Presentation on theme: "CNES concepts for microsatellites for CO2 observations"— Presentation transcript:
1 CNES concepts for microsatellites for CO2 observations Clémence Pierangelo on behalf of Microcarb team:CNES: C. Deniel, F. Bermudo, V. Pascal, P. Moro, D. Pradines, S. GaugainLSCE: F.-M. Bréon
2 Microcarb, a CO2 mission onboard a microsatellite 1- Science objective and contextScience objectiveMission and system high-level requirementContext of CNES studiesThe Myriade evolution satellite2- Instrument concepts and requirementsInstrument high-level requirementsStatic Fourier transform concept and specific requirementsDispersive concept and specific requirements
3 1- Science objective and context Mission and system high-level requirementContext of CNES studiesThe Myriade evolution satellite
4 Microcarb Science Objectives Natural sources and sinks of CO2 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 CO2 fluxes at the surface, very high quality CO2 concentration measurements are necessary.Weekly flux error reduction (ratio with OCO)Ocean regionsLand regionsLSCE/CEA-NOVELTIS-CNES
5 MicroCarb Science Objective 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 CO2 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 CO2 (no regression).However, as operational CO2 monitoring becomes a priority, a future CO2 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”
6 MicroCarb Phase A High Level Mission Requirements MicroCarb will measure vertically integrated CO2 concentrationto quantify CO2 surface fluxes at regional scales (carbon sources and sinks) through assimilationThe 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 MicroCarb System summary requirement SpecificationMICROCARBTropospheric gases measuredCO2 (CH4 option)CO2 sensitivityTotal Column including near surfaceCO2 uncertainty (ppm)0.5 to 1.5 ppmHorizontal resolution (pixel size)9 km2 to 120 km2InstrumentPassive instrumentGrating spectrometer or Fourier Transform interferometer3 spectral bands (0,76 µm; 1,6 µm; 2 µm) or 1 (2 µm)Observation ModeNadir, Glint, TargetOrbit Altitude705 km (A-Train)Local time13h30Revisit time/ orbits16 days / 233 orbitsLaunch date2017Nominal lifetime3 years
8 Context of CNES studies 2009: CNES phase 0 for a CO2 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 conceptsAn evolution of the Myriade platformOctober 2010: phase-A open competitive tender:Selection of both Eads/Astrium and Thales Alenia Space.February 2011: kick-off of Industry studies.
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 4TARANISDEMETERPARASOLPICARDESSAIM x 4MICROCARBMERLINMICROSCOPE
10 60 kg 60 W Payload 90 kg 90 W Payload Myriade in the futureCNES decided in 2010 to start the “Myriade Evolution project” with the following main goals:to enhance performances (Mass, Power…) to address future missions (10 satellites in )to deal with some componentsobsolescence's (computer)to comply with French Space Law:debris mitigation regulationMass and power of myriade payloadPower (W)In 2011, the Myriade Evolution Phase A, in close coordination with new mission requirements (MicroCarb, Merlin …) will define the improved flight and performance perimeterMass (kg)Current characteristics Future characteristics (TBC) 130 kg Satellite kg Satellite60 kg 60 W Payload kg 90 W Payload
11 2- Instrument concepts and requirements Instrument high-level requirementsStatic Fourier transform concept and specific requirementsDispersive concept and specific requirements
12 Instrument concepts and requirements 2 concepts are specified by CNES and studied by the industry during phase A1:A static fourier transform interferometerA grating spectrometerFor both concepts, the level 1 requirements are such that:The goal gives the same level 2 performance as OCOThe threshold is such that the level 2 performance is relaxed by 35%.Spectral bands:measurement in SWIR CO2 and O2 bands (aerosol, surface pressure)An imaging function at µmspatial resolution ~100 mto discriminate clouds-free acquisition in the field of view of the sounding sensor.For both concept, an option with only 2,06 µm CO2 band will be also considered for the trade Off. Studies are in progress:Impact on CO2 measurement in presence of aerosol/thin cloudUse of forecast and digital elevation map for surface pressure estimate
13 MicroCarb instrument summary requirement SpecificationStatic interferometerDispersive spectrometerCO2 accuracy (ppm)Goal: similar to OCOThreshold: +35%Spectral bands0.76 µm, 1.6 µm, 2.0 µmOptionally 2.0 µm onlyB1=0.76 µm, B2=1.6 µm, B3=2.0 µmOptionally B2’=1.66 µm (CH4)BandwidthB1: 60 / 200 cm-1B2: 40 / 115 cm-1B3: 80 / 190 cm-1B1: 50 to 150 cm-1B2/B2’: 30 to 90 cm-1B3: 30 to 90 cm-1sampling392 interferogram samples, OPD given in requirement documentSpectral resolving power: to 47000Sampling ratio > 2.3SNRGiven to reach CO2 accuracyGiven to reach CO2 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 km29 km2 to 120 km2Number of FOVAt least 2 (threshold) / 4 (goal) every 50 kmAcross track: Across track: 1 to 5
14 Static Fourier Transform interferometer Dynamic interferometertemporal aquisition (e.g. IASI)Static interferometerSpatial aquisitionFixed mirrorMoving mirrorDetectionI(x)beamsplitterStepped mirrorsIncident wavebeamsplitter(image of stepped mirrors on detection matrix)FilterMatrix detectorThis 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 Static interferometer concept The interest relies onselection 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 ppmA posteriori error (linear estimate)Regular samplingOptimal samplingNumber of samples
16 Static interferometer requirements Sample selection of Optical Path Differences (OPD):emphasizes CO2 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)OPD selection14 high stepsOptical Path Difference (cm)System SNRB1B2B3SNR threshold171089305120SNR goal253013200756014 Low steps
17 Dispersive spectrometer principle Width of the slitLength of the slit (swath)Satellite speedEach column is a monochromatic image of the slit2D spectrumDispersionNbinSpatial axisSpectral axisEntrance slit => IFOVPushbroom aquisition => FOV
18 Dispersive spectrometer principle Width of the slitLength of the slit (swath)Satellite speedEach column is a monochromatic image of the slit2D spectrumFOV 1NbinDispersionFOV 2NbinSpatial axisFOV 3NbinSpectral axis
19 Dispersive spectrometer requirements SNR, spectral resolution and bandwidthThey are the instrument driving parameter for CO2 retrieval accuracyAs 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 configurationParametric 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 configurationsk is fixed so that p=required performance in ppmMin and max values of BW, SNR, R are specified, together with inter-band variationsLinear error estimate+ possibility to include the number of FOV across track and along track
20 Example of instrument design Echelle grating spectrometerIt has the advantage of spectral multiplexing (one grating for 3 (or 4) spectral bands)Concept studied and breadboarded at CNESAn instrument based on an echelle grating spectrometer + a QMA telescope fits on a Myriade Evolution micro-satellite435 mm397 mmPatent Pending CNES :« High performances compact echelle grating spectrometer with double pass telescope »Assumptions :scan mirror: swath +/- 45° - rolling only.3 calibration views (lamp, sun, cold space)
21 Thanks for your attention! ConclusionMicroCarb has a challenging approach: high quality measurement of CO2 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 CO2 operational long-term monitoring:from a constellation of micro-satellitesor as a small size passenger onboard operational platforms (meteorological satellites…)please visitThanks for your attention!
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