GAS@IGARSS2011.ppt

Demonstrator Test Results for the GEO Atmospheric Sounder (GAS) Jacob Christensen 1 , Anders Carlström 1 , Johan Embretsén 2 , Andreas Colliander 3,4 , and Peter de Maagt 4 1 RUAG Space AB, Göteborg, Sweden 2 Omnisys Instruments AB, Göteborg, Sweden 3 Jet Propulsion Laboratory, Pasadena, California, USA 4 European Space Agency, Noordwijk, The Netherlands IGARSS 2011 Vancouver 28 July 2011

Project Overview ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],The ESA GEO Atmospheric Sounder Technology Project

Background and objectives ,[object Object],[object Object],[object Object],380 GHz Four frequency bands of interest centred around: 53, 118, 183, 380 GHz Temperature (AMSU-A) Most important for NWP ! High altitude temperature High altitude humidity Humidity (AMSU-B) 166 346

Driving requirements ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Interferometer element layout ,[object Object],[object Object],[object Object],[object Object],u-v sampling after rotation instantaneous u-v sampling u v x y

Instrument electronics ,[object Object],[object Object],[object Object]

Mechanical design Deployment hinge Attachment structure Rotational drive Boom structure Radiator Mounting support 53 GHz 380 GHz 118 GHz 183 GHz

Instrument budgets Four frequency bands with polarimetric capability Power: 406 W Mass: 375 kg The concept is scalable !

[object Object],[object Object],53 GHz demonstrator Demonstrator characteristics Parameter Value Remark Frequency band 49-53 GHz Single 90 MHz channel Number of elements 21 Dual polarisation Longest baseline 75 cm ~140  Image Resolution <10 mrad ~300 km on earth Relative accuracy < 2K

Antenna design Coupling between neighbouring elements: < -67 dB

Front-end design LO input Antenna RF inputs (2 pol) IF outputs MMIC designed in collaboration with Chalmers

Demonstrator integration 21 front-ends with antennas Cross-correlator core (42 inputs) Assembled on rotational drive

Demonstrator test campaign ,[object Object],[object Object],[object Object],[object Object],[object Object],Sources Calibration sources: Hot & Cold Loads Imaging sources: Noise point source CW point sources Distributed source Distributed source Noise CW CW

Demonstrator test results ,[object Object],Gain stability over 2 hours: 0.03 dB RMS @ 51 GHz Phase stability over 2 hours: 0.2 deg RMS @ 51 GHz

Demonstrator test results ,[object Object],Demonstrator configuration 1 deg/s Polarization XX-pol YY-pol Measured pol. isolation is dominated by co-polar sidelobes ! PS1 PS2

Demonstrator test results ,[object Object],11:30 12:30 12:00

[object Object],Demonstrator Test Results The resulting image is free from ambiguities!

Demonstrator Test Results ,[object Object],Linearity: 1.1 K RMS Variation over image: 0.7 K Note that both linearity error and variation across image are systematic effects that can be calibrated!

[object Object],Demonstrator Test Results Noise error (Ne  T) : 0.8 K RMS at 30 minutes of integration The theoretical model assumes a Gaussian density distribution of the baselines ! Theory:

[object Object],[object Object],[object Object],Test Results Summary Image brightness temp. rel. accuracy:

Related activities ,[object Object],Parallel study: Ultra-stable structure for interferometric instrument Parallel study: MMIC for 118 and 183 GHz Results show that the design is viable 90 & 118 GHz 166 & 183 GHz NF = 3.1 dB NF = 6.0 dB Packaging Expected with 50 nm mHEMT (flight design): NF = 2.5 dB NF = 4.8 dB Receivers produced using 100 nm mHEMT:

Conclusion ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

GAS@IGARSS2011.ppt

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GAS@IGARSS2011.ppt