Studies on high energy particle irradiation on Micro Sun Sensors for space applications

High accuracy micro sun sensors (angular resolution better than 0.1°) for space applications are designed and developed using n
⁺
/p junction twin triangular silicon photo detectors (planar process) anodically bonded with micro-optics (Corning 7740) having an etch cavity depth of around 100 μm on one side and a 300 μm wide slit patterned on high optical density black chrome on the other side. This sensor configuration determines sun angle by taking differential current outputs from the individual photo-detectors. A normalization technique adopted makes the output independent of flux variations, ambient temperature fluctuations and cosine effect of incidence. Micro sun sensor devices, whose field of view (FOV) is around ±50°, are characterized for sensor performance, which include mainly sensitivity and non-linearity in the linear range of ±25°. Achieved sensitivity and non-linearity of these devices are 140 mV/deg and better than 10% respectively. Further, the effect of gamma and electron irradiation on the sensor performance is studied. Few devices were subjected to gamma radiation (Dose:100 krad), with a rate of 23 rad/s using Co-60 source and found that the degradation in the short circuit current density is around 0.158% and 1.58% respectively. The devices which have undergone electron irradiation of energy 8 MeV with a fluence of 2×10
¹³
/cm
²
, and their post sensor performance evaluation revealed that sun presence, non-linearity and sensitivity are varied. The high energy particle irradiation effect was studied with the help of analytical models and the variation is substantiated quantitatively.