Cassini's Extended Mission, July 2008 to June 2010 Options

[Guest_Sunspot_*]

Well - when i actually get a Mac (this summer) then I'll speak with confidence...

Actually - it does kind of make sense

Doug

I'm getting a Mac Mini when Leopard is released. I've been using Windows ME since January 2001.

[Decepticon]

NT encounters will still happen? I don't mind Some of these far off looks!

[volcanopele]

Great blog post, John_s!

I noticed something in the image used that I didn't know. The last item listed for each tour is the Delta-V used in each tour. From a Titan perspective, the lower that number the better, as a lower delta-v would allow for a longer, extended-extended mission. The tour selected, PF6h9, has the highest delta-v of the tours in that Excel chart. IIRC, at the end of the nominal tour, there should be around 300 m/s of delta-v left...

[ugordan]

That certainly puts into perspective what we can expect from an extended-extended mission. These figures might be conservative delta-V costs, though.

[TritonAntares]

As presumed and the list above displays Iapetus will not be visited closely by CASSINI during this Extended Mission,
but what about far-encounters in a few 100.000 kilometres?
Remember the second closest approach to this strange moon so far on new year 2005 was in roughly 120.000 km!
There will probably be some occasions like this again, but only showing the saturn facing hemisphere with the dark Cassini Regio.
Due to Iapetus 15° inclination such far encounters could give the opportunity to have an additional look at northern or southern polar regions as well.

Bye.

[EccentricAnomaly]

The tour selected, PF6h9, has the highest delta-v of the tours in that Excel chart. IIRC, at the end of the nominal tour, there should be around 300 m/s of delta-v left...

The DV for the extended mission will probably total around 230 m/s when all of the tweaking is done and maneuvers that fall during good science are moved. The tanks are estimated to have about 340 m/s are the start of the XM, so that leaves only ~100 m/s for the XXM and spacecraft disposal (either crashing or putting into a stable parking orbit). But back when the tour was changed for the Huygens mission we thought we would only have 130 m/s for the XM, so 100 m/s for the XXM isn't that bad when put into perspective.

In many ways the XM is more intense than the prime misson... it will be very exciting.

[volcanopele]

As presumed and the list above displays Iapetus will not be visited closely by CASSINI during this Extended Mission,
but what about far-encounters in a few 100.000 kilometres?

I'll take a look.

EDIT: Here are the closest I could find:

2009 07 05 05:00:00 - 2,089,800 km (low phase, sub-saturn hemisphere, eastern Cassini regio, Snowman craters)
2009 09 11 19:47:00 - 1,161,000 km (high-phase leading hemisphere, extreme eastern Cassini Regio, western snowman crater)
2009 12 01 15:07:00 - 1,377,900 km (moderate phase (~100 deg.) , southern leading hemisphere, extreme eastern Cassini Regio, western Snowman crater,western Terra Incognita)
2010 02 21 10:00:00 - 1,469,800 km (moderate phase (~50 deg.), southern sub-saturn hemisphere, view of eastern Cassini Regio, Snowman craters, Terra Incognita)
2010 05 08 16:30:00 - 1,234,800 km (high phase (~110 deg.), southern leading hemisphere, crescent view of extreme eastern Cassini Regio and western Terra Incognita)

That appears to be about it. Sorry, TA! Hope the Sept. 2007 encounter is a REALLY good one!

EDIT to the EDIT: terrain coverage descriptions now accurate

[john_s]

Here's a list of Titan flybys in the PF6h9 tour:
 Titan_Flybys_UTC_NFB.PF_6h9L.txt ( 11.58K ) Number of downloads: 1317


And here's a list of small satellite flybys:
 Rocks_Flybys_UTC_NFB.PF_6h9L.txt ( 30.06K ) Number of downloads: 1160


Titan flyby geometries won't change much in the fine-tuning process, because you can't change Titan flybys without changing the rest of the tour. I'm not sure how stable the "rock" flybys are, though.

John

[JRehling]

Here's a list of Titan flybys in the PF6h9 tour:
 Titan_Flybys_UTC_NFB.PF_6h9L.txt ( 11.58K ) Number of downloads: 1317

Wow -- 27 flybys. A few of them are a little farther than normal, but that's still a large number -- 60% of the main mission's flybys. I'm eager to see the plans for RADAR coverage and at least one good look at the northern latitudes post-equinox. (Actually, at equinox, it will take a few looks to see all of the north polar region.)

[elakdawalla]

Just for grins, I took John's spreadsheet of the small moon encounters, plugged in the moons' diameters, calculated the pixel size at closest approach, and figured out how many NAC pixels across the moonlets would theoretically appear if they were, in fact, imaged at closest approach. Poor little 3-kilometer Methone -- nine of these relatively close flybys, and the biggest it'll appear will be 21 pixels across! The story isn't much better for 4-kilometer Pallene. But most of these moonlets will be quite well imaged by the end of the extended tour. I can't wait to put together a family portrait after these flybys are done.

Here's the best of each (and do remember that these are theoretical maxima; the actual number depends on where in the flyby Cassini snaps the pictures; and also keep in mind John's caveat that the flyby altitudes can change a lot with itty bitty tweaks to Titan flyby altitudes):
Atlas: 189 NAC pixels
Calypso: 145
Epimetheus: 856
Helene: 3,512
Janus: 995
Methone: 21
Pallene: 24
Pan: 68
Pandora: 608
Polydeuces: 66
Prometheus: 670
Telesto: 209

--Emily

Attached File(s)

 JS_Rocks_Flybys_UTC_NFB.PF_6h9L.NACpixels.txt ( 6.87K ) Number of downloads: 358

 

[TritonAntares]

2009 07 05 05:00:00 - 2,089,800 km
2009 09 11 19:47:00 - 1,161,000 km
2009 12 01 15:07:00 - 1,377,900 km
2010 02 21 10:00:00 - 1,469,800 km
2010 05 08 16:30:00 - 1,234,800 km
That appears to be about it. Sorry, TA!
Hope the Sept. 2007 encounter is a REALLY good one!

BAD NEWS...

EDIT to the EDIT:
please ignore descriptions of what terrain is visible.
Viewing software has incorrect rotation rate for moons.

Uuuu....
Only incorrect rotation rates or more?

[volcanopele]

Distances are correct, phase angle is correct, times are correct. However, rotation rate, and thus the terrain visible, is wrong.

EDIT: Terrain descriptions in above post now edited and accurate.

[volcanopele]

while that highest possible resolution for Helene would be nice, I'm not sure how much we'll get, probably a couple of snapshots, no time for a nice mosaic. The flybys is high-phase incoming, and low-phase outgoing. Helene will become smaller than the ISS NAC field of view at around 5 minutes after C/A.

[elakdawalla]

Now that an extended mission tour has been selected I thought it'd be a good idea to open a new topic for the discussion. I'm moving some of the posts from the "Primary Target for Extended Mission" poll into this topic.

--Emily

[EccentricAnomaly]

Poor little 3-kilometer Methone -- nine of these relatively close flybys, and the biggest it'll appear will be 21 pixels across!

I think the reason why there were no targeted rock flybys in the prime mission was that no one knew the ephermerides well enough to target these bodys. I don't know how well the rocks are known now, but I'd bet Methone, Pallene, and Polydeuces aren't known very well... being recently discovered and all would mean there would be a lot less data available to calculate their orbits.