Astrid Credit - Sven Grahn

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.

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.

Typical orbit: 1000km circular, 83 degree inclination. Length: 0.95 m (3.11 ft). Maximum Diameter: 0.45 m (1.47 ft). Mass: 30 kg (66 lb). Associated Launch Vehicle: Kosmos 11K65M.

• 1998 December 10 - Astrid-2 - Launch Site: Plesetsk. Launch Vehicle: Kosmos 11K65M. Mass: 30 kg (66 lb). Perigee: 978 km (607 mi). Apogee: 1,013 km (629 mi). Inclination: 83.00 deg.

  Swedish Space Corporation micro-satellite Astrid-2 was ejected from the Nadezdha 5 COSPAS satellite at 15:25 GMT and was to measure the auroral electromagnetic fields and particle environment.

• JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Accessed at: http://msl.jpl.nasa.gov/home.html.