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Posted by: remcook Jun 25 2005, 08:25 PM

Question for those who know:
When will there be proper ISS coverage of Titan's North Pole? All the maps upto now only show upto 30 degrees and the t4,T5 flybys only have a bit upto 60 degrees latitude, but that has probably a too high emission angle to see a lot of detail ( http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1479 )

there might be lots of clouds, since it's very cold out there at the pole (much more so than the south) and I'm pretty curious about them:)

Posted by: JRehling Jun 25 2005, 10:09 PM

Well, the north polar area is suffering through years of darkness right now. The north pole will not even be in light for several years, and then will suffer problems with high emission angle.

The next saturnian/titanian equinox will be c. 2010, two years after the end of the Cassini primary mission. As we approach that date, northern latitudes will slowly come into light (with haze making coverage good coverage only still later).

Presumably, about 2-3 years into an extended mission, we'll start to get coverage of those latitudes.

Remember that there isn't actually very much area above, say, 70N, since those parallels are shorter than ~equatorial ones. But of course, the north polar area could be very important. Particularly if, as a lone wolf hypothesis of mine holds out, the winter pole may seasonally store a big methane ice cap. We'll know by 2011.

Finally, RADAR can work on this much sooner, although I don't have a map of planned RADAR ground tracks. One pass now over the north pole would answer the ice cap question.

What we may have to look forward to is a long (series of) extended missions that will work towards completion of the RADAR map. ISS will probably complete its once-over of all areas by 2011.

Posted by: um3k Jun 25 2005, 10:10 PM

The reason there hasn't been any pictures of the north pole it that it is currently northern winter on Titan and therefore the north pole is not illuminated by the sun. However, seasons are changing, and we will see farther and farther north as time goes on.

EDIT: Nevermind. Just read what JRehling posted.

Posted by: Decepticon Jun 26 2005, 03:20 AM

I'm not sure but I think we got a radar pass this August?

I can't wait to see the Huygens sight on radar.

Posted by: remcook Jun 26 2005, 03:04 PM

I thought you might get some signal in the near-infrared...

anyway...you can see the haze of course...the layers in the polar hood for instance. The Nature article goes down to 200km. So maybe if you come closer, you will see clouds.

Posted by: volcanopele Jun 26 2005, 11:44 PM

VIMS still needs sunlight to illuminate surface features in the far north, just like ISS. There are a few north polar passes set for RADAR, don't remember which ones though. The T7 strip (September) covers the southern sub-Saturnian and trailing hemispheres, IIRC. The T8 strip (mid-October) covers "Australia", the large bright feature centered within an equatorial region of dark terrain near 210 W. The very end of this strip could cover the Huygens landing site at low resolution, but targeting uncertainties and the fact that the landing site isn't precisely known yet (AFAIK) would make being spot-on very difficult. The best we can hope for is that we would see the region NEAR the landing site.

Posted by: remcook Sep 29 2005, 08:44 PM

something I noticed a while ago...

http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=1666

The lack of North polar (well...above 30 degrees, below 60 degrees) surface images seems more like a haze/phase angle issue than a lack of sunlight.

Posted by: volcanopele Sep 29 2005, 11:21 PM

The reason I don't include it on any maps it because of an emission angle issue. The haze makes it difficult to see terrain outside of 45 degrees emission angle unless the surface contrast is high. If the north polar region and northern mid-latitudes are anything like the southern hemisphere, than contrast is low, making observing features there when sub-spacecraft points rarely exceed 10N (for inbound coverage) difficult at best.

Posted by: edstrick Sep 30 2005, 09:36 AM

volcanopele: ..." The haze makes it difficult to see terrain outside of 45 degrees emission angle unless the surface contrast is high. "....

One thing that's puzzled me... The titan images I've played with have had remarkably strong contrast relatively near the terminator despite low sun angles. I'd rather assumed that the surface illumination would be low and the scene totally dominated by atmosphere-haze scattered light, but that doesn't seem to hold.

Is the surface getting enough diffuse illumination that the low sun angle doesn't make that much difference?

Posted by: volcanopele Sep 30 2005, 06:52 PM

Incidence angle doesn't effect surface contrast nearly as much as emission angle. Depending on processing, I've been able to tease out features all the way to the terminator.

Posted by: remcook Oct 1 2005, 08:06 PM

I see. thanks