The Proba-3 Formation Flying Technology Demonstration Mission
- Paper number
IAC-07-C1.7.01
- Author
Dr. Alex Wishart, Astrium Ltd., United Kingdom
- Coauthor
Mr. Frédéric Teston, European Space Agency (ESA)/ESTEC, The Netherlands
- Year
2007
- Abstract
PROBA-3 is an ESA precursor technology demonstration mission to prove techniques and technologies which will be required for future operational Formation Flying missions. Astrium Satellites Ltd is leading a Phase A study to finalise the mission definition and system requirements. PROBA-3 will be a two year mission, with launch expected in the 2010-2011 timeframe. Formation Flying is an operational technique by which two or more satellites maintain a desired geometry to achieve the function of a single large spacecraft. It involves new GNC functions which allow each spacecraft to be controlled in attitude and position in both absolute and relative (i.e. with respect to each other) frames. It requires specific sensors for relative navigation, communications links, and high accuracy control. It also requires high stability positioning of each spacecraft and the capability to re-orient in space the constructed geometry. PROBA-3 comprises two spacecraft with a combined mass of order 600 Kg. The principal Formation Flying demonstration will be ASPIICS (Association de Satellite Pour ‘Imagerie et L’Interferometrie de la Couronne Solaire), which is a very large, externally occulted, solar coronagraph. One spacecraft flies the 1.5m diameter occulting disk, the other the coronagraph optical instrument. Nominal spacecraft separation in ASPIICS is 150m. A 72-hour HEO has been selected. The high apogee provides a benign environment for precision Formation Flying, closely representative of the environment of future operational missions flying in Lagrange orbits. System design of a formation flying mission is a complex problem, involving close interaction between various disciplines, including mission analysis, GNC and spacecraft design. The ASPIICS science requirements translate into pointing and relative position requirements which will be realised by the sensors, actuators and control algorithms of the PROBA-3 AOCS. The major challenge for ASPIICS is to maintain the relative lateral position of the two spacecraft to within ± 3 mm at a spacecraft separation of 150m, corresponding to an angular displacement of ~ 4 arcsec. This displacement includes the error in computing the absolute Line-of-Sight between the coronagraph optics and the sun. This poses a difficult problem for a classical AOCS sensor using star trackers or sun sensors, and will be solved on PROBA-3 by using a coronagraph payload sensor to calibrate the star trackers and the optical lateral relative metrology sensor. The required accuracy, as well as the need to maintain the geometry continuously, also put challenging requirements on the propulsion and control systems.
- Abstract document
- Manuscript document
IAC-07-C1.7.01.pdf (🔒 authorized access only).
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