AMIPAS. Advanced Michelson Interferometer for Passive Atmosphere Sounding. Concepts and Technology for Future Atmospheric Chemistry Sensors

Transcription

1 Earth Observation, Navigation & Science Concepts and Technology for Future Atmospheric Chemistry Sensors AMIPAS Advanced Michelson Interferometer for Passive Atmosphere Sounding Markus Melf, Winfried Posselt, Ralf Maurer EADS Astrium GmbH, München, Germany Donny M. A. Aminou ESTEC, Kepplerlaan 1, 2200 AG Noordwijk ZH, The Netherlands Contact: EADS Astrium GmbH Markus Melf Tel:

2 Astrium Experience Astrium ED was instrument prime contractor lead the interferometer subsystem page 2 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

3 Study Context Requirements compared to MIPAS observational spectral radiometric Architecture Configuration New Technologies page 3 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

4 Study context After the ACHECHEM study the Earth Sciences Advisory Committee recommended to continue scientific studies on candidate Earth Explorer Atmospheric Chemistry missions. Chemistry missions may become relevant during the next years in the frame of the ESA's Earth watch programme. Need for IR limb sounder in the MWIR identified built on the heritage of MIPAS for continuity limb-viewing IR cloud imager (LCI) instrument Astrium investigated Sept.02-Sept.03 on behalf of ESA a Phase A-study Concepts and Technology for Future Atmospheric Chemistry Sensors (AMIPAS) page 4 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

5 AMIPAS Study Advanced MIPAS (AMIPAS) Focus on investigation of concepts for new generation sensors, encompassing configuration, system, subsystems, assemblies. The reduction of the costs compared to the ACECHEM mission (Pre-Phase A Mission study including a submillimetre sounder Master and platform aspects) page 5 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

6 AMIPAS study Team: Astrium GmbH Astrium SAS Astrium Ldt. Contraves Space TNO Responsibilities Astrium GmbH Study management System engineering Optical design Structural and thermal design Electrical design digital electronics Performance analysis Development planning Astrium SAS FPA design FPA cooling (supported by Astrium Ltd) Electric design analog electronics Contraves Space AG Mechanism design TNO TPD Cloud imager page 6 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

7 AMIPAS requirements compared to MIPAS 10 NESR vs. Wavenumber NESR [nw/cm2srcm-1] Wavenumber [cm-1] Band A Band B Requirement AMIPAS Performance Expected value Instrument temperature 250 K Detector temperature 60 K Spectral range, Band A cm -1 Spectral range, Band AB cm -1 Spectral sampling 0.1 cm -1 Maximum optical path difference 50 mm NESR, Band A 9 nw cm -2 sr -1 cm * NESR, Band B 5.5 nw m -2 sr -1 cm * * apply to calibrated radiances, including photon noise EMIPAS Performance Expected value Instrument temperature 210 K Detector temperature 70 K Spectral range, Band A cm -1 Spectral range, Band AB cm -1 Spectral range, Band B cm -1 Spectral range, Band C cm -1 Spectral range, Band D cm -1 Spectral stability cm -1 Spectral resolution < cm -1 Spectral bin width cm -1 Maximum optical path difference 20 cm Mean dark NESR, Band A 50 nw cm -2 sr -1 cm -1 * Mean dark NESR, Band AB 40 nw cm -2 sr -1 cm -1 * Mean dark NESR, Band B 20 nw m -2 sr -1 cm -1 * Mean dark NESR, Band C 6 nw cm -2 sr -1 cm -1 * Mean dark NESR, Band D 4 nw cm -2 sr -1 cm -1 * Elevation scan range 5 to 150 km *NESR due to instrument only page 7 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

8 AMIPAS observational requirements R1.1 Lifetime 5 years R1.2.1 Vertical IFoV 2 km R1.2.2 Horizontal FoV <30 km R1.2.3* Vertical FoV homogeneity 10 % R1.2.5* Spatial aliasing vertical 15 % (5%) R1.2.7** Accessible vertical range 0 km 90 km R1.3.1 Vertical range 3-33 poles equ. R1.3.2 Vertical sampling step 2 km R1.3.3 Horizontal sampling step 100 km R1.3.4* Max. duration of each int. <3s page 8 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

9 Observational performance Homogeneity and crosstalk HORIZONTAL instrument response VERTICAL instrument response 1 1 pitch µm2 pitch µm2 normalised response 0.5 normalised response focal plane location instr. response b 80%ph 1750 cm-1 b 80%ph instr. response 1050 cm-1 instr. response 770 cm-1 PRNU= 0% focal plane location instr. response 770 cm-1 instr. response 1050 cm-1 instr. response 1750 cm-1 Instrument response model established The observational performance is achieved for all wavelengths with an aperture of 70 mm and a pixel pitch of 80 µm page 9 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

10 Observational performance Sampling & interferogram generation 15 s for one standard observation 4 interferograms will be co-added on board 0.75 s for slide turnaround Elevation Instantaneous FOV AMIPAS Flight Vector Nadir 0.75 s 0.75 s 32 km 16 * 2 km stroke forward backward time 3 s 3 s 3 s 3 s 0.75 s 0.75 s 15 sec page 10 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

11 Observational performance Pointing accuracy Pointing requirements at the limit assumed orbit of METOP 30km 30km AMIPAS FFoV 30 km * 30 km 25km 1km 27km 820 km altitude am descending node orbit distance of 3200 km to tangent point. 10km 3km LCI FFoV 27 km * 32 km 30km 1km 32km Parameter Required Performance Estimated Performance Azimuth Pointing Accuracy APE 188 arcsec 120 arcsec Pointing Knowledge AME 63 arcsec 20 arcsec Pointing Stability (3s) RPE 188 arcsec 20 arcsec Elevation Pointing Accuracy APE Pointing Knowledge AME Pointing Stability (3s) RPE 63 arcsec 16 arcsec 2 arcsec 60 arcsec 16 arcsec 2 arcsec 1000 m 250 m 33 m page 11 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

12 AMIPAS spectral requirements R1.4.1** Spectral coverage cm -1 band A cm µm band B cm µm R1.4.2 Spectral sampling 0.1 cm -1 R1.4.3* Spectral width 1.4* spectral sampling page 12 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

13 Spectral Performance Instrument Line Shape ILS imaging interferometer divergence in the interferometer: <9.4 mrad phase differences at off axis positions ILS modelling performed OPD max = ± 50 mm FWHM ILS (1750 cm -1 ) = cm -1 (0.121 cm -1 theo.) 770 cm ILS1 j ILS2 j ILS3 j ILS4 j ILS5 j ILS6 j 2 1 ILS7 j page 13 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03 σ 0 υ c + j cm cm -1

14 AMIPAS spectral and radiometric requirements R1.5.2 Radiometric sensitivity (NESR) 9.0 nw/cm2_sr cm -1 (band A: cm-1) 5.5 nw/cm2_sr cm -1 (band B: cm-1) R1.5.3 Absolute Radiometric Accuracy 1.5 % of radiance R * Radiometric gain 1% of radiance R * Radiometric linearity 0.5 % if radiance (after correction) cr2 cr1 calibrated radiance calibration points % +- 1 % +- real radiance rr1 rr2 AMIPAS: DC coupling allows for exact linearity correction page 14 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

15 NESR Performance single port Michelson interferometer consideration of AC and DC contributions of scene optics self emission front telescope relay optics detector housing self emission 4000 NESR Performance as Function of Scene Temperature simulated spectra and equivalent BB emission K 250 K 260 K 280 pole 2 pole 4 mid.latitude 6 mid.latitude 6 equator 10 equator 14 km NESR scene.temp, NESR re page 15 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

16 Radiometric Performance NESR Modelling Instrument self emission: warm optics: 250 K cold optics: 120 K instrument performance insensitive to the absolute warm optics temperature cold optics temperature chosen at plateau temperature stability < 1 K required, 0.5 K per orbit predicted NESR in band A Angle depending on inclination & LTDN Anti-sun un illuminated Satellite Instrument To earth NESR in band B page 16 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

17 AMIPAS Architecture page 17 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

18 Possible accommodation on the satellite MIPAS AMIPAS page 18 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

19 AMIPAS Setup page 19 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

20 Interferometer Principle interferometer with plan mirror and corner cubes for shear and tilt compensation relaxed requirements on:» corner cube accuracy» mechanisms bearing high requirements on:» optics stability» alignment Remark: Envisat MIPAS is a dual port Interferometer page 20 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

21 New Technologies MCT detectors with >14 µm cut-off wave length reduced dark noise performance required detector matrix 15 x 15 pixels, 80 µm pitch Cooler technology pulse tube coolers low exported vibrations under Astrium UK increase in cooling power page 21 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

22 Data rate Front-End Electronic Out I/F Two Outputs (Band A & B): 2 x 15 pixels a 14 bit at 15.6 khz results to 2 x 3.3 Mbps = 6.6 Mbps MIPAS: 5 channels à 16 bit at 77 khz = 6.2 Mps Frame Integration Output I/F Output of 2 Interferogram frames of 47 ksamples per 15 sec results to 2 x 0.87 Mbps = 1.8 Mbps Direct Storage (SSMM) and Downlink of Original Data Stored Data /Orbit: 1.8 Mbps x 6200 sec (103 min) = 10 Gbit per Orbit page 22 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03

23 Conclusion Outcome of the study compact and cost effective instrument design simple and robust design (e.g. mechanisms: flex pivots or springs, no lubrication, open loop control) drop of some functional n units, e.g. launch locks and azimuth scanner performance well within requirements well suited small satellites feasibility of integrated LCI in spectrometer with slightly reduced performance shown page 23 ASSFTS, October 2003 Bad Wildbad EADS Astrium 03