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"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 |
#12
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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. |
#13
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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 | |
#14
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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 |
#15
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Is this the same Sen. Robert C Byrd that opposed Martin Luther King
and asked J Edgar Hoover to put him in jail and throw away the key? Strange times we live in. Victor wrote: http://www.space.com/missionlaunches...mm_050114.html "For those at work who don't have streaming video available........." LIVE coverage of Huygens' Titan Descent 6:05 a.m. EST: Space News Writer Peter de Selding reports live from Huygens mission control: DARMSTADT, Germany-- A network of powerful ground telescopes has picked up the signal of Europe's Huygens descent probe 1.2 billion kilometers away, confirming that the probe is alive as it begins its descent into the thick atmosphere of Saturn's largest moon, Titan. European Space Agency officials at Huygens mission control here said the signal -- no more than the equivalent of a telephone dial tone -- was detected by a network of 18 telescopes deployed to listen for a signal coming directly from Huygens. The biggest of these antennas is the 100-meter-diameter Robert C. Byrd Green Bank Telescope, operated by the National Radio Astronomy Observatory in Green Bank, West Virginia. The signal did not confirm anything beyond the fact that Huygens is alive. But it was enough to cause a burst of applause here when announced at 10:35 a.m. GMT (5;35 a.m. EST) today. 'There is a lot of emotion in this room," said Jean-Pierre Lebreton, Huygens program manager at ESA. "It's great news." Leonid Gurvitz, mission manager for Huygens' communications with the ground telescope network, said 18 telescopes including Green Bank had been trained to pick up a signal and that it is the network itself, more than any single telescope, that received the Huygens signal. NASA's Cassini satellite, which carried Huygens to Saturn orbit, has been moved into position to receive Huygens mission data during the probe's 2.5-hour descent into Huygens' thick atmosphere. A more-complete assessment of whether Huygens' parachutes have deployed and its heat shield jettisoned to permit the start of observations is expected to be received by science teams from Cassini around 11:20 a.m. EST (1620 GMT) today. 6:00 a.m. EST: If it switched on as planned, a microphone instrument aboard Huygens may allow researchers to recreate the sound of the probe's descent as it plunged through Titan’s atmosphere, ESA mission scientists said. The instrument may also record thunder, and Huygens scientists hope to have at least initial data to present within 24 hours. 5:50 a.m. EST: Cautious ESA commentators stress the Huygens signal is just a carrier tone. There is no confirmation that the six science instruments aboard the probe are working as planned. "It looks like we heard the baby crying," said Huygens mission manager Jean-Pierre Lebreton from the floor of ESOC mission control. "But clearly it tells us the probe is alive, the entry has been successful and we are under parachutes." 5:35 a.m. EST: Huygens speaks from Titan! ESA has confirmed that the Green Bank Telescope successfully detected a Huygens signal tone. The signal, a confirmation that Huygen's transmitter is at least functioning, and activated on time at about 5:18 a.m. EST. About 600 people are at ESOC mission control for Huygens Titan descent and some engineers crowded around computer monitors when the signal confirmation was announced. "It's a tremendously exciting moment," said John Dodsworth, Huygens ground manager at ESOC. |
#16
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why dont the photo links work at this page?
Impact9 wrote: This is pretty exciting stuff! I hope and pray Huygens lands safely and this mission is a success. I'm watching the live feed from NASA TV and refreshing a good number of websites monitoring the mission. Here's a real good misson monitor link: http://www.planetary.org/saturn/huygens_mission.html -DH |
#17
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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 | |
#18
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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. |
#19
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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. |
#20
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In article ,
Tim Killian wrote: Was the lack of an RTG on Huygens a political decision, or a true engineering limitation? Yes. :-) Within the priorities, mass limits, and cost constraints of the project, there was definitely no engineering possibility of an RTG. (The "priorities" part is that Huygens was mainly an atmosphere mission with only a secondary role as a lander, as witness its primary mission being 153 minutes -- 150 minutes of descent, 3 minutes on the surface.) The priorities, mass limits, and cost constraints were ultimately mostly political decisions at one level or another. I don't believe there was an explicit political "no RTG" decision -- Huygens did have a whole bunch of RHUs (plutonium heater capsules) -- but the mission as defined couldn't really afford one (in dollars, mass, or engineering complications) and didn't really need one. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
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