Thermal Testing of the Beagle 2 Mars Lander 2003-01-2462
Beagle 2 is traveling to Mars aboard the European Space Agency Mars Express Orbiter. After an interplanetary cruise of almost seven months, Beagle 2 will be ejected and free-fly for five days before landing on the surface of Mars. The length of the landed mission is constrained by the environmental conditions on Mars (for example, dust settling out of the atmosphere). The baseline mission is planned for 180 Sols (Martian days) with options to extend as technical performance allows.
During 2002, tests were undertaken at the Rutherford Appleton Laboratory (RAL), UK, to verify the thermal design of Beagle 2 and to provide measured data for updating the thermal computer models. Two sets of tests were made to simulate (i) the journey from Earth to Mars, and (ii) the landed configuration on Mars.
Verifying the thermal design of the five day free-flying approach to Mars was critical. The thermal design for this phase is entirely passive, yet the operational temperatures for entry and landing must be achieved. Conceptually, the thermal design relies on balancing the heat input from the Sun, which is at an almost constant angle of incidence, with that lost through the multi-layer insulation that covers much of Beagle 2. Testing required Beagle 2 to be mounted on a cradle that could be rotated at a constant angle relative to a solar simulator. This configuration was also used for verification of the thermal control system employed during the interplanetary cruise phase (when attached to Mars Express).
Simulation of the Mars surface environment was a considerable technical challenge. RAL's 3 m diameter Space Test Chamber was modified so that tests could be conducted in a 7 mbar CO2 atmosphere with a shroud maintaining a uniform ‘sky’ temperature of about -100°C. A fan system was installed that could provide a wind velocity of 10 m/s over the Lander. A solar simulator was in a fixed position over the Lander. The diurnal cycle was simulated by varying the intensity of
the solar simulator, and by varying the temperature of a thermal plate representing the surrounding Martian surface.
This paper describes in detail the programme of testing undertaken at RAL. It covers the development of the experimental set-up and test cases for both test phases, and in particular the concessions that were necessary to enable a practical test of the Mars surface environment. A summary of the test operations is also presented.