The ExoMars Climate Sounder (EMCS) investigation is developed at the Jet Propulsion Laboratory (Principal Investigator J. T. Schofield) in collaboration with an international scientific team from France, the United Kingdom and the USA.



EMCS plans to map daily, global, pole-to-pole profiles of temperature, dust, water and CO2 ices, and water vapor from the proposed 2016 ExoMars Trace Gas Orbiter (EMTGO). These profiles are to be assimilated into Mars General Circulation Models (MGCMs) to generate global, interpolated fields of measured and derived parameters such as wind

Allen, M. A.

Barnes, J. R.

Bougher, S. W.

Bowles, N.

Calcutt, S. B.

Foote, M. C.

Forget, F.

Fouchet, T.

Haberle, R. M.

Irwin, P. G. J.

Jeganathan, M.

Kass, D. M.

Kleinböhl, A.

Lefèvre, F.

Lewis, S. R.

McCleese, D. J.

Millour, E.

Määttänen, A.

Read, P. L.

Schofield, J. T.

Spiga, A.

Talagrand, O.

English

International audienceThe ExoMars Climate Sounder (EMCS) investi- gation plans to map daily, global, pole-to-pole pro- files of temperature, dust, water and CO2 ices, and water vapor from the proposed 2016 ExoMars Trace Gas Orbiter (EMTGO). The measurements cover all local times, adding a new dimension to data pre- viously obtained from sun-synchronous spacecraft. These profiles are to be assimilated into Mars Gen- eral Circulation Models (MGCMs) to generate glob- al, interpolated fields of measured and derived pa- rameters such as wind

Mccleese, D. J.

Forget, François

Lefèvre, Franck

Määttänen, Anni

J. Irwin, P. G.

Barnes, Jeffrey R.

HAL-INSU

The Exomars Climate Sounder (EMCS) Investigation

The ExoMars Climate Sounder (EMCS) investigation is developed at the Jet Propulsion Laboratory (Principal Investigator J. T. Schofield) in collaboration with an international scientific team from France, the United Kingdom and the USA. EMCS plans to map daily, global, pole-to-pole profiles of temperature, dust, water and CO2 ices, and water vapor from the proposed 2016 ExoMars Trace Gas Orbiter (EMTGO). These profiles are to be assimilated into Mars General Circulation Models (MGCMs) to generate global, interpolated fields of measured and derived parameters such as wind. Sciences objectives of EMCS are to: Enhance understanding of Mars photochemistry by providing daily, global, high vertical resolution fields of atmospheric state, aerosol distribution, and water vapor concentration. EMCS atmospheric state measurements, combined with data assimilation, characterize the transport, sources and sinks of trace gases measured by the proposed EMTGO. The aerosol measurements reveal the heterogeneous photochemical pathways of trace gases. EMCS plans to map water vapor, the key source gas for odd hydrogen, known to be important in Martian photochemistry. Extend the MRO/MCS climatology of high vertical resolution measurements of the lower and middle atmosphere of Mars, with the improved coverage of local time provided by the proposed EMTGO. EMCS will determine the diurnal, seasonal &amp; long-term variability of temperature and aerosol, and its impact on photochemistry. EMCS climatology, combined with earlier data, would relate EMTGO observations to earlier trace gas measurements. Support future Mars missions with measured climatology and near real-time density profile retrievals for landing and aerocapture, in the same way that MRO/MCS supported the Phoenix landing and is supporting the Mars Science Laboratory (MSL) landing. EMCS could be the only instrument in orbit able to support Entry, Descent and Landing (EDL) for the proposed ExoMars 2018 Rover Mission

HAL-OBSPM

HAL-Polytechnique

Open Research Online (The Open University)

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsThe Exomars Climate Sounder (EMCS) InvestigationConference or Workshop ItemHow to cite:Forget, F.; Schofield, J. T.; Kass, D. M.; Kleinbo¨hl, A.; McCleese, D. J.; Allen, M. A.; Foote, M. C.; Jeganathan, M.;Millour, E.; Spiga, A.; Talagrand, O.; Bowles, N.; Calcutt, S. B.; Irwin, P. G. J.; Read, P. L.; Lewis, S. R.; Fouchet,T.; Lefe`vre, F.; Ma¨a¨tta¨nen, A.; Barnes, J. R.; Bougher, S. W. and Haberle, R. M. (2011). The Exomars ClimateSounder (EMCS) Investigation. In: EPSC-DPS Joint Meeting 2011, 2-7 Oct 2011, Nantes.For guidance on citations see FAQs.c© 2011 The AuthorsVersion: Version of RecordLink(s) to article on publisher’s website:http://meetingorganizer.copernicus.org/EPSC-DPS2011/EPSC-DPS2011-1521.pdfCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukThe Exomars Climate Sounder (EMCS) Investigation F. Forget (1), J. T. Schofield (2), D. M. Kass (2), A. Kleinböhl (2), D. J. McCleese (2), M. A. Allen (2), M. C. Foote (2), M. Jeganathan (2), E. Millour (1), A. Spiga (1), O. Talagrand (1), N. Bowles (3) S. B. Calcutt (3), P. G. J. Irwin (3), P. L. Read (3), S. R. Lewis (4), T. Fouchet (5), F. Lefèvre (6),  A. Määttänen (6) ,  J. R. Barnes(7), S. W. Bougher (8), R. M. Haberle(9) (1) Laboratoire de Météorologie Dynamique (LMD), IPSL, CNRS, Paris, France (forget@lmd.jussieu.fr) (2) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA, (John.T.Schofield@jpl.nasa.gov) (3) Atmospheric, Oceanic and Planetary Physics, Department of Physics (AOPP), University of Oxford, UK (4) Department of Physics and Astronomy, The Open University, Milton Keynes, UK (5) LESIA, Observatoire de Paris, Paris, France (6) LATMOS, IPSL, Paris, France (7) Oregon State University, Corvallis, Oregon, USA (8) AOSS Department, University of Michigan, Ann Arbor, Michigan, USA (9) NASA/Ames Research center, Moffett Field, California, USA.  1. Introduction The ExoMars Climate Sounder (EMCS) investigation is developed at the Jet Propulsion Laboratory (Principal Investigator J. T. Schofield) in collaboration with an international scientific team from France, the United Kingdom and the USA.  EMCS plans to map daily, global, pole-to-pole profiles of temperature, dust, water and CO2 ices, and water vapor from the proposed 2016 ExoMars Trace Gas Orbiter (EMTGO). These profiles are to be assimilated into Mars General Circulation Models (MGCMs) to generate global, interpolated fields of measured and derived parameters such as wind. Sciences objectives of EMCS are to: Enhance understanding of Mars photochemistry by providing daily, global, high vertical resolution fields of atmospheric state, aerosol distribution, and water vapor concentration. EMCS atmospheric state measurements, combined with data assimilation, characterize the transport, sources and sinks of trace gases measured by the proposed EMTGO. The aerosol measurements reveal the heterogeneous photochemical pathways of trace gases. EMCS plans to map water vapor, the key source gas for odd hydrogen, known to be important in Martian photochemistry. Extend the MRO/MCS climatology of high vertical resolution measurements of the lower and middle atmosphere of Mars, with the improved coverage of local time provided by the proposed EMTGO. EMCS will determine the diurnal, seasonal & long-term variability of temperature and aerosol, and its impact on photochemistry. EMCS climatology, combined with earlier data, would relate EMTGO observations to earlier trace gas measurements. Support future Mars missions with measured climatology and near real-time density profile retrievals for landing and aerocapture, in the same way that MRO/MCS supported the Phoenix landing and is supporting the Mars Science Laboratory (MSL) landing. EMCS could be the only instrument in orbit able to support Entry, Descent and Landing (EDL) for the proposed ExoMars 2018 Rover Mission. 2. Instrument description  Figure 1 – The MRO/MCS instrument during thermal vacuum testing at JPL EMCS is a copy of the Mars Climate Sounder (MCS) instrument on the Mars Reconnaissance Orbiter (MRO) spacecraft [1], with low impact modifications to 2 of 9 spectral filters and for interfaces with the proposed EMTGO spacecraft. MCS is now in its 5th year of returning atmospheric profiles from Mars [2]. EMCS is an infrared, limb sounding, filter radiometer which uses 9 spectral channels from 12 - 45 µm to address its measurement objectives. The 270° elevation/azimuth articulation of the instrument provides full coverage of the downward hemisphere allowing limb observations in all directions and giving daily, global, pole-to-pole coverage of Mars from the 74 ± 10° inclination EMTGO orbit. Uncooled, 21-element, linear thermopile arrays in each spectral channel are the enabling technology of EMCS, permitting atmospheric profiles to be derived from limb staring observations with better sensitivity and geometrical stability than limb scanning. By combining in-track limb and nadir observations, retrieved profiles could be extended to the surface over much of the planet. Table 1 – The response and measurement function of the nine EMCS spectral channels.  Table 1 summarizes the coverage of the nine EMCS spectral channels, their distribution between the two instrument telescopes, and the primary measurement function of each channel. With the exception of A6, their functions are identical to those of MRO/MCS. A6 was a broad-band visible channel, designed for polar radiative balance measurements, which cannot be addressed from the  74° inclination proposed EMTGO orbit. It has been replaced by a spectral interval designed to improve low altitude temperature and CO2 ice extinction profiling. Measurements. Based on the performance of MRO/MCS [3], and water vapor retrieval simulations, EMCS obtains atmospheric profiles with an accuracy of 1 - 2 K in temperature, < 0.0001 km-1 in aerosol opacity, and < 10 ppm (0.7 pr.µm) in water vapor mixing ratio, with 5 km vertical resolution and 0 - 90 km vertical coverage. This vertical resolution is necessary to resolve important atmospheric structure and to match the high vertical resolution trace gas measurements of the microwave and solar occultation instruments. EMCS measurements are uniquely synergistic with the rest of the proposed EMTGO payload. They would provide daily global fields to supplement the more sparsely sampled solar occultations, and supply the dust and ice opacities. Furthermore, the articulation provided by the actuators allows coincident measurements with occultation, limb, and nadir sounding instruments regardless of their orientation on the spacecraft.  Figure 2 shows a nighttime pole-to-pole transect of combined limb-nadir retrievals from MRO/MCS for a single orbit. The dashed lines indicate the individual profiles, and their slope is due to the altitude dependence of tangent point location. Temperature profiles are retrieved up to ~90 km altitude with a typical precision between 0.5 and 2 K over most of this altitude range. Errors tend to be larger only at very high altitudes and very low temperatures. Pressure is retrieved to a precision of 1 - 2% at 20 - 30 km, and profiles of dust and water ice extinction achieve precisions of 10-4 - 10-5 km-1.   Figure 2 - Transect of MCS temperature (top), dust opacity (middle) and water ice opacity (bottom) retrievals for a single orbit at Ls = 155° (12/23/2006). References [1] McCleese, et al., 2007, Mars Climate Sounder: An investigation of thermal and water vapor structure, dust and condensate distributions in the atmosphere, and energy balance of the polar regions, J. Geophys. Res., 112, E05S06, doi:10.1029/2006 JE002790. [2] McCleese, et al., 2008,  Intense polar temperature inversion in the middle atmosphere on Mars, Nature Geoscience 1, 745-749. [3] Kleinböhl, et al., 2009, Mars Climate Sounder limb profile retrieval of atmospheric temperature, pressure, and dust and water ice opacity, J. Geophys. Res. 114, E10006, doi:10.1029/2009JE003358

The ExoMars Climate Sounder (EMCS) investigation is developed at the Jet Propulsion Laboratory (Principal Investigator J. T. Schofield) in collaboration with an international scientific team from France, the United Kingdom and the USA. EMCS plans to map daily, global, pole-to-pole profiles of temperature, dust, water and CO2 ices, and water vapor from the proposed 2016 ExoMars Trace Gas Orbiter (EMTGO). These profiles are to be assimilated into Mars General Circulation Models (MGCMs) to generate global, interpolated fields of measured and derived parameters such as wind. Sciences objectives of EMCS are to: Enhance understanding of Mars photochemistry by providing daily, global, high vertical resolution fields of atmospheric state, aerosol distribution, and water vapor concentration. EMCS atmospheric state measurements, combined with data assimilation, characterize the transport, sources and sinks of trace gases measured by the proposed EMTGO. The aerosol measurements reveal the heterogeneous photochemical pathways of trace gases. EMCS plans to map water vapor, the key source gas for odd hydrogen, known to be important in Martian photochemistry. Extend the MRO/MCS climatology of high vertical resolution measurements of the lower and middle atmosphere of Mars, with the improved coverage of local time provided by the proposed EMTGO. EMCS will determine the diurnal, seasonal & long-term variability of temperature and aerosol, and its impact on photochemistry. EMCS climatology, combined with earlier data, would relate EMTGO observations to earlier trace gas measurements. Support future Mars missions with measured climatology and near real-time density profile retrievals for landing and aerocapture, in the same way that MRO/MCS supported the Phoenix landing and is supporting the Mars Science Laboratory (MSL) landing. EMCS could be the only instrument in orbit able to support Entry, Descent and Landing (EDL) for the proposed ExoMars 2018 Rover Mission

HAL UVSQ

Archive Ouverte en Sciences de l'Information et de la Communication

HAL Id: hal-00569133
https://hal.archives-ouvertes.fr/hal-00569133
Submitted on 24 Feb 2011
HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d’enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.
The Exomars Climate Sounder (EMCS) Investigation
J. T. Schofield, D. M. Kass, A. Kleinböhl, D. J. Mccleese, M. A. Allen, M. C.
Foote, M. Jeganathan, François Forget, A. Spiga, O. Talagrand, et al.
To cite this version:
J. T. Schofield, D. M. Kass, A. Kleinböhl, D. J. Mccleese, M. A. Allen, et al.. The Exomars Climate
Sounder (EMCS) Investigation. Fourth International Workshop on the Mars Atmosphere: Modelling
and Observations, Feb 2011, Paris, France. 5 p. ￿hal-00569133￿
THE EXOMARS CLIMATE SOUNDER (EMCS) INVESTIGATION.   
 
J. T. Schofield, D. M. Kass, A. Kleinböhl, D. J. McCleese, M. A. Allen, M. C. Foote, M. Jeganathan,  Jet 
Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA, 
(John.T.Schofield@jpl.nasa.gov),  F. Forget, A. Spiga, O. Talagrand,  Laboratoire de Météorologie Dynami-
que, ISPL, CNRS, Paris, France,  F. Lefèvre,  A. Määttänen, Laboratoire Atmosphères, Milieux, Observations 
Spatiale, Paris, France, T. Fouchet, Laboratoire d’Ètudes Spatiales et d’Instrumentation en Astrophysi-
que, Observatoire de Paris, Paris, France,  N. Bowles, S. B. Calcutt, P. G. J. Irwin, P. L. Read,  Atmos-
pheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, UK,  S. R. Lewis,  De-
partment of Physics and Astronomy, The Open University, Milton Keynes, UK,  J. R. Barnes,  Oregon State 
University, Corvallis, Oregon, USA,  S. W. Bougher,  AOSS Department, University of Michigan, Ann Arbor, 
Michigan, USA,  R. M. Haberle,  NASA/Ames Research center, Moffett Field, California, USA. 
 
Introduction:   
The ExoMars Climate Sounder (EMCS) investi-
gation plans to map daily, global, pole-to-pole pro-
files of temperature, dust, water and CO2 ices, and 
water vapor from the proposed 2016 ExoMars Trace 
Gas Orbiter (EMTGO). The measurements  cover all 
local times, adding a new dimension to data pre-
viously obtained from sun-synchronous spacecraft. 
These profiles are to be assimilated into Mars Gen-
eral Circulation Models (MGCMs) to generate glob-
al, interpolated fields of measured and derived pa-
rameters such as wind. 
Measured and assimilated fields from EMCS 
clearly delineate the diurnal, day-to-day, and season-
al variation of atmospheric state. Temperature and 
aerosol fields are essential for characterizing photo-
chemical processes and heterogeneous chemistry, 
water vapor acts as a key source gas for odd hydro-
gen (HOx) photochemistry in the Martian atmos-
phere, and the wind field is critical for localizing the 
sources that govern the distribution of trace gases 
measured by other proposed EMTGO instruments.. 
 
Figure 1 – The MRO/MCS instrument during ther-
mal vacuum testing at JPL 
EMCS is a copy of the Mars Climate Sounder 
(MCS) instrument on the Mars Reconnaissance Or-
biter (MRO) spacecraft [McCleese et al., 2007], with 
low impact modifications to 2 of 9 spectral filters 
and for interfaces with the proposed EMTGO space-
craft. MCS is now in its 5th year of returning atmos-
pheric profiles from Mars [McCleese et al., 2008]. 
The MCS flight instrument is shown in Figure 1. 
EMCS is an infrared, limb sounding, filter radi-
ometer which uses 9 spectral channels from 12 - 45 
µm to address its measurement objectives. EMCS 
instrument parameters are summarized in Table 1. 
The 270° elevation/azimuth articulation of the in-
strument provides full coverage of the downward 
hemisphere allowing limb observations in all direc-
tions and giving daily, global, pole-to-pole coverage 
of Mars from the 74 ± 10° inclination EMTGO orbit. 
Uncooled, 21-element, linear thermopile arrays in 
each spectral channel are the enabling technology of 
EMCS, permitting atmospheric profiles to be derived 
from limb staring observations with better sensitivity 
and geometrical stability than limb scanning. 
 
Table 1 – EMCS instrument parameters. 
 
 
Science and Measurement Objectives: 
The baseline science and measurement objectives 
of the EMCS investigation are to: 
Enhance understanding of Mars photochemi-
stry by providing daily, global, high vertical resolu-
tion fields of atmospheric state, aerosol distribu-
tion, and water vapor concentration. 
EMCS atmospheric state measurements, com-
bined with data assimilation, characterize the trans-
port, sources and sinks of trace gases measured by 
the proposed EMTGO. The aerosol measurements 
reveal the heterogeneous photochemical pathways of 
trace gases. EMCS plans to map water vapor, the 
key source gas for odd hydrogen, known to be im-
portant in martian photochemistry. 
Extend the MRO/MCS climatology of 
high vertical resolution measure-
ments of the lower and middle at-
mosphere of Mars, with the improved 
  
coverage of local time provided by 
the proposed EMTGO. 
EMCS would determine the diurnal, seasonal & 
long-term variability of temperature and aerosol, and 
its impact on photochemistry. EMCS climatology, 
combined with earlier data, would relate EMTGO 
observations to earlier trace gas measurements. 
Support future Mars missions with measured 
climatology and near real-time density profile re-
trievals for landing and aerocapture, in the same 
way that MRO/MCS supported the Phoenix land-
ing and is supporting the Mars Science Laboratory 
(MSL) landing. 
EMCS could be the only instrument in orbit able 
to support Entry, Descent and Landing (EDL) for the 
proposed ExoMars 2018 Rover Mission. 
 
French and UK Co-Investigators make a key con-
tribution to the EMCS investigation. The European 
component of the science team assimilates measured 
atmospheric fields into Mars General Circulation 
Models. The assimilation scheme is being developed 
using MRO/MCS data and will provide the derived 
fields, such as wind, needed to understand the trans-
port, sources, and sinks of trace gases. 
Based on the performance of MRO/MCS, and 
water vapor retrieval simulations, EMCS obtains 
atmospheric profiles with an accuracy of 1 - 2 K in 
temperature, < 0.0001 km-1 in aerosol opacity, and < 
10 ppm (0.7 pr.µm) in water vapor mixing ratio, 
with 5 km vertical resolution and 0 - 90 km vertical 
coverage. This vertical resolution is necessary to 
resolve important atmospheric structure and to match 
the high vertical resolution trace gas measurements 
of the microwave and solar occultation instruments. 
The 270° elevation and azimuth articulation of 
EMCS gives the instrument 360° coverage of the 
limb. This allows EMCS to compensate for space-
craft yaw and obtain pole-to-pole coverage every 
orbit, with daily resolution of 3.5° latitude and 30° 
longitude. By combining in-track limb and nadir 
observations, retrieved profiles could be extended to 
the surface over much of the planet. 
EMCS measurements are uniquely synergistic 
with the rest of the proposed EMTGO payload. They 
would provide daily global fields to supplement the 
more sparsely sampled solar occultations, and supply 
the dust and ice opacities not available to microwave 
measurements. Furthermore, the articulation pro-
vided by the actuators allows coincident measure-
ments with occultation, limb, and nadir sounding 
instruments regardless of their orientation on the 
spacecraft. 
 
Spectral Channel Selection: 
Table 2 summarizes the coverage of the nine 
EMCS spectral channels, their distribution between 
the two instrument telescopes, and the primary mea-
surement function of each channel. With the excep-
tion of A6, their functions are identical to those of 
MRO/MCS. A6 was a broad-band visible channel, 
designed for polar radiative balance measurements, 
which cannot be addressed from the  74° inclination 
proposed EMTGO orbit. It has been replaced by a 
spectral interval designed to improve low altitude 
temperature and CO2 ice extinction profiling. 
Table 1 – The response and measurement function of 
the nine EMCS spectral channels. 
 
 
Figure 2 compares the four EMCS temperature 
sounding channels with atmospheric limb emission 
spectra calculated for five tangent altitudes. The cal-
culations were performed at high spectral resolution 
by the MCS line-by-line transmission code and were 
smoothed to 5 cm-1 for clarity. The spectra are domi-
nated by emission from the 15-micron band of CO2. 
As noted in Table 2, the channels are optimized for 
different altitude ranges by placing them at differing 
opacities in the long-wavelength wing of the band. 
As the spectroscopy and mixing ratio of CO2 are 
well known, these channels allow accurate mea-
surements of temperature. Pressure is also derived 
from the ratio of A3 and A2 measurements. 
 
Figure 2 - EMCS temperature sounding channels. 
Figure 3 compares the EMCS aerosol sounding 
channels with extinction efficiency spectra calcu-
lated for dust, water ice, and CO2 ice models. These 
calculations assume Mie scattering, with particle 
sizes described by modified gamma distribution 
functions. The model effective radii are 1.06 µm for 
dust, 1.41 µm for water ice, and 2.0 µm for CO2 ice. 
The strong absorption feature of CO2 ice is masked 
by the gaseous CO2 band but, when the atmosphere 
is cold, A6 is sensitive primarily to CO2 ice. The B 
telescope channels provide sensitivity to aerosols at 
higher opacities in the limb path, when A4 and A5 
are opaque, and also to water ice at low temperatures 
when the concentration of water vapor is negligible. 
 
Figure 3 - EMCS dust and ice channels. 
Figure 4 compares the EMCS water vapor chan-
nels with water vapor limb emission spectra. A con-
stant water vapor volume mixing ratio of 300 ppm is 
assumed (~20 pr.µm). The relatively broad channel, 
B2, contains two strong water vapor emission fea-
tures, whereas the narrow channel B3 is centered on 
a window in the water vapor spectrum. These co-
centered channels have very similar responses to 
aerosol opacity, but very different responses to water 
vapor, allowing the two components to be separated. 
 
Figure 4 - EMCS water vapor channels. 
 
Limb Staring and Vertical Resolution: 
The half scale height (5 km) resolution needed to 
reveal key atmospheric structure is made possible by 
limb-viewing geometry and the 5-km field-of-view 
of the EMCS instrument. Micro-machined thermo-
pile arrays are the enabling technology that allows 
limb staring. Compared with scanning a single de-
tector across the limb, limb staring provides im-
proved signal-to-noise and greatly reduces the sensi-
tivity of measurements to spacecraft pointing drifts. 
 
Figure 5 - Nominal EMCS detector fields-of-view. 
Figure 5 shows a schematic of the nominal 
EMCS fields of view projected on the limb of Mars 
from the nominal 400-km orbit, with the surface and 
90 km levels indicated. Both telescopes, including 
all 189 detectors, are represented. The telescope 
fields-of-view are coincident, with arrays A4/B1 and 
A6/B3 superimposed. They are separated for clarity. 
The true vertical resolution of each measurement 
is determined by the limb path through the atmos-
phere as well as by its geometrical FOV. Figure 6 
shows a retrieved MCS temperature profile together 
with a corresponding set of vertical response or 
weighting functions for the EMCS temperature 
sounding channels (Figure 2). 
 
Figure 6 - EMCS weighting functions derived for 
a retrieved martian temperature profile. 
 
Atmospheric Profile Retrievals: 
The retrieval of atmospheric profiles from EMCS 
radiances is based on a modified Chahine method 
[Chahine, 1970]. The team of Co-Is at JPL has ex-
tensive experience with this technique and its adap-
tation for limb-viewing radiometers, as the approach 
has been successfully implemented for MRO/MCS 
[Kleinböhl et al., 2009]. The retrieval code contains 
a fast radiative transfer scheme, which includes sin-
gle scattering of radiation from aerosol. Profiles of 
temperature, pressure, dust and water ice opacity are 
retrieved simultaneously. For in-track measurements, 
retrievals are based on a combination of co-located 
limb and nadir measurements. The latter provide 
surface temperature, aerosol and water vapor column 
quantities, and improved temperature profiles near 
the surface. For off-track measurements, where co-
located nadir measurements are not available, the 
temperature near the surface can be retrieved with 
the new A6 channel (Figure 6). 
  
 
Figure 7 - Transect of MCS temperature (top), dust 
opacity (middle) and water ice opacity (bottom) re-
trievals for a single orbit at Ls = 155° (12/23/2006). 
Figure 7 shows a nighttime pole-to-pole transect 
of combined limb-nadir retrievals from MRO/MCS 
for a single orbit. The dashed lines indicate the indi-
vidual profiles, and their slope is due to the altitude 
dependence of tangent point location. Temperature 
profiles are retrieved up to ~90 km altitude with a 
typical precision between 0.5 and 2 K over most of 
this altitude range. Errors tend to be larger only at 
very high altitudes and very low temperatures. Pres-
sure is retrieved to a precision of 1 - 2% at 20 - 30 
km, and profiles of dust and water ice extinction 
achieve precisions of 10-4 - 10-5 km-1. 
 
Figure 8 - One day of night-time temperature cover-
age of Mars from MRO/MCS. 
Figure 8 shows 24 hours of MRO/MCS tempera-
ture retrievals displayed as curtains overlaid on Mars 
altimetry using Google Earth. The season is northern 
spring (Ls = 39°) and the curtains show temperatures 
from 0-80 km with a vertical resolution of 5 km 
ranging from 120 K (purple) to 200 K (green). 
 
Mission Operations: 
 
Figure 9 - EMCS 24 hr coverage of the northern 
hemisphere of Mars from the TGO orbit. 
EMCS plans to operate continuously, day and 
night, from the nadir-oriented spacecraft platform 
provided by the proposed EMTGO spacecraft. Ob-
servational flexibility is supplied by azi-
muth/elevation scanning, driven by scan tables 
stored in the instrument and timed relative to an 
equator crossing time command. Modifications to 
the observational strategy would be implemented by 
uploading scan tables, but observations are able to 
continue indefinitely without commanding.  
EMCS observations fall into the following cate-
gories. 1) Routine, repetitive, in-track and off-track 
limb and nadir sounding from pole-to-pole, using the 
azimuth actuator to compensate for spacecraft yaw. 
2) Routine calibration measurements using views of 
space and the instrument blackbody targets. 3) Cam-
paigns make simultaneous and coincident measure-
ments with other instruments. 
An example of the daily global coverage 
achieved by 1) above, from the 400 km, 74° inclina-
tion nominal orbit is shown in Figure 9. In-track 
observations reach 74°N and measurements made 
40° off-track extend to the pole. 
Data Products: 
The EMCS investigation has a data analysis and 
archiving plan that builds strongly on MCS heritage. 
Table 3 summarizes the planned EMCS data prod-
ucts, plans for data generation, validation, reprocess-
ing, and schedules and estimated volumes for deli-
very to the atmospheres node of the Planetary Data 
System (PDS). Team members responsible for prod-
ucts are indicated. This effort builds on MRO/MCS 
operational, software and hardware heritage. 
Table 3 – Planned EMCS Data Products 
 
References: 
Chahine, M. T., 1970, Inverse problems in radia-
tive transfer: Determination of atmospheric parame-
ters, J. Atmos. Sci. 27, 960-967. 
McCleese, et al., 2007, Mars Climate Sounder: 
An investigation of thermal and water vapor struc-
ture, dust and condensate distributions in the atmos-
phere, and energy balance of the polar regions, J. 
Geophys. Res., 112, E05S06, doi:10.1029/2006 
JE002790. 
McCleese, et al., 2008,  Intense polar tempera-
ture inversion in the middle atmosphere on Mars, 
Nature Geoscience 1, 745-749. 
Kleinböhl, et al., 2009, Mars Climate Sounder 
limb profile retrieval of atmospheric temperature, 
pressure, and dust and water ice opacity, J. Geophys. 
Res. 114, E10006, doi:10.1029/2009JE003358. 
This work was performed at the Jet Propulsion 
Laboratory, California Institute of Technology under 
contract to NASA. 


https://hal.archives-ouvertes.fr/hal-00569133

The Exomars Climate Sounder (EMCS) Investigation

Abstract

Similar works

Full text

Available Versions

HAL-INSU

HAL-OBSPM

HAL-Polytechnique

Open Research Online (The Open University)

HAL UVSQ

HAL-OBSPM

HAL-INSU

Archive Ouverte en Sciences de l'Information et de la Communication