Application of the Global Reference Atmospheric Model to polar orbitmissions

Abstract

The Global Reference Atmospheric Model (GRAM) is used extensively by NASA and other agencies for simulat.ions of a t m o s ~ ~ pheric conditions from surface to orbital altitudes. The original model W R S based on empirical data which did not include n u m e r ous observations at high altit.udcs (especially 60-100 km) and high latitudes. This altitude and latitude range is especially important for simulations of the planned Space Shuttle polar orbit missions. This paper describes same recent analyses which have yielded revised perturbation magni~tudes for pressure, density and tcmperature for use in GRAM in the height rnnge 65-90 km. Discussion is a l s o presented of other upper atmospheric data sources, such a s from the Middle Atmospheric Program (MAP), which will provide future updates of the 25-100 km altitude sections of GRAM.