Christmas Vigil Ensues
Red Planet’s Moment of Truth
Final decision to steer Mars Express into a Martian orbit
Beagle 2 lands on Mars
Mars Express orbital insertion
Mars Odyssey orbiter flies over Beagle 2 – first possible signal retrieval from the lander
06:30 -07:00 GMT
Mars Odyssey contacts NASA’s Jet Propulsion Lab, first possible signal from Beagle 2 received on Earth
First evaluation of Mars Express orbital insertion
Sunset on Mars (18:35 local solar time)
Sunrise on Mars (07:02 local solar time)
Possible direct capture of Beagle 2 signals at Jodrell Bank Observatory (UK)
Sunset on Mars (18:36 local solar time)
Launched six months ago from Russia’s Kosmodrome and reaching the martian surface on Christmas at 2:54 Greenwich Time, Europe’s first Mars surface explorer, Beagle 2, has reached its moment of truth, the dramatic interval when the tiny lander settles near the red planet’s equator.
The final moments are anxious ones for controllers, as they track a series of steps to prepare the companion lander-orbiter for six months on the surface and two years in orbit. Just six minutes after the lander reached the surface, its mapping probe overhead had to begin its orbital insertion, the first such maneuver attempted for a combination probe where the lander lacks any propulsion scheme other than its own release momentum.
At 4:35 GMT, the Beagle team announced that ‘Early indications suggest successful orbit inserion of Mars Express.’ At the European Space Agency’s Operations Control Center in Darmstadt Germany, the scientists and mission planners expressed elation that they ‘now have a mission’. For the next two years, their orbiting platform will map and measure the surface of Mars.
Yet by 6:15 GMT, early Christmas morning, no signal has been received from Beagle 2 during the first pass of the orbiting Mars Odyssey probe, a setback that will prompt a series of second attempts later in the day. "We’re disappointed, but it’s not the end of the world," said Beagle mission head, Colin Pillinger. That lack of a signal from the lander itself can be attributed to temperature shifts in the broadcast frequency, the orientation of the spacecraft or any number of setup issues associated with preparing communications to downlink.
After witnessing its first sunset and sunrise on Mars, the lander may signal confirmation directly to the giant 76 meter Jodrell Bank Observatory in the UK. The transmitter power, at 5 watts, is little more than that of a mobile phone, but the team at Jodrell Bank have installed a very sensitive receiver to pick up the Beagle 2 frequency.
On the first attempt with Jodrell Bank, no signal was detected from Beagle 2. The next attempt will be from Mars Odyssey.
To reach this point, the mission’s orbiter, called Mars Express, and its companion lander, Beagle, have traveled 400 million kilometers [240 million miles]. A quarter of a billion miles away, the lander will continue to follow the intrepid path of its namesake–another voyager, the HMS Beagle, that carried Charles Darwin as he searched for the origin of terrestrial species.
The orbiter mission should last at least one Martian year (687 days), while Beagle 2 is expected to operate on the planet’s surface for 180 days.
Beagle has targeted a large, flat sedimentary basin called Isidis Planitia–a plain named after the Egyptian goddess, Isis, queen of heaven. The flatness of the landing site centers around the broad, relatively flat plain that covers the floor of an extremely ancient, large basin which formed after an asteroid or comet impact perhaps more than 4 billion years ago.
Colin Pillinger, chief scientist for the Beagle lander, told Astrobiology Magazine: "We liked a place where there was a potential of different kinds of rocks. So Isidis is nice because it’s an in-fill basin, which might have lots of materials from the southern highlands washed down into it. We chose a place south of two recognizable sizable craters because we felt there was a possibility that some materials had been ejected from the floor of the craters. "
Isidis straddles the relatively young northern plains and ancient southern highlands, where traces of life could have been preserved. The vastness of this impact lowlands makes it the third largest basin on Mars.
|Landing ellipses centered on Mars’ third largest impact basis. At noon Central European Time (CET) on December 24, the Mars Express orbiter was 169,000 kilometers from Mars and 156,167,000 kilometers from Earth. Both the Mars Express orbiter and the Beagle 2 lander have a velocity relative to Mars of 2.8 kilometers per second, increasing under the influence of Martian gravity. At 12:00 CET, the two spacecraft were 2300 kilometers apart, and diverging at a rate of 6.5 meters per second. The orbiter is now in the final configuration for Mars Orbit Insertion. No more commands are being sent to the spacecraft until after its capture by Mars. Credit: NASA JPL/MSSS/MOC|
The landing site’s coordinates (11.6° N, 90.75° E) were selected near the equator because such lower latitudes minimize the amount of thermal protection (and hence mass) needed to protect the lander from the cold Martian night. The lander is tiny relative to previous Mars explorers and weighs on Earth about the same as an average person–only 60 kilograms (132 pounds). Conserving payload mass was a key cost-saving part of its design.
"Everything we could possibly think of went into choosing Isidis," said Pillinger. "We wanted somewhere we could keep the scientists happy and somewhere the engineers wouldn’t throw a wobbly. The engineers want low altitude, which makes the parachute work better; they don’t want the place strewn with rocks, it could burst the gas bags; they don’t want slopes because they give you lateral velocity that you don’t like; nobody wanted to go to high latitudes, because it gets cold up there; we chose the northern hemisphere because it was going toward spring and summer, and of course the altitude there as well."
The equator also offers a longer day for solar cells on the lander to charge during the Martian daylight hours. The efficiency of solar recharging will determine whether its power supply can weather its half-year stint with full communications and surface operations.
This is the first time that an orbiter has tried to deliver a lander without its own propulsion onto a planet and attempted orbit insertion immediately afterwards. Beagle 2 has no propulsion or steering control of its own. Since its release five days ago, its destination has been governed– ‘bullet-like’– by the laws of physics. During this final week, the landing probe has remained switched off for most of its final 5 million kilometer coast phase to the surface.
Protected by the same airbag system that was first demonstrated on the 1997 Mars Pathfinder mission, the research station itself collided with Mars, more than landed on its surface. Beagle 2 entered the Martian atmosphere at six times the speed of a rifle bullet, or 20,000 kilometers per hour, but friction with the thin atmosphere slowed it down. Once its speed decreased to about 1600 kilometers per hour, two parachutes deployed in sequence.
|Isidis Planitia MGS MOC Release No. MOC2-584, 24 December 2003|
This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small portion of the vast Isidis Planitia, the region in which the Beagle 2 is scheduled to land on 25 December 2003. The light-toned ridges and somewhat squiggly features are windblown dunes. This picture is located around 10.7 degrees N, 268.6 degrees W, which is in the vicinity of the projected Beagle 2 landing zone. The picture covers an area 3 km (1.9 mi) wide. Sunlight illuminates the scene from the left/lower left. Image Credit: Mars Global Surveyor, Malin Space Systems
Finally, large, gas-filled bags inflated to protect the lander as it bounced on the surface. Once Beagle 2 comes to a halt, the bags are ejected and the lander can open up and start operating. The landing area is not one spot but a large ellipsis, initially 300 kilometers long (186 miles) and 100 kilometers (62 miles) wide. The dimensions of this initial target encompassed an area big enough to swallow 500 copies of New York’s Manhattan island but as Beagle was tracked, eventually narrowed to a 70×11 square kilometer range (about the size of London itself). At entry, the exactness of positioning depends on varying local conditions, like wind, dust, atmospheric pressure and the entry trajectory. After five days of ballistic flight, the time from its entry into the atmosphere to landing has culminated in this short moment of truth.
The Isidis site is not too rocky to threaten a safe landing (but rocky enough to be interesting for the experiments), has few steep slopes down which the probe may have to bounce as it lands, and is not too dusty. Isidis Planitia is at a low enough elevation to provide sufficient depth of atmosphere to allow the parachutes to brake the lander’s descent.
Much of Isidis Planitia has low hills and mounds. Many of these are remnants of a layer (or group of sub-resolution layers) that once more extensively covered Isidis Planitia, but was later stripped away, revealing previously-buried meteor impact craters. As photographed from orbit, light-toned ridges and somewhat squiggly features are windblown dunes.
Surface investigations will provide clues as to why the north of the planet is so smooth and the south so rugged. Scraping rocks for signs of fresh lava flows may also give clues as to how the Tharsis and Elysium mounds were lifted up and whether active volcanoes exist on Mars today. The Tharsis plateau covers most of the western hemisphere and encompasses highlands of spectacular volcanoes, including Olympus Mons, the largest volcano in the solar system. The mounds of Elysium Mons are more heavily cratered than Tharsis, and thus older lava flows may have shaped this region from 600 to 2000 million years ago.
One theme of current Mars’ missions is the motto, ‘follow the water’. As part of tracking such hydrology, the orbiter passes within 250 kilometers [150 miles] of the surface at closest approach. Employing seven major instruments for its on-the-spot analyses, the orbiting Mars Express will be able to identify signs of water in liquid, solid, or vapor form on Mars. During each orbit, the overhead spacecraft will collect data from Mars between a half-hour to an hour, while spending the rest of its time broadcasting those results back to Earth.
Its onboard camera offers high-resolution stereo views of Mars. Its comprehensive maps will feature 10 meter resolution, but some particularly interesting regions will get a close-up view to 2 meters [about the size of small car, as seen from orbit].
|The early fiery entry of Beagle 2 probe into the thin Martian upper atmosphere at 12,000 miles per hour. Credit: ESA|
The orbiter will also probe beneath the Martian surface using ground-penetrating radar. If pockets of water are found to a depth of 2 kilometers [1.2 miles], then theories of active hydrology on Mars will be borne out. Subterranean aquifers are considered one possible way in which liquid water could exist in the frigid, hostile conditions, where the atmosphere is about one percent of the Earth’s pressure. The radar, called the MARSIS instrument, uses a large 40 meter antenna to collect the sound waves that bounce off any density pockets below the rusty-red soil.
But for the next six months, if the lander survived, it will take a good chemical and morphological look at its site, testing for water in the soil, on rocks, and in the Martian atmosphere. It will investigate the existence of carbonate minerals and organic residues to detect possible signs of past or present life.
Using some of the same mission elements, future European explorers will head towards Venus in 2005 and Mercury in 2009.