Astronomy News
Dr. Neal Sumerlin keeps us abreast of happenings in the night sky and the progress of the new Belk Astronomical Observatory.
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Other Posts:
Describing the Indescribable (07/22/2009)
Total Solar Eclipse in July (06/07/2009)
Other Earths (05/20/2009)
Save Those Old Computers! (04/13/2009)
Play With Pictures from Mars! (04/13/2009)
Saturn in 2009 (04/13/2009)
The New Worlds (02/04/2009)
Christmas at the Moon (12/10/2008)
Potpourri of Space News (12/10/2008)
Night Sky Happenings (11/17/2008)
R.I.P., Mars Phoenix Lander (11/17/2008)
Pictures of Planets (11/17/2008)
Ice Geysers of Enceladus (09/22/2008)
Constellations (09/22/2008)
Happy Equinox Day! (09/22/2008)
More News from Mars (06/04/2008)
Search (but no rescue) on Mars (05/20/2008)
We lose a friend (05/03/2008)
Quiz winner! (04/29/2008)
Seeing and Patience (04/22/2008)
The World at Night (03/31/2008)
New Stars that are Really Old (03/14/2008)
Latest From Planetary Spacecraft (03/14/2008)
Lunar Eclipse Update (02/18/2008)
Aiming a Telescope (02/18/2008)
Observatory Update (02/04/2008)
Venus and Jupiter in the Morning (02/04/2008)
Total Lunar Eclipse (02/04/2008)
Messenger Mission to Mercury (02/04/2008)
Power Sources for Space Probes
Posted on 11/17/2008Phoenix's fate was predetermined by her landing location and her reliance on solar power. Why don't we look for some other source of power that is less dependent on the environment?
Actually, we've been doing that for some time now. Think about the deep-space probes we have sent to the outer planets. Were they to rely on solar cells, they would quickly find themselves underpowered as they flew ever farther from the Sun. At Jupiter, the light level is about 4% of that at Earth. Spacecraft such as the Voyager missions and the current Cassini mission to Saturn rely on nuclear power.
No, they don't carry reactors, nothing anywhere near that complex. They carry a few kilograms of plutonium-238, a radioactive isotope with an 88-year half life. Its activity is so great that in any appreciable quantity, it glows red hot. It's radioactively "hot", of course, but it is its temperature that we are putting to use here. The isotope is surrounded by thermocouples, devices through which, when one end is at a very different temperature than the other, an electrical current will flow. The isotope is an absolutely reliable (although slowly diminishing) source of heat, regardless of its surroundings. The entire power source is known as a radioisotope thermal generator, or RTG.
The upcoming Mars Science Laboratory rover (http://marsprogram.jpl.nasa.gov/msl/; surely they will find a more evocative name before launch) will use an RTG. This will allow it to operate far longer and roam much farther than any rover before it. It is designed to last one Martian year (687 Earth days), but that is more like the warranty period-it should survive much longer. Its mission includes a search for evidence of past microbial life on Mars.