Pioneers 10 and 11 GTT

Termination of Pioneer 10's Mission

James A. Van Allen, 20 February 2003
  1. Dave Lozier of NASA/Ames Research Center called yesterday morning to inform me that he and Bob Hogan now despair of receiving any further data from Pioneer 10 and are terminating their attempts to do so.

  2. A (partially) successful contact by the two-way coherent technique was established on 4-5 December 2002. The Madrid DSN Station received the downlink signal but it was too weak to enable subcarrier lock on. Hence, no useful telemetry was obtained. The carrier signal was also received at Arecibo.

  3. On 22-23 January 2003, a downlink signal was received briefly at Madrid after the University of Iowa GTT instrument had been turned off to remove its small power requirement. But again there was no lock on to the subcarrier.

  4. The most recent attempt to contact Pioneer 10 was on 6-7 February 2003. But in this case, the Madrid station got conclusively null results after an assiduous search.

  5. Lozier's judgment is that the Earth Look Angle (angle between the S/C antenna axis and the S/C-Earth line) is probably satisfactory but that the available power is now inadequate to operate the transmitter. The bus voltage of the power supply held its nominal value of 28 volts for many years but was observed to have dropped to 24 volts last March. Experts on the TWT (transmitter tube) consider that 24 volts is about the drop-out level for the transmitter.

  6. The last telemetered data from the University of Iowa cosmic ray instrument were as follows:
    2 March 2002 (39 minutes of clean data) (r = 79.83 AU)
    27 April 2002 (33 minutes of clean data) (r = 80.22 AU)

  7. As a P. I., I am deeply grateful to NASA and in particular to its Ames Research Center and Deep Space Network for maintaining the flow of data from this historic mission.

  8. Pioneer 10 called home for over thirty years of spaceflight. Its future is now transferred from NASA to Isaac Newton and Johannes Kepler, neither of whom could be reached for comment.
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