Pioneer 10 and 11 Status 1 October 1998

 Pioneer 10

(Launched 2 March 1972)

Distance from Sun (1 October 1998): 71.01 AU Speed relative to the Sun:
12.24 km/sec (27,380 mph) Distance from Earth: 10.57 billion kilometers
(6.567 billion miles) Round-trip Light Time: 19 hours 34 minutes

PIONEER 10 JUST WON'T QUIT!! We have just successfully completed the fourth
precession maneuver in the past year and a half to point Pioneer 10 toward
Earth by cycling the transmitter off and on. This was a procedure that
naysayers doomed to failure for a 25+ year old TWT predicting that such a
turn-off and start-again would shatter the 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. We are deeply grateful for the gracious way that the
Lunar Prospector staff and the DSN have managed this extra burden on their
time. 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. AND WE ARE STILL GETTING SCIENCE
DATA! The low-power Geiger-Tube-Telescope instrument still yields valuable
scientific data. We also receive data from the Charged Particle Instrument
but only for a few hours each week to conserve battery power on Pioneer 10.
Tracking of Pioneer is expected to continue for approximately six months
under the current pointing arrangements, at which time another repositioning
maneuver would be due. The battery reading is very low - perhaps at a
minimum. Pioneer 10 persists longer than ever conceived or expected. Stay

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

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.

This page is maintained by Dr R J Smith ( .
Last modified on 17 October, 1998.