spase://CNES/Observatory/CDPP-AMDA/Pioneer10

This mission was the first to be sent to the outer
solar system and the first to investigate the planet Jupiter,
after which it followed an escape trajectory from the solar
system. The spacecraft achieved its closest approach to
Jupiter on December 3, 1973, when it reached approximately
2.8 Jovian radii (about 200,000 km). As of Jan. 1, 1997
Pioneer 10 was at about 67 AU from the Sun near the ecliptic
plane and heading outward from the Sun at 2.6 AU/year and
downstream through the heliomagnetosphere towards the tail
region and interstellar space. This solar system escape
direction is unique because the Voyager 1 and 2 spacecraft
(and the now terminated Pioneer 11 spacecraft mission) are
heading in the opposite direction towards the nose of the
heliosphere in the upstream direction relative to the
inflowing interstellar gas. The spacecraft is heading
generally towards the red star Aldebaran, which forms the eye
of Taurus (The Bull). The journey over a distance of 68 light
years to Aldebaran will require about two million years to
complete. Routine tracking and project data processing
operatations were terminated on March 31, 1997 for budget
reasons. Occasional tracking continued later under support
of the Lunar Prospector project at NASA Ames Research Center
with retrieval of energetic particle and radio science data.
The last successful data acquisitions through NASA's Deep
Space Network (DSN) occurred on March 3, 2002, the 30th
anniversary of Pioneer 10's launch date, and on
April 27, 2002. The spacecraft signal was last detected on
Jan. 23, 2003 after an uplink was transmitted to turn
off the last operational experiment, the Geiger Tube
Telescope (GTT), but lock-on to the sub-carrier signal for
data downlink was not achieved. No signal at all was
detected during a final attempt on Feb. 6-7, 2003. Pioneer
Project staff at NASA Ames then concluded that the spacecraft
power level had fallen below that needed to power the onboard
transmitter, so no further attempts would be made.

The history of the Pioneer 10 tracking status is available from the
web site of the former Pioneer Project at the following location:

http://spaceprojects.arc.nasa.gov/Space_Projects/pioneer/PNhome.html

Fifteen experiments were carried to study the interplanetary and
planetary magnetic fields; solar wind parameters; cosmic rays;
transition region of the heliosphere; neutral hydrogen abundance;
distribution, size, mass, flux, and velocity of dust particles;
Jovian aurorae; Jovian radio waves; atmosphere of Jupiter and some
of its satellites, particularly Io; and to photograph Jupiter and
its satellites. Instruments carried for these experiments were
magnetometer, plasma analyzer, charged particle detector, ionizing
detector, non-imaging telescopes with overlapping fields of view
to detect sunlight reflected from passing meteoroids, sealed
pressurized cells of argon and nitrogen gas for measuring the
penetration of meteoroids, UV photometer, IR radiometer, and an
imaging photopolarimeter, which produced photographs and measured
polarization. Further scientific information was obtained from the
tracking and occultation data.

The spacecraft body was mounted behind a 2.74-m-diameter parabolic
dish antenna that was 46 cm deep. The spacecraft structure was a
36-cm-deep flat equipment compartment, the top and bottom being
regular hexagons. Its sides were 71 cm long. One side joined a
smaller compartment that carried the scientific experiments.
The high-gain antenna feed was situated on three struts, which
projected forward about 1.2 m. This feed was topped with a
medium-gain antenna. A low-gain omnidirectional antenna extended
about 0.76 m behind the equipment compartment and was mounted below
the high-gain antenna. Power for the spacecraft was obtained by
four SNAP-19 radioisotope thermonuclear generators (RTG), which were
held about 3 m from the center of the spacecraft by two three-rod
trusses 120 deg apart. A third boom extended 6.6 m from the
experiment compartment to hold the magnetometer away from the
spacecraft. The four RTG's generated about 155 W at launch and
decayed to approximately 140 W by the time the spacecraft reached
Jupiter, 21 months after launch. There were three reference sensors:
a star sensor for Canopus which failed shortly after Jupiter
encounter and two sun sensors. Attitude position could be calculated
from the reference directions to the earth and the sun, with the
known direction to Canopus as a backup. Three pairs of rocket
thrusters provided spin-rate control and changed the velocity
of the spacecraft, the spin period near the end of the mission
being 14.1 seconds. These thrusters could be pulsed or fired
steadily by command. The spacecraft was temperature-controlled
between minus 23 deg C and plus 38 deg C. A plaque was mounted
on the spacecraft body with drawings depicting a man, a woman, and
the location of the sun and the earth in our galaxy.

Communications were maintained via (1) the omnidirectional and
medium-gain antennas which operated together while connected
to one receiver and (2) the high-gain antenna which was connected
to another receiver. These receivers could be interchanged by command
to provide some redundancy. Two radio transmitters, coupled to two
traveling-wave tube amplifiers, produced 8 W at 2292 MHz each.
Uplink was accomplished at 2110 MHz, while data transmission
downlink was at 2292 MHz. The data were received by NASA's
Deep Space Network (DSN) at bit rates up to 2048 bps enroute to
Jupiter and at 16 bps near end of the mission.

Space experiments mostly continued to operate for planetary or
interplanetary measurements until failure or until insufficient
spacecraft power from the RTG's was available for operation of all
instruments, such that some were turned off permanently and others
were cycled on and off in accordance with a power sharing plan
implemented in September 1989. The Asteroid/Meteroid Detector
failed in December 1973, followed by the Helium Vector Magnetometer
(HVM) in November 1975 and the Infrared Radiometer in January 1974.
The Meteroid Detector was turned off in October 1980 due to inactive
sensors at low temperatures. The spacecraft sun sensors became
inoperative in May 1986, and the Imaging Photopolarimeter (IPP)
instrument was used to obtain roll phase and spin period information
until being turned off in October 1993 to conserve power. The
Trapped Radiation Detector (TRD) and Plasma Analyzer (PA) were
respectively turned off in November 1993 and September 1995 for
the same reason. As of January 1996 the final power cycling plan
included part-time operations of the Charged Particle Instrument
(CPI), the Cosmic Ray Telescope (CRT), the Geiger Tube Telescope
(GTT), and the Ultraviolet Photometer (UV). As of August 2000,
only the GTT instrument was still returning data.

Various other spacecraft subsystems also either failed or were
turned off for power or other reasons, and an account of these
may be of interest for engineering design of long duration deep
space missions. The primary antenna feed offset bellows failed
sometime in 1976 but a redundant unit was available for use
thereafter. The Program Storage and Execution (PSE) subsystem
was turned off in September 1989 for power conservation, after
which spacecraft maneuvers were performed by ground command
sequences. A receiver problem in mid-1992 prevented uplink to the
high gain antenna, after which uplink commands could only be sent
with 70-meter DSN antennas which also supported the 16 bps downlink.
The Backup Line Heater experienced a sticking thermostat operation
in March 1993 for 30 days but the problem did not reoccur.
Undervoltage Protection Logic was turned off in December 1993 to
prevent loss of critical spacecraft systems in the event of a
transient undervoltage condition. Duration and Steering Logic (DSL)
was turned off in February 1995 to conserve power, after which it
was turned on again only for spacecraft maneuvers. RTG power levels
are low enough that the spacecraft occasionally relies in part on
battery power (accumulated during inactive periods) to run
experiments and other systems.

The total mission cost for Pioneer 10 through the 1997 end of
official science operations was about 350 million in FY 2001 U.S.
dollars. This included about 200 million dollars for pre-launch
design and development, and another 150 million for launch,
telemetry tracking, mission operations and data analysis.
These estimates were provided by the former Pioneer Project at
NASA Ames Research Center.