Mars Express is a space exploration mission being conducted
by the European Space
Agency
(ESA). The Mars Express mission is exploring
the planet
Mars, and is the first planetary
mission attempted by the agency. "Express" originally referred to
the speed and efficiency with which the
spacecraft was designed and built. However
"Express" also describes the spacecraft's relatively short
interplanetary voyage, a result of being launched when the orbits
of Earth and Mars brought them closer than they had been in about
60,000 years.
Mars Express consists of two parts, the
Mars Express
Orbiter and the
Beagle 2, a
lander designed to perform
exobiology and geochemistry research.
Although the lander failed to land safely on the Martian surface,
the Orbiter has been successfully performing scientific
measurements since early 2004, namely, high-resolution imaging and
mineralogical mapping of the surface, radar sounding of the
subsurface structure down to the permafrost, precise determination
of the atmospheric circulation and composition, and study of the
interaction of the
atmosphere
with the
interplanetary
medium.
Due to the valuable science return and the highly flexible mission
profile,
Mars Express has been granted three mission
extensions. The latest until December 31, 2009.
Some of the instruments on the orbiter, including the camera
systems and some spectrometers, reuse designs from the failed
launch of the Russian
Mars 96 mission in
1996 (European countries had provided much of the instrumentation
and financing for that unsuccessful mission). The basic design of
Mars Express is based on ESA's
Rosetta mission, on which considerable
sum was spent on development. The same design was also used for the
Venus Express mission in
order to increase reliability and reduce development cost and
time.
Mission profile and timeline overview
Mission overview
The Mars Express mission is dedicated to the orbital (and
originally in-situ) study of the interior, subsurface, surface and
atmosphere, and environment of the planet Mars.The scientific
objectives of the Mars Express mission represent an attempt to
fulfil in part the lost scientific goals of the Russian Mars-96
mission, complemented by exobiology research with Beagle-2. Mars
exploration is crucial for a better understanding of the Earth from
the perspective of comparative planetology.
The spacecraft originally carried seven scientific instruments, a
small lander, a lander relay and a Visual Monitoring Camera, all
designed to contribute to solving the mystery of Mars' missing
water. All of the instruments take measurements of the surface,
atmosphere and interplanetary media, from the main spacecraft in
polar orbit, which will allow it to gradually cover the whole
planet.
The overall Mars Express budget excluding the lander is
€150 million (roughly
US$185 million).
Spacecraft construction
The prime contractor for the construction of Mars Express Orbiter
was
EADS Astrium
Satellites.
Mission preparation
In the years preceding the launch of a spacecraft numerous teams of
experts distributed over the contributing companies and
organisations prepared the space and ground segments. Each of these
teams focussed on the area of its responsibility and interfacing as
required. A major additional requirement raised for the Launch and
Early Orbit Phase (LEOP) and all critical operational phases was
that it was not enough merely to interface; the teams had to be
integrated into one Mission Control Team. All the different experts
had to work together in an operational environment and the
interaction and interfaces between all elements of the system
(software, hardware and human) had to run smoothly for this to
happen:
- The flight operations procedures had to be written and
validated down to the smallest detail;
- The control system had to be validated;
- System Validation Tests (SVTs) with the satellite had to be
performed to demonstrate the correct interfacing of the ground and
space segments.
- Mission Readiness Test with the Ground Stations had to be
performed;
- A Simulations Campaign was run.
Launch
The spacecraft was launched on June 2, 2003 at 23:45 local time
(17:45 UT, 1:45 p.m.
EDT) from Baikonur Cosmodrome
in Kazakhstan
, using a Soyuz-FG/Fregat rocket. The Mars Express and Fregat
booster were initially put into a 200 km Earth
parking orbit, then the Fregat was fired again
at 19:14 UT to put the spacecraft into a Mars transfer orbit. The
Fregat and Mars Express separated at approximately 19:17 UT. The
solar panels were then deployed and a
trajectory correction maneuver was performed on June 4 to aim Mars
Express towards Mars and allow the Fregat booster to coast into
interplanetary space.
Near earth commissioning phase
The Near Earth Commissioning phase extended from the separation of
the spacecraft from the launcher upper stage until the completion
of the initial check out of the orbiter and payload. It included
the solar array deployment, the initial attitude acquisition, the
declamping of the Beagle-2 spin-up mechanism, the injection error
correction manoeuvre and the first commissioning of the spacecraft
and payload (final commissioning of payload took place after Mars
Orbit Insertion). The payload was checked out one instrument at a
time. This phase lasted about one month.
The interplanetary cruise phase
This five month phase lasted from the end of the Near Earth
Commissioning phase until one month prior to the Mars capture
manoeuvre and included trajectory correction manoeuvres and
payloads calibration. The payload was mostly switched off during
the cruise phase, with the exception of some intermediate
check-outs.Although it was originally meant to be a "quiet cruise"
phase, It soon became obvious that this "cruise" would be indeed
very busy. There were star Tracker problems, a power wiring
problem, extra manoeuvres, and on the 28th of October, the
spacecraft was hit by one of the largest
solar flares ever recorded.
Lander jettison
The
Beagle 2 lander was released on
December 19 at 8:31 UTC (9:31 CET) on a ballistic cruise towards
the surface. It entered Mars' atmosphere on the morning of December
25. Landing was expected to occur at about 02:45 UT on December 25
(9:45 p.m. EST December 24).
However, after repeated attempts to contact
the lander failed using the Mars Express craft and the NASA
Mars Odyssey orbiter, it was declared lost on
February 6, 2004, by the Beagle 2 Management Board. On
February 11, ESA announced an inquiry would be held into the
failure of
Beagle 2.
Orbit insertion
Mars Express arrived at Mars after a 400 million km journey and
course corrections in September and in December 2003.
On December 20 Mars Express fired a short thruster burst to put it
into position to orbit the planet. The Mars Express Orbiter then
fired its main engine and went into a highly elliptical
initial-capture orbit of 250 km × 150,000 km with an
inclination of 25 degrees on December 25 at 03:00 UT (10:00 p.m.,
December 24 EST).
First evaluation of the orbital insertion showed that the orbiter
had reached its first milestone at Mars. The orbit was later
adjusted by four more main engine firings to the desired
259 km × 11,560 km near-polar (86 degree inclination)
orbit with a period of 7.5 hours. Near
periapsis the top deck is pointed down towards the
Martian surface and near
apoapsis the high
gain antenna will be pointed towards Earth for uplink and
downlink.
After 100 days the apoapsis was lowered to 10,107 km and
periapsis raised to 298 km to give an orbital period of 6.7
hours.
MARSIS deployment
On May 4, 2005,
Mars Express deployed the first of its two
20-metre-long
radar booms for its
MARSIS (Mars Advanced Radar for Subsurface and
Ionosphere Sounding) experiment. At first the boom didn't lock
fully into place; however, exposing it to sunlight for a few
minutes on May 10 fixed the glitch. The second 20 m boom was
successfully deployed on June 14. Both 20 m booms were needed to
create a 40 m
dipole antenna for
MARSIS to work; a less crucial 7-meter-long monopole antenna was
deployed on June 17. The radar booms were originally scheduled to
be deployed in April 2004, but this was delayed out of fear that
the deployment could damage the spacecraft through a whiplash
effect. Due to the delay it was decided to split the four week
commissioning phase in two parts, with two weeks running up to July
4 and another two weeks in December 2005.
The deployment of the booms was a critical and highly complex task
requiring effective inter-agency cooperation ESA, NASA, Industry
and public Universities.
Nominal science observations began during July 2005. (For more
info, see ,, and
ESA Portal - Mars Express radar ready to work ESA
press release.)
Operations of the spacecraft
Operations
for Mars Express are carried out by a multinational team of
engineers from ESA’s Operation Centre (ESOC
) in Darmstadt
. The team began preparations for the mission
about 3 to 4 years prior to the actual launch. This involved
preparing the ground segment and the operational procedures for the
whole mission.
The Mission Control Team is composed of the Flight Control Team,
Flight Dynamics Team, Ground Operations Managers, Software Support
and Ground Facilities Engineers. All of these are located at ESOC
but there are additionally external teams, such as the Project and
Industry Support teams, who designed and built the spacecraft.The
Flight Control Team consists of:
- The Spacecraft Operations Manager
- Eight Operations Engineers
- Three Mission Planners
- One Spacecraft Analyst
- Five Spacecraft controllers
The team build-up, headed by the Spacecraft Operations Manager,
started about 4 years before launch . He was required to recruit a
suitable team of engineers that could handle the varying tasks
involved in the mission. For Mars Express the engineers came from
various other missions. Most of them had been involved with Earth
orbiting satellites.
Routine phase: Science return
Since orbit insertion Mars Express has been progressively
fulfilling its original scientific goals. Nominally the spacecraft
points to Mars while acquiring science and then slews to
earth-pointing to downlink the data, although some instruments like
Marsis or Radio Science might be operated while spacecraft is
earth-pointing.
Mars Express Spacecraft Orbiter and subsystems
Structure
The Mars Express Orbiter is a cube-shaped spacecraft with two
solar panel wings extending from
opposite sides. The launch mass of 1123 kg includes a main bus
with 113 kg of payload, the 60 kg lander, and 457 kg
of propellant. The main body is 1.5 m × 1.8 m × 1.4 m in size, with
an aluminium honeycomb structure covered by an aluminum skin. The
solar panels measure about 12 m tip-to-tip. Two 20 m long wire
dipole antennas extend from opposite
side faces perpendicular to the solar panels as part of the radar
sounder.
Propulsion
The Soyuz/Fregat launcher provided most of the thrust Mars Express
needed to reach Mars. The final stage of the Fregat was jettisoned
once the probe was safely on a course for Mars. The spacecraft's
on-board means of propulsion was used to slow the probe for Mars
orbit insertion and subsequently for orbit corrections.
The body is built around the main propulsion system, which consists
of a
bipropellant 400
N main engine. The two 267-liter propellant
tanks have a total capacity of 595 kg. Approximately
370 kg are needed for the nominal mission. Pressurized helium
from a 35 liter tank is used to force fuel into the engine.
Trajectory corrections will be made using a set of eight 10 N
thrusters, one attached to each corner of the spacecraft bus. The
spacecraft configuration is optimized for a Soyuz/Fregat, and was
fully compatible with a
Delta II launch
vehicle.
Power
Spacecraft power is provided by the solar panels which contain
11.42 square meters of silicon cells. The originally planned power
was to be 660
W at 1.5
AU but a faulty connection has reduced the
amount of power available by 30%, to about 460 W. This loss of
power is not expected to significantly impact the science return of
the mission. Power is stored in three
lithium-ion batteries with a total
capacity of 64.8 Ah for use during eclipses. The power is fully
regulated at 28
V. During routine phase, the
spacecraft's power consumption is in the interval 450 W - 550
W.
Avionics
Attitude control (3-axis stabilization) is achieved using two
3-axis inertial measurement units, a set of two
star cameras and two
Sun
sensors,
gyroscopes,
accelerometers, and four 12 N·m·s
reaction wheels. Pointing accuracy is 0.04
degree with respect to the inertial reference frame and 0.8 degree
with respect to the Mars orbital frame. Three on-board systems help
Mars Express maintain a very precise pointing accuracy, which is
essential to allow the spacecraft to communicate with a 35-metre
and 70-metre dish on Earth up to 400 million kilometres away.
Communications
The communications subsystem is composed of 3 antennas: A 1.7 m
diameter parabolic dish
high-gain
antenna and two omnidirectional antennas. The first one provide
links (Telecommands uplink and Telemetry downlink) in both
X-band (7.1 GHz) and
S-band (2.1 GHz) and is used during nominal
science phase around Mars. The low gain antennas are used during
Launch and early operations to Mars and for eventual contingencies
once in orbit.Two Mars lander relay UHF antennas are mounted on the
top face for communication with the Beagle 2.
Earth Stations
Although
communications with Earth were originally scheduled to take place
with the ESA 35-meter wide Ground Station in New Norcia (Australia)
New Norcia Station, the mission
profile of progressive enhancement and science return flexibility
have triggered the use of the newest ESA ESTRACK
Ground
Station in Cebreros Station,
Madrid
, Spain
.
In addition, further agreements with NASA
Deep Space Network have made possible the
use of American stations for nominal mission planning, thus
increasing complexity but with a clear positive impact in
scientific returns.
This inter-agency cooperation has proven effective, flexible and
enriching for both sides. On the technical side, it has been made
possible (among other reasons) thanks to the adoption of both
Agencies of the Standards for Space Communications defined in
CCSDS
Thermal
Thermal control is maintained through the use of radiators,
multi-layer insulation, and
actively controlled heaters. The spacecraft must provide a benign
environment for the instruments and on-board equipment. Two
instruments, PFS and OMEGA, have infrared detectors that need to be
kept at very low temperatures (about -180 °C). The sensors on the
camera (HRSC) also need to be kept cool. But the rest of the
instruments and on-board equipment function best at room
temperatures (10-20 °C).
The spacecraft is covered in gold-plated aluminium-tin alloy
thermal blankets to maintain a temperature of 10-20 °C inside the
spacecraft. The instruments that operate at low temperatures to be
kept cold are thermally insulated from this relatively high
internal temperature, and emit excess heat into space using
attached radiators.
Control Unit and Data storage
The spacecraft is run by two Control and Data management Units with
12 gigabits of solid state mass memory for storage of data and
housekeeping information for transmission. The on-board computers
control all aspects of the spacecraft functioning including
switching instruments on and off, assessing the spacecraft
orientation in space and issuing commands to change it.
Another key aspect of the Mars Express mission is the Mars Express
AI Tool (MEXAR2). The
primary purpose of the AI tool is the scheduling of when to
download various parts of the collected scientific data back to
Earth, a process which used to take ground
controllers a significant amount of time. The new AI tool saves
operator time, optimizes
bandwidth use on the
DSN, prevents data loss, and allows
better use of the DSN for other space operations as well. The AI
decides how to manage the spacecraft's 12 gigbits of storage
memory, when the DSN will be available and not be in use by another
mission, how to make the best use of the DSN bandwidth allocated to
it, and whenthe spacecraft will be oriented properly to transmit
back to Earth.
Lander
The
Beagle 2 lander objectives
were to characterize the landing site geology, mineralogy, and
geochemistry, the physical properties of the atmosphere and surface
layers, collect data on Martian meteorology and climatology, and
search for possible signatures of life. However, the landing
attempt was unsuccessful and the lander was declared lost. A
Commission of Inquiry on Beagle 2
identified four possible causes, including insufficiently strong
airbags and problems with parts of the landing system colliding,
but was unable to reach any firm conclusions.
Mars Express instruments
The scientific objectives of the Mars Express Payload are to obtain
global high-resolution photo-geology (10 m resolution),
mineralogical mapping (100 m resolution) and mapping of the
atmospheric composition, study the subsurface structure, the global
atmospheric circulation, and the interaction between the atmosphere
and the subsurface, and the atmosphere and the interplanetary
medium. The total mass budgeted for the science payload is
116 kg.
- Visible and Infrared Mineralogical Mapping Spectrometer
(OMEGA)(Observatoire pour la Minéralogie, l'Eau, les
Glaces et l'Activité) - France - Determines mineral composition of
the surface up to 100 m resolution. Is mounted inside pointing out
the top face. Instrument mass: 28.6 kg
- Ultraviolet and Infrared Atmospheric Spectrometer
(SPICAM) - France - Assesses elemental composition of the
atmosphere. Is mounted inside pointing out the top face. Instrument
mass: 4.7 kg
- Sub-Surface Sounding Radar Altimeter (MARSIS) - Italy - A radar altimeter used to assess composition of
sub-surface aimed at search for frozen water. Is mounted in the
body and is nadir pointing, and also incorporates the two 20 m
antennas. Instrument mass: 13.7 kg
- Planetary Fourier Spectrometer (PFS) - Italy -
Makes observations of atmospheric temperature and pressure
(observations suspended in September 2005). Is mounted inside
pointing out the top face. , currently working. Instrument mass:
30.8 kg
- Analyzer of Space Plasmas and Energetic Atoms (
ASPERA) - Sweden - Investigates interactions
between upper atmosphere and solar wind. Is mounted on the top
face. Instrument mass: 7.9 kg
- High Resolution Stereo Camera (HRSC)- Germany
- Produces color images with up to 2 m resolution. Is mounted
inside the spacecraft body, aimed through the top face of the
spacecraft, which is nadir pointing during Mars operations.
Instrument mass: 20.4 kg
- Mars Express Lander Communications (MELACOM) -
UK - Allows Mars Express to act as a communication relay for
landers on the Martian surface. (Has been tested with Mars Exploration Rovers, and was
used to support the landing of NASA's Phoenix mission)
- Mars Radio Science Experiment (MRSE) - Uses
radio signals to investigate atmosphere, surface, subsurface,
gravity and solar corona density during solar conjunctions. It uses
the communications subsystem itself.
- A small camera to monitor the lander ejection, VMC.
- More on Payload
Scientific discoveries and important events
For more than 5000 orbits, Mars Express Payload instruments have
been nominally and regularly operated.
HRSC camera has been consistently mapping the Martian surface with
unprecedented resolution and has taken dozens of breath-taking
pictures.
2004
- : ESA announced the discovery of water ice in the South Polar
ice cap, using data taken on January 18 with the OMEGA
instrument.
- : Mars Express Orbiter reaches final science orbit around
Mars.
- : Orbiter detects polar ice caps that contain 85% highly
carbon dioxide (CO2) ice
and 15% water ice.
- : A press release announces that the orbiter has detected
methane in the Martian atmosphere. Although
the amount is small, about 10 parts in a thousand million, it has
excited scientists ask about its source. Since methane is removed
from the Martian "air" very fast, there needs to be a current
source that releases fresh methane still today. Because one of the
possible sources could be microbial life, it is planned to verify
the reliability of this data and especially watch for difference in
the concentration in various places on Mars. It is hoped that the
source of this gas can be discovered by finding its location of
release.
- : ESA announced that the deployment of the boom carrying the
radar based MARSIS antenna was delayed. It described concerns with
the motion of the boom during deployment, which can cause the
spacecraft to be struck by elements of it. Further investigations
are planned to make sure that this will not happen.
- : Scientists working with the PFS instrument announced that
they tentatively discovered the spectral features of the compound
ammonia in the Martian atmosphere. Just like
methane discovered earlier (see above), ammonia breaks down rapidly
in Mars' atmosphere and needs to be constantly replenished. This
points towards the existence of active life or geological activity;
two contending phenomena whose presence so far have remained
undetected.
2005
- In
2005, ESA
scientists
reported that the OMEGA (Visible and Infrared Mineralogical Mapping
Spectrometer)(Observatoire pour la Minéralogie, l'Eau, les Glaces
et l'Activité) instrument data indicates the presence of hydrated
sulphates, silicates and various rock-forming minerals.
- : The delayed deployment of the MARSIS antenna has been given a
green light by ESA . It is planned to take place in early May
2005.
- : The first boom of the MARSIS antenna was successfully
deployed . At first, there was no indication of any problems, but
later it was discovered that one segment of the boom did not lock .
The deployment of the second boom was delayed to allow for further
analysis of the problem.
- : Using the Sun's heat to expand the
segments of the MARSIS antenna, the last segment locked in
successfully.
- : The second boom was deployed, and on June 16 ESA announced it
was a success .
- : ESA announces that MARSIS is fully operational and will soon
begin acquiring data. This comes after the deployment of the third
boom on June 17, and a successful transmission test on June
19.
2006
- : ESA's Mars Express High Resolution Stereo Camera (HRSC) has
obtained images of the Cydonia region, the location of the famous
"Face on Mars". The massif became
famous in a photo taken in 1976 by the American Viking 1 Orbiter.
The image recorded with a ground resolution of approximately 13.7
metres per pixel.
- : The Mars Express spacecraft has emerged from an unusually
demanding eclipse season introducing a special, ultra-low-power
mode nicknamed 'Sumo' - an innovative configuration aimed at saving
the power necessary to ensure spacecraft survival.
This mode was developed through tight teamwork between ESOC mission
controllers, principal investigators, industry and mission
management.
- : In October 2006 the Mars Express spacecraft has encountered a
superior solar conjunction (alignment of Earth-Sun-Mars Express).
The angle Sun-Earth-MEX reached a minimum on 23-Oct at 0.39 deg. at
a distance of 2.66 AU. Operational measures were undertaken to
minimize the impact of the link degradation, since the higher
density of electrons in the solar plasma heavily impacts the radio
frequency signal. More on
- :
Following the loss of NASA JPL
Mars
spacecraft Mars Global Surveyor
(MGS), Mars Express team was requested to perform actions in the
hopes of visually identifyng the American spacecraft. Based
on last ephemeris of MGS provided by JPL,
the on-board high definition HRSC camera swept a region of the MGS
orbit. Two attempts were made to find the craft, both
unsuccessful.
2007
- : First agreements with NASA-SPL undertaken for the support of
Mars Express on the landing of the American lander Phoenix in May 2008
- : The small camera VMC (used only once to monitor the lander
ejection) has been recommissioned and first steps had been taken to
offer students the possibility to participate in a campaign
"Command Mars Express Spacecraft and take your own picture of
Mars". Details to come.
- : As result of the important science return, the Science
Program Committee (SPC) has granted a mission extension until May
2009 to Mars Express.
- : The High Resolution Stereo Camera (HRSC) has produced
dramatic images of key tectonic features in Aeolis Mensae.
2008
The Mars Express Team was the winner of the
Sir Arthur Clarke Award for Best
Team Achievement.
2009
- : The ESA's Science Programme Committee has extended the
operations of Mars Express until December 31, 2009.
See also
External links
Payload Principal Investigators Links
- HRSC FU Berlin
- MARSIS Uni Roma "La Sapienza"
- PFS IFSI/INAF
- SPICAM
- OMEGA Institut Astrophysique Spatial
- MELACOM Qinetiq
- MRSE Uni Köln
- ASPERA
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