IEEE Robotics & Automation Magazine - September 2022 - 11

activities and test campaigns are also presented. Finally, the
article aims to give an insight into how to reduce the gap
between lab R&D and flight implementations by anticipating
system constraints when building these platforms. This allows
investigators to provide qualitative testing results that can
eventually have an impact in real space missions.
Current Rover Testbeds
Space robotics can be considered a niche field of engineering
in which the conditions given by the space environment present
particular constraints to the research activities conducted
in the area. Space representativeness is in a constant duel with
research in terms of cost and flexibility in the processes of
designing, manufacturing, and testing. This is mainly due to
the technologies and development tools employed in space,
which lack the mass production and community from which
other engineering fields benefit.
The space environment is harsh and remote and, therefore,
difficult to access. Restrictions come not only from the
available technology and components for space, which sometimes
can be years behind their terrestrial counterparts, but
even more drastically in the system mass and energy, which
leads to the need for highly optimized and customized systems.
One of the first questions engineers are faced with on a
space mission is whether they are capable of designing a system
that fulfills the mission requirements within the given
mass and power budgets.
Space missions are also what we call single-shot opportunities.
One cannot repair during-except for certain fixes
by software patches-or usually repeat a mission, which,
again, puts stringent requirements on system robustness
and design margins. All of these aspects eventually have a
high cost impact, limiting even more space missions or
activities related to space's access to a wider community.
Aware of these limitations, the Automation and Robotics
Section of the ESA has embarked for years on activities for
developing space robotics and, in particular, planetary rovers,
in the scope of conducting R&D of key technologies for
real space missions, such as ExoMars.
In this article, the authors aim to demonstrate how the
aforementioned constraints can be taken into account and
impact the work done in the context of research as well as
showcase this with specific prototyping activities. Therefore,
the first goal is to describe the main challenges and
design drivers in the development of laboratory planetary
rover testbeds. In this context, the article highlights how
MaRTA, the second-generation prototype, benefited from
the experience gained and lessons learned on the design
and testing of the earlier ExoTeR. Second, by providing an
overview of selected test campaigns, we demonstrate how
these platforms supported the actual ExoMars program
rover developments.
Looking at existing planetary rover testbeds, it is worth
noting that NASA's Jet Propulsion Laboratory (JPL) has led
and is performing many successful planetary exploration
missions with rovers. This is partially thanks to the
development of rover prototypes and testing done on
Earth, typically as part of the mission programs. With the
Mars Exploration Rovers (MERs) first and Curiosity later
on, the same model philosophy has ensured the provision
of a rover testbed throughout the different phases of the
development of the mission. These were used to perform
analyses of the traverse performance and predict their traversability
throughout the mission by mimicking on Earth
the apparent flight rover weight on Mars [1]. Among them,
we could highlight the Scarecrow rover, a vehicle that shares
the kinematic configuration of Curiosity and uses commercial
off-the-shelf electronics, which, for years, has provided
much useful data for Curiosity's rover operations team [2].
In addition, the NASA JPL continues working on the
development of new rover prototypes and platform configurations.
For example, the DuAxel rover for exploration in
very rough terrain, including rappelling motion, has shown
promising results for potential lunar lava tube exploration
missions [3].
The recently baptized Rosalind Franklin rover of the ExoMars
mission is the first European rover aiming to land on
Mars. Since its early conception, the ESA has been working
on the development of breadboard prototypes to analyze different
locomotion subsystems and their performance on a
Mars-like terrain [4]. Later, in cooperation with European
industrial partners, different breadboard rovers were assembled
with engineering models of the electronics, software, and
locomotion subsystems.
National space agencies around Europe have also developed
their own testbed rovers for research purposes. It is
worth mentioning the Lightweight Rover Unit developed by
the German Aerospace Center (DLR), an agile rover prototype
used to develop several software components for
autonomy [5]. The U.K. Space Agency developed the Mars
Utah Rover Field Investigation, which was used to perform
several field tests in collaboration with the Canadian Space
Agency [6]. The French Space Agency (CNES) also developed
the testbed rovers Illustrateur Autonome de Robotique
mobile pour l'Exploration Spatiale (called IARES) and Autonomous
Rover and Testbench for Exploration Missions (known
as ARTEMIS), which were used for years for the development
of the guidance, navigation, and control (GNC) software
that will eventually drive Rosalind Franklin [7].
In Asia, two testbed rovers developed by JAXA are worth
mentioning: Micro6 and Cuatro [8]. Both were conceived to
push the technology readiness level (TRL) of failure-tolerant
suspension systems and an intelligent navigation system
based on novel path-planning methods.
System Architecture
In this section, we describe the system architecture and subsystem
designs of the two ExoMars-representative laboratory
rover prototypes of the ESA's Automation and Robotics Section:
ExoTeR and MaRTA, both shown in Figure 1. The ExoTeR
rover concept was designed between 2008 and 2010, whereas
MaRTA was developed from 2017 to 2019. While both are
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IEEE Robotics & Automation Magazine - September 2022

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