ESA GNC Conference Papers Repository

Advantages of the GEO Orbit for Earth Observation<br> The geostationary orbit has long been used for telecommunication applications, as it offers both wide coverage (high altitude) and apparent motionlessness (null relative angular velocity). Compared to Low-Earth Orbit (LEO) observation, which can feature sub-metric resolutions, optical observation from the geostationary orbit (GEO) has long been limited to full-disk, kilometric resolution imaging for weather forecasting purposes (GOES, METEOSAT, MSG, NTSAT, COMS, MTG). Indeed, the high altitude has long limited attainable resolutions: a 20-m-resolution instrument in GEO requires roughly the same instrument pupil as a 30-cm-resolution instrument in LEO. However, recent advances in optical instrument technology for LEO observation now make it possible to take advantage of the geostationary orbit for high-resolution Earth observation. This opens up a whole new range of missions benefiting from the exceptional vantage point. Such new missions could offer valuable complementarity with LEO, sun-synchronous missions:<br> · arbitrarily short revisit time, offering extreme reactivity to observe unpredictable events;<br> · continuous observability, allowing to follow Earth processes throughout the day, or the year;<br> · repeatable observation conditions, allowing accurate periodic comparisons of the same scene;<br> · real-time capability, allowing monitoring of dynamic phenomena such as hurricanes, floods, fires;<br> · Permanent link with ground stations, allowing flexible programming, and simplifying on-board systems.