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The first use of the Polar Platform (PPF) is for the Envisat/PPF mission. The Envisat/PPF spacecraft has a launch mass of 8.5 tons and external dimensions of 10.0 metres x 2.8 metres x 2.1 metres. Due to it's large size it was necessary to perform the thermal balance and thermal vacuum testing in two modules. The first test was for the Service Module (SM) and the second for the Payload Module (PLM). This paper discusses the thermal balance testing and subsequent correlation of the Polar Platform Service Module thermal mathematical model.

MIXS (Mercury Imaging X-ray Spectrometer) is an instrument in the remote sensing suite of the Mercury Planetary Orbiter (MPO), part of the Bepi-Colombo mission to Mercury. The optics for the MIXS instrument is funded by the European Space Agency. The development of the MIXS instrument is undertaken by an international consortium, led by the University of Leicester, UK. This is funded by the UK's Science & Technology Facilities Council. The instrument is intended to address scientific issues including: the origin of Mercury, the evolution of Mercury, the nature of surface modifications on Mercury (e.g. cratering, volcanism), There are two adjacent X-ray optics, each with different layouts, for the imaging telescope and an adjacent flux-collector (collimator). Accurate thermal and geometrical mathematical models were needed to model the optics, taking into account the extreme thermal environment around Mercury.

Envisat is the largest and most ambitious earth observation spacecraft in the history of European space exploration. The Envisat spacecraft is funded by the European Space Agency, ESA, and was designed and built by Astrium. It carries a unique combination of instruments and sensors to make scientific measurements of our planet. Among the wide range of information being gathered, Envisat is looking at clouds, atmospheric temperature and composition, land temperature and topography, vegetation, flooding and fires, sea temperature and currents, global circulation, pollution and traffic, sea ice mapping and movement. Its total range of capabilities represents a significant advance over the previous generation of Earth observation spacecraft. Envisat was launched on an Ariane 5 launch vehicle on March 1st 2002, and flies in a sun-synchronous near polar obit at an inclination of 98° and an altitude of 800km, providing an orbital period of 101 minutes with a repeat cycle of 35 days.

The Envisat spacecraft has a launch mass greater than 8.0 tonnes and external dimensions of 10.0 metres x 2.8 metres x 2.1 metres. Due to it’s large size, it was necessary to perform the thermal balance and thermal vacuum testing in two stages. Firstly, there was the testing of the Service Module and, secondly, the testing of the Payload Module (PLM). This paper discusses the thermal balance testing of the PLM. The PLM, itself, is 7.5 metres tall; too large to fit into a test facility solar beam. Originally, it was intended to conduct two solar beam tests; one for the upper part and the second for the lower part. Following a revision and re-scheduling within the programme, it was decided to perform a single, non-solar beam, thermal balance test. The thermal balance test would be performed using test specific, electrical, heaters and test facility shroud control.