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CNES concepts for microsatellites for CO 2 observations Clémence Pierangelo on behalf of Microcarb team: CNES: C. Deniel, F. Bermudo, V. Pascal, P. Moro,

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Presentation on theme: "CNES concepts for microsatellites for CO 2 observations Clémence Pierangelo on behalf of Microcarb team: CNES: C. Deniel, F. Bermudo, V. Pascal, P. Moro,"— Presentation transcript:

1 CNES concepts for microsatellites for CO 2 observations Clémence Pierangelo on behalf of Microcarb team: CNES: C. Deniel, F. Bermudo, V. Pascal, P. Moro, D. Pradines, S. Gaugain LSCE: F.-M. Bréon

2 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 2 Microcarb, a CO 2 mission onboard a microsatellite ■1- Science objective and context  Science objective  Mission and system high-level requirement  Context of CNES studies  The Myriade evolution satellite ■2- Instrument concepts and requirements  Instrument high-level requirements  Static Fourier transform concept and specific requirements  Dispersive concept and specific requirements

3 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 3 ■1- Science objective and context  Science objective  Mission and system high-level requirement  Context of CNES studies  The Myriade evolution satellite

4 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 4 ■Natural sources and sinks of CO 2 are badly quantified and localized at a global scale, especially over land. We do not know how they will evolve with a changing climate. ■In order to better quantify the CO 2 fluxes at the surface, very high quality CO 2 concentration measurements are necessary. Microcarb Science Objectives Ocean regions Land regions LSCE/CEA-NOVELTIS-CNES Weekly flux error reduction (ratio with OCO)

5 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 5 ■The mission requirements are given by the microcarb science group (PI: F-M Bréon, LSCE/CEA). ■They are driven by the need to better constrain natural CO 2 fluxes at the Earth surface through data assimilation (LMDz). ■=> Priority is given to precision on measurement (in ppm) rather than high spatial resolution or sampling. ■OCO-2 (launch~2013) instrument will bring extremely valuable information for the error reduction on carbon sources and sinks; Microcarb shall thus reach (as close as possible) OCO-2 performances for CO 2 (no regression). ■However, as operational CO 2 monitoring becomes a priority, a future CO 2 instrument might be small/cheap enough for constellations or long-term series with several flight models. ■Microcarb in a nutshell : “to reach (as close as possible) OCO-2 performances (accuracy, sampling) in a MicroSatellite system constraint” MicroCarb Science Objective

6 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 6 MicroCarb Phase A High Level Mission Requirements ■MicroCarb will measure vertically integrated CO 2 concentration  to quantify CO 2 surface fluxes at regional scales (carbon sources and sinks) through assimilation ■The CO2 concentration will be retrieved by measurements of the absorption of reflected sunlight by CO2 in near infrared. The payload shall consist in a passive instrument. ■Myriade Evolution platform with Myriade Flight Operation Center design shall be used. ■Mission design shall be based on technology with moderate development schedule and risks: a compact and low cost concept mission. ■Mission target launch date: 2017 with 3 years mission life time

7 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 7 MicroCarb System summary requirement SpecificationMICROCARB Tropospheric gases measuredCO 2 (CH 4 option) CO2 sensitivityTotal Column including near surface CO2 uncertainty (ppm)0.5 to 1.5 ppm Horizontal resolution (pixel size)9 km 2 to 120 km 2 InstrumentPassive instrument Grating spectrometer or Fourier Transform interferometer 3 spectral bands (0,76 µm; 1,6 µm; 2 µm) or 1 (2 µm) Observation ModeNadir, Glint, Target Orbit Altitude705 km (A-Train) Local time13h30 Revisit time/ orbits16 days / 233 orbits Launch date2017 Nominal lifetime3 years

8 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 8 ■2009: CNES phase 0 for a CO 2 passive mission onboard a microsatellite. ■June 2010: CNES decided to start a Phase A to explore the feasibility of Microcarb mission based on new assumptions:  Two new instrument concepts  An evolution of the Myriade platform ■October 2010: phase-A open competitive tender:  Selection of both Eads/Astrium and Thales Alenia Space. ■February 2011: kick-off of Industry studies. Context of CNES studies

9 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 9 MYRIADE Line of Products ■Initial CNES development then partnership between CNES and Prime Contractors Astrium and Thales Alenia Space. ■19 satellites ordered:  10 in flight, 5 ready for flight, 4 under development. ■Multi Mission: 5 scientific, 10 defense, 4 export. ■Demonstrated performances:  >90% availability, >3 years lifetime (6 years reached on 6 satellites). ■Generic system architecture with standard interface. ELISA x 4 20002002200420062008201020122014201620182020 TARANIS DEMETER PARASOL PICARD ESSAIM x 4 MICROCARB MERLIN MICROSCOPE

10 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 10 Myriade in the future ■ CNES decided in 2010 to start the “Myriade Evolution project” with the following main goals: In 2011, the Myriade Evolution Phase A, in close coordination with new mission requirements (MicroCarb, Merlin …) will define the improved flight and performance perimeter Current characteristics Future characteristics (TBC) 130 kg Satellite 200 kg Satellite 60 kg 60 W Payload 90 kg 90 W Payload to enhance performances (Mass, Power…) to address future missions (10 satellites in 2015-2025) to deal with some components obsolescence's (computer) to comply with French Space Law: debris mitigation regulation Mass (kg) Power (W) Mass and power of myriade payload

11 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 11 ■2- Instrument concepts and requirements  Instrument high-level requirements  Static Fourier transform concept and specific requirements  Dispersive concept and specific requirements

12 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 12 Instrument concepts and requirements ■2 concepts are specified by CNES and studied by the industry during phase A1:  A static fourier transform interferometer  A grating spectrometer ■For both concepts, the level 1 requirements are such that:  The goal gives the same level 2 performance as OCO  The threshold is such that the level 2 performance is relaxed by 35%. ■Spectral bands:  measurement in SWIR CO 2 and O 2 bands (aerosol, surface pressure) ■An imaging function at 0.55-0.7 µm  spatial resolution ~100 m  to discriminate clouds-free acquisition in the field of view of the sounding sensor. ■ For both concept, an option with only 2,06 µm CO 2 band will be also considered for the trade Off. Studies are in progress:  Impact on CO 2 measurement in presence of aerosol/thin cloud  Use of forecast and digital elevation map for surface pressure estimate

13 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 13 MicroCarb instrument summary requirement SpecificationStatic interferometerDispersive spectrometer CO2 accuracy (ppm) Goal: similar to OCO Threshold: +35% Spectral bands0.76 µm, 1.6 µm, 2.0 µm Optionally 2.0 µm only Spectral bandsB1=0.76 µm, B2=1.6 µm, B3=2.0 µm Optionally 2.0 µm only B1=0.76 µm, B2=1.6 µm, B3=2.0 µm Optionally 2.0 µm only Optionally B2’=1.66 µm (CH 4 ) BandwidthB1: 60 / 200 cm -1 B2: 40 / 115 cm -1 B3: 80 / 190 cm -1 B1: 50 to 150 cm -1 B2/B2’: 30 to 90 cm -1 B3: 30 to 90 cm -1 sampling392 interferogram samples, OPD given in requirement document Spectral resolving power: 25000 to 47000 Sampling ratio > 2.3 SNRGiven to reach CO 2 accuracyGiven to reach CO 2 accuracy (200 to 500) Polarisation ratioGoal: 0.1%, threshold: 0.25% Pseudo-noisesTaken into account (knowledge of OPD position, inter-pixel calibration, spectral band co-registration…) Taken into account (spectral and radiometric calibration, spectral band co-registration, keystone and smile effect…) FOV (nadir)75 to 120 km 2 9 km 2 to 120 km 2 Number of FOVAt least 2 (threshold) / 4 (goal) every 50 km Across track: 1 Across track: 1 to 5

14 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 14 Static Fourier Transform interferometer Matrix detector Stepped mirrors Filter beamsplitter Dynamic interferometer temporal aquisition (e.g. IASI) (image of stepped mirrors on detection matrix) Fixed mirror Moving mirror Detection I(x) beamsplitter Incident wave Static interferometer Spatial aquisition ■This concept as a spectrometer has been studied and breadboarded in phase A for CNES instrument SIFTI, and for Microcarb phase 0. ■For Microcarb phase A: optimization of the concept for CO2 measurement through irregular sampling and direct retrieval on the interferogram

15 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 15 Static interferometer concept ■The interest relies on  selection of interferogram optical path difference samples with respect to their geophysical content (optimal estimation)  no Nyquist sampling rules to respect (=>optical filters less critical to make) 1.29 ppm A posteriori error (linear estimate) Regular sampling Optimal sampling Number of samples

16 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 16 Static interferometer requirements ■Sample selection of Optical Path Differences (OPD):  emphasizes CO 2 sensitivity and has been performed through optimal estimation analyses.  + regular sampling of low OPD for low resolution spectrum (instrument transmission monitoring) ■14 « high steps » x 14 « low steps » = 392 samples (x2 through phase modulation) 14 Low steps Optical Path Difference (cm) 14 high steps OPD selection System SNRB1B2B3 SNR threshold171089305120 SNR goal2530132007560

17 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 17 Entrance slit => IFOV Pushbroom aquisition => FOV Dispersion Each column is a monochromatic image of the slit Width of the slit Length of the slit (swath) Satellite speed Nbin Spatial axis Spectral axis 2D spectrum Dispersive spectrometer principle

18 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 18 Dispersion Each column is a monochromatic image of the slit Width of the slit Length of the slit (swath) Satellite speed Nbin Spatial axis Spectral axis 2D spectrum FOV 1 FOV 2 FOV 3 Dispersive spectrometer principle

19 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 19 Dispersive spectrometer requirements ■SNR, spectral resolution and bandwidth  They are the instrument driving parameter for CO 2 retrieval accuracy  As very different combinations of these parameters might give similarly good level 2 performances, we want to give such a freedom to the industry => trade-off based on instrument considerations for an optimal configuration ■Parametric relation (« virtue factor »)  Calculated through linear error estimates for a clear scene (no aerosol)  Search for the optimal values for α, β and γ on a set of ~50 instrument configurations  k is fixed so that p=required performance in ppm  Min and max values of BW, SNR, R are specified, together with inter-band variations + possibility to include the number of FOV across track and along track Linear error estimate

20 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 20 Example of instrument design Patent Pending CNES : « High performances compact echelle grating spectrometer with double pass telescope » ■Echelle grating spectrometer  It has the advantage of spectral multiplexing (one grating for 3 (or 4) spectral bands)  Concept studied and breadboarded at CNES ■An instrument based on an echelle grating spectrometer + a QMA telescope fits on a Myriade Evolution micro-satellite Assumptions : scan mirror: swath +/- 45° - rolling only. 3 calibration views (lamp, sun, cold space) 435 mm 397 mm

21 Satellite Hyperspectral Sensor Workshop – March 29-31, 2011 21 ■ MicroCarb has a challenging approach: high quality measurement of CO 2 but with high constraints induced by MicroSatellite capabilities limitation. ■A compact design approach associated with Myriade Evolution product line will allow CNES to offer a cost reduced solution to fulfill mission purposes. ■This solution will open the possibility for CO 2 operational long-term monitoring: ■ from a constellation of micro-satellites ■ or as a small size passenger onboard operational platforms (meteorological satellites…) ■ please visit http://smsc.cnes.fr/microcarb/ Conclusion Thanks for your attention!


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