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Dust Flux Monitor Instrument (DFMI)

NSSDC ID: 1999-003A-03
Mission Name: Stardust/NExT
Principal Investigator: Mr. Anthony J. Tuzzolino


The Dust Flux Monitor Instrument (DFMI) is designed to detect impacts and measure particle flux, intensity profile, and mass distribution. The instrument consists of a dust sensor unit and two acoustic sensors, all mounted on the main Whipple sheild on the front of the spacecraft. The primary scientific objective of the investigation is to carry out quantative measurements of particle impact rate and particle mass distribution throughout the flyby of Comet Wild 2. The secondary objective is to measure background interplanetary dust over the 7 year course of the mission.

The dust flux monitor sensor unit is a metal frame with two disks of polyvinylidene flouride (PVDF). The PVDF is piezoelectric material which produces a local depolarization when impacted by a high-speed particle. Electrodes on each surface can detect the resulting charge pulse. The large disk has a sensitive area of 200 square cm (diameter of 15.94 cm) and a thickness of 28 microns. The small disk has a sensitive area of 20 square cm (diameter of 5.04 cm) and a thickness of 6 microns. The two disks sit side-by-side in the metal frame, which is 27.3 cm long, 1.6 cm thick, and is mounted directly on the outward facing wall of the bumper shield, a composite honeycomb structure which is the first layer of the main Whipple shield. Each disk is a separate sensor, and each has four mass threholds of detection. Together they can detect particle impacts (at 6.1 km/s) from about 10^-11 (10 to the minus 11) to 10 ^-4 grams at a rate up to 10000 counts per second. Readouts occur every 100 ms to 1 s. The sensor unit has a mass of 0.332 kg and is connected to an electronics box by a 1.5 m long cable. The electronics box, 11.2 x 12.1 x 14.0 cm with a mass of 1.2 kg, is mounted within the spacecraft body.

The two acoustic sensors are identical quartz piezoelectric accelerometers and comprose the Dual Acoustic Sensor System (DASS). One is mounted on the inner side of the bumper shield, which has an area of 0.7 square meters. The other is mounted on the acoustic plate, a thin 0.5 square meter carbon-fiber composite sheet attached to a nextel blanket mounted behind the bumper shield. This sensor will only detect particles with enough mass to penerate the bumper plate. The sensors work by detecting the oscillations in the plates generated by the impact. The number of oscillations detected is proportional to the impact energy. Each sensor has two thresholds, a low threshold with a time width of 510 microseconds and a high threshold of 210 microseconds. The DASS will detect any particles of mass less than 10^-4 g up to several grams (at 6.1 km/s) striking the bumper or acoustic plates. The flux of this particle size is expected to be low. Each sensor is attached to the electronics box by a 2.4 m long cable. The acoustic sensors each have a mass of 0.032 g.

Alternate Names

  • DFMI

Facts in Brief

Mass: 1.76 kg
Power (avg): 1.8 W

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Planetary Science: Small Bodies

Additional Information

Questions or comments about this experiment can be directed to: Dr. David R. Williams.



NameRoleOriginal AffiliationE-mail
Mr. Anthony J. TuzzolinoLead InvestigatorUniversity of Chicago 

Selected References

Tuzzolino, A. J., et al., Dust Flux Monitor Instrument for the Stardust mission to comet Wild 2, J. Geophys. Res., 108, No. E10, 8115, doi:10.1029/2003JE002086, 2003.

Tuzzolino, A. J., et al., Dust measurements in the coma of comet 81P/Wild 2 by the Dust Flux Monitor Instrument, Science, 304, No. 5678, 1776-1780, June 2004.

Green, S. F., et al., The dust mass distribution of comet 81P/Wild 2, J. Geophys. Res., 109, E12S04, doi:10.1029/2004JE002318, 2004.

Image of the Dust Flux Monitor Instrument (DFMI) experiment

Dust Flux Monitor Instrument (DFMI)

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