The Microcomputer Spacecraft Thermal Analysis Routines (MSTAR) software package is being developed for NASA/Goddard Space Flight Center by Swales and Associates, Inc. (S&AI). Thermal analysis of large-scale spacecraft are currently being performed with industry standard programs such as SSPTA1, VIEW2, and TRASYS3. These software packages, however, are based on solution algorithms developed as much as 25 years ago. Many of the algorithms used in these programs are based on software and hardware available at that time. In recent years, the computer industry has made tremendous technological advances in providing powerful yet inexpensive desktop computers capable of competing with small mainframe computers. In December 1992, S&AI was awarded a Phase I Small Business Innovative Research contract from NASA to develop a microcomputer based thermal analysis program to replace the current SSPTA and TRASYS programs. Using software and hardware tools available today the program will include both diffuse and specular analysis capabilities, a user friendly graphical interface, interactive geometric model generation and visualization capabilities, an interface to read existing SSPTA and TRASYS geometry files as well as provide output in SINDA-854, SINDA/G5 and TAK III6 compatible formats. Phase I consists of a six month effort which will focus on developing geometric model generation and visualization capabilities using a graphical user interface (GUI).