Scientists await first call from Beagle 2

Early this morning, the Beagle 2 spacecraft landed on the surface of Mars at the end of a 250 million mile (400 million km), six-month trek to the Red Planet. Although the first attempt to use NASA's Mars Odyssey orbiter to communicate with the lander three hours later was unsuccessful, scientists and engineers are still awaiting the best Christmas present possible - the first faint signal to tell them that Beagle 2 has become only the fourth spacecraft to make a successful landing on Mars.

"This is a bit disappointing, but it's not the end of the world", said Professor Colin Pillinger, lead scientist for the Beagle 2 project. "We still have 14 contacts with Odyssey programmed into our computer and we also have the opportunity to communicate through Mars Express after 4 January."

The next window to receive confirmation that Beagle 2 has successfully landed and survived its first night on Mars will be between 10 pm and midnight (GMT) tonight, when its simple carrier signal (rather than the tune composed by Blur) may be picked up by Jodrell Bank radio observatory in Cheshire, UK. This has a much greater chance of success because the giant telescope is able to scan the entire side of the planet facing the Earth.

Another overflight by Mars Odyssey will take place around 18.15 GMT tomorrow evening, followed by daily opportunities to contact Beagle 2 via the Mars Odyssey spacecraft and the radio telescopes at Jodrell Bank and Stanford University in the United States.

There are several possible explanations for the failure of Odyssey to pick up Beagle 2's signal. Perhaps the most likely is that Beagle 2 landed off course, in an area where communication with Mars Odyssey was difficult, if not impossible. Another possibility is that the lander's antenna was not pointing in the direction of the orbiter during its brief passage over the landing site. If the onboard computer had suffered a glitch and reset Beagle 2's clock, the two spacecraft could be hailing each other at the wrong times.

The Beagle 2 lander entered the thin Martian atmosphere at 2.47 GMT today. Travelling at a speed of more than 12,500 mph (20,000 km per hour), the probe was protected from external temperatures that soared to 1,700 degrees C by a heat shield made of cork-like material.

As friction with the thin upper atmosphere slowed its descent, onboard accelerometers were used to monitor the spacecraft's progress. At an altitude of about 4.5 miles (7.1 km), Beagle's software was to order the firing of a mortar to deploy a pilot parachute, followed one minute later by deployment of the 33 ft (10 m) diameter main parachute and separation of the heat shield.

At a few hundred metres above the surface, a radar altimeter was to trigger the inflation of three gas-filled bags. Cocooned inside this protective cushion, Beagle 2 was expected to hit the rust-red surface at a speed of about 38 mph (60 km/h). As soon as the bags made contact with the surface, the main parachute was to be released so that the lander could bounce away unhindered. Like a giant beach ball, the gas bag assembly was expected to bounce along the surface for several minutes before coming to rest at 2.54am GMT.

Finally, a system of laces holding the three gas-bags onto the lander was to be cut, allowing them to roll away and drop Beagle 2 about 3 ft (1 m) onto the surface. The whole descent sequence from the top of the atmosphere to impact was to take less than seven minutes.

The "pocket watch" design of Beagle 2 ensured that it would turn upright irrespective of which way up the little lander fell. After the onboard computer sent commands to release the clamp band and open the lid, the way would be clear to deploy the four, petal-like solar panels and initiate charging of the batteries.

Confirmation of the successful landing would be provided by a musical "beeping" signal of 9 digitally encoded notes, composed by British rock group Blur. This signal should be picked up by Mars Odyssey as it passes overhead and then relayed to Earth.


Update added December 26, 2003:

The next opportunity to detect Beagle 2 came later on 25 December between 23:40 and 00:20 CET when the 76-metre radio telescope dish at Jodrell Bank Observatory, UK, tried to detect the 5 Watt signal from more than 157 million kilometres away, again without success.

On 26 December, Mars Odyssey will carry out another pass of the landing site at 19:14 CET. This will be followed up by another sweep by Jodrell Bank early in the morning of 27 December, between 00:20 and 01:00 CET. Mars Odyssey can try again later that day at 07:57 CET.

On 28 December, Jodrell Bank once more becomes available at 00:16 to 00:56 CET. Beyond that date, Mars Odyssey will continue the search daily, and the Stanford University radio telescope will also join in the effort.

If all those attempts are unsuccessful, then Mars Express itself flies over the landing site in the first week of January 2004. Of all these potential signal detectors, Mars Express is the only one that has been specially designed and tested to transmit and receive signals from Beagle 2.

The hope is strong that the Mars Express orbiter will be successful in this task.


Update added December 30, 2003:

The sixth attempt by NASA's Mars Odyssey orbiter to communicate with Beagle 2 was made this morning, but, as on previous occasions, no data were received.

The next Mars Odyssey communication opportunity will take place at 20.20 GMT this evening. The results of this session will be announced on the Beagle 2 and PPARC websites.

Other opportunities to communicate with Beagle 2, including pre-programmed sessions with Mars Express, are listed on the Beagle 2 website.

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