Astrid-2

Swedish earth magnetosphere satellite. Swedish Space Corporation's second microsatellite (based on Astrid-1) was slated to perform high resolution E-field and B-filed measurements in the Earth's auroral regions. Science satellite for SSC, Sweden. Launched 1995-1998. Used Freja-C bus.

Additional objectives included the measurement of electron density, electron and ion distribution functions, UV auroral imaging, and UV atmospheric absorption. The spacecraft was a spin stabilized, sun pointing platform with about 10 kg of instrument mass. Dimensions were 170 x 110 x 30 cm with deployed solar panels, which generated about 90 W. After release from the launch vehicle, and spin up (using a tiny solid rocket thruster) the spacecraft employed the SSC "sunseeker" algorithm to find and remain pointed at the sun. Attitude control was accomplished with magnetic torque coils, and a nutation damper. Attitude was determined with a star sensor, sun aspect sensor, and magnetometer. Spacecraft radios downlinked at 128kbps, and accepted uplinked commands at 10kbps. Data reception and satellite control was at SSC in Stockholm.

Astrid-2 flew several distinct instrument packages: EMMA was a comprehensive scientific experiment measuring both electrical and magnetic fields. LINDA was a Langmuir probe experiment, consisting of two 10mm diameter spherical probes mounted on two light weight booms with a probe to probe separation distance of 2.9 meters. By using two probes, scientists hoped to not only measure the fine structure of the plasma density irregularities down to 1 m scales but also distinguish between temporal and spatial effects. MEDUSA was a combined electron and ion spectrometer. The instrument FOV was nearly parallel to the satellite spin plane; this area was split into 16 sectors for measurement. PIA consisted of two spin-scanning photometers (PIA-1/2) for auroral imaging and one sun pointing photometer (PIA-3) for atmospheric absorption measurements. As of 4 October 1997 Astrid had passed three system acceptance tests including EMI compatibility, vibration, and spin balancing.