Subject: Rosetta Mission: Where’s Philae?
From: Alex Kemp
Date: Tuesday, 18 November 2014 02:50:59 +0000
To: Oliver Kemp, Micaela Kemp, Liisa Kemp, Davin Kemp

There is a kind of “Where’s Wally?” going on at the moment, as the Philae lander has still not been found. However, the ESA folks have issued some interesting photos...

philae separation anxiety
Bye bye, Philae. Be careful out there. (Rosetta OSIRIS; 12 October 2014 10:23 GMT)

Rosetta & Philae have spent 10 years together, travelling 6.5 billion km through space. Then, after an almost unimaginable journey together, last Wednesday 12 October at 08:35 GMT, Philae was cast out on her own for a 7 hour un-powered drop to the comet 67P surface.

The haunting photo above was taken by the Rosetta OSIRIS narrow-angle camera a couple of hours after separation (10:23 GMT). You can see that both the 3 landing legs & also the aerials are deployed.

Philae has a downward-facing camera (ROLIS) and this sent back a photo of the landing site from just 40m away, shortly before it touched down at 15:35 GMT:-

philae merge anxiety
Hello 67P (Philae ROLIS; 12 October 2014 15:35 GMT)

The large rock at top-right is about 5m in diameter. The rest of the structure at top-right is part of the Philae lander. This dusty corner of the comet is also the last known location for Philae...

Compare these 2 images carefully:-

identical before (left, 15:30 GMT) / after landing (right, 15:35:32 GMT) images

The red circles are the identical before (left, 15:30GMT) / after landing (right, 15:35:32GMT) images of the same bit of the comet. The green square is where the lander actually touched down, whilst the grey blob inside the right circle is the shadow of a plume of dust. But there is more!

ESA released the 15:35:32 image & the commentators said: “that looks like the lander and it’s shadow, to the right of the dust plume”. ESA checked it out, and they were right! Now compare these 2 images (identical except for the annotation) (the first one is essentially the same as the second one above, just without the green square):-

15:35:32 edit
15:35:32 annotated
Annotated images of the 15:35:32 GMT touchdown

It took a long time for ESA to realise that Philae had bounced. We got a possible reason for the bounce from the results of the MUPUS experiment. It had a drill bit to test temperature & other things... but it broke! It may well be, then, that the harpoon & foot-screws all failed because the surface is so hard that they could not penetrate it. Whatever the reason, Philae ended up spending 110 minutes bouncing a mile vertically & (possibly) 3.3 km horizontally.

Using the OSIRIS narrow-angle camera, ESA have been able to spot Philae as it dropped to it’s first touch-down:

Philae heading for a touchdown, viewed from Rosetta

The photo-mosaic above covers a 30 minute period (times shown are GMT). The camera was 15.5 km from the surface. The main photo resolution is 28 cm/pixel, whilst each enlarged inset is 17 x 17m.

You can see that the lander sharply changed direction after first touchdown (heading ‘East’ at about 0.5 m/sec).

Here is another photo from a commentator, showing the same info, but with greater scope & less clutter:

Overview 2 (credit: commentator)

Finally, and also from a commentator, here is where it may have ended up on a 3D-model of 67P (although using a 2.4km flightpath):

end game?
Is this where Philae ended up? (credit: commentator)
Alex Kemp