A thermal controller was designed to maintain constant temperature for the attitude sensor carried on satellites in the Globalstar constellation. The sensors could tolerate a maximum temperature range of two degrees centigrade, while the satellite could vary by 30 degrees centigrade. Normal spacecraft voltage ranged between 14 and 23 volts, and could reach a maximum of 50 volts. Current limiting was required, as well as power limiting. High reliability and worst-case design practices were employed.