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HIC - Heavy Ion Counter

MISSION OBJECTIVES

• Monitor the flux of energetic heavy ions (C to Ni) to gather information on this form of radiation, to which electronic circuitry is highly susceptible, and there by enable the design of better radiation hardened electronics for future applications.

• Complement the science observations being made by other Galileo instruments.

• Improve and extend observations made, of these energetic heavy ions, by the Voyager and Pioneer missions.

SUMMARY

These measurements would then provide basic information on a form of radiation that can cause random changes in a spacecraft's electronics and perhaps provide the basis for the design of better radiation resistant electronics for future missions. However, HIC data would be useful to scientists as well. For example, the heavy ions observed by the HIC during solar flares have been analyzed to determine the composition of the Sun.

The HIC is really a repackaged and updated version of some parts of the flight spare of the Voyager Cosmic Ray System. The HIC detects heavy ions using stacks of single-crystal silicon wafers. The HIC can measure heavy ions with energies as low as 6 MeV and as high as 200 MeV per nucleon (that would be 3200 MeV for sulfur's charge of 16). This range includes all atomic substances between carbon and nickel.

The HIC and the EUV share a communications link and, therefore, must share observing time.

The HIC weighs 8 kilograms and uses an average of 2.8 watts of power.

HIC DESCRIPTION

• The HIC is composed of two solid-state detector telescopes called the Low-Energy Telescopes (LET B and LET E).

• The LETs have aluminized kapton windows to filter out light, RF, some of the background protons, and to provide the detectors with thermal protection.

• The HIC Electronics, except for the spacecraft interface, are from the Voyager CRS test model.

• The HIC shares an interface to the CDS and with the EUV instrument. Therefore, data is available from only one of these instruments at a time.

DESIGN DETAILS

• The HIC detects ions form 6C to 28Ni with energies from about 6 MeV/nucleon to more than 20 Mev/nucleon.

• The LET E detects ions with energies with 15 MeV/nucleon to 200 MeV/nucleon.

• The LET B detects ions with energies down to 6 Mev/nucleon.

• LET B has four silicon surface barrier detectors (LE1-LE4) and LET E has five detectors (LE1-LE5). The first three are silicon surface barrier devices and the other tow are the thick lithium drifted type.

INSTRUMENT PARAMETERS

• Instrument Mass: 8.33 kg
• Power Consumptions:
  • Instrument - 2.8 W
  • Supplemental Heaters - 0.5 W
• Microprocessors: None
• ROM/RAM: None
• Fields of View:
  • LET B (half angle) - 25 degrees
  • LET E (half angle) - 46 degrees
• Electronic Box Size: 30x32x12 cm
• Telescope Vertical Extension: 15 cm
• Thermal Range:
  • Operating (GLL 3-210)
    • Electronics - 5 to 40 degrees C
    • Detectors - -27 to 40 degrees C
  • Non-Operating (GLL 3-210)
    • Electronics - 5 to 40 degrees C
    • Detectors - -27 to 40 degrees C
• Instrument Modes:
  • Off
  • POR
  • ON
  • Calibrator ON