- Cassini-Huygens Mission status report

On 2004-06-10, Henry Spencer wrote:

If you want to do anything with the outer planets (ie with RTGs)...

It's not unthinkable to do non-RTG missions to Jupiter in particular.

Or in the case of one conceptually elegant Discovery proposal - do it
"conventionally", from the place we best know how to work "conventional"
satellites... earth orbit. The mission, if memory serves, was to study
Jovian (weather patterns?) by putting a tailored telescope in orbit and
dedicating it to the task. Unsexy, but quite likely to work (at least
from a technical standpoint).

Looking at the 2000 proposals, since I have a summary to hand:

http://www.space.com/news/discovery_sidebar000828.html

(I keep meaning to dig out old press releases and write a little bit on
each of these throughout the Discovery program; it's interesting what
people choose to get excited over)

* one lunar rover (south pole, looking for volatiles);
* one sample return (ditto);
* a Martian microlander net (24 of them, 13lb each!) to study the
atmosphere (plus an orbiter thrown in);
* a plan to run multiple (!) gliders through Valles Marineris to look at
the geology;
* a Martian roving balloon with magnetometer;
* Kepler, an orbiting telescope to look for extrasolar transits;
* a proposal to have a system which "cancels out" starlight to look for
reflected light from their planets;
* and one to look for orbital pertubations with gravitational lensing;
* a mission to refly CRAF! Well, sort of. Nine-month mission to study
the nucleus of Kopff, which was one of CRAFs targets, and a flyby of
Themis thrown in;
* one to study Vesta and Ceres;
* one to study Vesta;
* INSIDE Jupiter - " Interior Structure and Internal Dynamical Evolution
of Jupiter", which does what it says on the tin;
* one to study rhe abundance of water/ammonia in Jupiter's interior
* a probe to study Venus regarding 'how it got that atmosphere, and how
it evolved';
* a Venus orbiter to "undertake an investigation of the planet's global
meteorology, chemistry and volcanism" - big plans for a small mission;
* and the intriguingly named Venus Sounder for Planetary Exploration;

16 there, which means there's ten or so not listed. But you get the idea
of the variety...


--
-Andrew Gray

Neil Gerace wrote:
"Christopher M. Jones" wrote in message
...
Few members of the cabinet have the ability to
dissolve the senate or congress.

Neither does any member of the PM's cabinet, though. Only the PM himself
through the head of state. Many European parliamentary republics work like
that too.

The comparison being made was between the unelected
cabinet and the unelected PM. Both represent
positions of power, both are nominally accountable
to elected bodies. My comment was meant to imply
that the PM has rather more power than cabinet
members and thus greater power being held by
persons less directly accountable to the electorate
makes for a less direct and less populist democracy.

(Henry Spencer) wrote in message ...
In article ,
Duncan Young wrote:
The problem is much of the low hanging fruit is gone - we've had the
asteroid mission, the moon mapper, the comet probe, the IPM sample
return...

But there are lots of other low-hanging fruit remaining, as witness all
the rejected Discovery proposals.

There were reasons why those missions got rejected - some more than
others.

Saying "the" asteroid mission is a joke -- asteroids are a very diverse
collection of bodies and we still know very little about them, especially
their interiors.

Well, it was a joke (-ish), but witness DAWN - an extremely extended
flight time at the edge of technical capabilities. A mission that, in
retrospect, might not have been funded. Detailed investigation in the
main belt are hard to fit in the time and budget constraints of
Discovery, unless you are content with flybys. The sort of work
required to investigate their interiors requires rendezvous and
resonable power sources (unless you go the Deep Impact route).

The Moon remains poorly mapped in several important ways, e.g. we still
do not have good topographic maps of the poles or gravity maps of the
farside.

True - but the moon now has its own entire Office outside of
Discovery.

I predict that we're going to find out that comets, like asteroids, are
much more diverse than we'd thought. We've barely scratched the surface
of what can be done with low-cost missions to them.

And its a damn shame about CONTOUR. A tightly-proscribed program like
Discovery might not be the best program for investigating diversity.
My thought is that we need to think in terms of assets - simple, long
lived, low maintaince spacecraft in orbits with access to Earth and
Venus, that could be redirected as needed to comets and asteroids of
interest. CONTOUR had thoughts along this line, NEAR demonstrated the
flexibilty when it missed Eros first time round, but it would be a
hard thing to get past review for Discovery.

If you want to do anything with the outer planets (ie with RTGs)...

It's not unthinkable to do non-RTG missions to Jupiter in particular.
Farther out it is admittedly hard, except perhaps for fast-flyby missions
which don't need high power for very long.

It seems to me that propulsion requirements for entering Jupiter orbit
and DSN support issues limit what you can do with non-nuclear power at
Jupiter, especially when you include the mission duration constraints
of Discovery.

or non-martian landers (Venus)...

Cheaply landing on Mercury or Venus is pretty hard. But there are plenty
of more-accessible unexplored bodies in the inner solar system.

Again, Moon and Mars have their own offices.

Finally, let us not forget that if you're willing to limit yourself to
carefully-chosen objectives in the inner solar system, there are people in
several places who think they could give you a sizable program of unmanned
missions for the cost of one Discovery mission. There's no inherent
reason why planetary missions have to cost hundreds of millions each.

Beagle 2 and Deep Space 2 remain counterpoints.

In article ,
Duncan Young wrote:
But there are lots of other low-hanging fruit remaining, as witness all
the rejected Discovery proposals.

There were reasons why those missions got rejected - some more than others.

*Some* of them certainly had problems, or were pushing things too hard.
Others were perfectly reasonable missions which simply didn't make the cut.

The Moon remains poorly mapped in several important ways, e.g. we still
do not have good topographic maps of the poles or gravity maps of the
farside.

True - but the moon now has its own entire Office outside of
Discovery.

And it could be back in Discovery a year from now. But what relevance has
that to the topic? The issue at hand is that there is still significant
work that could be done there at relatively low cost. Which office it's
run from is irrelevant.

I predict that we're going to find out that comets, like asteroids, are
much more diverse than we'd thought. We've barely scratched the surface
of what can be done with low-cost missions to them.

And its a damn shame about CONTOUR. A tightly-proscribed program like
Discovery might not be the best program for investigating diversity.

The big problem with Discovery for that is that it's not really a
"program", just a random grab-bag of missions, whoever did the best sales
pitch last year. For properly investigating diverse objects, you want a
series of similar spacecraft, and there's no home for that in Discovery.
(In fact, there isn't really a comfortable home for that anywhere in NASA.
Even the Mars program, which really is a *program* to some extent, finds
it difficult to just repeat a successful mission, even when that would be
scientifically a very interesting thing to do.)

It's not unthinkable to do non-RTG missions to Jupiter in particular...

It seems to me that propulsion requirements for entering Jupiter orbit
and DSN support issues limit what you can do with non-nuclear power at
Jupiter, especially when you include the mission duration constraints
of Discovery.

Some of this is a matter of artificial limitations of Discovery, rather
than inherent difficulties of doing low-cost missions. The DSN issue
definitely is a bad one, though.

Cheaply landing on Mercury or Venus is pretty hard. But there are plenty
of more-accessible unexplored bodies in the inner solar system.

Again, Moon and Mars have their own offices.

I wasn't thinking of either one. And again, I'm talking about missions,
not about bureaucratic turf.

Finally, let us not forget that if you're willing to limit yourself to
carefully-chosen objectives in the inner solar system, there are people in
several places who think they could give you a sizable program of unmanned
missions for the cost of one Discovery mission. There's no inherent
reason why planetary missions have to cost hundreds of millions each.

Beagle 2 and Deep Space 2 remain counterpoints.

Note the words "carefully-chosen objectives". If you insist that the
objective has to be a Mars landing, and you have no tolerance for failure
so the hardware has to work the first time, that does make for an
expensive mission which can't be slimmed down below a certain point.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

Henry Spencer wrote:

In article ,
Duncan Young wrote:


snip


Finally, let us not forget that if you're willing to limit yourself to
carefully-chosen objectives in the inner solar system, there are people in
several places who think they could give you a sizable program of unmanned
missions for the cost of one Discovery mission. There's no inherent
reason why planetary missions have to cost hundreds of millions each.

Beagle 2 and Deep Space 2 remain counterpoints.


Note the words "carefully-chosen objectives". If you insist that the
objective has to be a Mars landing, and you have no tolerance for failure
so the hardware has to work the first time, that does make for an
expensive mission which can't be slimmed down below a certain point.


Even on the Mars landing side, the problem usually isn't scaling down,
per se. The problem is usually in the scale in terms of what they
want to load onto any given mission. It only gets expensive in the
boundry conditions. One one side is the boundry condition of a working
vehicle and no payload. Then, incremental discrete costs for payload
packages. Then an upper limit where they try to cut back the core
delivery vehicle (or its testing) for more payload.

They never scale down. Only up.

They would have had exactly the same results from the Beagle mission
had they not tried to crowbar in the lander.

(Henry Spencer) wrote in message ...
In article ,
Duncan Young wrote:
But there are lots of other low-hanging fruit remaining, as witness all
the rejected Discovery proposals.


The Moon remains poorly mapped in several important ways, e.g. we still
do not have good topographic maps of the poles or gravity maps of the
farside.

True - but the moon now has its own entire Office outside of
Discovery.

And it could be back in Discovery a year from now. But what relevance has
that to the topic? The issue at hand is that there is still significant
work that could be done there at relatively low cost. Which office it's
run from is irrelevant.


Henry, I think we are talking past each other. I was questioning
Christopher's statment that sticking more slots in Discovery would be
a better way to go than New Frontiers - so I was discussing the
bureaucratic realities of that.

It is also worth pointing out that New Frontiers was in part a
response to the Decadal Survey's high priority questions - most of
which seem to require RTG's, Mars landings, or worse, sample return.
Any of this would be damn hard for Discovery.

There is a place for Discovery - but after the last few missions,
anything proposed will be subject to intense scrutiny. Palming off
the more ambitious stuff to Frontiers will probaby be beneficial to
Discovery.

"Henry Spencer" wrote in message
...
The DSN issue
definitely is a bad one, though.

Somebody tell me why adding stations to the DSN isn't a top priority? I'd
think that Japan, Diego Garcia, South Africa, Britain, Nova Scotia, Brazil,
Kansas, Easter Island and others should be good candidates. In addition, a
couple of satellites similar to the "Big Ear" spy sats should work AND have
the advantage of being able to access far more sky without bothering about
weather.

If the DSN is the bottleneck, let's spend a little less adding to the
bottleneck and a lot more relieving it.

Christopher M. Jones wrote:
To date we have seen imagery from the surface or
within the atmosphere of three plantary bodies
which were not Earth (Moon, Mars, Venus).
Huygens will raise that number to 4, the Rosetta
Lander to 5, and Muses-C/Hayabusa to 6.

I would count the NEAR on the surface of asteroid "433 Eros" too.
These last images of NEAR Shoemaker:
http://near.jhuapl.edu/iod/20010212f/index.html
while it was descending, were *almost* surface images. Actually the very
last image was taken from 120m (4000ft) height, but the resolution is good
enough that you could (I think...) recognize human faces if they were there.
And the spacecraft did descent and worked also after that for a while.


Matti Anttila
--
http://masa.net/

In article ,
Scott Hedrick wrote:
The DSN issue definitely is a bad one, though.

Somebody tell me why adding stations to the DSN isn't a top priority?

Basically, because it's hard to get serious money for infrastructure
upgrades like that. It doesn't help that (I'm told) DSN's management is
bureaucratic and timid, and is reluctant to face the need for major
growth. They are making improvements, but relatively modest ones that
aren't going to keep up with demand.

think that Japan, Diego Garcia, South Africa, Britain, Nova Scotia, Brazil,
Kansas, Easter Island and others should be good candidates.

There is no dire need for lots more sites, especially in places like Diego
Garcia and Easter Island where overhead costs would be high. DSN *could*
definitely use one more Southern Hemisphere site -- currently the Canberra
site is often a bottleneck -- perhaps in Argentina or South Africa. And
I'd think it would mildly benefit from a third, plus a third Northern
Hemisphere site somewhere like Japan, so that both hemispheres could have
round-the-clock coverage of most sky directions.

But the big requirement is not more sites, but more antennas. There's no
reason to spread the antennas out over a dozen sites, which will just run
up operations costs. What you want to do is not to commission a bunch
more sites, but to commission a bunch more big dishes at the same three or
four sites.

In addition, a
couple of satellites similar to the "Big Ear" spy sats should work AND have
the advantage of being able to access far more sky without bothering about
weather.

A space-based DSN has been studied repeatedly, but the extremely high
costs of mass, power, and maintenance up there have always led to the
conclusion that spending the same amount of money on the ground would give
better results.

The time when you really start thinking hard about orbital infrastructure
is when you take the next big jump up the frequency scale and go laser.
*Then* weather, even light cloud, bites hard. Still not a clear-cut win
for orbital receiving stations, but it makes them much more competitive.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

On Wed, 16 Jun 2004 03:31:10 GMT, (Henry Spencer)
wrote:

But the big requirement is not more sites, but more antennas. There's no
reason to spread the antennas out over a dozen sites, which will just run
up operations costs. What you want to do is not to commission a bunch
more sites, but to commission a bunch more big dishes at the same three or
four sites.

....I'd settle for a split down the middle. One more SH site, with a
couple of extra antennas spread amongst the other sites, followed by a
periodic expansion of say one antenna every 2-3 years for the
forseeable future. Then, every decade or so, adding a new site to
increase continuous coverage.

It's sort of like housing in Monopoly. When you ge four houses, trade
them in for a hotel...

OM

--

"No ******* ever won a war by dying for | http://www.io.com/~o_m
his country. He won it by making the other | Sergeant-At-Arms
poor dumb ******* die for his country." | Human O-Ring Society

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