AAS 95-331
Properties of a Class of Elliptical Sunsynchronous Orbits For Regional Communications and Remote Sensing
G. Perrotta, Alenia Spazo, Rome, Italy
Abstract
The paper discusses the characteristics of a small 'family' of elliptical, sunsynchonous, orbits having a period of about three hours, an inclination of about 116o, and a relatively small orbit energy: the orbit injection requirements are quite modest, reducing the launch costs. They exhibit acceptable insensitivity to the space radiation environment, and compare well to other non sunsynchronous elliptical orbits and also to circular MEOs. Besides, the effect of external perturbations is also quite modest.
The sunsynchronicity of these orbits can be better exploited choosing a near dawn-dusk orbit plane, in which the satellites will be almost always illuminated by the sun. This greatly simplifies the satellite design, since the solar array utilization efficiency increases, and the battery size decreases. Besides, the satellites will experience a very stable thermal condition, one side of the satellite being permanently hit by the sun, the opposite side always facing the black sky. The apogee altitude and the orbit plane inclination makes these orbits highly suitable for regional communications over the northern and southern latitude belts, where the 'wealthy countries' are located. For example 82% of the Gross World Product (GWP) and 55% of the world's population is concentrated in the 20o to 70o latitude belt.
The paper will describe a few constellations (Alenia Spazio patent) based on this orbits 'family', with multiple satellites either in single or multiple planes, to provide Regional Communication Services to countries located in the northern or southern Earth hemisphere, or both. In addition, the apogee altitude of about 8000 Km, makes these orbits highly attractive for Earth Remote Sensing Services requiring the capability of better observing the polar caps and sites at high latitudes, as in the case of Meteorology and 'nowcasting'.