZ-BAEZA
Dep.nt of Thermodynamics, Faculty of Physics, University of Valencia, Spain
Guido VISCONTI
Department of Physics, University of L'Aquila, Italy

21. Conclusions
Strong requirements exist for frequent precipitation observation.
From GEO, a new physical principle needs to be exploited.
GOMAS is proposed as a demonstration mission.
It would be a precursor for future operational applications.
From the technical standpoint, and building on the studies conducted in the U.S. on GEM, it is believed that no enabling technology is currently missing.
The GOMAS satellite could be developed in time for a launch before 2010, in phase with GPM and possible overlap with GIFTS.
It would provide simultaneous retrieval of:
- temperature profile (x  30 km)
- humidity profile (x  20 km)
- cloud liquid/ice water total column and gross profile (x  20 km)
- precipitation rate (x  10 km)
each 15 minutes ! over  1 / 12 of the disk covering sea and land !