JumpStart - Space Science
Pioneer - Going, Going...*

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Introduction

Launched on 2 March 1972, Pioneer 10 was the first spacecraft to travel through the Asteroid belt, and the first spacecraft to make direct observations and obtain close-up images of Jupiter. Famed as the most remote object ever made by man, Pioneer 10 is now over 7 billion miles away (Until 17 February 1998, the heliocentric radial distance of Pioneer 10 had been greater than that of any other manmade object. But late on that date Voyager 1's heliocentric radial distance, in the approximate apex direction, equaled that of Pioneer 10 at 69.419 AU. Thereafter, Voyager 1's distance will exceed that of Pioneer 10 at the approximate rate of 1.016 AU per year). The spacecraft made valuable scientific investigations in the outer regions of our solar system until the end of its mission on 31 March 1997.

Pioneer Project History

The Pioneer 10 & 11 Spacecraft Missions are two of a series of eight spacecraft missions managed by the Pioneer Project Office at NASA, Ames Research Center. The following is a brief description of the other Pioneer Missions.

Pioneer 6-9
Pioneers 6-9 were launched into Solar orbit between 1965 and 1968. Their prime mission completed years ago, the spacecraft were then tracked only occasionally.

Pioneer 6 was launched on 16 December 1965. Some time after 15 December 1995 (almost 30 years after it was launched) the primary transmitter (TWT) failed. During a track on 11 July 1996 the spacecraft was commanded to switch to the backup TWT, and the downlink signal was re-acquired. The spacecraft and a few of the science instruments were again functioning.

Pioneer 6 was featured on the Star Date radio broadcast by the University of Texas McDonald Observatory on 16 December 2000 - the 35th anniversary of its launch. Pioneer 6 is the oldest NASA spacecraft extant. There was a successful contact of Pioneer 6 for about two hours on 8 December 2000 to commemorate its anniversary.

Pioneer 7 was launched on 17 August 1966. It was last tracked successfully on 31 March 1995. The spacecraft and one of the science instruments were still functioning.

Pioneer 8 was launched on 13 December 1967. Its primary TWT failed several years ago, but on 22 August 1996 the spacecraft was commanded to switch to the backup TWT, and the downlink signal was re-acquired. The spacecraft and one of the science instruments were again functioning.

Pioneer 9 was launched on 8 November 1968. The spacecraft failed in 1983.

Pioneer Venus

The Pioneer Venus Orbiter spacecraft was launched on 20 May 1978. It orbited the planet Venus for 14 years until it entered the Venus atmosphere on 8 October 1992 and was destroyed.

The Pioneer Venus Multiprobe spacecraft was launched on 8 August 1978. Three small probes, one large probe, and the spacecraft bus entered the Venus atmosphere on 9 December 1978.

Good News!! Pioneer 10 lives on

Pioneer 10 distance from Sun : 77.76 AU Speed relative to the Sun: 12.24 km/sec (27,380 mph) Distance from Earth: 11.77 billion kilometers (7.31 billion miles)
Round-trip Light Time: 21 hours 49 minutes
Round-trip Light Time: 21 hours 49 minutes

At GMT 17:27:30, Saturday, 4/28/01, the signal from Pioneer 10 was received at station 63 in Madrid, the first time since August 5/6 of last year. So it appears that Pioneer 10 has life, albeit in another mode - i.e., only in a two-way coherent mode. We have been listening for the Pioneer 10 signal in a one way downlink non-coherent transmission mode since last summer with no success. We therefore conclude that in order [for Pioneer 10] to talk to us, we need to talk to it. This means from now on, we need two-way round-trip light time (RTLT) passes to allow the Deep Space Network (DSN) to send up a strong stable signal to lock up with a coherent downlink signal.

The status of the Geiger Tube Telescope instrument (James Van Allen, P.I.) is on. Due to power considerations, this is the only instrument that has been powered on for the last 4 years. Last month, we successfully processed tracks, previously thought null. The scientific data on the 5 and 6 August 2000 passes of Pioneer 10 were analyzed by Dr. Van Allen, who reported clean data. The cosmic ray intensity was identical within statistics to that on DOY 190 (7/9/00), the date of the last maneuver. There was no indication that the Solar wind boundaries have yet to be reached.

Some Questions and Answers

Question:
How far will Pioneer travel and on what path?
Answer:
Pioneer 10 will be in galactic orbit for billions of years. It is moving in a straight line away from the Sun at a constant velocity of about 12 km/sec. Until Pioneer 10 reaches a distance of about 1.5 parsec (309,000 AUs) - about 126,000 years from now - it will be dominated by the gravitational field of the Sun. After that Pioneer 10 will be on an orbital path in the Milky Way galaxy influenced by the field of the stars that it passes.

Question:
How much has Pioneer been eroded?
Answer:
All the wear, pitting, and erosion that Pioneer 10 has sustained are probably over now. The asteroid belt and the severe conditions of Jupiter have already been experienced. Now, Pioneer is in the vacuum of space where the average spatial density of molecules is one trillionth the density of the best vacuum we can draw on Earth. We expect Pioneer to last an indeterminate period of time, probably outlasting its home planet, the Earth. In 5 billion years, the Sun will become a red giant, expand, envelop the orbit of the Earth, and consume it. Pioneer will still be out there in interstellar space. Erosional processes in the interstellar environment are largely unknown, but are very likely less efficient than erosion within the solar system, where a characteristic erosion rate, due largely to micrometeoritic pitting, is of the order of 1 Angstrom/yr. Thus a plate etched to a depth ~ 0.01 cm should survive recognizable at least to as distance ~ 10 parsecs, and most probably to 100 parsecs. Accordingly, Pioneer 10 and any etched metal message aboard it are likely to survive for much longer periods than any of the works of Man on Earth.

Question:
If the spacecraft are leaving the Solar System, why does the distance from Earth sometimes get shorter?
Answer:
It is a matter of a hyperbolic escape trajectory, geometry, and relative velocity vectors. The distance from the Sun is always increasing. However, since the Earth travels around the Sun faster than the spacecraft moves away from the Sun, the spacecraft-earth distance decreases for a few months, and then rapidly increases again.