Lunar Polar Volatiles 2022 (LPI Contrib. No. 2703)

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A LUNAR RECONNAISSANCE DRONE MISSION CONCEPT FOR MAPPING AND CHARACTERIZINGPOLAR REGIONS V. Pozsgay1, D. Rodríguez-Martínez1, and J-P. Kneib1, 1eSpace – EPFL Space Center (PPH 335,Station 13, 1015 Lausanne, Switzerland; contact: david.rodriguez@epfl.ch).
Introduction: Upcoming exploration missions
demand ever more capable robotic systems including
the capability to explore longer distances (>100 km)
under highly constrained time windows (e.g., lunarpolar mission experiencing shorter daylight cycles) andto do so under extreme environmental conditions ofwhich little to no data is readily available.
An effective, faster, and ideally unalteredcharacterization of these regions requires improved
mobility systems as well as the use of high-resolution
mapping and imagery, which most missions to date stilllack. The highest resolution maps acquired from lunar
orbit have been measured by the Narrow-Angled
Camera (NAC) on board of NASA’s Lunar
Reconnaissance Orbiter (LRO). Despite the NAC being
capable of imaging at resolutions as low as 0.5 m/px,
permanently shadowed regions (PSRs) have been
mapped at a maximum resolution of 10-20 m/px due tothe need for longer exposure times [1]. Remote sensing
from orbit has clear benefits when it comes to acquiringglobal measurements in a cost-effective manner. The
data provided, however, is not of sufficient quality to
pre-validate regions of interest for downstream
scientific or commercial activities to follow.
We herein present the preliminary design of alightweight, compact, and reusable reconnaissancedrone capable of assisting other on-ground roboticsystems for the characterization and high-resolution
mapping of particularly challenging and pristine
locations on the lunar surface.
Use case: The lunar reconnaissance drone isdesigned to assist other planetary robots operating on
the surface into inaccessible environments—or those ofwhich scattered, low-resolution data is available—,
across unstructured, dynamic, and hazardous terrains,
and over areas expected to hold highly valuable
scientific information. The drone shall be capable ofproducing high-resolution maps (~0.1 m/px) of targeted
regions of interest. It shall be fast to deploy and provide
a simple, low-cost solution that prevents thecontamination of scientifically significant locations.
Reusability—capableofmultiple
flights—,
modularity—capable of hosting different instruments
for different purposes—, and adaptability—capable ofbeing used across and alongside multiple platforms—
are key design requirements for the implementation ofthese drones in a wide array of mission scenarios.
The Lunar Reconnaissance Drone payload
envelope: The lunar reconnaissance payload envelope
includes two main systems: the drone and its associatedservice station, i.e., a base located on top of the rover orvehicle the drone services, which apart from acting as a
take-off and landing (TOL) pad provides shelter fromradiation and low temperatures when in standby, refuels
the tanks of the drone and recharges its batteries, andallows for major data transfers to take place on the rover
itself; all with the objective of keeping the drone assimple, lightweight, and compact as possible.
The preliminary concept of operations (CONOPS)
for the system defined thus far assumes the drone takes
off from and always lands on its service station.

Figure 1: Illustration of the Lunar Reconnaissance Drone concept ofoperations: 1) standby mode, 2) flight preparation and deployment, 3)
take-off and vertical ascent, 4) horizontal flight and mapping of thelunar surface, 5) vertical ascent and landing for data transmission,refueling, and standby. [2]After take-off, the drone flies above the region ofinterest at a constant altitude while mapping the terrain
or acquiring the necessary data. The altitude can be set
to minimize the interaction with and potential
contamination of the ground. The drone never lands on
the surface. At the end of its flight, and while
maintaining a constant altitude, the drone autonomously
returns to its initial location to land back on the service
station from which it took off. Data is then transferredto the rover for on-board processing or furthertransmission to ground or orbiting stations. The rover
can afterward traverse to a different location for further
examinations much more efficiently and with a higher
locational awareness. Repeated flights can be performed
ad hoc at different locations.
The drone is being designed to be completely
autonomous. A preliminary study of the drone design
resulted in a total wet mass, including margins, of about
17 kg, with a peak power consumption of 324 W, andexternal dimensions of 450x480x378 mm3. A
preliminary design of the service station is currently
being conducted.
Propulsion system, trajectory, and control: For a
combination of efficiency, low mass, and simplicity, themost effective way we found to design the propulsion
system is the use of monopropellant thrusters. Four ofthese thrusters generate enough lift and thrust for TOL
and hovering, with the added benefit that they can also
be used for precise attitude control, eliminating the needfor additional heavier reaction wheels or more complex
engines.

Lunar Polar Volatiles 2022 (LPI Contrib. No. 2703)

The flight strategy we adopted resulted from a
tradeoff between fuel consumption, mass, andreliability, especially during landing. Taking advantageof the capability of monopropellant thrusters to throttle,
we opted for a semi-ballistic trajectory—a mix between
an initial short vertical take-off, followed by a ballistic
climb and a constant 50-m altitude flight profile. The
trajectory is followed in reverse during landing. This
mixed profile increases safety, since small corrections
can be performed during the vertical TOL, and presents
over 13% lower fuel consumption than a completely
vertical TOL. A 50-m altitude was chosen to achieve therequired resolution with the selected payload (see“Mapping instrument”) and to prevent any
contamination of the surface from the plume of thethrusters.

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the service station), which simplifies the design from amechanical and thermal standpoint compared to othersolutions such as landing or hopping on the ground [4].
Minimizing the interaction with the ground, which
potentially harbors scientifically valuable information
and resources, was a must.
The current drone design lacks any power
generation device on board and instead carries a 22.5
kWh battery pack that can be recharged while on theservice station. While docked on the station, data can betransmitted either through a wired communication or a
UHF wireless system.
The outer structure and inner skeleton are made ofcarbon fiber plates.
All the electronic components are located inside awarm electronic box to maintain them at a uniform
operating temperature.

Figure 2: Drone’s 2D symmetric flight trajectory.

Flight simulations of this trajectory output a total
flight time of 120.4 s for an 800 m flight, and a total fuelconsumption of 1.86 kg per flight.
A requirement for our mission concept is that thedrone shall perform at least 10 flights, refueling after
every single flight, which means the service station shallcarry at least 27 kg of additional propellant.
Payload: As a reference for our preliminary design
study, we opted for a single payload that could be usedboth for mapping the terrain and as the prime sensory
input for hazard detection and avoidance maneuvers.
We chose a flash Lidar for this application. Despite
being an emerging technology, it provides highresolution, a 3D mapping capability, and it is highly
reliable in fast-moving, unstructured environments. Inaddition, the use of a flash Lidar prevents the need for
additional moving mechanisms such as gimbals or panand-tilt units. The European Space Agency (ESA) iscurrently pursuing the development of lightweightminiature flash Lidars for future space exploration [3].
The requirements formulated by ESA, particularly theones concerning expected mass, volume, and powerconsumption, were used as a baseline to model thepayload in our analysis.
Final configuration: The drone has been designed
to be as compact as possible, with a low center of gravity
for better control, while striving for simplicity andreliability during landing and docking with the station.
TOL is always conducted from a known location (i.e.,Figure 3: Drone’s final configuration.

Conclusion: We have presented a preliminary
design of a lightweight and compact lunar drone usable
under multiple scenarios (PSRs, skylights, etc.). Whilefurther analyses need to be conducted, particularly on
the design of the service station and the optimization of
the thermal design of the drone, and insights from thescientific community need to be considered in theselection and adaptation of different payloads, theresults presented here constitute a promising baseline
for an effective, low-impact, and faster characterizationof scientifically valuable regions on the Moon.
References:[1] Robinson, M.S., Brylow, S.M., Tschimmel, M. et al. (2010)
Lunar Reconnaissance Orbiter Camera (LROC) Instrument Overview.
Space Sci Rev 150, 81–124.
[2] Pfeiffer, T., Uythoven, E., Rodríguez-Martínez, D., Kneib, JP., Koizumi, H. (2022) Feasibility study and preliminary design of a
lunar reconnaissance drone, LSIC Spring Meeting 2021, Laurel, MD.
[3] Tzeremes, G. D. et al. (2019) Altimetry, Imaging and Landing
Location Selection Lidars for ESA Space Applications, IGARSS 2019
IEEE International Geoscience and Remote Sensing Symposium.
[4] Babak Cohanim. (2013) Mission design for safe traverse ofplanetary hoppers. Massachusetts Institute of Technology