GLIMPSE communications satellite link availability model

Communications satellite link availability assessments have traditionally been based on a minimum terminal-satellite elevation angle. This approach is generally acceptable for transmission frequencies below approximately 10 GHz. At the higher SHF and EHF frequencies employed by recent and future systems, however, rain attenuation effects become significant. For these systems, link availability is strongly influenced by the rainfall characteristics of the areas in which the ground terminals are located. While models have been developed to estimate rain attenuation and link availability for specific locations, there has been no way to easily generate global or regional contours of availability for systems operating at these rain-sensitive frequencies. The GLIMPSE (Graphical Link Margin Plotting Software) computer model was developed by The Aerospace Corporation to address this void. GLIMPSE generates color-coded world or regional maps showing link availability contours for a specified satellite constellation, link margin, transmission frequency, and terminal antenna diameter. GLIMPSE can also solve the inverse problem of generating contours of link margin required to achieve a specified target link availability. GLIMPSE incorporates Crane's (1982) two-component model of rain attenuation as well as standard models of atmospheric attenuation (water vapor and oxygen) and low elevation fade effects. GLIMPSE has been used extensively in several military satellite communications (Milsatcom) programs. Although originally developed for use with geosynchronous Milsatcom systems, GLIMPSE can be applied to other satellite communications systems utilizing frequencies in the 1-100 GHz range and operating in any type of orbit.