Plasma wave observation using waveform capture in the Lunar Radar Sounder on board the SELENE spacecraft

The waveform capture (WFC) instrument is one of the subsystems of the Lunar Radar Sounaer (LRS) on board the SELENE spacecraft. By taking advantage of a moon orbiter, the WFC is expected to measure plasma waves and radio emissions that are generated around the moon and/or that originated from the sun and from the earth and other planets. It is a high-performance and multifunctional software receiver in which most functions are realized by the onboard software implemented in a digital signal processor (DSP). The WFC consists of a fast-sweep frequency analyzer (WFC-H) covering the frequency range from 1 kHz to 1 MHz and a waveform receiver (WFC-L) in the frequency range from 10 Hz to 100 kHz. By introducing the hybrid IC called PDC in the WFC-H, we created a spectral analyzer with a very high time and frequency resolution. In addition, new techniques such as digital filtering, automatic filter selection, and data compression are implemented for data processing of the WFC-L to extract the important data adequately under the severe restriction of total amount of telemetry data. Because of the flexibility of the instruments, various kinds of observation modes can be achieved, and we expect the WFC to generate many interesting data.