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Longest-Lived Mars Orbiter is Back in Service (Mars Odyssey)
On Jun 28, 2:27*pm, Doug Freyburger wrote:
wrote: http://www.jpl.nasa.gov/news/news.cfm?release=2012-189 Longest-Lived Mars Orbiter is Back in Service Jet Propulsion Laboratory June 27, 2012 Mission Status Report PASADENA, Calif. -- NASA's Mars Odyssey orbiter has resumed its science observations and its role as a Mars rover's relay, thanks to a spare part that had been waiting 11 years to be put to use. One of the most amazing photos I've ever seen is from Odyssey. *It shows the purchute of one of the rover missions as it decended through the Martian atmosphere. *The first photograph of a spacecraft at another planet taken by a spacecraft at another planet. wonder if a work around is possible to point with just 2 reaction wheels? didnt they do this with hubblev for awhile? |
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Longest-Lived Mars Orbiter is Back in Service (Mars Odyssey)
On 1/07/2012 1:46 AM, Fred J. McCall wrote:
bob haller wrote: wonder if a work around is possible to point with just 2 reaction wheels? Oh, good God! THINK, Bobbert! You need pointing control in 3 dimensions. You cannot do that with only two axis control So no, you cannot 'work around' the laws of physics. If the axes of rotation of the three wheels are orthogonal, and one reaction wheel rotates, it changes the axes of rotation of the other two. Indeed, the axes of the other two can be interchanged. Sylvia. |
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Longest-Lived Mars Orbiter is Back in Service (Mars Odyssey)
On 1/07/2012 4:02 PM, Fred J. McCall wrote:
Sylvia Else wrote: On 1/07/2012 1:46 AM, Fred J. McCall wrote: bob haller wrote: wonder if a work around is possible to point with just 2 reaction wheels? Oh, good God! THINK, Bobbert! You need pointing control in 3 dimensions. You cannot do that with only two axis control So no, you cannot 'work around' the laws of physics. If the axes of rotation of the three wheels are orthogonal, and one reaction wheel rotates, it changes the axes of rotation of the other two. Indeed, the axes of the other two can be interchanged. Now hold it steady.... Hint: You can eventually get it pointed anywhere, but you can't KEEP it there in order to do science. Well, that's going to depend on what science you're trying to do, and on whether the craft has any net angular momentum. If it has no net angular momentum, it should be possible to get it pointed in any direction with minimal drift, which will be good enough for many purposes. Sylvia. |
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Longest-Lived Mars Orbiter is Back in Service (Mars Odyssey)
"Sylvia Else" wrote in message ...
On 1/07/2012 4:02 PM, Fred J. McCall wrote: Sylvia Else wrote: On 1/07/2012 1:46 AM, Fred J. McCall wrote: bob haller wrote: wonder if a work around is possible to point with just 2 reaction wheels? Oh, good God! THINK, Bobbert! You need pointing control in 3 dimensions. You cannot do that with only two axis control So no, you cannot 'work around' the laws of physics. If the axes of rotation of the three wheels are orthogonal, and one reaction wheel rotates, it changes the axes of rotation of the other two. Indeed, the axes of the other two can be interchanged. Now hold it steady.... Hint: You can eventually get it pointed anywhere, but you can't KEEP it there in order to do science. Well, that's going to depend on what science you're trying to do, and on whether the craft has any net angular momentum. If it has no net angular momentum, it should be possible to get it pointed in any direction with minimal drift, which will be good enough for many purposes. Sylvia. As I recall, the Hubble typically spends hours pointing at the same spot. I don't think you can get the drift that minimal. -- Greg D. Moore http://greenmountainsoftware.wordpress.com/ CEO QuiCR: Quick, Crowdsourced Responses. http://www.quicr.net |
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Longest-Lived Mars Orbiter is Back in Service (Mars Odyssey)
On Sat, 30 Jun 2012 06:21:52 -0700 (PDT), bob haller
wrote: One of the most amazing photos I've ever seen is from Odyssey. *It shows the purchute of one of the rover missions as it decended through the Martian atmosphere. *The first photograph of a spacecraft at another planet taken by a spacecraft at another planet. wonder if a work around is possible to point with just 2 reaction wheels? didnt they do this with hubblev for awhile? They got down to only two working gyros in 1999 before the next servicing mission, but Hubble was out of commission until the Shuttle arrived. That's why NASA split up Hubble Servicing Mission 3 into two parts (3A and 3B.) Brian |
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Longest-Lived Mars Orbiter is Back in Service (Mars Odyssey)
On 2/07/2012 12:55 AM, Fred J. McCall wrote:
Sylvia Else wrote: On 1/07/2012 4:02 PM, Fred J. McCall wrote: Sylvia Else wrote: On 1/07/2012 1:46 AM, Fred J. McCall wrote: bob haller wrote: wonder if a work around is possible to point with just 2 reaction wheels? Oh, good God! THINK, Bobbert! You need pointing control in 3 dimensions. You cannot do that with only two axis control So no, you cannot 'work around' the laws of physics. If the axes of rotation of the three wheels are orthogonal, and one reaction wheel rotates, it changes the axes of rotation of the other two. Indeed, the axes of the other two can be interchanged. Now hold it steady.... Hint: You can eventually get it pointed anywhere, but you can't KEEP it there in order to do science. Well, that's going to depend on what science you're trying to do, and on whether the craft has any net angular momentum. If it has no net angular momentum, it should be possible to get it pointed in any direction with minimal drift, which will be good enough for many purposes. And yet the folks who run the thing think it requires at least 3 working reaction wheels to do any science.... These things are rarely back-and-white. Sylvia. |
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Longest-Lived Mars Orbiter is Back in Service (Mars Odyssey)
On 2/07/2012 1:26 AM, Greg (Strider) Moore wrote:
"Sylvia Else" wrote in message ... On 1/07/2012 4:02 PM, Fred J. McCall wrote: Sylvia Else wrote: On 1/07/2012 1:46 AM, Fred J. McCall wrote: bob haller wrote: wonder if a work around is possible to point with just 2 reaction wheels? Oh, good God! THINK, Bobbert! You need pointing control in 3 dimensions. You cannot do that with only two axis control So no, you cannot 'work around' the laws of physics. If the axes of rotation of the three wheels are orthogonal, and one reaction wheel rotates, it changes the axes of rotation of the other two. Indeed, the axes of the other two can be interchanged. Now hold it steady.... Hint: You can eventually get it pointed anywhere, but you can't KEEP it there in order to do science. Well, that's going to depend on what science you're trying to do, and on whether the craft has any net angular momentum. If it has no net angular momentum, it should be possible to get it pointed in any direction with minimal drift, which will be good enough for many purposes. Sylvia. As I recall, the Hubble typically spends hours pointing at the same spot. I don't think you can get the drift that minimal. Hubble is looking into deep-space. I doubt that the martian probe is doing that. Sylvia. |
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Longest-Lived Mars Orbiter is Back in Service (Mars Odyssey)
On 2/07/2012 3:42 PM, Fred J. McCall wrote:
Sylvia Else wrote: On 2/07/2012 12:55 AM, Fred J. McCall wrote: Sylvia Else wrote: On 1/07/2012 4:02 PM, Fred J. McCall wrote: Sylvia Else wrote: On 1/07/2012 1:46 AM, Fred J. McCall wrote: bob haller wrote: wonder if a work around is possible to point with just 2 reaction wheels? Oh, good God! THINK, Bobbert! You need pointing control in 3 dimensions. You cannot do that with only two axis control So no, you cannot 'work around' the laws of physics. If the axes of rotation of the three wheels are orthogonal, and one reaction wheel rotates, it changes the axes of rotation of the other two. Indeed, the axes of the other two can be interchanged. Now hold it steady.... Hint: You can eventually get it pointed anywhere, but you can't KEEP it there in order to do science. Well, that's going to depend on what science you're trying to do, and on whether the craft has any net angular momentum. If it has no net angular momentum, it should be possible to get it pointed in any direction with minimal drift, which will be good enough for many purposes. And yet the folks who run the thing think it requires at least 3 working reaction wheels to do any science.... These things are rarely back-and-white. And yet the folks responsible for operating the thing think it is. Do they? Have they expressly stated that this is a black and white issue? Sylvia. |
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Longest-Lived Mars Orbiter is Back in Service (Mars Odyssey)
On 2/07/2012 4:50 PM, Fred J. McCall wrote:
Sylvia Else wrote: On 2/07/2012 3:42 PM, Fred J. McCall wrote: Sylvia Else wrote: On 2/07/2012 12:55 AM, Fred J. McCall wrote: Sylvia Else wrote: On 1/07/2012 4:02 PM, Fred J. McCall wrote: Sylvia Else wrote: On 1/07/2012 1:46 AM, Fred J. McCall wrote: bob haller wrote: wonder if a work around is possible to point with just 2 reaction wheels? Oh, good God! THINK, Bobbert! You need pointing control in 3 dimensions. You cannot do that with only two axis control So no, you cannot 'work around' the laws of physics. If the axes of rotation of the three wheels are orthogonal, and one reaction wheel rotates, it changes the axes of rotation of the other two. Indeed, the axes of the other two can be interchanged. Now hold it steady.... Hint: You can eventually get it pointed anywhere, but you can't KEEP it there in order to do science. Well, that's going to depend on what science you're trying to do, and on whether the craft has any net angular momentum. If it has no net angular momentum, it should be possible to get it pointed in any direction with minimal drift, which will be good enough for many purposes. And yet the folks who run the thing think it requires at least 3 working reaction wheels to do any science.... These things are rarely back-and-white. And yet the folks responsible for operating the thing think it is. Do they? Have they expressly stated that this is a black and white issue? Yes. You see, Sylvia, you think you want to argue with me. I'm telling you you're arguing with the folks who control the thing. You're making certain representations as to what they think. I'm questioning whether they actually think whay you claim they think. So the argument is about what they think, not whether they're right in thinking it. The argument is thus definitely with you, not with them. Sylvia. |
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