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ROBOTIC PROGRAMMES AND APPLICATIONS AT ESA:
PRESENT AND PERSPECTIVES
Gianfranco Visentin
Automation and Robotics Section (TEC-MMA),
European Space Agency, P.O. box 299 Noordwijk, The Netherlands
Email:[email protected]
ABSTRACT
This paper provides an overview of the existing ESA
robotics programmes, their perspectives and the
possibility for ESA and its European partners to make
an adequate, yet significant contribution to
international space robotics endeavours.
of further study work (Phase-A) and some of its
characteristics have changed since the initial concept.
Still the robot does not to pretend to emulate human
features but tries to exploit all possible robotic
advantages. The system (see Figure 1 for reference)
features three 7-dof identical arms (a) arranged around
a body. The arms are multi-functional and may be used
as "arm" or "leg".
A systematic overview will be given of the application
scenarios in Low Earth Orbit (system servicing and
payload tending on the ISS, assembly of large
structures), in other Earth Orbits (satellite monitoring
and servicing), and for planetary exploration (Moon,
Mars, Mercury, Venus, comets, asteroids).
Wherever detailed presentations on these scenarios are
included in the iSAIRAS programme, reference will be
made to them.
The paper will also refer to the strengths of the
Research and Development (R&D) base in Europe,
derived from significant national and ESA programs
and a judicious cross-fertilisation with R&D in nonspace domains.
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CURRENT MISSION SCENARIOS
ESA’s missions containing elements of Automation
and Robotics (A&R) are (structured in the classical 3
domains):
• Low Earth Orbit: The EUROBOT robot system onboard the ISS and the TeleFoton on-board the
Foton platform for microgravity sciences
• Geostationary Servicing: The ConeXpress-Orbital
Life Extension Vehicle (CX-OLEV) satellite life
extension system
• Planetary Exploration: The Exomars and the
Sample Return missions to Mars
In the following paragraph the missions and their A&R
content are illustrated.
2
EUROBOT
At the last ISAIRAS ESA had announced a concept of
a new robotic system for the ISS. This system named
EUROBOT, was intended to help or even replace EVA
crew. In the meantime the EUROBOT has been subject
Figure 1: Two views of the present Eurobot
configuration
The EUROBOT carries a tool rack (b). Each arm may
pick-up/release wrist mounted tools (c showed as
cylindrical volumes) at selected locations on the tool
rack by means of tool exchange devices (d). These
tools may be specialised (e.g. wrench) or general
purpose (a hand tool comparable to the DLR hand 2).
EUROBOT is equipped with a lighting and imaging
head (e), allowing human compatible stereoscopic
vision, as well as optional lighting and imaging units at
the wrists (f). The robot controller is housed in the
body (g) and it is powered by a large replaceable
battery (h). An IEEE 802.11g transceiver guarantees
communication with a control station inside the space
station. EUROBOT features two main modes of
operation: Programmed mode and telemanipulation.
The first is used when EUROBOT has to perform
routine tasks that do not require involvement of a
human operator, such as relocation from one side of
the ISS to another. Whenever the task contains
Proc. of 'The 8th International Symposium on Artifical Intelligence, Robotics and Automation in Space - iSAIRAS’, Munich, Germany.
5-8 September 2005, (ESA SP-603, August 2005)
elements of unpredictability or of high dexterity, the
second mode is used.
Since EUROBOT is designed with dimensions and
kinematics compatible with human ones, it enables to
Figure 2: Telepresence dress-up for
EUROBOT. The operator wears an haptic arm
exoskeleton (ESA), a haptic hand glove
(commercial) , and a stereoscopic helmet
(commercial)
experimentation in low Earth orbit for about 15 days.
FOTONs have been flying since 1985. The design is
based on the famous Vostok spacecraft, which carried
Yuri Gagarin as the first man into space in 1961. ESA
has been participating in this type of scientific mission
for 18 years. The last three FOTONs have included a
TSU which allows:
- autonomous running of the experiments
between contacts to ground (including video
processing to measure data for closed-loopcontrol)
- Video/data compression and storage
The use of the TSU has allowed more flexible use of
the scientific payloads allowing the principal
investigators (PI) to monitor and condition the
experiment during flight from their home base through
internet connections.
The next FOTON M3 will feature a new TSU with
serial bus connections to payloads (rather than the
current point-to-point) and a ground segment
articulated on two geographically distant stations.
Smart ground station software will allow PI to
seamlessly control their payload irrespective from
which ground station is linked to the spacecraft.
use the most effective and intuitive telepresence by
means of a newly developed haptic device.
To allow effective and comfortable telepresence in the
peculiar environment of the ISS, ESA has developed
and patented a new arm exoskeleton [1]. The device,
produced in a first proof-of-concept prototype is being
further developed with focus on the control of the
actuation means.
Figure 3: The EUROBOT testbed allows a
functional breadboard of the EUROBOT to
walk and operate over mockups of modules of
the ISS.
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TELEFOTON
One important application of A&R in low Earth orbit is
support to microgravity research. The TeleScience
Support Unit (TSU) for the FOTON spacecraft is an
automation package to allow autonomous operation of
microgravity experiments on board the Russian
FOTON spacecraft. FOTON are unmanned recoverable
capsules, which are used to carry out scientific
Figure 4: The FOTON spacecraft during
integration. The "ball" hosts microgravity
experiments and the Telescience Support Unit
(silver box in the top part)
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CX-OLEV
1) a task driven design: previous satellite servicing
concepts were often too focussed on advanced
A&R and over-designed for the task. CX-OLEV
is designed to do just one operation with the
simplest technology available. This makes CXOLEV much more credible.
2) the economics of the concept: thanks to the
ConeXpress spacecraft, which can lift off with
virtually every launch of Ariane 5, the launch cost
of the servicing spacecraft is no longer
prohibitive. Furthermore the development of
some key technologies (the grasping tool, the
Rendez-Vous algorithms) has already been paid
by space Agencies
Figure 5:The CX-OLEV approaches a client
telecom satellite
Figure 6: CX-OLEV is about to insert the DLR
capture tool in the nozzle of the client. . Note
that the main structure of ConeXpress is the
payload adapter of the Ariane 5, this makes
possible CX-ORS to fly with each launch of
Ariane 5.
For many years the space robotics community has
proposed GEO servicing concepts. These were
supported by robust R&D programmes and by
demonstration missions. Unfortunately all proposals
have failed to gain support from the GEO user
community mainly because the cost/benefit ratio was
never favourable. However in the last 2 years there has
been a remarkable change. The Orbital Recovery
Group has been able to capitalise on two European
space developments (the small spacecraft ConeXpress
by ESA and the Satellite grasping tool by DLR) to
build the CX-OLEV GEO servicing spacecraft, that is
finally convincing the GEO user community.
CX-OLEV (CX-OLEV) is a spacecraft developed by
Dutchspace and others, under contract to ESA for use
by the Orbital Recovery Group.
The CX-OLEV is designed to dock to the zenith side
of a fuel-depleted GEO telecom satellite to provide 5+
more years of operational life.
The CX-OLEV mission is not new and it has been
proposed in the past in various flavours [2]. What
changes with respect to the past is:
Figure 7:Artist impression of the ExoMars
rover (top) and 1/2 scale prototype of it
(bottom)
5
EXOMARS
The ExoMars mission, to be launched in 2011, features
a descent module that will land a large (200 kg), highmobility 6-wheels rover (see Figure 7) on the surface
of Mars.
The primary objective of the ExoMars rover will be to
search for signs of life, past or present. Additional
measurements will be taken to identify potential
surface hazards for future human missions, to
determine the dis-tribution of water on Mars, to
measure the chemical composition of the surface rocks
and to deploy seismic instruments.
A demonstrator of the rover has been build by ESA
contractors (RCL) based on an innovative chassis
design, which allows overcoming isolated obstacles
twice the diameter of a wheel (see video
Exomader.mov). The final chassis configuration is not
yet frozen, however it will certainly feature the so
called wheel-walking mode.
The development of the rover is addressed in a paper in
this same conference [3].
6
2.
For mission safety reasons the SFR will require
higher locomotion performance, in terms of types
of terrain it can cope with. Compared to the
ExoMars Rover, which will transmit the results of
scientific analysis to Earth, an unrecoverable loss
of mobility for SFR means loss of the collected
samples on-board and inability to complete the
mission. In other words locomotion is much more
critical to mission success.
The above considerations, still to be confirmed in the
frame of a Phase-A study, are the base for activities
ESA is starting as part of an R&D programme for
exploration.
7
7.1
TECHNOLOGY DEVELOPMENT
Aerobots
Although aerobots are not included in any of the
approved planetary missions, ESA still performs some
R&D on them in different directions.
MARS SAMPLE RETURN
ESA, as other space Agencies has been studying a
Mars Sample Return mission for quite some time. The
studied scenario was based on a stationary lander.
Recently, through negotiation with NASA a new
scenario has emerged. Now ESA is considering the
participation to a NASA-led international sample
return mission in 2016, in which ESA’s contribution
would consist of a Sample Fetching Rover (SFR). The
contribution of the SFR will allow ESA to re-use large
parts of the ExoMars Rover development, however it is
already clear that while ExoMars Rover and SFR The
configuration of the mission is still to be studied
however the following assumptions can be made:
The SFR rover will be delivered to the surface with a
descent module separated from the module hosting a
Mars Ascent Vehicle (MAV). Current landing
technology allows to deliver a lander with a precision
in the order of 100 km. Even considering that in the
near future such precision may go down of 1 order of
magnitude, it still means that the ascent vehicle and the
rover may land some 20 km apart.
The MAV will have to spend a fairly short time on the
Mars surface not to increase chances of
malfunctioning, still allowing enough time for the
collection of sufficiently diverse samples.
From these assumptions the following considerations
may be derived:
1. The SFR, compared to the ExoMars Rover, will
require a longer range in combination with shorter
duration of surface operations (hence higher
average speed, hence higher locomotion speed
and/or higher level of navigation autonomy)
Figure 8: 3D reconstruction and camera
calibration for one of the aerial photo
sequences
taken
by
the
hardware
demonstrator of the ILP. The pyramids show
the reconstructed position of the camera when
a picture was taken.
One field of development is Autonomy of operation.
ESA has developed two different prototypes of an
Imaging and Localization Package (ILP) for a Martian
balloon. The package allows (see Figure 8):
- Optimal acquisition of images to reconstruct
accurate models of the surface of the explored
planet.
- Accurate localization of the balloon with
respect to Martian surface
The package, uses computer vision techniques, to:
- Acquire and store images/3D models of the
surface at various resolutions avoiding waste
of storage memory
-
Provide continuous estimate of the position
(longitude, latitude and height) of the aerobot
as well as its motion with respect to the
surface
- Decide on the base of the communication
budget, of the morphology of the surface and
of the information content of the images,
which
images
at
which
resolution
/compression need to be transmitted to Earth.
The Structure and Motion computer vision technology
produced in the frame of the ILP development has
found application in aerial mapping of archaeological
sites.
Autonomy is also part of another R&D activity in
which a prototype of small Martian airplane is being
developed.
Figure 10: The first prototype of the SkySailor
airframe, made to check flight worthiness
Figure 9: Artist's impression of the SkySailor
motor glider
The airplane (actually a motorglider), named
SkySailor, is designed to guarantee continuous flight
over prolonged time (several days) in the Martian
atmosphere by just using solar energy.
The airplane uses ultra-lightweight materials, high
efficiency solar cells (integrated in the wing structure)
and high-density Lithium-Polymer batteries to achieve
the very difficult balance between energy
acquisition/storage and total mass.
The work has shown that although continuous flight on
Mars is not yet possible, with the present trend of
development of batteries it may become possible in the
next 5 years.
The last field of development in Aerobots is the one
which deals with collection of scientific data. In the
DALOMIS activity ESA targets the development of
the data transmission and localization system for
swarms of microprobes to collect atmospheric data
while plunging in the Venerean atmosphere. In the
preliminary mission design, the probes are released by
a balloon. The balloon is designed to have a nominal
lifetime of about 30 days at an average floating altitude
of 55 km. Each probe has a mass of less then 120 g.
The microprobes are released in clutches over a period
of several days, while the balloon drifts over a range of
latitudes. The microprobes record in-situ measurement
profiles of pressure, temperature, wind speeds and light
flux at vertical resolutions of 100 m during their drop.
The development of the DALOMIS system is
illustrated in a paper in this same conference [4].
7.2
Underground Mobility
Access to the underground is believed to be capital for
the in-situ analysis and collection of pristine soil/rock
samples not corrupted by the surface weathering
processes.
The EXOMARS and Mars Sample Return missions
will feature multi-stem drills, pioneered by the MIRO
driller [5] (see Figure 11), capable of acquiring
samples 2 meters down in the ground.
Guided Mole development, illustrated in a dedicated
paper in this same conference [7] had to solve complex
problems such us drilling efficiently with limited
power, disposing of large quantities of debris,
guaranteeing vertical drilling without a structural
connection to the surface.
7.3
Alternative mobility
The surface of certain cliffs on Earth provides
immediate access to the layers, stratified over time,
which make the crust.
Figure 11: The MIRO driller, first 2 m multistem driller
Multi stem drillers are the right solution for shallow
depths, however for reaching deeper they present
problems that are too difficult to solve within the
constraint of space missions.
First of all, drillers of this type require a cumulated
length of drill pipes as long as the depth reached,
which translates into a large mass allocated to drill
pipes.
Figure 12: Assembly view of the ESA Guided
Mole. The system is articulated in 3 bodies
(boring head on the left, middle section and
tail on the right) connected by 1 actuated and
1 passive joints.
Furthermore friction increases with depth. Hence for
any dept larger than few meters, lining of the well is
required in order to contain the power needed by the
drill head rotation and by the debris disposal means.
Lining pipes introduce additional mass penalty.
An alternative class of Subsurface Explorers or Moles
can being considered to serve as deep drillers. These
systems eliminate the rigid connection between the
surface and the drilling head by allowing the latter to
move independently.
ESA, after promoting the use of moles in small
missions [6] is currently developing a prototype of a
guided Mole capable of transporting 10 cm3 of
scientific instruments to a depth of 100 metres. The
Figure 13: The prototype of the ARAMIES
rover
Hence by exploring certain cliffs on Mars it is believed
that a great deal of information on the history of the
planet could be gathered.
Furthermore orbital imaging of the Martian surface
(MOC image PIA01032) suggests that water resources
and water-rich material may be concentrated near cliff
bases.
Accessing the surface of cliffs or the bottom of gullies
is well beyond the capabilities of rovers similar to the
EXOMARS and in general to any system based on
wheels.
ESA has initiated the ARAMIES project to develop a
walking system for extremely difficult terrain,
especially steep and uneven slopes.
To explore the close-to-vertical walls of the cliffs
ARAMIES will walk down them attached by means of
a tether to a large rover (similar to the EXOMARS)
stationed on top of the cliff.
The ARAMIES, activity [8] funded by ESA and DLR
and run by the Bremen University has produced so far
a prototype (see Figure 13), which will enable testing
and tuning of bio-inspired walking algorithms.
These algorithms are perceived to be the best means to
control the complex locomotion system (4 legs with 7
d.o.f.), with minimal computational load and best
performance.
8
CONCLUSIONS
The present paper has provided an overview of the
activities being pursued at the European Space Agency
in the field of Automation and Robotics, with emphasis
given to new or recent developments. Some long
running activities (e.g. the ISS European Robot Arm,
the Columbus facilities for microgravity investigation,
the Nanokhod microrover) have not been mentioned as
already addressed in previous ISAIRAS conferences.
Furthermore also for some of the activities here
addressed the description has been limited to the scope
of introducing
papers submitted in this same
conference.
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