Instrument Host Information
IDENTIFIER urn:esa:psa:context:instrument_host:spacecraft.mpo::1.3
NAME Mercury Planetary Orbiter
TYPE Spacecraft
DESCRIPTION BepiColombo is an interdisciplinary mission to explore Mercury, the planetclosest to the sun, carried out jointly between the European Space Agency andthe Japanese Aerospace Exploration Agency. From dedicated orbits two spacecraftwill be studying the planet and its environment. The scientific payload of bothspacecraft will provide the detailed information necessary to understand theorigin and evolution of the planet itself and its surrounding environment. Thescientific objectives focus on a global characterization of Mercury through theinvestigation of its interior, surface, exosphere and magneto-sphere. Inaddition, instrumentation onboard BepiColombo will be used to test Einstein?stheory of general relativity. Major effort was put into optimizing thescientific return of the mission by defining a payload complement such thatindividual measurements can be interrelated and complement each other. The BepiColombo MPO accommodates the 11 scientific instruments and has abox-like shape with a size of 3.9x2.2x1.7 m. The entire MPO totals up to 1075 kgof nominal dry mass. A specific primary double-H structure allows mounting mostunits and payloads on the outer face of it, ensuring good accessibility duringthe integration process. The primary structure carries a thin cage structure towhich the high-temperature multi- layer-insulation (MLI) is fixed. In the centreof the MPO two tanks are placed carrying the propellant for the propulsionsystem. The MPO is designed to take scientific measurements in all parts of theorbit throughout the Mercury year, implying that most of the apertures of theremote sensing instruments are continuously nadir pointing. As a consequence, 5out of 6 spacecraft faces may be illuminated by the Sun at some point. Thisleaves only one spacecraft side for a radiator to dump excess heat into spaceand to avoid solar exposure of the radiator. A further consequence is aspacecraft flip-over manoeuvre, which is needed twice per Mercury year. The heatload is tremendous: at the perihelion subsolar point it is 14kW/m2 from the Sunand 6kW/m2 from Mercury. This environment imposes strong requirements on thespacecraft design, particularly to all elements that are exposed to Sun andMercury, such as the solar array, mechanisms, antennae, multi-layer insulation,thermal coatings and radiator. The development of these elements,together withthe solar electric propulsion system are the main cost drivers for this missionand at the same time are responsible for a sizable share of the overallspacecraft mass.
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