[X] My Assistant

[Guest_AlexBlackwell_*]

The mission description document is now online (1.03 Mb PDF).

[edstrick]

Is there any GOOD reason....

The perpetual sub-competence of government P.I.O. offices is not a good reason...

for the mission description documents to only cover the titan flybys?.... Every periapsis pass there are other interesting observation sequences, non-targeted moon encounters, etc. Why do they <BLEEP> only press-release a Titan Encounter ONLY document, instead of an "Orbit 18 Titan and Periapsis Observations" document?

[angel1801]

I get annoyed by the same problem too.

I would dearly like each "Revolution" document to state ALL icy moon and Saturn relating imaging and observations.

I have to use the Solar System Simulator to find out all this infomation. And it is time consuming!

[Guest_Sunspot_*]

And it is time consuming!

There's your answer .........

[Mariner9]

For that matter, how much new, or particularly specific, information even on the Titan flyby is in typically in there?

As I recall, last time we had to dig and dig to find any reference at all to the Radar pass. I think I finally found a reference to it in the data playback schedule.

[remcook]

I think part of it is that the only targeted flybys between 2006 and halfway 2007 only involve Titan. There are no other targeted moon flybys.

[Decepticon]

OOOOO nice radar observation! Crosses other sars strips!

[volcanopele]

If it makes you feel any better, there really isn't any icy sat observations this orbit, except for a half-decent observation of Janus, IIRC.

[Matt]

Where was the sar coverage during this flyby?

I know there is going to be more north polar sar covergae but I thought that was the next flyby, T19....

I remember somebody once posted a Titan mosaic showing all the planned sar swaths, and they were outlined in yellow if I remember correctly, not that the yellow outline colour is particularly important, but I can't find it anywhere now!

[ugordan]

I remember somebody once posted a Titan mosaic showing all the planned sar swaths, and they were outlined in yellow if I remember correctly, not that the yellow outline colour is particularly important, but I can't find it anywhere now!

That would be Joe Knapp a.k.a. jmknapp. It's an old post, perhaps a year or so, look it up in the old posts. Note the map only shows reference passes, the RADAR team can turn the spacecraft in the other look direction, i.e. left-right so a different area is mapped. In fact, they might have done just that with this flyby.

[volcanopele]

IIRC, it is another ride-along pass for RADAR, so T18's swath was not as long as say T16 or T8, for example. This pass covered a swath located between the Ta and T16 SAR passes, reach as far north as 70-75 N near 40 W longitude. Like Ta and T16, it then curves south, down to around 30N, 350 W. This is just going from memory, so I may be a bit off, but it lies basically between Ta and T16.

T19 is a prime coverage swath covering terrain basically parallel to T16. The mid point of the swath is a bit north of T16, around 85-86 N. The swath then crosses the T16 swath on to the east and west of that mid-point, halfway out to the ends.

[Decepticon]

I remember somebody once posted a Titan mosaic showing all the planned sar swaths, and they were outlined in yellow if I remember correctly, not that the yellow outline colour is particularly important, but I can't find it anywhere now!

Here ya go Matt!

http://cassinicam.com/titanflybys/

At the bottom.

[Guest_AlexBlackwell_*]

PIA08740: Titan's "Kissing Lakes"
NASA/JPL
September 26, 2006

[ugordan]

Also, see PIA08741: Shorefront Property, Anyone?

[volcanopele]

PIA08740: Titan's "Kissing Lakes"
NASA/JPL
September 26, 2006

These two lakes appear to share the same basin. You can see the bottom margin quite clearly, though the northern one is a little more obscure.

[Matt]

Thankyou for the info people, this site is top notch for that.

Oh yeah and the new Sar images aren't bad either!

What a nice suprise, was not necessarily expecting this.

[volcanopele]

Here is where I see the boundaries of the basin shown in PIA08740 (outlined in red):

[ermar]

Just wondering (not sure if this is a stupid question), has Cassini seen any specular reflections from the lakes yet, and if not, when might it be in a position to do so? Thanks!

[volcanopele]

Just wondering (not sure if this is a stupid question), has Cassini seen any specular reflections from the lakes yet, and if not, when might it be in a position to do so? Thanks!

No specular reflection thus far. The lakes RADAR has seen are currently in polar night, and are probably too far north for ISS or VIMS to ever see a specular reflection, but you never know in an extended-extended mission. RADAR SAR won't see a specular reflection from these lakes because of the non-nadir pointing in that mode. You could see a specular reflection when RADAR is in altimetry mode since that the antenna is nadir pointed in that mode, but that would require RADAR to sacrifice a polar SAR swath An attempt is possible when Cassini flies right over Ontario Lacus, a possible lake feature in the south polar region, during T38 (or was that T39...).

[remcook]

my god, it's full of lakes! This fits with the recently discovered ethane clouds, which covers all longitudes in the north.

[ngunn]

my god, it's full of lakes!

Have you seen more of the swath than the two bits in the press releases posted above?

This is all very exciting and I'm getting used to press releases claiming certainty for these observations of lakes. I have no reason to doubt the experts, but I will be much happier when the evidence for standing liquids becomes incontrovertible. What would that take, I wonder?

[remcook]

No, I haven't seen any more of it, but of the two times we had a look at the north we've seen lake-like things. And more than one as well! I'm also not convinced they are actually lakes, but I was just expressing my enthusiasm over these exciting finds. But I think lakes are certainly not unexpected from what we now learned about clouds from Cassini.

Specular reflections would be nice...

[ugordan]

Specular reflections would be nice...

The problem is those high latitudes are pretty much in darkness right now. By the time they start receiving enough sunlight in a few years, they might be all gone.
It's kind of like the light inside the fridge -- you know it goes out when you shut the door, but you can never actually see that. In cartoons anyway.

The best case we might get is seeing Ontario Lacus' specular point close to the end of nominal mission (was it T38?). That's a south polar "lake" however. The flyby geometry would need to be just right as well for the northern passes - a nontrivial constraint.

[remcook]

radar doesn't have that problem

edit: in fact -

" The echo appears consistent with reflection from localized hydrocarbon liquid regions embedded in mostly nonspecularly reflecting terrain."
from: "Cassini First Radio Science Observations of Titan's Atmosphere and Surface" , Marouf et al., DPS 2006 presentation 36.02I

though that's not the polar lakes I believe.

[ngunn]

If one wanted to design an instrument specifically for remotely detecting liquids per se, what would it consist of? Are specular reflections really the best hope? I wonder why is it so difficult to make such an obvious and fundamental observation?

[volcanopele]

The problem is those high latitudes are pretty much in darkness right now. By the time they start receiving enough sunlight in a few years, they might be all gone.
It's kind of like the light inside the fridge -- you know it goes out when you shut the door, but you can never actually see that. In cartoons anyway.

The best case we might get is seeing Ontario Lacus' specular point close to the end of nominal mission (was it T38?). That's a south polar "lake" however. The flyby geometry would need to be just right as well for the northern passes - a nontrivial constraint.

That's assuming of course that these lakes fill up in winter. However, given that the size of these lakes and the regular cloud activity at the southern pole, these probably fill up in the summer. We see plenty of dark, little spots in the south polar region, and not just Ontario Lacus, that are probably lakes.

[helvick]

That's assuming of course that these lakes fill up in winter.

Slightly OT question but I'm curious - what exactly is the definition of winter and summer on Titan?

[remcook]

winter is between solstice and equinox, like on Earth.

[angel1801]

Slightly OT question but I'm curious - what exactly is the definition of winter and summer on Titan?

Titan orbits Saturn. But Saturn, like the earth is tilted in it's orbit. So over a Saturn year (29.46 Earth years), Saturn will be sunlit over a "Saturn year" just like the Earth does in a "Earth Year".

ie One pole is in darkness while the other one is in contstant sunlight.

Titan is tilted about 1 degree to Saturn's equator so Titan also expriences seasons as well.

At the moment, Titan's south pole is in constant sunlight while the moon's north pole is in darkness. We call the south pole in constant sunlight "Summer" and "Winter" at the darkened north pole.

Also, allmost all of Saturn's regular moons (ie Mimas, Tethys, etc) are in the same position to.

Only Iapetus and possibily Hyperion are in a position now to have both poles in sunlight.

However, in August 2009 the subsolar latitude of Saturn will be at zero degrees. So both poles of Saturn (and most of it's moons) will be sunlit. After that, the north pole will be more and more sunlit (Summer) and
more and more of the south pole will go into darkness (Winter) until the next solstice in 2017 where Saturn's subsolar latitude will be at the highest northerly latitude. The south pole will be in darkness.

It is hoped the Cassini misson is extended to allow observations after July 2008.

[Guest_AlexBlackwell_*]

Dave Seal's glog entry for today is pretty good.

[Guest_AlexBlackwell_*]

PIA09179: Titan (T18) Viewed by Cassini's Radar - Sept. 23, 2006

[Mongo]

Looking at the T18 swath, I noticed this apparent alignment:



Could this be tectonic in origin?

Bill

[volcanopele]

Could be. Would make sense, if these are caldera lakes, then tectonic fractures could have acted as conduits of cryomagma to the surface (like on Io). If these are sink holes, then the weakened crust around these fractures could have focused the locations of these lakes.

[Big_Gazza]

Is it just me or does this SAR pass appear coarser than previous scans? Compared to the T16 pass, this one shows much greater granulation.

Could this just be an artifact of the data processing, or was the T18 pass simply a less favourable encounter?

[ugordan]

It's all about the flyby distance and the map scale these images are reprojected onto. T18 was probably just farther away so the resolution is coarser.

[elakdawalla]

T18 was actually one of the closest flybys at 960 km but the RADAR observation was riding along with INMS, which was controlling the pointing. I'm not sure why that would decrease the resolution though -- was RADAR being pointed at a larger look angle than it prefers?

--Emily