SETI [Fwd: [seti] [ASTRO] Pioneer 10 Update - October 1, 1999]


Robert Owen (rowen@technologist.com)
Mon, 04 Oct 1999 14:38:10 -0400


Larry Klaes wrote:

> From: Larry Klaes <lklaes@bbn.com>
>
> >Date: Sat, 2 Oct 1999 0:38:42 GMT
> >From: Ron Baalke <BAALKE@KELVIN.JPL.NASA.GOV>
> >To: astro@lists.mindspring.com
> >
> >http://spaceprojects.arc.nasa.gov/Space_Projects/pioneer/PNStat.html
> >
> >------------------------------------------------------------------------
> >
> > STATUS UPDATED: 1 October 1999
> >
> > ------------------------------------------------------------------------
> >
> > Pioneer 10
> >
> >(Launched 2 March 1972)
> >
> >Distance from Sun (1 October 1999): 73.59 AU Speed relative to the Sun:
> >12.24 km/sec (27,380 mph) Distance from Earth: 10.95 billion kilometers
> >(6.806 billion miles) Round-trip Light Time: 20 hours 17 minutes
> >
> >ANOMALOUS GRAVITATIONAL FORCE? A discussion of this phenomenon appears in
> >the 4 October 1999 issue of Newsweek magazine (See also the December 1998
> >issue of Scientific American.) The mystery of the tiny unexplained
> >acceleration towards the sun in the motion of the Pioneer 10, Pioneer 11 and
> >Ulysses spacecraft remains unexplained. A team of planetary scientists and
> >physicists led by John Anderson (Pioneer 10 Principal Investigator for
> >Celestial Mechanics) has identified a tiny unexplained acceleration towards
> >the sun in the motion of the Pioneer 10, Pioneer 11, and Ulysses spacecraft.
> >The anomalous acceleration - about 10 billion times smaller than the
> >acceleration we feel from Earth's gravitational pull - was identified after
> >detailed analyses of radio data from the spacecraft. A variety of possible
> >causes were considered including: perturbations from the gravitational
> >attraction of planets and smaller bodies in the solar system; radiation
> >pressure, the tiny transfer of momentum when photons impact the spacecraft;
> >general relativity; interactions between the solar wind and the spacecraft;
> >possible corruption to the radio Doppler data; wobbles and other changes in
> >Earth's rotation; outgassing or thermal radiation from the spacecraft; and
> >the possible influence of non-ordinary or dark matter. After exhausting the
> >list of explanations deemed most plausible, the researchers examined
> >possible modification to the force of gravity as explained by Newton's law
> >with the sun being the dominant gravitational force. "Clearly, more
> >analysis, observation, and theoretical work are called for," the researchers
> >concluded. The scientists expect the explanation when found will involve
> >conventional physics.
> >
> >HELIOPAUSE NOT REACHED YET! Van Allen reports that there was a 5% reduction
> >in cosmic rays detected at Pioneer 10 in February corresponding to the solar
> >flare experienced on Earth in April of last year. This suggests that Pioneer
> >10 is still under the influence of the Sun and therefore has not passed
> >through the heliopause yet. We are still looking into extending the tracking
> >of Pioneer 10 past September. It would be wonderful to detect the
> >heliopause. The Van Allen instrument readings are the best chance for
> >Pioneer 10. Voyager is, of course, looking for it also. A solar maximum is
> >expected late this year. This provides another opportunity to see whether
> >the cosmic ray readings on Pioneer 10 after the time lag will reflect this
> >cycle or not and therefore indicate whether we are still in the heliopause
> >or not.
> >
> >Larry Lasher, Pioneer Project Manager
> >
> >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.

=======================
Robert M. Owen
Director
The Orion Institute
57 W. Morgan Street
Brevard, NC 28712-3659 USA
=======================



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