Comments on: Cassini Extended Mission Tour http://joshuacolwell.com/blog/index.php/2007/cassini-extended-mission-tour/ Science, astronomy, politics, movies, and various minutiae. Tue, 13 Mar 2012 23:50:00 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: JC http://joshuacolwell.com/blog/index.php/2007/cassini-extended-mission-tour/comment-page-1/#comment-4190 JC Wed, 28 Mar 2007 15:25:38 +0000 http://joshuacolwell.com/blog/?p=139#comment-4190 Wow, a lot of great questions. Thanks for your interest. There are indeed optimum view angles and distances for studying the response of the ring particles to equinox, but we are constrained by the fact that we're just orbiting Saturn and can't position ourselves at the best spot and stay there. There is also the pesky matter of those other scientists who are interested in things other than the rings (incredible as that may seem). So it's a matter of compromise. The selected tour for the extended mission does a good job of satisfying multiple requirements. The inclination profile (how the inclination varies with time) peaks at the end of the nominal mission, stays high for a little while, and then gradually comes down to the equator, and pops up to small inclinations before the end of the extended mission. The reason we have the high inclination sequence at the end of the nominal mission rather than at the beginning is that there were strong geometric reasons for meeting some of the low-inclination goals early in the mission (for example: delivering the Huygens probe, getting radio occultations of the rings, and also arriving at Saturn near the equatorial plane). There will be more good views of Mimas, but not Iapetus in the extended mission, and I think we're done with Hyperion as well. There is another look at Iapetus in the prime mission, however. Hyperion is definitely an interesting beast. I'm not sure about a formal publication of the XM plan. John Spencer had a good summary at the Planetary Society blog a few weeks ago. We're all hoping Cassini gets more than one extension, but decades is probably out of the question because maneuvering fuel will run out. We're using more than half of our remaining budget of fuel in the first two-year XM, so any subsequent extensions will have to be run in a more conservative manner. And that usually means cheaper. Wow, a lot of great questions. Thanks for your interest. There are indeed optimum view angles and distances for studying the response of the ring particles to equinox, but we are constrained by the fact that we’re just orbiting Saturn and can’t position ourselves at the best spot and stay there. There is also the pesky matter of those other scientists who are interested in things other than the rings (incredible as that may seem). So it’s a matter of compromise. The selected tour for the extended mission does a good job of satisfying multiple requirements. The inclination profile (how the inclination varies with time) peaks at the end of the nominal mission, stays high for a little while, and then gradually comes down to the equator, and pops up to small inclinations before the end of the extended mission. The reason we have the high inclination sequence at the end of the nominal mission rather than at the beginning is that there were strong geometric reasons for meeting some of the low-inclination goals early in the mission (for example: delivering the Huygens probe, getting radio occultations of the rings, and also arriving at Saturn near the equatorial plane).

There will be more good views of Mimas, but not Iapetus in the extended mission, and I think we’re done with Hyperion as well. There is another look at Iapetus in the prime mission, however. Hyperion is definitely an interesting beast.

I’m not sure about a formal publication of the XM plan. John Spencer had a good summary at the Planetary Society blog a few weeks ago. We’re all hoping Cassini gets more than one extension, but decades is probably out of the question because maneuvering fuel will run out. We’re using more than half of our remaining budget of fuel in the first two-year XM, so any subsequent extensions will have to be run in a more conservative manner. And that usually means cheaper.

]]> By: Todd http://joshuacolwell.com/blog/index.php/2007/cassini-extended-mission-tour/comment-page-1/#comment-3714 Todd Mon, 26 Mar 2007 03:14:47 +0000 http://joshuacolwell.com/blog/?p=139#comment-3714 The equinox view of the rings sounds exciting. Do you have optimal distances and view angles for those studies, or is it best to have a variety? They probably won't leave Cassini in the high inclination '08 orbit for a whole year, would they? Or did the mission planners cross their fingers on a possible extension and have Cassini right where they wanted it? Will the icy satellite people get any more flybys of Mimas, Hyperion, and/or Iapetus? I know the latter two are inclined to and beyond Titan's orbit, but they seem like such interesting targets. No other irregular moon in the solar system is as large as Hyperion. The empty spaces within that body...aside from the curiosity factor, I can imagine 23rd century spelunkers itching to delve into that moon. Will we have to wait for NASA/gov approval before the XM plan is published? Can you pass along any other hints aside from what's been gossiped about on other sites? What if Cassini works like Spirit and Opportunity at a pace of multiples past warranty? Would it be a disappointment if Cassini operating for another few decades delays another mission out there? The equinox view of the rings sounds exciting. Do you have optimal distances and view angles for those studies, or is it best to have a variety? They probably won’t leave Cassini in the high inclination ’08 orbit for a whole year, would they? Or did the mission planners cross their fingers on a possible extension and have Cassini right where they wanted it?

Will the icy satellite people get any more flybys of Mimas, Hyperion, and/or Iapetus? I know the latter two are inclined to and beyond Titan’s orbit, but they seem like such interesting targets. No other irregular moon in the solar system is as large as Hyperion. The empty spaces within that body…aside from the curiosity factor, I can imagine 23rd century spelunkers itching to delve into that moon.

Will we have to wait for NASA/gov approval before the XM plan is published? Can you pass along any other hints aside from what’s been gossiped about on other sites? What if Cassini works like Spirit and Opportunity at a pace of multiples past warranty? Would it be a disappointment if Cassini operating for another few decades delays another mission out there?

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