Pionner 10 just won’t quit even when 19 hours 40 minutes out at 10.61 billion kilometers from Earth. Mission controllers have successfully completed the fourth precession maneuver in the past year and a half to realign Pioneer 10 toward Earth by cycling the transmitter off and on.
This was a procedure that naysayers said was doomed to failure for a 25+ year old satellite predicting that such turn-off and start-again would shatter the TWT mechanism. But it was either try it or lose the antenna pointing towards Earth. Needless to say, even experts can be wrong. The mission formally ended on 31 March 1997 when funding ended in favor of more scientifically productive Heliospheric missions.
However, a waiver was given to operate Pioneer 10 as part of the Lunar Prospector controller training program as long as other NASA missions were not interfered with. Pioneer 10 has continued at a much reduced activity level under those guidelines, with Lunar Prospector staff doing their best to manage Pioneer in the time they have available.
The spacecraft is at a distance of 6.6 Billion miles (71 AU’s) and is the
farthest out in the opposite direction to which the Sun moves. Voyager 1
passed Pioneer 10 in mileage out of the Solar System earlier this year but
is travelling in the opposite direction. Despite its age and limited power supplier the low-power Geiger-Tube-Telescope instrument still yields valuable scientific data. With additional data from the Charged Particle Instrument only a few hours each week to conserve battery power on Pioneer 10.
Tracking of Pioneer is expected to continue for at least another six months under the current pointing arrangements. The battery reading is very low – perhaps at a minimum. Pioneer 10 by the grace of God persists longer than ever conceived or expected.
Distance from Sun (1 August 1998): 70.58 AU Speed relative to the Sun: 12.24 km/sec (27,380 mph) Distance from Earth: 10.61 billion kilometers (6.595 billion miles) Round-trip Light Time: 19 hours 40 minutes. Pioneer 10 was launched March 2, 1972.
Pioneer 10 will continue into interstellar space, heading generally for the red star Aldebaran, which forms the eye of Taurus (The Bull). Aldebaran is about 68 light years away and it will take Pioneer over 2 million years to reach it.
Pioneer 11
Launched 5 April 1973
The Mission of Pioneer 11 has ended. Its RTG power source is exhausted.
The last communication from Pioneer 11 was received in November 1995,
shortly before the Earth’s motion carried it out of view of the spacecraft
antenna.
The spacecraft is headed toward the constellation of Aquila (The Eagle),
Northwest of the constellation of Sagittarius. Pioneer 11 may pass near one of the stars in the constellation in about 4 million years.
