Cluster WBD Data and the Cluster Active Archive

The Cluster Wideband (WBD) Plasma Wave Receiver obtains high resolution waveform measurements over approximately 4% of the Cluster orbit. The frequency range covered by WBD is 100 Hz to 577 kHz with time between samples ranging from 5-36 microseconds. Both electric field and magnetic field antennas can be used as the sensor. The data are telemetered directly to the ground in real time to the Deep Space Network ground stations. Cluster WBD contributions to the Cluster Active Archive (CAA) currently consist of the following: overview calibrated spectrograms (multispacecraft if available) of ~ 1-4 hours in duration; 30second uncalibrated full-time resolution spectrograms (one spacecraft only per spectrogram); listings of the time periods during which WBD data were taken; and documentation on the WBD instrument, its various modes and interpretation issues. Digital WBD waveform data are available through the Iowa WBD website, and through the Cluster PEACE High Resolution Data System at Southwest Research Institute in San Antonio, Texas. In order to provide WBD digital waveform data through the CAA, we are assessing the possibility of the CAA mirroring the SwRI website. 1. THE WBD PLASMA WAVE INVESTIGATION The Cluster Wideband (WBD) Plasma Wave Receiver is a digital wide-band receiver that provides very highresolution waveforms over a wide range of frequencies from 100 Hz to 577 kHz with a time resolution of 5-36 microseconds between samples depending on the mode. WBD makes measurements along one axis only and uses only one electric or magnetic field sensor at any given time. WBD receivers are mounted on each of the four Cluster spacecraft. A description of the WBD instrumentation and investigation is available in [1]. The first results obtained from the Cluster WBD investigation can be found in [2]. The WBD publication list is provided on the WBD website (see Section 4). With one exception in March 2001, all WBD data obtained during the Cluster Mission Operations Phase have been obtained by directly downlinking the data to a Deep Space Network ground station at about 220 kbits/second in real time, rather than recording the data onboard at 73 kbits/second. Because WBD data are not routinely recorded onboard, WBD receives only about 4% orbit coverage (2 hours per spacecraft per 57-hour orbit). Thus, all of WBD’s operations have been targeted to specific regions of Earth for which high time resolution waveform measurements will be crucial in understanding the physics of that region or of the region from which Cluster observes wave emissions remotely. A 4 ms sample of the calibrated WBD time series data obtained in the magnetosheath using the 77 kHz bandpass filter with a base frequency of 0 kHz is shown in Fig. 1. This example shows a series of solitary waves in the form of very short time duration pulses, which are typical for this region. The calibrated electric field scale is given on the left-hand vertical axis for the WBD data plotted as a solid black line with time provided on the horizontal axis. The angle of the electric field antenna used by WBD to the magnetic field, using the Cluster FGM data, is plotted as a dashed red line with the scale given on the right-hand vertical axis. Fig. 1. Four ms sample of WBD waveform data obtained in the magnetosheath on 26 March 2002. (From [3]) 2. WBD ARCHIVING PLANS The WBD archiving team at The University of Iowa will archive data graphics for the first four years of the Cluster mission, documentation, and software at the Cluster Active Archive (CAA). Below we describe these in more detail. _________________________________________________________________ Proceedings Cluster and Double Star Symposium – 5 th Anniversary of Cluster in Space, Noordwijk, The Netherlands, 19 23 September 2005 (ESA SP-598, January 2006) 1