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Nicodemus

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Space Mission News [Jan. 20th, 2012|09:25 pm]
Nicodemus

  • GRAIL Spacecraft Enter Lunar Orbit, Get New Names

    The twin GRAIL spacecraft entered orbit around the moon early this year. They are measuring the distance between them for minute variations and thereby mapping the moon's gravity field. Following a contest open to schoolchildren, the twin probes have been given the callsigns Ebb and Flow. Perfect names!

  • NASA Debunks 'UFO Sighting' on Probe Video Feed

    The Stereo-B solar probe is in an interested polar orbit around the sun allowing it to get a view out across the inner solar system, including looking back at Earth. It sends a video feed back that, recently, had a weird enormous triangular shape moving across it. OMG! Aliens! NASA responded with, basically, "Dude, it's a lens flare. Simmer down."

  • Voyager Instrument Heater Turned Off

    Voyager 1, waaaaaay out beyond the solar system now, has had one of its last heaters turned off in order to conserve power. The RTG power system is producing less electricity and they are trying to keep the probe able to send signals back to Earth through 2025(!) when they were originally slated to end their missions in 1989.

  • New Horizons Spacecraft Enters Final Cruise Toward Pluto

    A longtime personal favorite, the New Horizons spacecraft goes into third and final phase of its cruise out to Pluto. Entering this phase, controllers are checking spacecraft health and trajectory. It begins actual observations in Jan 2015 and should arrive at (well, whiz past) Pluto in July of that year. It's a long wait but I'm really excited to see what we learn from the last unexplored (former) planet!

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Comments:
[User Picture]From: fjmccloud
2012-01-21 07:13 pm (UTC)
I would love to know more about the RTG. Because honestly, that decision makes no sense at all to me.

RTGs produce heat (and thereby power) constantly, whether you use it or not. Turning off a load isn't going to save any power at all. It's just wasting it.

From the article "470 Watts and a 30-Volt DC supply at launch in 1977. By 2008, radioactive decay of the plutonium fuel source had caused the output to drop to 285 Watts."

This also makes no sense to me. Plutonium-238 has a half life on the order of a human lifetime. Plunging that much over only 30 years seems wrong to me. Unless something else has degraded along the way. (Does the thermocouple also deteriorate somehow?)
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[User Picture]From: porsupah
2012-01-21 08:53 pm (UTC)
That's a very good point. I'd be interested to learn more, also. (The Register has fallen very far from its peak of being an insightful and snarky news source, I would say. Now, they seem mostly powered by decade-old observance of cliches)
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[User Picture]From: nicodemusrat
2012-01-21 11:52 pm (UTC)
The Register article links to this NASA JPL mission page which provided those statistics.

Note that the decrease in power output does not mean the radioactive material has decreased in mass by the same proportion. Generation is based on radioactive emission and other degradable parts, such as electric thermocouples.

This wikipedia page on RTGs notes that the Voyager 1 and Voyager 2 generators have dropped by a third in electrical output due to a combination of these factors.
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[User Picture]From: mothermonster
2012-01-22 01:01 am (UTC)
thanks for the update!
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