Abstract-This paper describes the design, fabrication, characterization, and satellite integration of a miniaturized two axis sun sensor which has been used in the attitude control system of the Spanish nano-satellite NANOSAT-1B. This device is made of four silicon photodiodes monolithically integrated in a crystalline silicon substrate, protected by a transparent cover glass assembled on the same silicon die against space radiation damage. The sensor fabrication combines standard silicon processing technology with a high performance solar cell fabrication process. The sensor, including electronics and mechanical and electrical interfacing with the satellite, has a small size (3 cm 3 cm) and low weight (24 gr.), with a sun field-of-view greater than 60 with an angle accuracy better than 0.15 . Three of these sensors have already been integrated in the NANOSAT-1B platform that has been successfully launched in July 2009. Index Terms-Angle measurement, cover glass, field-of-view (FOV), satellite attitude control, silicon photodiodes, sun sensor.

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Abstract-The objective of this work is to explore the capability of a charge trapping control loop to continuously compensate charge induced by ionizing radiation in the dielectric of MOS capacitors. To this effect, two devices made with silicon oxide have been simultaneously irradiated with gamma radiation: one with constant voltage bias, and the other working under a dielectric charge control. The experiment shows substantial charge trapping in the uncontrolled device whereas, at the same time, the control loop is able to compensate the charge induced by gamma radiation in the second device.

Abstract-In this work we investigate the effect of the laser-firing process on the back surface passivation of p-type silicon heterojunction solar cells. For that purpose, two different nanosecond laser sources radiating at ultraviolet (355 nm) and visible (532 nm) wavelengths are employed. Firstly, we optimize the laser-firing process in terms of the electrical resistance of locally diffused point contacts. Specific contact resistance values as low as 0.91 mΩ⋅cm 2 and 0.57 mΩ⋅cm 2 are achieved for the visible and ultraviolet laser sources, respectively. In addition, the impact of the laser-firing process on the rear surface passivation is studied by analyzing the internal-quantum-efficiency curves of complete devices. Low surface recombination velocities in the range of 300 cm/s are obtained for the ultraviolet laser with a 1% fraction of contacted area. This value increases to about 700 cm/s for the visible laser, which indicates a significantly higher recombination at the contacted area. The best heterojunction solar cells with rear laser-fired contacts are obtained for the ultraviolet laser and reached a 17.5% conversion efficiency.