CHARACTERIZATION OF SOLAR SENSORS FOR SMALL SATELLITES

A. MORENO; M.J.L. TAMASI; M. G. MARTÍNEZ BOGADO; C.G. BOLZI; M. DÍAZ SALAZAR; N. KONDRATIUK

CIUDAD AUTÓNOMA DE BUENOS AIRES

Simposio; 1st IAA Latin American Symposium on Small Satellites; 2017

Instituto Colomb - UNSAM; CONAE

The attitude control system is an important part of a satellite. The attitude control must have precision and it must be a very robust and reliable system to ensure the success of the mission. Coarse or primary sun sensors (CSS) are used to guide a satellite or a rocket to the sun. The CSS are usually used in pairs or in an array of sensors. The attitude control system orients the satellite to the sun using the previously calibrated CSS output signal. Some satellite bus technologies, which have been developed for traditional larger satellite platforms, can be adapted and be suitable for use with small satellites, particularly if these technologies have a low cost and easy customization process. CSS is a low-cost attitude determination sensor suitable for a wide range of space missions. The Solar Energy Department (DES) of the Argentine National Atomic Energy Commission (CNEA) performs R&D activities related with photovoltaic solar energy conversion for space and terrestrial applications. Silicon CSS were designed and manufactured by DES at CNEA using previous experience in silicon solar cells. Since 1995, the DES has been working in the development of solar devices for artificial satellites, in the framework of a corporation agreement with the National Commission of Space Activities (CONAE).National sensors have been integrated into several Argentine Satellite Missions, for ex. SAC-A and Aquarius/SAC-D, and the analysis of telemetry carried out shows a correct operation of the sensors included in the satellites. Among the advantages of these sensors are: wide field of view, low weight, low cost, high electrical signal that can be customized to mission requirements, space qualified components and technologies. Six silicon CSS were integrated at Cubebug-2 (also called ?Manolito?), an Argentinian cubesat launched from Rusia. Manolito is a type of parallelepiped shape with a base of about 10 cm x 10 cm and a height of 20 cm. It has the solar arrays located at the sides of the largest surface (-X, +X, -Y and +Y). The panel -X has 5 commercial ATJ solar cells and the other solar arrays have 4 cells each. The coarse sun sensors have been integrated in the four solar arrays (-X, +X, -Y and +Y) and +Z and -Z sides. CNEA at the Constituyentes Atomic Center has the necessary facilities and equipment to perform the characterization and qualification tests of both position sensors and solar cells. The environmental tests that can be performed are thermal cycling, proton or electron irradiation to simulate the space environment to study the degradation of its electrical and electronic parameters. For the electrical characterization, the current-voltage (I-V) curve is measured under controlled conditions. A TS-Space "Close-match" high fidelity steady-state solar simulator with AM0 spectrum and irradiance equivalent to 1367 W/m2 normalized is used to obtain the I-V curve. Another electrical characterization that is performed on a CSS is the angular response, which is established as the variation of the short-circuit current as a function of the incidence angle. For the electronic characterization, the spectral response can be measured using the equipment designed and manufactured in the DES that complies with IRAM Argentina Standard 210013-14 and ASTM No. E 297. Among the electronic characteristics that can be measured there is the minority carrier effective lifetime using the OCVD technique, it was done before and after 10 MeV proton irradiation at normal incidence with fluences of about 10-11 p/cm2 with a national development equipment.