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 2012-12-29, 09:46 #23 fivemack (loop (#_fork))     Feb 2006 Cambridge, England 11001001101012 Posts I'd like to put three small satellites 120 degrees apart around Callisto's orbit, to get real-time full-planet-scale imagery of the Jovian atmosphere. Jupiter is about two degrees wide as seen from Callisto-orbit, so a well-corrected six-inch telescope onto a large CCD (e2v offers a 9Mx9M device with 10um pixels) gets you adequate imagery, 20km pixels are about the same as the closest flyby missions have produced to date but this would give coverage comparable to Earth's meteosat network. (hmm, yes, you'd also want IR imaging since Jupiter is strongly self-luminous and that would mean you didn't waste the time when one and a half of the satellites are looking at the unilluminated side of Jupiter) Callisto orbit is well outside the radiation belts; I don't know what the gravitational stable points in the Galilean system look like so this may need prohibitively much fuel for orbit control.
 2012-12-29, 13:01 #24 xilman Bamboozled!     "𒉺𒌌𒇷𒆷𒀭" May 2003 Down not across 19·599 Posts I'd like to put something useful in the solar focal sphere but although it just about might be within budget, it would take far too long to get there. Increase both constraints by a factor of a few and it would become possible. Closer to home, it would be nice to land a technology prototype on Mars which converts atmospheric carbon dioxide into carbon monoxide and oxygen. The products are used as rocket fuel for sample return to earth. Once again, budgetary constraints are likely to be the limiting factor.
2012-12-29, 14:23   #25
science_man_88

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Quote:
 Originally Posted by Uncwilly For all of you space buffs and fans, it is time to vent! What is the most overlooked mission that you think should happen now? What is a mission that you think should be given priority? What mission would fill in some vital piece of knowledge or provide a new window of insight or explore new territory? The rules:It must be an unmanned mission. It must not be directly overlap any current or currently planned mission. This includes ESA (and all other European space agencies), NASA, RSA, B612, JAXA, and all other national agencies. You have ~$1billion to work with. No breakthrough tech allowed. Must launch within 7 years and flight time to destination must be under 10 years. Primary Mission time is open, but must be covered by the funding. Launch vehicles must be near term available (no SLS, but Falcon Heavy is ok), max of 2 launches, and the cost of the launches are part of the$1B. (Assume that the launched craft can auto-dock if needed). A nominal amount of Deep Space Network support is available for a token charge. Surprise us. Be creative.
this limit and dawns max acceleration in space can give us distances for specific types of mission, d=0 mpd * 3652 d +.5*60mph/d*(3652 d)^2 = 2.5 miles/h/h * (87648 h)^2 = 2.5 miles/h/h * 7682171904 h^2 = 19205429760 miles for a 10 year 1 way mission.

2012-12-29, 15:11   #26
xilman
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Quote:
 Originally Posted by science_man_88 this limit and dawns max acceleration in space can give us distances for specific types of mission, d=0 mpd * 3652 d +.5*60mph/d*(3652 d)^2 = 2.5 miles/h/h * (87648 h)^2 = 2.5 miles/h/h * 7682171904 h^2 = 19205429760 miles for a 10 year 1 way mission.
Where do you get those numbers from? I understand the 3652 as being hours per ten years. Though if you insist on using ludicrously precise results, you should use 3652.425 instead. Personally I'd say 3650 is more than adequate precision and your conclusion should be 19G miles.

In particular, where does that "60"? come from?

19G miles is 30G km in more conventional units and 20 AU is even more conventional in this area. It's about the right order of magnitude in that Uranus is about that distance from us and the Voyager probes took about that length of time to get there, though not in a straight line of course. The distance they actually travelled to reach Uranus was significantly greater.

If you want to go as far as possible outwards you should be able to do significantly better by bouncing off at least two of the Moon, Venus, the Earth, Jupiter and Saturn en route, especially if you use a long-duration low-thrust ion engine during the cruise phases. Voyager was constrained by having to visit Uranus after its earlier and compulsory gravity assists from Jupiter and Saturn. A long distance mission to the middle of nowhere doesn't have that limitation.

The science from such a package would, in my view, best be devoted to observing charged particles, magnetic fields and ultra low frequency radio. Put cameras on board if you wish for the planetary fly-bys, but heading out into interstellar space is likely to be better served by using a significant fraction of the payload for electrical power, reaction mass (presumably Xe or Hg0, a very large comms antenna and even longer ULF radio antennae. If the comms antenna is large enough, in the 20 to 100m class, it could do double duty for radio astronomy and, in particular, enable mult-AU baseline interferometry. I haven't yet worked out the numbers but it may be possible to detect parallax shifts for the nearest quasars which would get the cosmologists excited.

2012-12-29, 17:40   #27
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Quote:
 Originally Posted by Uncwilly There have been discussions about this. The idea has been floated, but there is no current mission being planned. I like this one.
Quote:
 Originally Posted by fivemack There is a mission planned to the Sun: Solar Probe Plus http://solarprobe.jhuapl.edu being built at JHU APL to launch 2018. Interesting trajectory with repeated Venus flybys to lower perihelion to 0.04AU.
Did not know that had moved from the thought about to the doing phase.

Quote:
 Originally Posted by fivemack I'd like to put three small satellites 120 degrees apart around Callisto's orbit, to get real-time full-planet-scale imagery of the Jovian atmosphere.
This would also be really cool for seeing asteroid strikes. Imagine if this was out there when Shoemaker-Levy 9 arrived.

Quote:
 Originally Posted by xilman The science from such a package would, in my view, best be devoted to observing charged particles, magnetic fields and ultra low frequency radio. Put cameras on board if you wish for the planetary fly-bys, but heading out into interstellar space is likely to be better served by using a significant fraction of the payload for electrical power, reaction mass (presumably Xe or Hg0, a very large comms antenna and even longer ULF radio antennae. If the comms antenna is large enough, in the 20 to 100m class, it could do double duty for radio astronomy and, in particular, enable mult-AU baseline interferometry. I haven't yet worked out the numbers but it may be possible to detect parallax shifts for the nearest quasars which would get the cosmologists excited.
I like this mission. Which direction would you send this probe? Note in this image, that 3 of the four interstellar probes have gone off in one general direction.

2012-12-29, 17:59   #28
xilman
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Quote:
 Originally Posted by Uncwilly I like this mission. Which direction would you send this probe? Note in this image, that 3 of the four interstellar probes have gone off in one general direction.
It depends very much on where the planets are located at time of launch.

An attractive proposition is to send it significantly out of the plane of the solar system but that can only be done at the final planetary encounter, for obvious reasons. If the interferometry idea pans out, a vector at right angles to (the maximum number of) the interesting point sources would also be indicated. I don't yet know what that might be.

 2012-12-29, 18:09 #29 xilman Bamboozled!     "𒉺𒌌𒇷𒆷𒀭" May 2003 Down not across 19·599 Posts Recent supernovae detection Another mission: fly a soft-gamma ray observatory with a high-resolution (arcsec or better) telescope optimized for the 1.809MeV gammas emitted by the decay of 26Al. This isotope is created a few earth-masses at a time in supernovae explosions and has a half live approaching a million years. Current observations have an angular resolution measured in degrees so it's possible to say that there have been quite a lot of SN towards the galactic centre (big surprise!) and a clump out Cygnus way, but not much more than that can be deduce. Being able to map the locations, ages, distribution and velocities of supernovae and, especially, their ejecta would be rather useful. This one could fly in relatively low earth orbit and wouldn't need excessive fuel and comms requirements, so several tonnes could be used for the telescope if desired.. It could even be designed to be user-serviceable. Do you yet get the idea that I could propose missions at the rate of a few a week for a significant length of time if I set my mind to it? There's no shortage of ideas, only a shortage of cash.
2012-12-29, 19:23   #30
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Quote:
 Originally Posted by xilman Do you yet get the idea that I could propose missions at the rate of a few a week for a significant length of time if I set my mind to it? There's no shortage of ideas, only a shortage of cash.
Indeed. The pair of scopes that NASA received from the NRO. Those would be fun to play with. Put them out near one of the Lagrange points. Tie them together as far apart as practical to make a full time space based optical interferometer.

 2012-12-29, 21:47 #31 fivemack (loop (#_fork))     Feb 2006 Cambridge, England 33×239 Posts I'm afraid I do get a bit annoyed by the way that, whenever someone mentions space telescopes in quantities greater than one, someone else mentions interferometry. Particularly with the NRO telescopes, which are short focal length and optimised for very-wide-field work in the visual in almost exactly not the way that you'd want for interferometer elements. NASA put about a billion dollars into space interferometry development, to discover that building an exciting space interferometer cost more than they would be prepared to spend ... planet-hunting by interferometric astrometry is so much more expensive than Kepler. VLBI with an actually-long baseline is more interestingly practical - big deployable antenna are off-the-shelf, JAXA has launched a test comsat with a 17-metre one. Regrettably the very biggest ones are off the NSA's shelf and so you probably have to pay for the development again. With current 10,000km baselines you can get 10-microarcsecond precision, which allows pretty good parallax measurements out to 10kpc within the Milky Way, and direct measurements of Keplerian motion of water masers to 60Mpc - there are admittedly issues of getting enough signal for those fairly weak sources. So you probably do need a billion-kilometre baseline for direct parallax to quasars, but the water-maser work might well be possible with sufficiently large dishes at Earth-Sun L4 and L5.
 2012-12-29, 21:58 #32 tServo     "Marv" May 2009 near the Tannhäuser Gate 23×32×11 Posts EUROPA !! We must go to this moon of Jupiter for the obvious reason that it may harbor life in its oceans. Even if not, it is one of the most interesting places in the solar system. Anyway, we've got to check it out to see if one of A.C. Clarke's monoliths stands guard there !
2012-12-29, 22:40   #33
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Quote:
 Originally Posted by fivemack Particularly with the NRO telescopes, which are short focal length and optimised for very-wide-field work in the visual in almost exactly not the way that you'd want for interferometer elements.
Yes, but they are FREE.

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