[X] My Assistant

[ngunn]

Good grief, it's the middle of the night here and this appears:
http://ciclops.org/view/5419/Rev_97

[Decepticon]

This flyby is a Holiday Treat!

[dsmillman]

The JPL Cassini web site has undergone major changes. Does anyone know where the mission descriptions are?

[peter59]

The JPL Cassini web site has undergone major changes. Does anyone know where the mission descriptions are?

http://saturn.jpl.nasa.gov
Video
Other products
Mission descriptions

[ugordan]

Under Video?

Logical.

On a related note, I'm unimpressed with the speed of the RAW pages (might be temporary) and the lower resolution of thumbnails. Not a fan of flashy flash animations either. The layout's not that bad. Nothing some getting used to won't fix.

[dsmillman]

http://saturn.jpl.nasa.gov
Video
Other products
Mission descriptions

Thanks.

I do want to note that at this time that neither the document previewing the upcoming T49 flyby nor the
dcoument covering the recent T48 flyby are show on the web page.

[djellison]

Why note it here. This is not the Cassini website tech support forum. Tell the Cassini web team.

[jamescanvin]

Why not note it here? It saves people clicking through all the links to get to the page, only to find that the more recent stuff that they are likely to be after (considering this is a T49 thread) is not there yet.

[djellison]

Why not note it here?

It doesn't help fix the problem.

[jamescanvin]

Well it fixes the problem of people waste their time navigating through four links to try and find the T49 document. Saved me a minute or two - so it was worthwhile to point it out IMO.

Of course if the point was to try and get the documents to appear, then as you say, posting here clearly isn't going to help.

[ngunn]

I'm still having problems with the raw images and I've saved a copy of the long error report that came up. However I can't find an e-mail address or indeed any 'Contact us' link on the new web page. Has anybody got that address?

[djellison]

Send it my way - I'll fwd it on.

[ngunn]

Thanks. Here it is:

Attached File(s)

 Cassini_raw_image_search_error_report.doc ( 38K ) Number of downloads: 311

 

[Juramike]

T49 Flyby mission description availalbe: http://saturn.jpl.nasa.gov/files/20081221_...description.pdf

[ngunn]

I was intrigued by this statement in the 'looking ahead' article:

QUOTE "Altimetry observations would allow RADAR to confirm the presence of liquid within Ontario."

Can anybody explain how this works? I was of the impression that the lake surface would be invisible to the RADAR, as it is in the imaging mode, meaning any altimetry there would be from the lake bottom. So how exactly will the presence of liquid be confirmed ?

[rlorenz]

I was intrigued by this statement in the 'looking ahead' article:
QUOTE "Altimetry observations would allow RADAR to confirm the presence of liquid within Ontario."
Can anybody explain how this works? I was of the impression that the lake surface would be invisible to the RADAR, as it is in the imaging mode, meaning any altimetry there would be from the lake bottom. So how exactly will the presence of liquid be confirmed ?

This is misleading, and a lesson that you shouldnt read CICLOPS for the plans or capabilities of
other Cassini instruments. (This text wasn't written by the radar team, nor checked by them). The official
mission summary
http://saturn.jpl.nasa.gov/files/20081221_...description.pdf
(which I did check before release) says
RADAR: T49 features altimetry across Ontario Lacus, the first time in the mission RADAR has obtained altimetry across a known or suspected lake. The topography profile will help us understand the slopes driving drainage into Ontario as well as providing evidence about whether it is presently liquid-filled. T49 also includes SAR of the almost completely unmapped southwestern quadrant of Titan, as well as of south polar terrain.

We may (dunno if the data is down yet, and in any case won't get processed until the new year. First
report likely at LPSC...) be able to
- tell if the surface is flat (not a discriminator between a dry playa and a liquid filled lake, but circumstantial
support)
- detect a bottom echo as well as a surface echo - IF the liquid layer is neither too shallow (for the two
echoes to merge within the ~30m range resolution) nor too deep (for the bottom echo to be attenuated)
Again, says that there is a flat layer that is radar-transparent - support, but not total proof of liquid
- through detailed modeling of the echo shape determine the small-scale roughness and dielectric constant
of the surface - which would be somewhat constraining of composition. The microwave brightness from
passive radiometry would come into play here too.

Pathologically, a 'lake' filled with porous, emissive but transparent and dead flat 'foo foo dust' might
fit all of these data, but would be perhaps implausible. Such a scenario would not, I think, be compatible with
the spectral characteristics that were reported by VIMS, albeit on observations acquired a year ago.

So these data could eliminate a number of alternative scenarios, but likely not 'prove' liquid by themselves.

[volcanopele]

Yes, by itself RADAR can't "prove" the presence of liquid, but at least two of the tests, showing that Ontario is flat, and that you get both surface and bottom echos, can go a long way into confirming the presence of a lake at Ontario, building on what VIMS found in T38.

[Decepticon]

I'm sure getting impatient! I can't wait.

I Lived close to lake (Toronto) Ontario all my life. Playing at the parks the border the lake as kids makes this something I've been looking forward to a long time.


I can't wait to see if any draining channels surround the lake. Surrounding area should be spectacular!

[ngunn]

- detect a bottom echo as well as a surface echo -

That is an exciting possibility.

Thanks for the whole of that very helpful explanation of what could come out of the altimetry data. It seems a rich science harvest is in store.

[rlorenz]

I'm sure getting impatient! I can't wait.
....
I can't wait to see if any draining channels surround the lake. Surrounding area should be spectacular!

Patience is a necessary quality (is it a skill, can you learn it?) in outer solar system
exploration. Took 11-odd years between my building the Huygens penetrometer and my
getting the 50 milliseconds of data from it.....

As for channels draining into Ontario - you won't see any in the T49 data : it is altimetry.
(doing altimetry near closest approach, when we could instead be doing SAR imaging, is
always a tough choice. We did it on half of T30, to validate the sartopo technique, and
we are doing in on Ontario....special occasions only!)

We will get SAR imaging of Ontario later in the equinox mission , somewhere in the upper T-fifties

[Decepticon]

We will get SAR imaging of Ontario later in the equinox mission

Oh I didn't realize that.

[Juramike]

We will get SAR imaging of Ontario later in the equinox mission , somewhere in the upper T-fifties

That will be a really good thing (<---note smiley emoticons)

IIRC, when this happens, this will make the lakeshore of Ontario Lacus one of the few places with ISS, VIMS, altimetry AND RADAR coverage.

It'll be neat to compare the altimetry and RADAR ovelap of Ontario Lacus and see how it compares to the projected altimetry/RADAR overlay of the northern lake region (from the RADAR look angle overlaps of T25 and T28).

[VIMS/ISS shows that Ontario Lacus is "filled", but I don't think ISS or VIMS has viewed the T25/T28 overlap region yet....too far north.]

-Mike