Philae landing on the nucleus of Comet 67P C-G Options

[jmknapp]

Is there a cylindrical projection available?

As for the exact geometry, I was thinking that it's possible that just a few degrees change in declination might make a big difference in lighting at a specific site, more than if it was a smooth ellipsoid, because of nonlinear shadow effects.

[scalbers]

There has been Phil's map (post #44) and some rotating shape models posted in this thread: http://www.unmannedspaceflight.com/index.php?showtopic=7883. The original landing site was somewhat north of the equator.

And indeed - one can hope we are seeing a nearby cliff or something that is barely blocking out the sun over some period of time (in the best scenario). Judging from Phil's map and the bounce ellipse posted recently (Jorn Barger #511 in this thread), the crater/cliff faces may be looking off to the southwest. That would bode fairly well for improvement with the sun's shift, even though it looks to have bounced to a slightly more northerly latitude.

This appears consistent with Malmer's shape model here: http://www.unmannedspaceflight.com/index.p...st&p=214013. This shape model I suppose could be visualized for various solar declinations.

[Rakhir]

Philae spotted after first landing

http://blogs.esa.int/rosetta/2014/11/16/ph..._first_landing/

[Ron Hobbs]

Oh those couple of images are just so COOl!

Hats off to the Rosetta team for all that they have accomplished.

[centsworth_II]

Philae spotted...

As previewed by Gerald and Emily in posts 534 and 537 of this thread.

Big, big thanks to the Rosetta team for providing these images! Great job, getting that shot!

[alphasam]

The first landing site is certainly 'fluffy' (judging by the bounce mark), but the actual area Philae ended up looks much more like a solid. Vertical surfaces don't get much dust on Earth, so there shouldn't be much accumulation there either.

Perhaps on Earth but define vertical on a body with a negligible gravitational field where the material below the surface is out-gassing. If you heard during one of the media events ROLIS member Stefano Mottola noted in the image from ~40m (IIRC) above landing site #1 that the dust appeared "active", partially covering one of the boulders in view.

Reading the early science results from Rosetta starts to make a lot more sense. e.g.;

http://www.planetary.org/blogs/emily-lakda...-darmstadt.html

"@ESA_Rosetta sees strong diurnal variation in vapor production. Probably from first 2 cm of surface #DPS14"

"MIRO sees "porous, dusty surface that is incredibly insulating"You only need to go down a mm or 2 to go down 50K in temp #DPS2014"


Indeed as alluded to in the MUPUS tweets similar material to where Philae ended up possibly underlies the first landing site, hence the bounce.

Philae spotted after first landing

http://blogs.esa.int/rosetta/2014/11/16/ph..._first_landing/

A guy at Jodrell has done a difference image to bring it out.
https://twitter.com/Eamonn_Kerins/status/533967071705448448

[Ron Hobbs]

There is so much chatter on the internet, "it is fool's errand" to try and sort through it all.

While following the MUPUS discussion here and on twitter, I found this blog entry from Rachel Feltman at the Washington Post. I think it is a decent review of the significance of the events of the last week.

Why we all fell in love with Philae

Or if you prefer the twitter link:

Washington Post twitter link

[brellis]

Looking forward with healthy optimism, will Philae simply wake up once it's received enough sunlight? Or, will it need a signal from us to phone home?

edit: ESA blog answers this question.

The next possible communication slot begins on 15 November at about 10:00 UTC / 11:00 CET. The orbiter will listen for a signal, and will continue doing so when its orbit enables communication visibility in the future.

However, given the low recharge current available from the solar cells, it is considered unlikely that contact with Philae will be established in the coming days.

[fredk]

Philae spotted after first landing

http://blogs.esa.int/rosetta/2014/11/16/ph..._first_landing/

Confusing comment in that post:

the image that was indicated to have been taken at 15:30:32 UTC, just before touchdown, was actually an image taken at 16:30:32 UTC, about an hour after touchdown.

This would mean that the dark landing mark wasn't permanent, but dissipated over the hour, as if it was just a cloud that dispersed. Still it's surprizing that the dark mark would apparently completely disappear, leaving no bounce mark or debris field visible on the ground.

[Sohl]

Philae spotted after first landing

http://blogs.esa.int/rosetta/2014/11/16/ph..._first_landing/

I don't find this second image convincing as a definitive sighting of Philae. There are stronger shadows in the second, later image. Maybe the bright area and shadow are just some natural feature more easily seen with the shifted angle of lighting? Or perhaps the initial lander bounce threw some debris to the location suspected as Philea itself? I'm sure there are several other equally plausible explainations for the difference between these two images.

Furthermore, what happened to the 1 km estimated separation of the first bounce location to the second? How far apart is this purported location of Philae from the area disturbed from the initial impact? Less than 100m? Less than 50? It seems very unlikly that a bounce of several hundred meters vertically would not have any appreciable horizontal drift considering the rotation of the comet nucleous and possibly uneven terrain from which it bounced. And what of the signal triangulation results that placed the final location much further over at the rim of a large crater in very rugged terrain? That seems to be a much closer match to the surface imagery than the smooth-appearing area targeted for the landing and at the supposed final location.

I'm surprised this blog got posted with such confident language. Sure, I suppose it _could_ be Philae, but I'd think folks would want to go over it a lot more, especially if other evidence contradicts it.

I'm not trying to diminish this spectacular achievement. I'm glad to be alive at a time humans could send something out to touch a comet!

[ugordan]

I'm surprised this blog got posted with such confident language. Sure, I suppose it _could_ be Philae, but I'd think folks would want to go over it a lot more, especially if other evidence contradicts it.

What other evidence? Your numbers that seem to be pulled out of thin air? There is an official number floating around for the estimated bounce-off velocity. There is a known time for the image timestamp and for the landing time. A fairly accurate height estimate can be made for Philae at that point in time, an exercise that I'll leave to the reader.

Furthermore, I would hope the ESA team have a better idea of where the vector normal to the surface (and thus which groundtrack direction Philae was actually going to) points in that image and whether or not this particular trajectory is consistent with the final resting point. To quote the blog entry:

However, some careful work by a number of people in ESA's Flight Dynamics team and by followers of our Rosetta blog has shown that these NAVCAM images show more, namely Philae itself, just after the bounce!

bold mine.

[Gerald]

Confusing comment in that post:
This would mean that the dark landing mark wasn't permanent, but dissipated over the hour, as if it was just a cloud that dispersed. Still it's surprizing that the dark mark would apparently completely disappear, leaving no bounce mark or debris field visible on the ground.

This should be a plausible explanation, starting with

The images show what appears to be the shadow of a dust cloud kicked up when Philae made its first touch down on the surface of the comet at 15:35 UTC.

of the Rosetta blog post:
The dark mark is the shadow of a cloud of debris, which has been dense that shortly after the impact.
An hour later the cloud has been dispersed or settled, no obvious shadow visible any more.

[djellison]

Furthermore, what happened to the 1 km estimated separation of the first bounce location to the second?

Nothing happened to it. The 'after' image is - to cite ESA themselves " 1 min 26 seconds after first touchdown"

Assuming an approx 1km traverse across the comet in the 113 minutes until the second bounce..... that 1min 26sec should only be 13 meters from the first touchdown point.

That correlates well with what we see in the image.

[Jorn Barger]

Another view of the putative "resting place". Image from 14 September.

[attachment=34298:ROS_CAM1...nnotated.jpg]

This fits the new, 'photographed' direction much better than mine-- it's the far end of the blue diamond.

[xflare]

With the primary battery designed for the decent to the surface and first few days of surface operations depleted, the solar panels were intended to be used to recharge the backup batteries. So could the 90 mins of daylight (possible more after moving the lander) recharge the battery after maybe a week or two - can they hold onto that little bit of charge they receive each day? Or would they discharge ones it moves back into shadow. - this is probably wishful thinking !!!