Thursday, September 27, 2007

The Loss of Beagle 2

Credit: NASA/JPL/Malin Space Science Systems/Virtual Analytics Ltd.

Credit: NASA/JPL/University of Arizona

As yesterday's photo caption indicates, Beagle 2 was released from Mars Express on December 19, 2003. Beagle 2 coasted for five days after release, and is believed to have entered the Martian atmosphere on the morning of December 25th. As no signals were received after the separation, nothing is known as to what happened during the landing sequence.

After an initial deceleration in the Martian atmosphere from simple friction, parachutes were to have been deployed and, about 1 km above the surface, large gas bags would have inflated around the lander to protect it from the surface impact. Landing was expected to occur at about 02:54 UT on December 25th (9:54 p.m. EST, December 24th). After landing the bags would deflate and the top of the lander would open. The top would unfold to expose the four solar array disks. Within the body of the lander a UHF antenna would have been deployed. A panoramic image of the landing area was to have been taken using the stereo camera and a pop-up mirror. A signal was scheduled to be sent after landing (and possibly an image) to Mars Odyssey at about 5:30 UT and another the next (local) morning to confirm that Beagle 2 had survived the landing and the first night on Mars. No signal was received at this time nor at any time afterwards. Nothing further is known about the lander.

Attempts were made throughout late December 2003, January, and early February 2004 to contact Beagle 2 using Mars Express. Although regular calls were made, particular hope was placed for communications occurring on January 12th, when Beagle 2 was pre-programmed to expect Mars Express to fly overhead, and on February 2nd, when the probe was supposed to resort to the last communication back-up mode, autotransmit. Beagle 2 was declared lost on February 6, 2004. A board of inquiry was appointed to look into the reason for the failure, and they released their report on August 24, 2004. No concrete reason for the probe's failure was determined. Factors that were considered as plausible causes of the failure included:
  • Beagle 2 entered an atmosphere that was not predicted by scientists (e.g., the atmosphere may have been unusually thin) and could have burned up.
  • Beagle 2 may have "bounced off into space."
  • The probe's parachute or cushioning airbags failed to deploy or deployed at the wrong time.
  • Beagle 2's backshell tangled with the parachute, preventing it from opening properly.
  • Beagle 2 became wrapped up in its airbags or parachute on the surface and could not open.
  • Other possible reasons included electronic glitches, damage to the heat shield, a broken communications antenna, or a collision with an unforeseen object.

    On December 20, 2005, the British media reported that Professor Colin Pillinger, the Beagle 2 chief scientist, had discovered the location of the spacecraft. Per The Times of London:

    They suggest that the probe was lost because of cruel luck as it touched down in one of the worst possible places for a soft and successful landing. Rather than dropping to the surface on a flat plain, it appears to have first struck the downslope of a small crater about 18.5 m (60 ft) in diameter, before crashing into its opposite wall, bouncing several times around the rim and eventually coming to rest at the bottom. Even if the gas bags that were meant to cushion its impact were fully inflated, and there is some evidence that they were not, their design would not have allowed them to protect the probe properly under these unlikely circumstances.

    “It’s a bit like hitting the side of the pocket in snooker,” said Professor Colin Pillinger, of the Open University, who led the mission. “The plan was for it to bounce along a flat surface, but instead it seems to have hit the wall of the crater and that messed up the bounce sequence, damaging the lander. If this is all true we were very unlucky. A sideswipe like this was just what we didn’t want.”

    The first picture above shows a specially processed Mars Global Surveyor (MGS) image taken by the Mars Orbiter Camera (MOC) of the crater Dr. Pillinger believed Beagle 2 came down in.

    The Beagle scientists believe that out of the many thousands of craters and hundreds of square kilometers of Beagle 2’s landing ellipse, no other candidate site has come close to providing such compelling evidence of Beagle’s landing.

    Impact ejecta can be seen similar to the one produced by MER-A’s [Spirit] front shield in the Bonneville crater and a cluster of symmetrically arranged objects that match a successful gas bag segment separation, dropping the lander to the ground. (Source)

    However, on January 1, 2007, the HiRISE camera aboard Mars Reconnaissance Orbiter took a photo of Dr. Pillinger's crater (the second photo above). As can be seen in this high-resolution image, no sign of Beagle 2 can be observed. As of this time, the remains of Beagle 2 are still lost.
  • No comments: