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Whipple Shield and Dust Flux Instrument

The purpose of the Whipple Shield is to protect the spacecraft from damage from impacting dust particles. The Dust Flux Monitor Instrument (DFMI) is used to monitor the dust particle impacts and transmit this information directly back to Earth.

Whipple Shield

The Whipple shield is designed to shadow the spacecraft to protect it during the high speed
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encounter with particles in the cometary coma. Bumper shields are composite panels which disrupt particles as they impact. Nextel blankets of ceramic cloth further dissipate and spread the particle debris. Three blankets are used in the main body shield, and two are used in the solar array shields. The composite Catcher absorbs all of the debris for solid particles up to 1 cm in diameter for the shield protecting the spacecraft main body.

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Whipple Shield

 

Dust Flux Monitors

The Dust Flux Monitor Subsystem includes a dedicated, sophisticated instrument, the DFMI for small particles, and two separate acoustic impact sensors that monitor for larger impact events by the relatively rare, but especially dangerous larger particles.

The Dust Monitoring System has four basic goals:

  1. To monitor the dust environment for spacecraft health and interpretation of any spacecraft anomalies;
  2. To provide real-time flux measurements for large impacting comet dust particles for early determination of the potential hazard to the spacecraft when the spacecraft begins to experience the coma environment;
  3. 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 (particle diameter range 2 mm to 518 mm), as well as cumulative flux for particles with mass >2 x 10-4 g;
  4. To provide the context for the collected dust samples.

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 very special polarized plastic (PVDF) that generates electrical pulses when impacted or penetrated by small high speed particles.

The DFMI is derived from the flight heritage obtained from earlier and current dust instruments and sensors. 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:

  1. The Dust Counter and Mass Analyzer (DUCMA) instruments successfully flown on the Vega missions to Comet Halley:
  2. The ERIS Observer instrument (developed by Lockheed) which utilized PVDF dust sensors provided by the University of Chicago. Excellent data were obtained but remain classified;
  3. The Space Dust (SPADUS) instrument for the Advanced Research and Global Observation Satellite (ATGOS) to be launched December 1998 (Earth orbiter).
  4. The High Rate Detector (HRD) on the Cassini mission to Saturn (launched October 15, 1997).
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Dust Flux Monitor Test Panel

The Dust Flux Monitor Instrument (DFMI) consists of a Sensor Unit (SU), Electronics Box (EB), and the two acoustic sensors mounted to the STARDUST spacecraft. The SU is mounted to the Whipple shield, and the EB is mounted internally to the spacecraft enclosure.

The SU consists of two independent PVDF dust particle sensors (sensor 1 and sensor 2) mounted in a frame. Each sensor will be connected to the EB by a cable with a length of 1.4 meter. The combined eight mass thresholds of sensor 1 and sensor 2 provide cumulative and differential particle fluxes over the particle mass range.

The acoustic sensors are in two different locations.
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Dust Flux Monitor Instrument
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 so-called Bumper 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.

STARDUST Webmaster Tom Meyer, meyert@colorado.edu
Last Update Wednesday, 07-Jun-2000 13:51:17 PDT