Solar Terrestrial Physics

ASTRID to Explore Neutral Particle Physics

ASTRID is a microsatellite carrying scientific instruments designed to investigate the near-Earth plasma environment with emphasis on neutral particle phenomena. By making novel measurements of uncharged particles, it will be possible to increase the knowledge of charged particles in the Earth's radiation belts and ring current. The energetic ions in the ring current charge exchange with cold hydrogen atoms in the Earths' exosphere. The resulting energetic neutral atoms (ENA) escape from the ring current. ENA can thus be used to remotely "image" the ring current in order to study the morphology and dynamics of this region. Another important field of study is the outflow of neutrals from the auroral region.

ASTRID marks the first use of the FREJA-C, a generic microsatellite bus which has been developed by the former Space Systems Division (now OHB Sweden) of the Swedish Space Corporation in Solna. The size of the platform box is 420 x 354 x 290 mm. The weight is 27 kg.

ASTRID was successfully launched on January 24, 1995 at 03:54:22 UT from the Russian launch site Plesetsk, using a piggyback arrangement on a COSMOS launch vehicle. The orbit is circular at 1,000 km altitude, inclined 83 degrees to the equator. For an artists impression of ASTRID in space, click here.

The payload, designed by The Swedish Institute of Space Physics, consisted of three experiments:

  • -A Neutral Particle Imager (PIPPI) which measured energetic neutral particles in the Earths' magnetosphere. It was the first time ever that an instrument of this type flew on a spacecraft.
  • -A miniature UV imaging system (MIO) which measured UV in two pass bands and provided the Lyman-alpha intensity, an important parameter for evaluation of the Neutral Particle Imager data.
  • -An electron spectrometer (EMIL) which provided the electron distribution function, thus supporting the Neutral Particle Imager in terms of relating the measurements of neutrals to different magnetosphere regions.

    A data compression card, RONJA, built by the Finnish Meteorological Institute in Helsinki was used for reduction and lossless compression of data. The compressed data were transmitted at 8 kbps to a ground station operating at 400 MHz at the Swedish Institute of Space Physics in Kiruna. The scientists also had an uplink capability to the instruments from this ground station (nicknamed "Snickerboa"). One pass per day was covered by the Esrange ground station at 128 kbps using S-band, Esrange is also responsible for the platform operations.

    For further information about the FREJA-C microsatellite platform, please contact the program manager Anna Rathsman at SSC.

    For further information about the scientific project ASTRID, please contact the Solar Terrestrial Physics research programme at IRF.

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    Last update 2015-09-01 by Jesper Lindkvist, jesper*