THE EMIRATES MARS INFRARED
OVERVIEW AND SURFACE RESULTS

SPECTROMETER

(EMIRS)

C. S. Edwards, Northern Arizona University, Flagstaff, AZ, USA (Christopher.Edwards@nau.edu), P. R. Christensen, Arizona State University, Tempe, AZ, USA, M. D. Smith, NASA Goddard Space Flight Center, Greenbelt,
MD, US, C. A. Wolfe, Northern Arizona University, Flagstaff, AZ, USA, C. Haberle, Northern Arizona University, Flagstaff, AZ, USA, S. Atwood, University of Colorado Boulder, Boulder, CO, USA, K. Badri, Mohammed
Bin Rashid Space Centre, Dubai, UAE, M. Wolff, Space Science institute, Boulder, CO, USA, M. M. Osterloo,
Space Science institute, Boulder, CO, USA, E. Al Tunaiji, Mohammed Bin Rashid Space Centre, Dubai, UAE, N.
Al Mheiri, Mohammed Bin Rashid Space Centre, Dubai, UAE, M. Yousuf, Mohammed Bin Rashid Space Centre, Dubai, UAE, S. Anwar, Arizona State University, Tempe, AZ, USA, N. Smith, Northern Arizona University,
Flagstaff, AZ, USA, K. Saboi, Northern Arizona University, Flagstaff, AZ, USA, and the EMIRS Team
Introduction:
The Emirates Mars Mission (EMM, Amiri et al.,
2022) Emirates Mars Infrared Spectrometer
(EMIRS, Edwards et al., 2021, Fig. 1) currently
around Mars is acquiring remote measurements of
the martian surface (temperature and composition)
and lower atmosphere. EMIRS is a FTIR spectrometer covering the range from 6.0-100 µm (1666-100
cm-1) with a spectral sampling as high as 5 cm-1 with
a 5.4-mrad IFOV with direct heritage from the
Thermal Emission Spectrometer (TES, Christensen
et al., 2001) and OSIRIS-REx Thermal Emission
Spectrometer (OTES, Christensen et al., 2018). The
EMIRS optical path includes a flat 45˚ pointing mirror to enable one degree of freedom while the spacecraft provides the other to build up a 2-dimensional
array of observations. The primary goals of EMIRS
are to characterize the geographic and diurnal variability of key atmospheric constituents (water ice,
water vapor, and dust) along with temperature profiles and surface temperature on sub-seasonal timescales
EMIRS acquires data of the full martian disk and
thus provides an integrated view of the martian surface and atmosphere in every spectrum. These observations include complete diurnal, seasonal, and
geographic coverage of atmospheric properties, surface temperature, and also surface composition/mineralogy at wavelengths not regularly acquired of the martian surface. Due to the unique nature of the EMM orbit, EMIRS also collects data that

Fig. 1) EMIRS Flight instrument prior to integration with
the spacecraft

Fig. 1) EMIRS R-OS1 (top, A & B) and R-OS2 (bottom, D &
E) synoptic observation strategies observed. These observations are simulated for a S/C altitude of 43,000 km (left, A
& C) and 20,000 km (right, B & D). Mars is scaled to the
same apparent size.
spans the full local solar time range (all solar incidence angles), at multiple emission angles. These
unique observations permit the interrogation of diurnal surface ices/frost, thermophysics (including subsurface layering from both a seasonal and diurnal
skin depth), surface roughness, and rock abundance
in addition to the primary science goals.
EMIRS Overview and Status:
EMM Concept of Operations (CONOPS, Fig. 2)
strategy provides opportunities for complete geographic coverage of all times of day in less than 10
days of observations. During the primary science
phase, EMIRS acquires data of ~1/2 the martian disk
within 1/2 an hour of observing. This observation
sequence, which include calibration activities, is
carried out ~20 times per orbit and produces data
with surface sampling of better than 300 km/px up to
70˚ emission angle, with the highest resolution data
being ~100km in diameter. EMIRS uses these data to
provide global maps over 8 local time bins of the
column integrated dust opacity, column integrated

Fig. 3) EMIRS in flight performance exceeds requirements
with significant margin

Surface Results and Associated Challenges:
Due to the unique nature of the EMM observation strategy, nearly every EMIRS pixel covers multiple geologic and thermophysical units, includes a
range of local times and incidence/phase angles and
is observed from a unique spacecraft viewing geometry (e.g. range of emission angles). This combination of multi-angle viewing when convolved with
the multi-time of day observations provide a unique
but complicated lever arm on the surface roughness
(e.g. Bandfield & Edwards, 2008), rock abundance
(e.g. Nowicki & Christensen, 2007) and surface heterogeneity (e.g. Edwards et al., 2018; Wolfe et al.,
2021). When compared to the nominally nadir looking TES data of Mars, with a fixed local time, the
complexity of the EMIRS dataset becomes apparent
(Fig. 6). While good diurnal fits are achievable for

Fig. 4) Example of an EMIRS L2 quicklook product.
ice opacity, water vapor abundance and atmospheric
temperature profiles to 60 km altitude.
The calibration pipeline of EMIRS leverages the
well-established pipelines of TES and OTES and
folds in atmospheric retrievals into the standard process (Fig. 3). Level 2 data (calibrated radiance and
associated geometry, along with quick look that depict the acquisition geometry, Fig. 4) are released on
3 month cadence and lag by ~4 months from the
time of collection. Level 3 data (including water
vapor column abundance, water ice optical depth,
dust optical depth, and atmospheric temperature profiles, including quickook products, Fig. 5) lag by an
additional 3 months to allow sufficient time for the
quality of the data to be assessed.

Fig. 5) Example of an EMIRS L3 dust opacity quicklook
product.

Fig. 6) EMIRS and TES daytime data acquired around the
same season and local time vs wavelength and emission
angle.
regions with stringent data observation geometry
restrictions, the impact of multiple emission angle
data on effective surface temperatures can be significant (Bandfield & Edwards, 2008) and necessitates a
more sophisticated approach to deriving surface
properties/temperatures than most nadir-looking
spacecraft. Specifically, we find that during the day,
fine-scale surface roughness and macro-scale slopes
play an important role in the overall shape of the
diurnal curve, while at night the mixing of surface
units and rock abundance also plays an important
role, causing differential cooling.
Summary and Future Work:
The derivation of an accurate surface radiance is
a key input into the atmospheric retrieval used for
EMIRS (Atwood et al., 2021; Badri et al., 2021;
Smith et al., 2021; Wolfe et al., 2021). As such we
are developing a comprehensive parameterization of
the EMIRS observation sequence that permits the
fitting of anisothermal surface radiance to measured
EMIRS radiances using a combination multicomponent mixtures that account for the complex
viewing geometries and sub-pixel variability.

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