Mars: Separation Anxiety
Mars Express, the European Space Agency’s first probe to Mars, still has some challenges to face. The spacecraft has successfully come through its first power test after the gigantic solar flare on 28 October.
|Airbag landing is a crash collision Credit: NASA/JPL/Cornell|
Since 17 November the on-board software has been ‘frozen’ after several updates and the spacecraft is now quietly proceeding to its destination. The next major task, starting on 19 December, will be to safely release the Beagle 2 lander.
To deliver Beagle 2 where planned, Mars Express has been put on a collision course with Mars, since Beagle 2 does not have a propulsion system of its own and must therefore be aimed precisely at its destination.
Intense activity will begin six days before the arrival at Mars on 25 December with the release of Beagle 2. The orbiter will follow Beagle 2 for a while until, three days before arrival at Mars, ground controllers must make it change trajectory to avoid crashing onto the planet.
This will be the first time that an orbiter delivers a lander without its own propulsion onto a planet and attempts orbit insertion immediately afterwards.
The spacecraft speed will be reduced from about 11 kilometers per second to 9 kilometers per second. At that speed, the planet’s gravitational field will be enough to capture’ Mars Express and put it into Martian orbit.
|The early fiery entry of Beagle 2 probe into the thin Martian upper atmosphere at 12,000 miles per hour Credit: ESA|
Several manuevers will follow to set the spacecraft into its final operational orbit. This orbit is a highly elliptical polar orbit, taking Mars Express as close as 260 kilometers from the Martian surface, and out to more than 11 000 kilometers away at its furthest from the planet.
This is another crucial moment, as it is the first time after the launch that the orbiter’s propulsion system comes into action. On top of this, the deployment of the radar booms will take place – one of the most critical instrument activities.
The landing itself is another very complicated and challenging operation. Beagle 2 will enter the Martian atmosphere at 20 000 kilometres per hour, but friction with the thin atmosphere will slow it down. Once its speed has decreased to about 1600 kilometres per hour, two parachutes will be deployed in sequence.
Finally, large, gas-filled bags will inflate to protect the lander as it bounces on the surface. Once Beagle 2 comes to a halt, the bags are ejected and the lander can open up and start operating.
Any one of these operations could go wrong. An incorrect alignment of the lander could mean it burns up in the atmosphere. The parachutes could fail to deploy, plunging Beagle 2 into the surface at great speed. The balloons could become detached, or get punctured, again possibly causing Beagle 2 to crash.
If the lander does not land on the planned spot, then this is less serious. The landing area is not one spot’ but a large ellipsis’, 300 kilometers long and 100 kilometers wide.
|Landing ellipses centered on Mars’ third largest impact basis Credit: NASA JPL/MSSS/MOC|
It has been calculated taking into account the density of the Martian atmosphere, the winds and many other factors. So the risk of missing the landing site is very small. If the winds are stronger than calculated, for instance, they may push’ Beagle 2 a little further away, but still within the selected area.
"We are addressing a series of noble objectives," says Agustin Chicarro, Mars Express Project Scientist. "As well as helping to answer the big questions about water and life, our investigations will provide clues as to why the north of the planet is so smooth and the south so rugged, how the Tharsis and Elysium mounds were lifted up and whether active volcanoes exist on Mars today. We should also find out about the minerals in the rocks and the composition of the atmosphere in greater detail than ever before". If all goes well, the lander will settle near the equator in a region known as Isidis Planitia.
On the orbiter, if one or more of the instruments fail, then the mission could still carry on. All seven instruments on board are designed to work independently. So even some instruments fail, it would still be possible to perform top-class science.
Past missions to Mars have been lost due to a variety of problems, ranging from trivial errors in calculations to system problems. Errors can always happen, but all aspects of the Mars Express mission have been tested as much as possible to be confident that there will be no errors due to trivial mistakes. Mars Express has been developed in a record-breaking time, but there have been no compromises in testing.
New images have been released by the orbiting instruments around Mars which will support communication between the surface rovers and Earth.
Hematite Outlier and Sand Dunes (Released 4 December 2003)
|Hematite Outlier and Sand Dunes (Released 4 December 2003)
Image Credit: NASA/JPL/Arizona State University
This image shows a crater just south of the edge of the famous hematite-bearing surface, which is visible in the context image as a smooth area to the north. The crater has two features of immediate note. The first is a layered mound in the north part of the crater floor. This mound contains hematite, and it is an outlying remnant of the greater deposits to the north that have otherwise completely disappeared in this crater. The second feature is a dune field in the center of the crater floor, with dark dunes indicating winds from the northwest. The dunes grade into a dark sand sheet with no coherent structure, indicating that the sand layer thins out to the south and east.
Left: Latitude -4.4 Longitude 357.3E (2.7W) Image Size (km) 61.4×26.5 Mars 2001 Odyssey, Thermal Emission Imaging System (THEMIS), Mars Orbital Laser Altimeter (MOLA) Team
Crater in Marte Vallis
|Crater in Marte Vallis MGS MOC Release No. MOC2-566, 6 December 2003
Image Credit: Mars Global Surveyor, Malin Space Systems
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image right shows a streamlined tail–pointing toward the upper right (northeast)–in the lee of a meteor impact crater in Marte Vallis, a large valley and channel complex southeast and east of the Elysium volcanic region. The fluid that went through Marte Vallis, whether water, mud, lava, or otherwise, created this form as it moved from the lower left (southwest) toward the upper right. The crater is located near 19.0 degrees N, 174.9 degrees W. The image covers an area 3 km (1.9 mi) wide and is illuminated from the left.
About the Supporting Map Missions
By launching the Mars Global Surveyor (MGS) spacecraft in November 1996, NASA and the Jet Propulsion Laboratory began America’s return to Mars after a 20-year absence. The Surveyor spacecraft is a rectangular-shaped box with wing-like projections extending from opposite sides. When fully loaded with propellant at the time of launch, the spacecraft weighed only 1,060-kilograms (2,342 pounds). The spacecraft travelled nearly 750 million kilometers (466 million miles) over the course of a 300-day cruise to reach Mars on September 11, 1997. During mapping operations, the spacecraft circled Mars once every 118 minutes at an average altitude of 378 kilometers (235 miles). After mapping finishes, the spacecraft will function as a communications satellite to relay data back to Earth from surface landers launched as part of future Mars missions.
2001 Mars Odyssey launched on April 7, 2001, and arrived at Mars on October 24, 2001. The mission is mapping the amount and distribution of chemical elements and minerals that make up the Martian surface. The spacecraft especially looks for hydrogen, most likely in the form of water ice, in the shallow subsurface of Mars. One of its three primary instruments is called THEMIS (Thermal Emission Imaging System), for determining the distribution of minerals, particularly those that can only form in the presence of water. It also provides the communications relay for U.S. and international landers, including missions in NASA’s Mars Program, the Mars Exploration Rovers. The name "2001 Mars Odyssey" was selected as a tribute to the vision and spirit of space exploration as embodied in the works of renowned science fiction author Arthur C. Clarke.