CHEOPS Platform Thermal Architecture
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CHEOPS - CHaracterising ExOPlanet Satellite - is the first ESA’s Science Programme of class S (Small mission) devoted to the observation and characterisation of stars, already known to host exoplanets. CHEOPS Instrument will perform ultrahigh precision photometry to characterize the planetary systems with unprecedented precision. AIRBUS Defence & Space (Spain) is responsible for the system level design and assembly, integration and test activities, including the provision of the Platform. University of Bern (Switzerland) is in charge of the Instrument. The overall spacecraft is designed to fit within small launcher fairing volume (in dual launch configuration) with a mass not exceeding 300 kg. CHEOPS platform is based on a design-to-cost approach with maximum reuse of previous experience, such as SEOSAT, an Earth Observation satellite based on AS250 AIRBUS Defence and Space product line, featuring 3 deployable solar panels for a platform mass of 650 kg. CHEOPS hexagonal shaped platform is adapted to perform inertial pointing observations and is equipped with 3 body-mounted solar arrays. The total mass of the Platform is 220 kg. The main challenges regarding CHEOPS platform thermal architecture are: - To minimize flux exchanges between the Platform and the Instrument to achieve the very stringent requirements for instrument detector low temperature and thermal stability. - To accommodate several medium to high dissipative electronic units and ensure dedicated heat rejection capacity while minimizing heating power. - To adapt SEOSAT existing thermal architecture to CHEOPS Platform specific constraints (smaller Platform, inertial pointing towards a wide range of targets, only 3 walls available for radiators because of the solar arrays). Platform thermal architecture is based on passive means (MLIs, Second Surface Mirror foils, thermal fillers…) complemented by an active heating system with a limited power consumption, which average orbital value is always kept below 20W during observation phases.