Mars Express
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This article documents a current spaceflight. Information may change rapidly as the mission progresses. |
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Mars Express is a Mars exploration mission of the European Space Agency and the first planetary mission attempted by the agency. "Express" originally referred to the spacecraft's relatively short interplanetary voyage, a result of being launched when the orbits of Earth and Mars brought them closer than ever before in recorded history (about 60,000 years). However "express" also describes the speed and efficiency with which the spacecraft was designed and built.
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 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.
Its because of these valuable science return and the highly flexible mission profile that Mars Express has been granted two consecutive mission extensions until (at least) May 2009.
Some of the instruments on the orbiter, including the camera systems and some spectrometers, are inherited of those lost in 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 money was spent developing the spacecraft. The same design was also used for the Venus Express mission in order to increase reliability and reduce development cost and time.
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[edit] Mission profile and timeline overview
[edit] Mission overview
The Mars Express mission is dedicated to the orbital and possibly 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 fulfill 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 will carry seven scientific instruments, a small lander, a lander relay and a Visual Monitoring Camera, all of which will contribute to solving the mystery of Mars missing water. All of the instruments will 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).
[edit] Spacecraft construction
The prime for the construction of Mars Express Orbiter was EADS Astrium Satellites.
[edit] Mission preparation
In the years preceding the launch of a spacecraft numerous teams of experts distributed over the contributing companies and organisations are preparing the space and ground segments. Each of these teams is focusing on the area of its responsibility and is interfacing as required. A major additional requirement is raised for the Launch and Early Orbit Phase (LEOP) and all critical operational phases: interfacing is not enough, integrating the teams into one Mission Control Team is a must. All the different experts shall work together in an operational environment and the interaction and interfaces between all elements of the system (software, hardware and human) have to run smoothly for this to happen:
- The flight operations procedures have to be written and validated down to the smallest detail;
- The control system has to be validated;
- System Validation Tests (SVTs) with the satellite must be performed to demonstrate the correct interfacing of the ground and space segments.
- Mission Readiness Test with the Ground Stations have to be performed;
- A Simulations Campaign is run.
[edit] Launch
The spacecraft was launched on June 2, 2003 from Baikonur Cosmodrome in Kazakhstan, using a Soyuz-Fregat rocket, and began its inter-planetary voyage.
Launch took place on a Soyuz/Fregat from Baikonur Cosmodrome on June 2 2003 at 23:45 local time (17:45 UT, 1:45 p.m. EDT), with the Mars Express and Fregat booster put into a 200 km Earth parking orbit. The Fregat was fired again at 19:14 UT to put the spacecraft into a Mars transfer orbit, and the Fregat and Mars Express separated at approximately 19:17 UT. The solar panels have been 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.
[edit] Near earth commissioning phase
The Near Earth Commissioning phase extends 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 includes 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 takes place after Mars Orbit Insertion). The payload are checked out one instrument at a time. This phase lasts about 1 month.
[edit] The interplanetary cruise phase
This phase lasts from the end of the Near Earth Commissioning phase until one month prior to the Mars capture manoeuvre. It includes trajectory correction manoeuvres and payloads calibration. The payload is mostly switched off during the cruise phase, with the exception of some intermediate check-outs. This phase lasts about 5 months. Although it was originally meant to be a "quiet cruise" phase, It soon became obvious that this "cruise" would be indeed very busy. Star Tracker problems, power wiring problem, extra manoeuvres, and on the 28th of October, the Spacecraft was hit by one of the largest Solar Flares ever recorded. More on this, consult "published papers"at the bottom of the article.
[edit] 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. 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).
The Beagle 2 lander was supposed to coast for five days after release and enter the martian atmosphere on the morning of 25 December. Landing was expected to occur at about 02:45 UT on 25 December (9:45 p.m. EST 24 December).
After several fruitless contact attempts by Mars Express and NASA Mars Odyssey Orbiter the lander was declared lost.
[edit] Orbit insertion
Mars Express arrived at Mars after a 400 million km journey and a course correction in September and in December 2003.
The orbiter entered Mars orbit on December 25, 2003, and Beagle 2 entered Mars' atmosphere the same day. After repeated attempts to contact the lander failed, 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.
First evaluation of the orbital insertion showed that the orbiter 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 has been lowered to 10,107 km and periapsis has been raised to 298 km to give an orbital period of 6.7 hours.
[edit] 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 have been a critical and high complex task and has shown the efficiency of interagency cooperation ESA, NASA, Industry and public Universities Nominal science observations began during July 2005. (For more info, see [1], [2], and ESA press release.)
[edit] Operations of the spacecraft
Operations for Mars Express are carried out by a mulitnational 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 comprised 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 Analysts
- Five Spacecraft controllers
The team build-up started about 4 years before launch headed by the Spacecraft Operations Manager. 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. Mainly engineers previously involved with Earth orbiting satellites.
[edit] 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 too while spacecraft is earth-pointing. Refer to "scientific discoveries" bullet down the article
[edit] Mars Express Spacecraft Orbiter and subsystems
[edit] Structural
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.
[edit] Propulsion
Most of the energy needed to propel Mars Express from Earth to Mars was provided by the four-stage Soyuz/Fregat launcher. The Fregat upper stage separated from the spacecraft after placing it on a Mars-bound trajectory. The spacecraft used its on-board means of propulsion solely for orbit corrections and to slow the spacecraft down for Mars orbit insertion.
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.
[edit] 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 A/h 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.
[edit] 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.
[edit] 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.
[edit] Earth Stations
Although communication with the Earth were originally scheduled to take place with ESA 34 meters diameter Ground Station in New Norcia (Australia) New Norcia Station, the mission profile 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 made possible the use of American stations to the nominal mission planning, thus increasing complexity but with a clear positive impact in science return.
This cooperation inter-agencies has been proven effective, flexible and both-sided enriching. In 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
[edit] 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 encapsulated in thermal blankets made from gold-plated aluminium-tin alloy, to keep the interior at 10-20°C. The instruments that need to be kept cold are thermally insulated from the warm interior of the spacecraft and attached to radiators that lose heat to space, which is very cold (about -270°C).
[edit] Control Unit and Data storage
The spacecraft is run by two Control and Data management Units with a 10 gigabit 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.
[edit] 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. An underdimension on the parachuting device had been deemed as plausible cause of the loss.
[edit] 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.[1]
- 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.
- Ultraviolet and Infrared Atmospheric Spectrometer (SPICAM) - France - Assesses elemental composition of the atmosphere. Is mounted inside pointing out the top face.
- 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.
- 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. [3], currently working)
- Energetic Neutral Atoms Analyser (ASPERA) - Sweden - Investigates interactions between upper atmosphere and solar wind. Is mounted on the top face.
- 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.
- Mars Express Lander Communications (MELACOM) - UK - Allows Mars Express to act as a communication relay for landers on the Martian surface.
- Mars Radio Science Experiment (Mars) - 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 [4]
[edit] Scientific discoveries and important events
For more than 4000 orbits, Mars Express Payload instruments have been nominally and regularly operated.
HRSC camera has been stubbornly mapping the Martian surface with unprecedented resolution and has taken dozens of breath-taking pictures.
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 Fourier spectrometer has detected methane in the atmosphere coming from areas near the equator with subsurface ice, a very important discovery indicating either some form of active vulcanism or subsurface microorganisms.[2]
In November 2005, with just a few months of measurements having been taken thus far, ESA released data from MARSIS which included buried impact craters, and hints of the presence of underground water-ice.
[edit] 2004
- January 23
- ESA announced the discovery of water ice in the South Polar ice cap, using data taken on January 18 with the OMEGA instrument.
- January 28
- Mars Express Orbiter reaches final science orbit around Mars.
- March 30
- 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.
- April 28
- 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.
- July 15
- 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. [5]
[edit] 2005
These image, taken by the High Resolution Stereo Camera (HRSC), show a patch of water ice sitting on the floor of an unnamed crater near the Martian north pole. [12]
[edit] 2006
ESA's Mars Express High Resolution Stereo Camera (HRSC) has obtained images of the Cydonia region, site 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. [13]
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. [14]
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 [15]
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.
[edit] 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. [16]
[edit] See also
[edit] External links
[edit] Payload Principal Investigators Links
- HRSC FU Berlin [17]
- MARSIS Uni Roma "La Sapienza" [18]
- PFS IFSI/INAF [19]
- SPICAM
- OMEGA Institut Astrophysique Spatial [20]
- MELACOM Qinetiq [21]
- RSE Uni Köln [22]
- ASPERA [23]
[edit] Published papers on Operations
The Flight Control Team (FCT) in charged of operating Mars Express has encounter and solved countless engineering problems derived from the challenging task of maintenance and explotation of a Spacecraft in Orbit around Mars. The following papers published by the FCT gather invaluable expertise gained during the operational phase of the mission:
- Image:Mars Express Orbit Insertion, a first success in Interplanetary Europe.pdf
- Image:Deployment of the MARSIS Radar Antennas on MEX.pdf
- Image:From Mission Concept to Mars Orbit.pdf
- Image:Mars Express Power Subsystem In flight Experience.pdf
- Image:Mission Planning Experience Gained from the Mars Express Mission.pdf
- Image:File transfer, Mass Memory and Mission Time Line – providing spacecraft remote commanding at Mars.pdf
- Image:Flying Mars Express – A Day in the Cockpit.pdf
- Image:MARS EXPRESS OPERATIONAL CHALLENGES AND FIRST RESULTS.pdf
- Image:MEX science data - from the instrument to the PIs.pdf
- Image:Planning Science Data Return of Mars Express with Support of Artificial Intelligence.pdf
- Image:Star Tracker Operational Usage in different phases of the Mars Express mission.pdf
- Image:Long Term Preservation of MEx.pdf
- Image:The Mars Express Training and Simulations campaign.pdf
- Image:Ensuring readiness for Europes first Mars mission, team building through simulations.pdf
