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Huygens' Titan Descent



 
 
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  #1  
Old January 14th 05, 04:17 PM
richard schumacher
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Default Huygens' Titan Descent

In article .com,
"Impact9" wrote:

JPL is reporting it made the landing and transmitted for 1.5 hours
after impact.

I am a bit puzzled why they only made the probe last the few short
hours after it detached from cassini. They could of built a better
battery when Voyager I is like 28 year and still going. I know it is
like -300F and mechanical things won't operate long in that harsh
environment. Assuming the probe could survive the environment it would
of been nice to be able to tap it for everything possible.



The issue is how long the orbiter is in range to relay data from Huygens
to Earth. It's only a few hours, so a longer-life battery for Huygens
would have been pointless.
  #2  
Old January 14th 05, 11:06 PM
Glenn Mulno
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Default

"richard schumacher" wrote in message news:no-spam-

I am a bit puzzled why they only made the probe last the few short
hours after it detached from cassini. They could of built a better
battery when Voyager I is like 28 year and still going. I know it is
like -300F and mechanical things won't operate long in that harsh
environment. Assuming the probe could survive the environment it would
of been nice to be able to tap it for everything possible.



The issue is how long the orbiter is in range to relay data from Huygens
to Earth. It's only a few hours, so a longer-life battery for Huygens
would have been pointless.


If that were the "only" reason then I would disagree. Cassini will be
passing by Titan again in a few weeks. I would think they could have held
data and then blasted it at the satellite each time it passed.

However, as I understand it that is not really why they kept the life to
only a few hours. I think it had more to do with just getting it down
safely, the weight of the probe on Cassini, cost, and probably just the
general expectation that conditions were not favorable to the life of the
unit being long.

Glenn


  #3  
Old January 15th 05, 02:30 AM
Scott M. Kozel
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Posts: n/a
Default

"Glenn Mulno" wrote:

"richard schumacher" wrote:

I am a bit puzzled why they only made the probe last the few short
hours after it detached from cassini. They could of built a better
battery when Voyager I is like 28 year and still going. I know it is
like -300F and mechanical things won't operate long in that harsh
environment. Assuming the probe could survive the environment it would
of been nice to be able to tap it for everything possible.


The issue is how long the orbiter is in range to relay data from Huygens
to Earth. It's only a few hours, so a longer-life battery for Huygens
would have been pointless.


If that were the "only" reason then I would disagree. Cassini will be
passing by Titan again in a few weeks. I would think they could have held
data and then blasted it at the satellite each time it passed.

However, as I understand it that is not really why they kept the life to
only a few hours. I think it had more to do with just getting it down
safely, the weight of the probe on Cassini, cost, and probably just the
general expectation that conditions were not favorable to the life of the
unit being long.


The Voyagers and Cassini itself receive electrical power from a
Radioisotope Thermoelectric Generator (RTG). An RTG can provide
electrical power to a robust suite of spacecraft systems for 20 years or
more, but an RTG would have been way too heavy to install on the Huygens
spacecraft.

The Mars lander spacecrafts utilize solar cell panels to create
electrical power which is stored in rechargable batteries, and Mars has
very little cloud cover that would interfere with that system, and Mars'
night is similar in length to Earth's; so that system is workable on
Mars.

Titan has a dense, hazy atmosphere, and even in the clear, the Saturn
system is way too far from the Sun, making a solar power system to be
infeasible (the solar panel system would have to be gargantuan).

The Huygens spacecraft could not utilize an RTG or solar power, so it
was limited to un-rechargable batteries, and given the number of
instruments on board, battery capacity was limited to a matter of hours.

--
Scott M. Kozel Highway and Transportation History Websites
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Philadelphia and Delaware Valley http://www.pennways.com
  #4  
Old January 15th 05, 04:18 AM
Scott M. Kozel
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Default

"Glenn Mulno" wrote:

"richard schumacher" wrote:

I am a bit puzzled why they only made the probe last the few short
hours after it detached from cassini. They could of built a better
battery when Voyager I is like 28 year and still going. I know it is
like -300F and mechanical things won't operate long in that harsh
environment. Assuming the probe could survive the environment it would
of been nice to be able to tap it for everything possible.


The issue is how long the orbiter is in range to relay data from Huygens
to Earth. It's only a few hours, so a longer-life battery for Huygens
would have been pointless.


If that were the "only" reason then I would disagree. Cassini will be
passing by Titan again in a few weeks. I would think they could have held
data and then blasted it at the satellite each time it passed.

However, as I understand it that is not really why they kept the life to
only a few hours. I think it had more to do with just getting it down
safely, the weight of the probe on Cassini, cost, and probably just the
general expectation that conditions were not favorable to the life of the
unit being long.


The Voyagers and Cassini itself receive electrical power from a
Radioisotope Thermoelectric Generator (RTG). An RTG can provide
electrical power to a robust suite of spacecraft systems for 20 years or
more, but an RTG would have been way too heavy to install on the Huygens
spacecraft.

The Mars lander spacecrafts utilize solar cell panels to create
electrical power which is stored in rechargable batteries, and Mars has
very little cloud cover that would interfere with that system, and Mars'
night is similar in length to Earth's; so that system is workable on
Mars.

Titan has a dense, hazy atmosphere, and even in the clear, the Saturn
system is way too far from the Sun, making a solar power system to be
infeasible (the solar panel system would have to be gargantuan).

The Huygens spacecraft could not utilize an RTG or solar power, so it
was limited to un-rechargable batteries, and given the number of
instruments on board, battery capacity was limited to a matter of hours.

--
Scott M. Kozel Highway and Transportation History Websites
Virginia/Maryland/Washington, D.C. http://www.roadstothefuture.com
Philadelphia and Delaware Valley http://www.pennways.com

  #5  
Old January 15th 05, 04:29 AM
richard schumacher
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Default

In article ,
"Glenn Mulno" wrote:

"richard schumacher" wrote in message news:no-spam-

I am a bit puzzled why they only made the probe last the few short
hours after it detached from cassini. They could of built a better
battery when Voyager I is like 28 year and still going. I know it is
like -300F and mechanical things won't operate long in that harsh
environment. Assuming the probe could survive the environment it would
of been nice to be able to tap it for everything possible.



The issue is how long the orbiter is in range to relay data from Huygens
to Earth. It's only a few hours, so a longer-life battery for Huygens
would have been pointless.


If that were the "only" reason then I would disagree. Cassini will be
passing by Titan again in a few weeks. I would think they could have held
data and then blasted it at the satellite each time it passed.

However, as I understand it that is not really why they kept the life to
only a few hours. I think it had more to do with just getting it down
safely, the weight of the probe on Cassini, cost, and probably just the
general expectation that conditions were not favorable to the life of the
unit being long.


A lifetime of weeks would have required nuclear heaters at least, and
perhaps a nuclear thermal electric source as well. That means more
mass, probably more then anyone wanted to pay to send.
  #6  
Old January 15th 05, 05:36 AM
Henry Spencer
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Default

In article ,
Glenn Mulno wrote:
However, as I understand it that is not really why they kept the life to
only a few hours. I think it had more to do with just getting it down
safely, the weight of the probe on Cassini, cost, and probably just the
general expectation that conditions were not favorable to the life of the
unit being long.


A long surface life would have required, at the very least, an RTG, which
would have run up the cost, mass, and various other complications quite a
bit. Moreover, Huygens was planned and sold as primarily an *atmosphere*
mission -- even the camera (which is a US contribution, incidentally) was
optimized as much for cloud imaging and sunlight measurements as for
surface pictures.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |
  #7  
Old January 15th 05, 05:45 AM
furtig
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Default

I have another question. The one photo I have seen from the surface
(unprocessed?) seems to have plenty of light. I found this surprising and
am assuming this was considered in the planning stage and the photo system
is extra sensitive. (?) Any comments on the data size of the images.

--
Detective Tom Polhaus: " Heavy. What
is it?"
Sam Spade: "The, uh, stuff that dreams
are made of."
"Glenn Mulno" wrote in message
...
"richard schumacher" wrote in message news:no-spam-

I am a bit puzzled why they only made the probe last the few short
hours after it detached from cassini. They could of built a better
battery when Voyager I is like 28 year and still going. I know it is
like -300F and mechanical things won't operate long in that harsh
environment. Assuming the probe could survive the environment it would
of been nice to be able to tap it for everything possible.



The issue is how long the orbiter is in range to relay data from Huygens
to Earth. It's only a few hours, so a longer-life battery for Huygens
would have been pointless.


If that were the "only" reason then I would disagree. Cassini will be
passing by Titan again in a few weeks. I would think they could have held
data and then blasted it at the satellite each time it passed.

However, as I understand it that is not really why they kept the life to
only a few hours. I think it had more to do with just getting it down
safely, the weight of the probe on Cassini, cost, and probably just the
general expectation that conditions were not favorable to the life of the
unit being long.

Glenn




  #8  
Old January 15th 05, 09:29 AM
muldar
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Posts: n/a
Default

it still is one HUGE success. Monumental, really. Just too bad the major news
networks didnt even mention it or show a photo tonight.
This sorry state of socially irresponsible affairs in the USA must end soon.



Henry Spencer wrote:

In article ,
Glenn Mulno wrote:
However, as I understand it that is not really why they kept the life to
only a few hours. I think it had more to do with just getting it down
safely, the weight of the probe on Cassini, cost, and probably just the
general expectation that conditions were not favorable to the life of the
unit being long.


A long surface life would have required, at the very least, an RTG, which
would have run up the cost, mass, and various other complications quite a
bit. Moreover, Huygens was planned and sold as primarily an *atmosphere*
mission -- even the camera (which is a US contribution, incidentally) was
optimized as much for cloud imaging and sunlight measurements as for
surface pictures.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |


  #9  
Old January 15th 05, 11:36 PM
Al Dykes
external usenet poster
 
Posts: n/a
Default

In article ,
muldar wrote:
it still is one HUGE success. Monumental, really. Just too bad the major news
networks didnt even mention it or show a photo tonight.
This sorry state of socially irresponsible affairs in the USA must end soon.


That's what you get for getting your news from TV :-)

NPR and BBC radio haev given it decent coverage so far, and it would
supise me if they don't have more on NPR's Sunday AM hour.
--

a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.
  #10  
Old January 16th 05, 12:19 AM
Tim Killian
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Default

Was the lack of an RTG on Huygens a political decision, or a true
engineering limitation?



Scott M. Kozel wrote:



The Huygens spacecraft could not utilize an RTG or solar power, so it
was limited to un-rechargable batteries, and given the number of
instruments on board, battery capacity was limited to a matter of hours.


 




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