Extended lifetime Laplace plane GEO SAR mission design

Geosynchronous synthetic aperture radar (GEO SAR) promises novel imaging capabilities which complement low Earth orbit missions. Many configurations for GEO SAR have been studied (e.g. monostatic, bistatic, multistatic): this study considers use of Laplace plane orbits which potentially offer longer lifetimes. In the Laplace orbit plane gravitational perturbations cancel out which reduces orbit maintenance costs. Choosing a GEO Laplace plane orbit defines the semimajor axis, inclination (about 7.4°.) and right ascension: the mission designer is only free to choose eccentricity and argument of perigee. Velocity relative to Earth is moderately fast (~400 m s^-1) so integration times needed are minutes to 10s of minutes for resolution of 10 - 50 m. Squint viewing supports more versatile coverage. The study proposes a baseline mission concept. Lifetime for a single satellite can be extended beyond the conventional 15 yr for geostationary comsats, and the optimal lifetime is probably in the range 20-30 yr. Advantages of the concept include (a) long lifetime and feasibility with current technology, (b) improved area coverage, and less demanding technology relative to quasi-geostationary GEO SAR, and (c) lower power and smaller antenna than high inclination GEO SAR.