MARLI: MARS LIDAR FOR MEASURING GLOBAL WIND AND
AEROSOL PROFILES FROM ORBIT
J. B. Abshire1,2, M.D. Smith1, D.R. Cremons1, S.D. Guzewich1, X. Sun1, A. Yu1, F. Hovis3
1

NASA Goddard Space Flight Center, Greenbelt MD USA (james.b.abshire@nasa.gov),
2
University of Maryland College Park MD USA
3
Fibertek Inc, Dulles Technology Drive, Herdon VA USA
April 7, 2022

Abstract:
NASA’s Mars Exploration Analysis
Group’s Next Orbiter Science Analysis Group
(NEX-SAG) identified atmospheric wind measurements as one of most compelling science objectives
for a future Mars orbiter [1]. To date, only very few
direct observations of Mars winds exist. Winds are
the key variable to understand atmospheric transport
and answer fundamental questions about the three
primary cycles of the Mars climate: CO2, H2O, and
dust. However, the lack of direct observations and
imprecise and indirect inferences from temperature
observations leave many basic questions about the
atmospheric circulation unanswered. In addition to
addressing high priority science questions, direct
wind observations from orbit would help validate 3D
general circulation models (GCMs) while also
providing key input to atmospheric reanalyses.
The dust and CO2 cycles on Mars are partially coupled and their influences on the atmospheric circulation modify the global wind field. Dust
absorbs solar infrared radiation and its varying temporal and spatial distribution forces changes in the
atmospheric temperature and wind fields. Hence it is
important to simultaneously measure the heightresolved wind and dust profiles. NASA Goddard
Space Flight Center is developing the MARLI lidar
to provide a unique capability to observe these variables continuously, day and night, from orbit.
Measurement Approach:
The MARLI lidar [2-3] is designed to observe the atmosphere from a nominally circular polar
orbit around Mars. The lidar measurement concept
and an instrument illustration are shown in Figure 1.
The simplest version of the instrument would be
pointed ~30° off-nadir in a cross-track viewing direction. The lidar will continuously measure dust
aerosol backscatter profiles, cross-polarized
backscatter profiles (to identify water ice aerosols),
the component of the aerosol Doppler shift from
wind profiles along the instrument’s line-of-sight,
and the line-of-sight range to the planet’s surface.
These measurement types are shown in Figure 2.
The MARLI development is being supported by the
NASA ROSES PICASSO and MatISSE Programs.
Lidar Description:
The laser backscatter from the Mars atmos-

phere is weak and is distributed in range and thus a
highly sensitive lidar approach is necessary. The
present MARLI approach measures the heightresolved atmospheric characteristics along a single
line-of-sight. The lidar uses an efficient pulsed
Nd:YAG laser with flight heritage, a low-mass receiver telescope, a direct detection receiver with an
etalon-based Doppler discriminator, and a photonsensitive detector.
The MARLI design, shown in Figure 3, utilizes a pulsed single-frequency diode-pumped
Nd:YAG laser. The optical emission frequency of
the laser is locked to a single frequency non-planar
ring oscillator seed laser. The laser emits linearly
polarized ~40 nsec wide pulses at a nominal 1 kHz
pulse rate. The lidar receiver uses a ~50 cm diameter telescope and its optics split the returned signal
into 3 paths. One path is a cross-polarized channel to
allow discrimination of dust and ice in the laser
backscatter profiles. The other two paths are used to
illuminate a 5 cm diameter etalon at different angles
that are then focused onto separate detector pixels.
These receiver elements are configured as a doubleedge Doppler (optical frequency-shift) discriminator
for the aerosol backscatter profiles.
The MARLI approach leverages several
new lidar components developed for NASA, including a new single frequency seed laser developed for
the Laser Interferometer Space Antenna (LISA) mission, a single frequency ring laser developed by Fibertek Inc. and a photon-sensitive HgCdTe APD
from Leonardo DRS Technologies. Our targeted
instrument size is a ~70 cm cube, comparable to a
medium-sized instrument such as the Mars Orbiter
Laser Altimeter (MOLA). Nominal payload parameters are 40 kg, < 90W, and ~50 kbits/sec at 100%
duty cycle. Our approach leverages our work on
measuring terrestrial winds and lidar technology
supported by the NASA ESTO IIP program.
Development status & plans:
We have developed all components and
demonstrated many aspects of the measurement with
an instrument breadboard. A brassboard version of
the lidar is being completed during spring 2022 and
is shown in Figure 4. It uses flight-like components
and will be used demonstrate measurements from the
ground to thin cirrus clouds.

Calculated Measurement Performance:
We have calculated the expected performance of MARLI using lidar measurement models
that we developed as part of this project. For the
Mars atmosphere we selected several cases that represent the atmosphere under a range of atmospheric
aerosol (dust and water ice) loading. To date the bulk
of current spacecraft observations of the global Mars
atmospheric state have come from the Mars Global
Surveyor (MGS) and Mars Reconnaissance Orbiter
(MRO) spacecraft, which show large temporal variations in the amount and vertical distribution of dust
and ice aerosols and water vapor. For this work we
extracted aerosol profiles shown in Figure 5 using
extinction profiles (version 5.2.4) from the Mars
Climate Sounder (MCS) on the MRO [6-8]. The
MCS extinction retrievals were then scaled to the
MARLI wavelength of 1064 nm. Since the Mars

atmospheric pressure is low, we chose to neglect
molecular scattering.
The MARLI lidar will obtain atmospheric
profile measurements at a rate of ≥ 2 Hz with nominally 150 m vertical resolution. The lidar measurement performance depends on the orbit altitude, laser
pulse energy and pulse rate, telescope diameter, the
atmospheric vertical bin depth and averaging time.
The vertical and time averaging will be performed
on the ground, so are adjustable during data analysis.
The performance plots in Figures 6 and 7 were calculated assuming averaging over 40 seconds (~2°
latitude for a nominal 400 km polar orbit) with 2 km
thick vertical bins.
Details of the instrument and its planned
measurements will be shown in the presentation.

References:
[1] MEPAG: Chaired by B. Campbell and R. Zurek (2015), Report from the Next Orbiter Science Analysis
Group, http://mepag.nasa.gov/reports.cfm
[2] J.B. Abshire et al., MARLI, 2015 European Planetary Science Congress (EPSC),
http://meetingorganizer.copernicus.org/EPSC2015/EPSC2015-258.pdf
[3] S. D. Guzewich et al., MARLI, 2016 Lunar and Planetary Science Conference (LPSC),
http://www.hou.usra.edu/meetings/lpsc2016/pdf/1497.pdf
[4] D. R. Cremons, J. Abshire, G. Allan, X. Sun, H. Riris, M. Smith, S. Guzewich, A. Yu, F. Hovis, “Development of a Mars lidar (MARLI) for measuring wind and aerosol profiles from orbit,” SPIE Proceedings Volume 10791, 1079106 (2018) https://doi.org/10.1117/12.2325408
[5] D. R. Cremons, J. B. Abshire, X. Sun, G. Allan, H. Riris, M. D. Smith, S. Guzewich, A. Yu, F. Hovis,
“Design of a direct-detection wind and aerosol lidar for mars orbit,” CEAS Space Journal (2020) 12:149–162
https://doi.org/10.1007/s12567-020-00301-z
[6] McCleese, et al., 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.: Planets.
112, (2007). doi:10.1029/2006JE002790
[7] Kleinböhl, A., et al.,A single-scattering approximation for infrared radiative transfer in limb geometry
in the Martian atmosphere. J. Quant. Spectrosc. Radiat. Transf. 112, 1568–1580 (2011).
doi:10.1016/j.jqsrt.2011.03.006
[8] Kleinböhl, A., Friedson, A.J., Schofield, J.T.: Two-dimensional radiative transfer for the retrieval of
limb emission measurements in the martian atmosphere. J. Quant. Spectrosc. Radiat. Transf. 197, 511–522
(2017). doi:10.1016/j.jqsrt.2016.07.009.

Figure 1. (Left) The MARLI approach continuously measures the aerosol backscatter profiles, the cross polarized (ice) backscatter profiles, and the Doppler (wind profiles), Nominally the lidar is pointed cross-track at ~ 30
degrees off nadir, to measure the Doppler shift of the wind in the cross-track direction. (Right) Drawing of
MARLI from an engineering study. The telescope diameter is ~ 50 cm and other components are labelled.

Figure 2. Illustrations of the MARLI measurement types. (Left) Range (height) resolved aerosol backscatter
profiles. (Middle Left) Profiles of cross-polarized backscatter, caused by ice clouds. (Middle Right) Height resolved Doppler backscatter profiles as seen by the two detector channels after passing through the etalon used as
the double-edge filter. (Right) The horizontal wind profile is computed from the detected signal ratio after the
double-edge filter.

Figure 3. Block diagram of the MARLI lidar showing major components and subsystems.

Figure 4 - Drawing of the MARLI brassboard lidar assembly. This will be used to demonstrate measurements
from the ground at NASA Goddard Space Flight Center. The lidar brassboard uses a smaller 14 cm diameter
receiver lens instead of the 50 cm diameter flight telescope. The brassboard is being assembled during spring
2022 and will be used to demonstrate aerosol backscatter profile measurements and measurements to windblown thin cirrus clouds.

Figure 5 - The Mars atmospheric backscatter profiles used to predict MARLI measurement performance were computed from
MCS retrievals:
(A) Attenuated backscatter (βT2) with polarization parallel to the transmitter
for the three atmospheric test cases as
a function of altitude.
(B) Attenuated backscatter with polarization perpendicular to the transmitter
for the same three cases.

Figure 6 - The RMS wind-speed uncertainty from the MARLI instrument
model computed as a function of altitude from the surface for the case of a
uniform cross-track horizontal wind
speed of 18 m/s. The performance was
calculated assuming averaging over 40
seconds (~2° latitude for a nominal
polar orbit) with 2 km thick vertical
bins.

Figure 7 - Calculated relative error as a function of height for the MARLI atmospheric backscatter profile measurements in the parallel (A) and cross polarization (B) channels. The relative errors are plotted on a log scale.
The performance was calculated assuming averaging over 40 seconds (~2° latitude for a nominal polar orbit)
with 2 km thick vertical bins.