Re: The power of nuclear power

[Scott D Kniffin <Scott.D.Kniffin.1@gsfc.nasa.gov>]

John, thanks for passing this along.  It's another great case of
bad/ignorant reporting, at least we aren't alone.  

Pioneer 10 would have passed through the asteroid belt on the way to
Jupiter, not after.  The spacecraft's RTG won't be producing enough power
to keep everything on much longer, the thermocouples are not wearing out.
The Voyager 1 spacecraft will pass the termination shock in 2002 and the
heliopause in 2019.  Through the middle of last month, she has traveled
more than 8 billion miles total and is just over 7.1 billion miles from the
sun (10h:39m light time vs 10h:21m for Pioneer), and is moving at 38,655
mi/hr relative to the sun.  Voyager 2 is not far behind either.  Pioneer 10
is over 200 million miles behind Voyager 1 at this point and the distance
is increasing at about 270,600 miles per day.  Voyager 1 passed Pluto's
orbit in May 1988 and Voyager 2 passed below Pluto's orbit in August 1990.
Pioneer 10 was launched earlier on a much smaller vehicle with much less
initial speed and hence is now behind the younger Voyagers.  

The power of the transmitter is also not explained well.  The initial power
of the transmitter is not the amazing part.  The effective power when it
reaches earth is much more so.  Voyager's signal strength, at Earth, is
presently 10E-16 Watts and perfectly readable by the Deep Space Network.
(For reference that's about 20 billion times less power than it takes to
run a digital wrist watch.)  

For more see: http://www.nasa.gov/projects.html and go to the Voyager and
Pioneer links towards the bottom in Planetary and Solar System Exploration.
 The NASA web page makes a mistake too, it says Pioneer is 11 billion miles
from Earth, that should be kilometers.  I sent them a note too.  

Scott Kniffin

RSO Unisys Federal Systems, Lanham, MD
CHO Radiation Effects Facility, GSFC, NASA
mailto:Scott.D.Kniffin.1@gsfc.nasa.gov

The opinions expressed here are my own. They do not necessarily represent
the views of Unisys or NASA.  This material has not been reviewed by my
manager or NASA.  

At 10:15 03/06/00 -0600, you wrote:
>I saw this in passing.
>
>----- Original Message -----
>From: ArcaMax <ezines@arcamax.com>
>To: <jenday1@email.msn.com>
>Sent: Monday, March 06, 2000 12:17 AM
>Subject: ArcaMax Science News for March 06, 2000
>.. . .
>>    FADING FAST, BUT STILL ON THE AIR.
>>    Pioneer 10 was launched on March 2, 1972, on a voyage to Jupiter slated
>> to last two years. Now, 28 years later, the little spacecraft is still
>> operating, though it is now as far from the Sun as the planet Pluto, and
>is
>> speeding out of the solar system at a speed of 28,000 miles per hour. The
>> plutonium in its nuclear reactor is still producing heat, but the
>> thermocouples that convert it into electricity are wearing out, says NASA
>> mission control. Its transmitter has just 8 watts of power, and the weak
>> signal it sends home takes more than 10 hours -- at the speed of light --
>> to reach Earth. Pioneer 10 was the first spacecraft to visit Jupiter. It
>> then became the first to pass through the asteroid belt, and it will soon
>> be the first human-made artifact to venture beyond Pluto's orbit into deep
>> space.
>>
>> --
>> Copyright 2000 by United Press International.
>> All rights reserved.
>.. . .
>
>-- John
>
>John Jacobus, MS
>Medical Health Physicist
>3050 Traymore Lane
>Bowie, MD  20715-2024
>jjacobus@exchange.nih.gov (w)
>jenday1@email.msn.com (H)
>
>
>************************************************************************
>The RADSAFE Frequently Asked Questions list, archives and subscription
>information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html
>
>
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html