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Ion Mass Spectrometer (BIMS)

NSSDCA ID: 1978-078A-02

Mission Name: Pioneer Venus Probe Bus
Principal Investigator:Mr. Harry A. Taylor, Jr.


The Pioneer Venus Probe Bus Ion Mass Spectrometer (BIMS) experiment obtained measurements which provided information on the solar wind interaction with Venus, upper atmosphere photochemistry, and the mass and heat transport characteristics of the atmosphere. A Bennett radio-frequency ion spectrometer, similar to those flown on OGO and Atmospheric Explorer satellites, measured Venus' upper atmosphere ion concentrations in the mass range from 1 to 56 atomic mass units (amu) from the time of crossing Venus' bowshock to bus burnup.

Identical Ion Mass Spectrometers were mounted on the Pioneer Venus Orbiter and the Probe Bus. Each spectrometer, with a mass of 3.0 kg, consisted of two parts, an analyzer tube and an electronics package. The electronics package held printed circuit boards inside a machined magnesium housing mounted inside the spacecraft. The package contained low- and high-gain pre-amplifiers, amplifiers, a log A/D converter, an RF generator, voltage regulator, command and control, and data handling. It uses 1.5 W of power, and functions to supply RF and DC potentials to the ion analyzer tube; detect and amplify ion current flowing to the collectors; digitize, process, and format data for telemetry; configure the sensor for subsequent measurements; and decode and implement commands.

The analyzer tube is a hollow cylinder of aluminum containing a series of knitted tungsten mesh grids and gold-plated aluminum spacers. These are backed by a supressor, a low-gain collector and a high-gain collector. At the head of the tube is a guard ring and an accelerating voltage. The analyzer can be set to measure any of 16 common ion masses from 1 to 56 amu (1, 2, 4, 8, 12, 14, 16, 17, 18, 24, 28, 30, 32, 40, 44, and 56 amu). It also has the ability to produce simulated ion currents for calibration.

The instrument operated with repeated explore/adapt cycles, each 6.3 seconds in duration. The first 1.8 seconds of the cycle is the explore portion, which consists of measuring each of the 16 pre-selected masses for approximately 0.1 second each. In the 4.5 second adapt portion of the cycle, up to 8 ions that are found to be present in the explore portion are measured repeatedly. The ion current values from each measurement are sampled, held for A/D conversion, and transfered to telemetry storage registers.

Alternate Names

  • BIMS
  • PioneerVenusProbeBus/BIMS
  • urn:nasa:pds:context:instrument:pvmp.bus.bims

Facts in Brief

Mass: 3 kg
Power (avg): 1.5 W

Funding Agency

  • NASA-Office of Space Science (United States)


  • Planetary Science: Atmospheres
  • Planetary Science: Fields and Particles

Additional Information

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



NameRoleOriginal AffiliationE-mail
Mr. Henry C. BrintonOther InvestigatorNASA Goddard Space Flight Center
Dr. F. Curtis MichelOther InvestigatorRice
Prof. Thomas M. DonahueOther InvestigatorUniversity of
Dr. Richard E. HartleOther InvestigatorNASA Goddard Space Flight Center
Dr. Siegfried J. BauerOther InvestigatorUniversitat Graz, Austria
Dr. Paul A. CloutierOther InvestigatorRice
Mr. Harry A. Taylor, Jr.Principal InvestigatorNASA Goddard Space Flight Center

Selected References

  • Taylor, H. A., Jr., et al., Bennett ion mass spectrometers on the Pioneer Venus bus and Orbiter, IEEE Trans. Geosci. Rem. Sens., GE-18, 44-49, doi:10.1109/TGRS.1980.350259, Jan. 1980.
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