The Promises Of Optical Earth Observation From The Geostationary Orbit

Paper number

IAC-07-B1.2.05

Author

Mr. Eric Maliet, EADS Astrium, France

Coauthor

Mr. Didier Alary, EADS Astrium, France

Coauthor

Mr. Dominique Pawlak, EADS Astrium, France

Coauthor

Mr. Jean-Paul Gardelle, Astrium, France

Year

2007

Abstract

For many years, Earth observation missions have been mainly flown in Low Earth Orbit (LEO), whilst the Geostationary Earth Orbit (GEO) was primarily dedicated to telecommunication missions. The only exception to this rule was the use of GEO for meteorological Earth observation missions, in order to guarantee a permanent monitoring capacity over a given region of the globe. This was made possible by the relaxed spatial resolution requirements which were needed for these missions. Low Earth orbits, due to their proximity to the Earth, favour high resolution missions, with fair sized optical instruments and low free-space losses for high-rate image downlink. Low Earth orbits also provide a global coverage of the Earth, with fixed lightning conditions in case of Sun-synchronous orbits, but, on another hand, are limited in terms of revisit performances. The improvements in all space technologies now make it possible to consider flying higher resolution optical missions in GEO, and thus to benefit from a near-to-continuous observation capacity over a given region.
Three classes of missions have been identified, which could benefit from this permanent access. Resolution in the range of a few hundred meters is particularly applicable to oceanography missions, with e.g. ocean colour imaging instruments, which require a quick revisit in order to follow some fast varying phenomena (for instance algae blooms). Higher resolutions, around a few 10 m, can be used for land monitoring, and can offer daily revisit over an entire continent. This is of particular interest for vegetation related applications during fast growing periods, but also in the security domain. These two ranges of resolutions can be made with monolithic telescopes, and rely on high performance platforms in terms of pointing and data transmission capacities. Much higher resolution missions, below 5 m, are also possible from the GEO orbit, but require to switch from a monolithic telescope concept to an aperture synthesis technique, where the telescope pupil is synthesised through several lower size elementary telescopes, covering part or all of the pupil.
Astrium Satellites have studied possible implementation of the three classes of missions, and thanks to their experience in GEO satellites and in optical Earth observation (can offer credible and cost-effective solutions of each of them.

Abstract document

IAC-07-B1.2.05.pdf

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