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Dust Impact Detector (DID)

NSSDCA ID: 1985-056A-08

Mission Name: Giotto
Principal Investigator:Dr. J. A. M. McDonnell


The investigation uses a system comprised of an array of dust impact sensors to answer some of the fundamental questions in cometary science, namely, the measure of the particulate mass efflux from a comet, its mass distribution, and the particulate grain density. Using the entire surface of the meteoroid shield of the spacecraft system, the array of sensors is able to detect masses over the range 1.E-17 to 1.E-3 g, and perhaps even larger. The upper limit is dependent on the maximum mass of the particulate matter intercepted by the probe during the fly-by. This mass range encompasses almost all the non-volatile comet nucleus component, currently believed to comprise 50% of the comet mass. The range also encompasses about 90% of the mass and scattering area distributions of the zodiacal cloud. The instrumentation is comprised of (1) an impact plasma micro-perforation and sensing array which determines the mass, penetration properties, density and ionization of the impacting particles in the range 1.E-17 to 1.E-10 g; (2) a penetration-initiated capacitor discharge array for determining the impacting flux above a precisely defined threshold of 1.E-9 g; and (3) a meteoroid shield array incorporating three transducers on the front shield and one on the rear shield. The latter array determines the impact position and momentum exchange of the entire probe from the mass range 1.E-10 to 1.E-3 g, or larger. The techniques have been selected with a special regard for Halley's comet environment and the anticipated high flux rates based on experience from previous missions. The comparison of different detection techniques and correlation of independent sensor outputs has guided the design. Reliability of event detection in the unexplored environment of the comet is high and the limiting accuracy of the measurements is believed to be better than 20% over a dynamic range of 1.E+14. A microprocessor is used to monitor each sensor status and to process each event as well as the cumulative data, which represents the total event amplitude distribution from each sensor.

Alternate Names

  • DID
  • Giotto/DID
  • urn:esa:psa:context:instrument:gio.did

Facts in Brief

Mass: 2.26 kg
Power (avg): 1.9 W
Bit rate (avg): 0.361 kbps

Funding Agencies

  • European Space Agency (International)
  • Max-Planck-Institut (Federal Republic of Germany)
  • Science Research Council, UK (United Kingdom)


  • Planetary Science: Small Bodies

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. Bertil A. LindbladCo-InvestigatorLund
Dr. Wesley M. AlexanderCo-InvestigatorBaylor University
Dr. Rejean J. L. GrardCo-InvestigatorESA-European Space Research and Technology
Dr. Eberhard GruenCo-InvestigatorMax-Planck-Institut fur
Dr. Martha S. HannerCo-InvestigatorNASA Jet Propulsion
Prof. David W. HughesCo-InvestigatorUniversity of
Dr. J. C. MandevilleCo-InvestigatorCentre d'Etude et de Recherche (Toulouse)/Off Nat d'Etude et Recherc
Dr. Gerhard H. SchwehmCo-InvestigatorRuhr-Universitat Bochum
Dr. Eduard B. IgenbergsCo-InvestigatorTechnische Universitat
Dr. Zdenek SekaninaCo-InvestigatorNASA Jet Propulsion
Dr. D. H. ClarkCo-InvestigatorRutherford Appleton Laboratory
Prof. A. MinafraCo-InvestigatorUniversity of Bari
Prof. Ezio BussolettiCo-InvestigatorUniversita degli Studi di Lecce
Dr. J. A. M. McDonnellGeneral ContactUniversity of Kent,
Dr. J. A. M. McDonnellPrincipal InvestigatorUniversity of Kent,

Selected References

  • Goldstein, R., et al., The composition and plasma signature of a large dust impact on the Giotto spacecraft, J. Geophys. Res., 96, No. A8, 13739-13747, doi:10.1029/91JA01013, Aug. 1991.
  • McDonnell, J. A. M., et al., The Giotto dust impact detection system, in The Giotto Mission--Its Scientific Investigations, ESA SP-1077, edited by R. Reinhard and B. Battrick, pp. 85-107, Mar. 1986.
  • McDonnell, J. A. M., et al., Dust density and mass distribution near comet Halley from Giotto observations, Nature, 321, No. 6067, 338-341, doi:10.1038/321338a0, May 1986.
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