The Toroidal Imaging Mass-Angle Spectrograph (TIMAS) is a novel 3-D ion mass spectrograph which has been optimized for the POLAR mission. It overcomes most of the shortcomings of ion mass spectrometers carried on previous magnetosphere missions. Specifically it simultaneously performs three-dimensional distribution function measurements of all major magnetospheric ion constituents twice per satellite spin. Due to the extremely large data volume produced by these measurements, these data must be highly compressed to fit within the limited telemetry allocation. This compression is carried out by a combination of data prioritization, distribution function integration to reduce velocity space resolution, and lossless data compression. Versatile control of both data acquisition and onboard data compression permit optimal operation in all regions of the magnetosphere to be surveyed by the POLAR spacecraft.
The authors wish to express their appreciation for the excellent support of the GGS project office. In particular we want to thank Len Rabb, our instrument manager, who faithfully represented our interests. We also want to thank the many engineers and other support people at all of the participating institutions whose expertise and dedication were essential to the realization of a successful instrument. The development of this instrument was supported by NASA under Contract NAS5-30302, by the Swiss National Science Foundation under grants 32591.91 and 20-29868.90 and the state of Bern, and by the UK Science and Engineering Research Council.
Last modified February 1996 by Bill Peterson email@example.com