Aura

Aura is an astronomy mission of the French space program developed in the late 1960s by CNES. It is the third satellite of the D-2 series. It is historically the first family of French scientific satellites which also includes the D-2A Tournesol (launched in 1971), D-2A Polaire, and Signe 3 missions. These spacecraft are more elaborate than the previous generation (D-1), in particular, because they have an active attitude control system using cold gas micro-propellants. The realization of Aura is entrusted to the Matra company. It is the first French artificial satellite to be built entirely under industrial prime contractorship. Aura's scientific mission was set by the CNES Scientific Council, which met on May 1, 1969, and defined two major themes: the study of solar ultraviolet radiation and its absorption by the Earth's atmosphere (Laboratoire de Physique Stellaire et Planétaire du CNRS) and the study of ultraviolet radiation from stars located near the plane of the ecliptic (Laboratoire d'Astronomie Spatiale du CNRS) and zodiacal light. Aura is a rotationally stabilized satellite. The body of the satellite is shaped like a cylinder 70 cm in diameter and 80 cm high. This central part supports 4 antennas and 4 solar panels. The structure is made of aluminum honeycomb. The collected data is recorded on magnetic tape or transferred to the ground stations at a rate of 256 bits per second. Attitude control is ensured by cold gas (nitrogen) thrusters. The satellite's axis is kept permanently pointed in the direction of the Sun. Due to the small volume and reduced mass available, the performance of the instruments making up the payload is modest: the spectral and spatial resolutions reach respectively about 16 angstroms and 1 arc minute.