Temporal Variation of Earth Thermal Environmental Parameters for Spacecraft at Low Inclination Orbits

The temporal variation of Earth emitted infrared radiation (IR) and albedo are examined for the case of a spacecraft operating in a Space Station Freedom (SSF)-like orbit with a period of 94 minutes and an inclination 28.75°. Seventy three randomly selected days of daily average Earth IR and albedo measurements from the Earth Radiation Budget Experiment were used to calculate the effective IR and albedo constants for the Earth during representative orbits. The time average effective IR and albedo extreme values, including a correction for diurnal effects, are presented for multiple periods of up to 4 hours. The statistical variation of IR and albedo over various time intervals is also presented, as are the results of a study of the correlation between IR and albedo. The results of the present study are used to recommend the design environments that should be used for future spacecraft in orbits with inclination and altitude similar to SSF.