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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, D. Pradines, S. Gaugain LSCE: F.-M. Bréon . Microcarb, a CO 2 mission onboard a microsatellite . 1- Science objective and context

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Cnes concepts for microsatellites for co 2 observations l.jpg

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. Gaugain

LSCE: F.-M. Bréon


Microcarb a co 2 mission onboard a microsatellite l.jpg
Microcarb, a CO2 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


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Microcarb science objectives l.jpg
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 regions

Land regions

LSCE/CEA-NOVELTIS-CNES


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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”


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MicroCarb Phase A High Level Mission Requirements

  • MicroCarb will measure vertically integrated CO2 concentration

    • to quantify CO2 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



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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 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.


Myriade line of products l.jpg

2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020

TARANIS

PARASOL

PICARD

ELISA x 4

DEMETER

MICROCARB

MERLIN

ESSAIM x 4

MICROSCOPE

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.


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Myriade in the future

  • 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 and power of myriade payload

Power (W)

In 2011, the Myriade Evolution Phase A, in close coordination with new mission requirements (MicroCarb, Merlin …) will define the improved flight and performance perimeter

Mass (kg)

Current characteristicsFuture characteristics (TBC)130 kg Satellite200 kg Satellite

60 kg 60 W Payload90 kg 90 W Payload


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  • 2- Instrument concepts and requirements project” with the following main goals:

    • Instrument high-level requirements

    • Static Fourier transform concept and specific requirements

    • Dispersive concept and specific requirements


Instrument concepts and requirements l.jpg
Instrument concepts and requirements project” with the following main goals:

  • 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 CO2 and O2 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 CO2 band will be also considered for the trade Off. Studies are in progress:

    • Impact on CO2 measurement in presence of aerosol/thin cloud

    • Use of forecast and digital elevation map for surface pressure estimate


Microcarb instrument summary requirement l.jpg
MicroCarb instrument summary requirement project” with the following main goals:


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Fixed mirror project” with the following main goals:

beamsplitter

Moving mirror

Detection

I(x)

Dynamic interferometer

temporal aquisition (e.g. IASI)

Static interferometer

Spatial aquisition

Static Fourier Transform interferometer

Stepped mirrors

  • 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

Incident wave

beamsplitter

(image of stepped mirrors on detection matrix)

Filter

Matrix detector


Static interferometer concept l.jpg

A posteriori error (linear estimate) project” with the following main goals:

Regular sampling

Optimal sampling

1.29 ppm

Number of samples

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)


Static interferometer requirements l.jpg
Static interferometer requirements project” with the following main goals:

  • 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 selection

14 high steps

Optical Path Difference (cm)

14 Low steps


Dispersive spectrometer principle l.jpg

Satellite speed project” with the following main goals:

Length of the slit (swath)

Width of the slit

Each column is a monochromatic image of the slit

2D spectrum

Dispersive spectrometer principle

Dispersion

Nbin

Spatial axis

Spectral axis

Entrance slit => IFOV

Pushbroom aquisition => FOV


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Satellite speed project” with the following main goals:

Length of the slit (swath)

Width of the slit

Dispersive spectrometer principle

Each column is a monochromatic image of the slit

2D spectrum

FOV 1

Nbin

Dispersion

FOV 2

Nbin

Spatial axis

FOV 3

Nbin

Spectral axis


Dispersive spectrometer requirements l.jpg
Dispersive spectrometer requirements project” with the following main goals:

  • SNR, spectral resolution and bandwidth

    • They are the instrument driving parameter for CO2 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

Linear error estimate

+ possibility to include the number of FOV across track and along track


Example of instrument design l.jpg
Example of instrument design project” with the following main goals:

  • 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

435 mm

397 mm

Patent 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)


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Conclusion project” with the following main goals:

  • MicroCarb 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-satellites

    • or as a small size passenger onboard operational platforms (meteorological satellites…)

  • please visit http://smsc.cnes.fr/microcarb/

Thanks for your attention!


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