Jupiter question

"Brian Gaff" writes:

I just wondered if it might be possible to get some radar images of Jupiter
so that the clouds could be 'seen' at the different levels.

Not from Earth.

Radar suffers from an inverse _FOURTH_ power signal loss --- 1/r^2 out, and
another 1/r^2 back. Also, it's resolution pretty much sucks compared to light,
because its wavelength is so much longer.


It was indeed intriguing that the probe seems to have contradicted what
everyone supposed was the case, or did it just hit a strange point by a
fluke?

It is now generally believe that it had the flukey bad luck of hitting a
"Jovian Hot Spot" --- a deep hole through the cloud decks, probably caused
by an energetic plume of hot, dry gas rising up from deep within Jupiter.


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

(Gordon D. Pusch) wrote:
"Larry G" writes:

Here's a question I've always wondered about. How come no space probe
(that I'm aware of) has taken photos inside Jupiter's (or any of the
large planets') atmosphere?
[snip-o-rama]
Limited uplink bandwidth plus limited available light.
Both factors imply that It Would Cost Too Much To Fly It.

Is it because the atmospheric temperature would melt the probe/camera
before it reached the low orbit and/or descent?

No. It is because of Limited Bandwidth, Limited Light, and Limited Budget.

Limited bandwidth and limited budget I'll buy, but not limited light.
Modern imaging technology is just too good to give that any weight.
Keep in mind that the '70s vintage Voyager spacecraft did a fair job
out at Neptune with light less than 2% of the levels at Jupiter.
Modern imaging systems are light-years beyond what was available in
the '70s, so much so that "night-vision" systems can be mass produced
and sold commercially at reasonable prices. The sorts of things
available for use on a multi-million dollars spacecraft give little
wiggle room for ideas that a probe would not actually be able to image
anything worthwhile, even "deep" within Jupiter's cloud cover(s).

Limited bandwidth, too, is not so much a primary concern as much as a
secondary concern due to limited *time*. The setup for imagery on
Saturn's moon Titan will be no better than within the Jovian
atmosphere but there at least the probe has the chance to land on the
surface and spool off all its recorded images. Whereas with Jupiter
you'd likely need some sort of baloon (which, I hardly need to say,
would be difficult) to keep the spacecraft high up before it got
crushed and/or melted when falling to lower levels in the atmosphere.
Either that or really high bandwidth communications which work well
over several hundreds of thousands of kilometers (which, I hardly need
to say, would be difficult). There are other options as well but
they're too risky and too novel to be tried by the current crop of
folks in charge of interplanetary missions.

In article ,
Christopher M. Jones wrote:
Limited bandwidth and limited budget I'll buy, but not limited light.
Modern imaging technology is just too good to give that any weight.
Keep in mind that the '70s vintage Voyager spacecraft did a fair job
out at Neptune...

Bear in mind that the only probe yet to enter Jupiter's atmosphere was
built only a few years after the Voyagers, with quite similar technology.

The two situations also are not quite comparable. Voyager 2 at Neptune
could, and did, use quite long exposures. That option isn't available
when parachuting down through an atmosphere.

...The setup for imagery on
Saturn's moon Titan will be no better than within the Jovian
atmosphere but there at least the probe has the chance to land on the
surface and spool off all its recorded images.

No, the data and images from Huygens will be coming back in real time.
There is no assurance that it will survive the landing, since we know
almost nothing about the nature of the surface. Whether it will remain in
communication is also a little uncertain; in particular, if it lands on a
slope, its antenna may be pointed too far off vertical for Cassini to
continue receiving it. And finally, even if all goes well, it won't be
sending data from the surface for more than a half hour or so (I forget
the exact number), partly because its batteries will be getting very low
but mostly because Cassini will go below its horizon. Huygens is
primarily an atmosphere probe, not a lander, so long surface life was
not a design goal.

The difference in imaging is partly better technology, but mostly just
that the people designing Cassini/Huygens gave imaging a higher priority.
There wasn't any law of nature saying that the Galileo atmosphere probe's
data rate had to be too low for effective imaging; that number emerged from
the design tradeoffs that were made, based partly on the assumption that
the probe didn't *need* a high data rate.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |