ABSTRACT
Indian Regional Navigation Satellite System (IRNSS) spacecraft to be launched into geo-synchronous orbit carries on board two star sensors namely Mark-I and Mark sensors differ in their configuration. In Mark detector and electronics are conductively isolated while the electronics surrounds the detector in Mark-II construction. The later while shrinks the size of the package, provides a different boundary condition to the detector. To reduce the dark current noise effect on the sensors, it should be mounted on the spacecraft in a manner where no direct sun rays fall on the optics system. The Mark-I sensor is flown in earl missions in sun-synchronous orbit and the mounting of the sensor avoids sun load falling on it. However in IRNSS orbit both Mark-I and Mark-II are being flown for the first time and mounting configuration does not preclude sun load falling into the baffle of the sensor. This situation requires a careful study based on a suitable thermal model.
This paper presents the development of the thermal model and analysis of the sensors. The following study details are discussed.
• Passive cooling of sensor, baffle and electronics
• Sun angle variation on sensor mounting
