[X] My Assistant

[Bob Shaw]

My recollection is that it does not quite wark this way. The Voyager craft for example I believe still have several hours of com time each week. This must be followed by a ground transmission of an aknowledgement of receipt otherwise it would just keep repeating the transmission and wasting power. In sleep mode the craft still need to maintain attitude, charge batteries, regulate temp and constant self diagnosis and be regularly monitored by com with the ground.

See my comment within the 'Interstellar Probe' thread re the conceptual DSN 11m antenna 'Farm'.

[Bob Shaw]

Space.com article which includes details of a trajectory change for the extended mission:

http://www.space.com/missionlaunches/05072...yby_update.html

And Space Daily's take on it:

http://www.spacedaily.com/news/deepimpact-05o.html

[gpurcell]

The Decadal Survey places a flyby of Trojan/Centaur asteroids as a medium priority.

Would it be possible to get DI out to the Centaurs?

[tedstryk]

The Decadal Survey places a flyby of Trojan/Centaur asteroids as a medium priority.

Would it be possible to get DI out to the Centaurs?

Being solar powered, even if some gravity assists could be rigged, which I doubt, the spacecraft wouldn't operate out there.

[Decepticon]

"Personally, I don’t understand the fuss over whether the crater will be visible."

This comment made me mad.

[edstrick]

"Personally, I don’t understand the fuss over whether the crater will be visible."

Aesop: "he grapes were probably sour, anyway."

[Comga]

Being solar powered, even if some gravity assists could be rigged, which I doubt, the spacecraft wouldn't operate out there.

Correct. The spacecraft is designed for a maximum of about 1.5AU from the sun. Much futher out and it couldn't generate enough power to operate or keep its internal components warm. The Centaurs are a long, long way out, and there are other interesting things to observe in the inner solar system, like Comet Boethin. As each of the four imaged comet nuclei have been distinct, adding a fifth is a good idea.

[Bob Shaw]

On Spaceflight Now today:

http://www.spaceflightnow.com/news/n0605/16deepimpact/

A clone mission, and a new target for Deep Impact. Pity NH2's was made so artificially expensive by the bean counters...

Bob Shaw

[Guest_BruceMoomaw_*]

I don't think that DI clone mission has a chance in hell of being picked for Discovery -- notice that the DI people just shot themselves in the foot by cheerfully stating in the same release that "half of the science return from DI came before the impact". That is, a CONTOUR-type mission that makes non-impact flybys of several comets for comparative studies will provide far more scientific bang for the buck than smashing another impactor into one more comet and getting the same (highly ambiguous) results.

[Guest_Analyst_*]

The engineering aspect of Deep Impact (hitting a small speeding comet etc.) has been (and has to be) the focus of development and testing. Science has almost been secondary, more so after the out of focus HRI and the (predictable?) dust cloud.

This "engineering bias" has also been a problem of MPF (EDL) and Dawn (ion engine, descope with even less instruments) and to some extent Stardust and Genesis (entry capsule). The reason is the limited Discovery budget: it's barely enough to built a special spacecraft (to land somethere etc.) and launch it, there is not much left for science instruments. Compare this with Rosetta, MEX and VEX or Cassini, MGS, MER and MRO. That's imo the better approach: if you go there, why not carry "all" you have.

I like the European approach: less missions, but with a full instrument suite. And missions with a longer time to observe. Even without a lander, Rosetta will tell us much more about comets than Deep Impact, Stardust and Contour (which failed, I know) did. Rosetta will see changes over time, can revisit interesting areas etc.

Btw, NEAR, Contour and Messenger (over budget) have a better instrument suite. I'm not sure about the very small Lunar Prospector and Kepler. Bruce, I understand more and more the problem of the 11th AO to find a mission within the budget.

Analyst

[Guest_BruceMoomaw_*]

Actually, Deep Impact is the only comet mission so far whose science rationale I have serious doubts about. Stardust, by dint of actually returning samples to Earth (even if they are small samples exposed to high temperature by the friction of their passage through the aerogel) will allow many extremely sensitive analyses which are simply impossible to the in-situ instruments on Rosetta, and a CONTOUR-type survey of multiple comets is vital because of the major differences in both morphology and composition that clearly exist among comets. (The difference in composition between Oort and Kuiper comets, given their formation in different parts of the initial solar nebula, is perhaps the single most important scientific subject for comet studies right now.)

I have always suspected that Dan Goldin, given his obsession with PR stunts, had something to do with the unexpected selection of Deep Impact -- but even if that is true, just try proving it at this point.

[Mariner9]

I don't think DI 2 has much chance either. I recall one of the project scientists in an interview a couple years ago saying that Deep Impact wouldn't be a very logical mission if we knew much about comets, but it was useful since we knew so little.

So now we have flown such a mission, have completed the Stardust sample return, flown by several comets, and will probably do close flybys of one and maybe two more before DI 2 would be launched. And DI 2 would then plow into a comet that is being studied by a long lived orbiter, and a lander, each with a full suite of instruments.

Methinks not.

As for Deep Impact being a publicity stunt? I would certainly wager that people at least had that on their mind when selecting it. I remember NEAR: the flyby of Mathilda was a blip on the news radar. Orbiting Eros for a year was the occasional 15 second news story. But the "landing", followed by the one week operation on the surface with the only instrument left that could actually return any useful data from that position .... well that made the news for several days. On every channel. International even.

Lunar Prosepector. Who in the general public even knew it existed? Yet dollar for dollar, it was probably the most cost effective Discovery mission ever flown.

Same thing with Mars Global Surveyor VS Mars Pathfinder. From a scientific standpoint, MGS is vastly more signifigant. Hell, even from an exploration "look at the pictures" standpoint I think MGS did more. Yet Mars Pathfinder got more internet hits over the first few days than had ever happened up to that point.

Try explaining to the average person the value of the gravity field mapping experiment on JUNO. We are talking about a measurment that might help nail down Gas Giant formation theory. That's pretty big from a pure science standpoint. But even if the person follows your explanation, I bet he puts it out of his mind five minutes later, never to care again.

But that same person probably remembers the Sojourner rover. People on the street really get, on a gut level, what a landing is. Exploration to most people means "being there". They can live vicariously through the exploits of Sojourner and MER. Lots of people know what Huygens was. Far fewer would remember that Cassini is still out there.

So yes, people were excited when we slammed into Temple 1. They felt like mankind reached out and touched something.

I vote for a strong Discovery program with the occasional Publicity Stunt mission. I think it helps pay the bills.

[monitorlizard]

A Deep Impact 2 probably won't be approved, but what about a Stardust 2? Getting samples from
a different type of comet ought to be worth the effort. The infrastructure for sample analysis
already exists, and sample return missions give you the most science for the buck IMO. Anybody
know if this is being considered for Discovery? Or does it make too much sense for NASA to go
for it?

[Guest_BruceMoomaw_*]

This is a real possibility -- especially if you jazz it up further: what about combining Stardust and CONTOUR to produce a comet-sampling mission that flies by several comets before returning to Earth (as a CONTOUR-type mission will do periodically anyway, in order to make gravity-asist flybys to set it up for its next comet encounter)? We already have the right spacecraft design -- the "Aladdin" concept for sampling Mars' moons, which twice became a Discovery finalist, used a conveyor-belt type aerogel strip to take separate samples from a total of five different flyby encounters.

The one problem is that most or all of these comet flybys would be at much higher speed than Stardust's flyby of Wild 2, thus damaging the dust particles -- that mission took so long only because of the careful sequence of maneuvers used to minimize its flyby speed at Wild 2 -- but the samples would still be scientifically useful, especially if taken from several comets for comparative purposes.

[mars loon]

Both the DI extended mission, nicknamed "DIXI", and the DI clone nicknamed "DeepR for Deep Rosetta" are absolutely worth doing and funding. DeepR would impact Comet 67P/Churyumov-Gerasimenko as the ESA Rosetta spacecraft watches nearby with a suite of 11 science instruments.

Contrary to some earlier posts, there are no currently approved NASA follow-on missions to comets, making these proposals as well as the Stardust extended mission even more crucial for cometary research.