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Dust Flux Monitor Instrument
The Dust Flux Monitor Subsystem includes a dedicated, sophisticated Dust Flux Monitor Instrument (DFMI) for small particles, and two separate acoustic impact sensors that monitor for strikes by the relatively rare, but especially dangerous larger particles.
The Dust Monitoring System has four basic goals:
- To monitor the dust environment for spacecraft health and interpretation of any spacecraft anomaly.
- To provide real-time flux measurements of large comet dust particles, for early determination of the potential hazards when the spacecraft begins to experience the coma environment.
- To measure the spatial and temporal variations of particle flux and mass distribution during the Stardust flyby of Comet P/Wild-2. The DFMI measurements will provide cumulative and differential fluxes over the particle mass range 1 x 10-11g to 2 x 10-4g, as well as cumulative flux for particles with mass >2 x 10-4 g.
- To provide the context for the collected dust samples. Originally developed under the direction of Tony Tuzzalino at the University of Chicago, the DFMI is a highly sensitive instrument designed to detect particles as small as a few microns. It is based on a special polarized plastic (PVDF) that generates electrical pulses when struck by small high speed particles.
Dust Flux Monitor Test Panel
The DFMI was built on the advances made from dustinstruments and sensors that have flown on previous missions. These instruments make exclusive use of the polyvinylidene fluoride (PVDF) dust sensor developed in the laboratory of Professor John Simpson at the University of Chicago, which include:
- The Dust Counter and Mass Analyzer (DUCMA) instruments successfully flown on the Vega missions to Comet Halley.
- The ERIS Observer instrument (developed by Lockheed) which utilized PVDF dust sensors provided by the University of Chicago. Excellent data was obtained but remains classified.
- The Space Dust (SPADUS) instrument for the Advanced Research and Global Observation Satellite (ATGOS) to be launched December 1998 (Earth orbiter).
- The High Rate Detector (HRD) on the Cassini mission to Saturn (launched October 15, 1997).
DFMI consists of a Sensor Unit (SU), Electronics Box (EB), and the two acoustic sensors mounted to the Stardust spacecraft. The SU is mounted on the Whipple shield, and the EB is mounted internally to the spacecraft enclosure.
The SU consists of two independent PVDF dust particle sensors mounted in a frame. Each sensor will be connected to the EB by a cable with a length of about four feet (1.4 meter). The combined eight mass thresholds of these sensors provide cumulative and differential particle fluxes over the particle mass range.
The acoustic sensors are in two different locations. Each device is a quartz piezoelectric transducer that converts any vibrations in the shield it is monitoring into electrical signals that are relayed to the DFMI. The first sensor is mounted to the first Whipple shield. The second is mounted to a special acoustic plate, consisting of a thin, stiff graphite-fiber epoxy sheet sewn to the first Nextel blanket. It has been shown, by testing in the laboratory of J.A.M. McDonnell (University of Kent, Canterbury, England) that particles of about 1-mm and larger will penetrate the bumper shield to produce a signal in this detector.
