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Onwards to Uranus and Neptune!
nprev
post Jan 19 2008, 09:54 PM
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Well, don't we all, though? smile.gif Sad fact of the matter is that planetary exploration budgets are very limited, launch opportunities to the outer Solar System are severely constrained, and harmonizing these two major domains of influence is anything but easy. We live in the real world, not the ideal one.

(Dammit; I am a geezer; now I'm lecturing!!! Gonna go drink beer till I reboot....)


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JRehling
post Jan 20 2008, 07:15 AM
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Gladstoner
post Jan 20 2008, 07:38 AM
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edstrick
post Jan 21 2008, 10:19 AM
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"...I'll always think of them as Mariners 11 and 12......"
My briefcase carries a VERY battered decal of "Mariner Jupiter Saturn". I'll have to take a photo of it and post it.
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nprev
post Jan 21 2008, 06:22 PM
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Dou you think that Alan will hate me if I privately refer to NH as "Mariner 13"...? tongue.gif


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tedstryk
post Jan 21 2008, 07:06 PM
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While imaging systems have certainly improved, Voyager's vidicon imaging was quite good. Much of the "inferior" quality comes from the use of old 1970s and 80s style processing and copying of the images. Also, many of the images are blown up to rather insane levels. The problem for Voyager with the Uranian moons was that when the planet is near solstice, approaching it from a flyby trajectory is like hitting a dartboard - you pass through the plane in which the moons orbit all at once, so you can only have one close encounter (and one more semi-decent one, such as Voyager-2 at Ariel), and all the encounters happen at about the same time. Since Voyager could only hold ~30 frames on its tape recorder and was limited by distance in what it could send in real time, the number of images that could be taken of the Urianian moons was limited. It was correct to say that Miranda would not have been picked for a dedicated Uranus mission - the Voyager team was quite frustrated by this, but it was the only moon that could receive a close flyby and still allow a trajectory that would send the spacecraft on to Neptune. Due to its small size, they were expecting it to be another Mimas, but by luck it turned out to be one of the most interesting worlds Voyager encountered. In fact, during the approach phase, when Voyager was bearing down on the Uranian system but not yet at closest approach, the lions share of the images were spent on Titania, which would likely have received the close encounter had they had the choice.

Voyager-2 at Triton was another spectacular encounter. It seem to me that the coverage seems in many classes cleaner than the coverage of the Galileans. While the increased speed, lower data rate, and lower light levels were an issue, when one looks at Voyager's early encounters, there is a lot of over and under exposure, partial (and total) misses of the target (a lot of close images of the Galileans were off the limb or on the dark side of the terminator), as well as smear from moving the spacecraft in the middle of exposures. While conditions at Neptune were more severe, by this time the Voyager controllers were veteran experts at operating the spacecraft and knew all its idiosyncrasies, rendering it almost like a new mission.


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JRehling
post Jan 21 2008, 07:56 PM
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dvandorn
post Jan 22 2008, 06:11 AM
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QUOTE (nprev @ Jan 21 2008, 12:22 PM) *
Dou you think that Alan will hate me if I privately refer to NH as "Mariner 13"...? tongue.gif

I'd argue that Galileo was Mariner 13 and Cassini is Mariner 14.

And here they thought they'd get around any possible numerological issues by renaming these programs before they got to a Mariner 13...!

rolleyes.gif

-the other Doug


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edstrick
post Jan 22 2008, 10:19 AM
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"I'd argue that Galileo was Mariner 13 and Cassini is Mariner 14."

You left two out: Magellan was Mariner 14 and Galileo was Mariner 15.
There are also two "Honerable Mention Mariners": the two Viking Orbiters.

I have a rather technical but straightforward technical point that this is based on.

ALL, repeat, ALL, the Mariner and Mariner like spacecraft up to Galileo used a polygonal ring shaped set of electronics and equipment bays as the "core" of the spacecraft. EVERYTHING else, damn near, was attached to the ring. On Mariner 4 (as the classiest example of the layout) solar panels were mounted on 4 of the 8 sides of the octagon (number of bays varied from design to design), antenna and magnetometer boom on the sunside, scan platform on the anti-solar-side. Mariner 9 mounted a bit set of fuel tanks and a rocket engine on the sunside, scan platform on the cold side, solar panels as usual. Viking orbiters added the attached bioshield and lander on the cold side, scan platform on the side of the enlarged polygon. Voyagers had no solar panels, RTG booms and scan platform on the sides instead, mounted the big antenna on the solar side. Magellan stuck a monstrously large radar electronics box between the (Voyager derived) antenna and the (I think Voyager derived) electronics bay ring. Galileo was the last to carry the electronics bay ring, despun scan platform on the cold side, the @#$#@ antenna on the sun side. It's spinning attitude control didn't change the fact that it was essentially a Mariner.

Cassini is the first "Mariner" that uses the modern "brick" shaped rectangular box for the main spacecraft body.
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MarcF
post Feb 6 2008, 09:37 PM
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After the proposal of a New Horizons-like mission to Uranus and KBOs (NH 2), a new mission to Neptune is now proposed (NH 3 ?) :

http://www.lpi.usra.edu/meetings/lpsc2008/pdf/1117.pdf

Will surely have the same fate as NH 2, even if the mission is interesting.
Marc.
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Big_Gazza
post Feb 7 2008, 10:33 AM
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Oh Great Maker, let it be so.... biggrin.gif

(for the record, I'm a staunch atheist, but if prayer has one part in a trillion chance of success... laugh.gif
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ugordan
post Feb 7 2008, 11:00 AM
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To me, any new mission to Neptune that isn't an orbiter will be a tough concept to sell. Spending considerable time and money on an essentially Yet Another Flyby mission. An orbital mission would be significantly costlier, but the increased science return would most likely far outweigh the cost increase.


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Doc
post Feb 7 2008, 11:24 AM
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QUOTE (ugordan @ Feb 7 2008, 02:00 PM) *
To me, any new mission to Neptune that isn't an orbiter will be a tough concept to sell. Spending considerable time and money on an essentially Yet Another Flyby mission. An orbital mission would be significantly costlier, but the increased science return would most likely far outweigh the cost increase.


I totally agree. But try and tell that to the bean counters. They'll never take their eyes off the $numbers.


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vjkane
post Feb 7 2008, 03:45 PM
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QUOTE (ugordan @ Feb 7 2008, 12:00 PM) *
An orbital mission would be significantly costlier, but the increased science return would most likely far outweigh the cost increase.

From various outer planet mission studies, we can safely say that a Neptune or Uranus orbiter will likely cost in the $2-3B range (one Flagship mission to outer planets every 10-20 years). (The last outer planets new start was Cassini in 1990.) This proposed flyby is in the ~$850M range (one New Frontiers mission every 3-5 years). We'll pick either Jupiter or Titan for the next Flagship mission, and then presumably will pick the other one 10-20 years later. That pushes an ice giant mission out to the 2040-2050s or so by the time it arrives. So if we want to learn anything about ice giants from a spacecraft mission in the working lifetime of the present cadre of scientists (and for many of us, in our lifetime at all), it will have to be a mission like this. My only complaint about the proposal is that it doesn't have an atmospheric probe, which could be very minimal and provided by an international partner. Understanding the elemental composition of ice giants is key to understanding the formation of the solar system.


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nprev
post Feb 7 2008, 04:18 PM
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QUOTE (JRehling @ Jan 21 2008, 11:56 AM) *
I have a sort of Moore's Law optimism for far-future missions that the ability to perform operations rapidly and store everything will increase so that the very crowded encounter sequence can be managed. It would definitely be a challenge with a slower spacecraft.


I do too, but am convinced that it will have to come in the form of both increased data-handling capability and major advances in propulsion technology. The whole IT revolution experience makes the idea of sustaining (or re-developing & procuring) the necessary systems to interpret data received decades after launch seems like a significant added consideration.


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