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Cosmic Dust Detector

NSSDCA ID: 1967-123A-04

Mission Name: Pioneer 8
Principal Investigator:Mr. Otto E. Berg

Description

This experiment was designed to (1) measure the cosmic dust flux density in the solar system, (2) determine the distribution of cosmic dust concentrations in the earth's orbit, (3) determine the gradient, flux density, and speed of particles in meteor streams, and (4) perform an in-flight control experiment on the reliability of the microphone as a cosmic dust sensor. The experiment instrumentation, which was mounted in the equator of the satellite with its axis radial to the satellite spin axis facing in the ecliptic plane, consisted of a front film-grid sensor array and a rear film-grid sensor array, spaced 5 cm apart, and an acoustical impact plate upon which the rear film was mounted. The sensor arrays consisted of four vertical film strips crossed by four horizontal grid strips to form 16 front and 16 rear film-grid arrays (each 2.5 cm sq), creating 256 possible combinations. Each grid strip and film strip was connected to a separate output amplifier whose signals were used to determine the segment in which an impact occurred. The front film sensor, which was recessed 3 cm into the experiment housing, consisted of an eight-layer composite -- 700-A parylene encapsulation, 500-A copper, 300-A aluminum, 3000-A parylene substrate, 300-A aluminum, 500-A copper, support mesh, and 500-A parylene encapsulation. Each of the rear sensor-array film strips consisted of a 60-micrometer molybdenum sheet cemented to a quartz acoustical sensor plate. The operation of the sensors was based on two basic measurable phenomena that occur when a hypervelocity particle impacts on a surface -- (1) formation of plasma and (2) transfer of momentum. When the front film was penetrated by a particle, a time-of-flight 4-MHz electronic clock was activated. The clock was shut off when the particle impacted on the rear film thus measuring particle speed and direction. Three general cosmic dust particle types were detectable -- (1) high-energy, hypervelocity particles (greater than 1 erg), which produced responses at both front and rear film sensors, (2) low-energy, hypervelocity particles (less than 1 erg), which produced responses only at the front film sensor, and (3) relatively large high-velocity particles (greater than 0.1 nanograms), which could pass through the front and rear film sensor arrays without generating a detectable plasma but could still impart a measurable impulse to the acoustical sensor. The acoustical sensors were designed to perform an in-flight study on the reliability of the microphone as a cosmic dust sensor in addition to performing as an impact sensor for this experiment. In-flight calibration was provided and initiated by ground command and monitored the experiment electronics in addition to providing a check on the physical condition of the plasma sensors. The sensors were calibrated prior to the flight by impacts with iron spheres ranging in mass from 1 nanogram to 0.1 picogram, accelerated by a 2-mv electrostatic accelerator to 2 to 10 km/s.

Alternate Names

  • Electric Field Detector
  • Pioneer8/CosmicDustDetector
  • urn:nasa:pds:context:instrument:cdd.p8

Funding Agency

  • NASA-Office of Space Science (United States)

Disciplines

  • Space Physics: Zodiacal Light/Interplanet Dust
  • Planetary Science: Small Bodies

Additional Information

Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office

 

Personnel

NameRoleOriginal AffiliationE-mail
Mr. Luc SecretanOther InvestigatorNASA Langley Research Center
Mr. Otto E. BergPrincipal InvestigatorNASA Goddard Space Flight Center
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