Long-Term Evolution of SCD-1 Satellite Temperatures Based on Comparative Analysis of Telemetric Data Measured in Orbit

This paper presents results of the research investigation regarding the causes for temperature variation of the SCD-1 (data-collection satellite) by analyzing its thermal behavior evolution throughout 13 years in orbit. SCD-1, the first satellite designed and built in Brazil, was launched in 1993 and is still in operation. A mathematical model has been developed to simulate thermal behavior of SCD-1 in orbit, which was used as a working tool during project design phase, and is presented here. Temperatures of SCD-1 in orbit have been monitored and recorded in the Control and Tracking Center (Sao Jose dos Campos, SP, Brazil) since its launch. An analysis carried out at the mission's beginning showed that all the temperatures were within the ranges predicted in model. Over the years, the battery, which is the most temperature-sensitive equipment in the satellite, had an increase in temperature approaching upper limit. A method has been developed to investigate the causes of this upswing in which an optimization routine linked to the mathematical model corrects a selected set of parameters in order to adjust the theoretical temperature values to the experimental values. By means of this methodology, data from SCD-1 were analyzed from 1995 to 2005 period and it was concluded that the rise in temperature was caused by an increase in internal battery heat dissipation and absorptivity in solar spectrum of some of the external satellite shielding, both consequences of a long-term degradation.