Mars Express / Beagle 2 Mission Chronology

From 2 June to 19 th December 2003 - Cruise Phase

After launch of Mars Express/Beagle 2 on a Soyuz Fregat rocket from Baikonur on 2 June 03, the first key operation was the release of the structural connection between the Beagle 2 Probe and Mars Express. This was successfully performed on the third day by the Pyrotechnic and Frangibolt Unit or PFU, which was designed, manufactured and tested by EADS Astrium. Thereafter the Probe was only attached to the spacecraft by the Spin Up and Ejection Mechanism (SUEM). Between July and September, the probe was switched on at intervals to confirm that all was well and, during October, software upload trials were successfully conducted and the on-board battery charged. Final software and parameter updates were transmitted to the probe in November. On 17 th December final preparations for ejection will be performed with ejection itself scheduled for the morning of 19 th December.

EADS Astrium was responsible for the management and system design of all hardware and software employed during the cruise phase.

19 th to 25 th December- Coast Phase

On 19 th December Mars Express will use its manoeuvring thrusters to adjust the interplanetary trajectory for the correct release of the Beagle 2 Probe. It will accurately point Beagle 2 to hit a specific point at the top of the Martian atmosphere five days later. The SUEM will impart a spin rate and small velocity to the Probe on ejection. The velocity will move the Probe away from the spacecraft in a defined manner and the spin will stabilise it during the coast phase and atmospheric entry. The 68.8 kg Probe will follow a ballistic trajectory and will remain switched off for most of the 5 million kilometre coast phase to Mars. Then, a few hours before entering the Martian atmosphere, an onboard timer will power it up and boot up the onboard computer.

Directly after it releases the Probe, Mars Express will fire its main engine. These Mars insertion manoeuvres, performed with the main engine, will be complemented by the thrusters for attitude control. This will bring the Mars Express spacecraft into an elliptical orbit over the planet. After initial Mars capture, Mars Express will, with repeated firings of its attitude control thrusters, be brought into its final orbit, circling the planet’s poles every 7.5 hours. On its elliptical orbit, the probe will close to within 250 kilometres of the surface at perigee and will remain at 11,500 kilometres at apogee.

The seven scientific instruments on Mars Express can study Mars for between 30 and 60 minutes per orbit, when the satellite is closest to the planet on its elliptical orbit. At this point, the spacecraft is nadir pointing during pericentre passes. It can collect scientific data from the Beagle 2 Lander and store it on board until it can transferit, during Earth communications sessions, when it is 3-axis stabilised and Earth pointing.

25 th December 2003 – Entry, Descent and Landing Phase

The toughest challenge yet is to successfully decelerate the Beagle 2 Probe from 21,000 km per hour at atmospheric entry to zero on the Martian surface, without using complex propulsion systems. The initial deceleration is achieved by atmospheric drag, internal equipment being protected against high temperatures of up to 1,600 °C by an outer shield of cork-like material. On board accelerometers will monitor the deceleration profile and software will then sequence the mortar firing of the pilot parachute, the back cover and front shield release and deployment of the 10m diameter main parachute. This will slow the lander package down to about 57 km per hour. At a few hundred metres above the surface, a radar altimeter built into the lander structure will trigger the 3 gas-filled bags to deploy and cushion the impact. The whole sequence from the top of the atmosphere to impact will take less than six minutes. Then the gasbag assembly will bounce along the surface for several minutes before coming to rest. The bags will be released and the lander will drop approximately one metre onto the surface. Impact protection within the lander structure will cushion the shock loading on the vital internal equipment.

Once again EADS Astrium is responsible for the management and system design of all hardware and software employed during the entry, descent and landing phase. In addition EADS Astrium designed the back cover structure and managed the design and manufacture of the main parachute. EADS SPACE Transportation provided the thermal protection on the heat shield and back cover.

25 th December onwards Opening sequence and Scientific Operations

After coming to rest, the onboard computer will automatically release a clamp band and deploy the lid from the panel. If the Probe lands upside down the motorised hinge is capable of deploying the base from the lid. Then the solar panels will deploy with automatic stops if they touch a rock. The sequence will then put the lander electronics into a safe mode, start battery charging and, at a suitable time, will attempt to communicate via the first available relay satellite (NASA’s Mars Odyssey). The software will also initiate a panoramic photograph of the environment for transmission to Earth before instrument arm deployment. Incorporating innovative design and packaging techniques, the Beagle 2 lander has achieved the highest ratio of scientific instrument mass to lander/probe weight ever. The mass of the lander itself is just 33.2 kg of which 11.4 kg is instruments.

Once the spacecraft is declared safe then scientific operations can commence. A key element of these surface operations will be the three joint, five degree of freedom instrument arm which will allow the PAW instruments to move close to rocks and the mole and corer grinder to collect samples for analysis in the Gas Analysis Package.

EADS Astrium is responsible for the management and system design of all hardware and software employed during this phase except for the instruments themselves. In addition EADS Astrium was responsible for the design and manufacture and test of the core electronics, main and solar panel hinges, the clampband, the instrument arm and the lander /solar panel structure design.