WAVES: THE RADIO AND PLASMA WAVE INVESTIGATION ON THE WIND SPACECRAFT

The WAVES investigation on the WIND spacecraft will provide comprehensive measurements of the radio and plasma wave phenomena which occur in Geospace. Analyses of these measurements, in coordination with the other onboard plasma, energetic particles, and field measurements will help us understand the kinetic processes that are important in the solar wind and in key boundary regions of the Geospace. These processes are then to be interpreted in conjunction with results from the other ISTP spacecraft in order to discern the measurements and parameters for mass, momentum, and energy flow throughout geospace. This investigation will also contribute to observations of radio waves emitted in regions where the solar wind is accelerated. The WAVES investigation comprises several innovations in this kind of instrumentation: among which the first use, to our knowledge, of neural networks in real-time on board a scientific spacecraft to analyze data and command observation modes, and the first use of a wavelet transform-like analysis in real time to perform a spectral analysis of a broad band signal. 1. Investigation Objectives T h e g o a l o f the W A V E S inves t i ga t i on on the W I N D spacec ra f t is to p r o v i d e c o m p r e h e n s i v e c o v e r a g e o f r ad io and p l a s m a w a v e p h e n o m e n a in the f r e q u e n c y r a n g e f r o m a f r ac t ion o f a Her t z up to abou t 14 M H z for the e l ec t r i c f ie ld and 3 k H z for the m a g n e t i c f ield. Th i s p a c k a g e wi l l p e r m i t s eve ra l k ind o f m e a s u r e m e n t s , a l l o f Space Science Reviews 71: 231-263, 1995. (~) 1995 Kluwer Academic Publishers. Printed in Belgium. 232 J.-L. BOUGERET ET AL. which are essential to understanding the Earth's environment Geospace and its response to varying solar wind conditions. The WIND orbit will have an apogee as large as 250 earth radii and a perigee of at least 5 earth radii. It is described in more detail in this issue and will permit observations in the solar wind and through key boundary regions of the Geospace. The spacecraft will spin at 20 revolutions per minute. We briefly describe below how the WAVES measurements will contribute to both large scale, global analyses and small scale analyses.