This paper discusses the development of an in-house computer code for the thermal analysis of satellites. The code uses Thermal Network Method (TNM) in conjunction with the Method of Lines (MOL) for the solution of the energy equation in the presence of radiative heat transfer. The predictive accuracy of the code is demonstrated on a test problem involving a cubic satellite with two solar panels and a single representative payload at its center to account for all other possible equipments in the satellite. The results produced by the present code were compared with the predictions of commercial thermal analysis software on the same test problem and a good agreement between the two sets of results was obtained. The code is a promising tool for the thermal analysis of satellites.