CE-2 flyby of Toutatis Options

[Phil Stooke]

No, but radar does that very well.

Phil

[Paolo]

speaking of which, the first radar image of the 2012 flyby
http://echo.jpl.nasa.gov/asteroids/Toutati...2_planning.html

[Paolo]

from this post to the mpml asteroids and comets group http://tech.groups.yahoo.com/group/mpml/message/27635 the two pics will be taken one on the inbound leg, the other on the outbound leg. my Chinese sources say the targeted distance will be 1000 km.
I guess what this means is that CE2 will aim at the point in space where Toutatis is supposed to be and wait for it to cross the field of view of its push-broom camera at the correct angular rate. then it will be reoriented to take a second picture with the same technique on the outbound leg

[machi]

So we can expect images with resolution ~100 m/pix at best. This isn't much for such small body like Toutatis (~2.5 km diameter), but still it can be very interesting.
~25 image elements per diameter is enough for major units, like albedo regions or big craters and it's sufficient for Emily's size comparison poster.

[Explorer1]

So the images will be the equivalent of what Deep Space 1 did, assuming they pull them off?

[machi]

Deep Space took images of Braille with resolution around 180 m/pix. Braille is two times smaller than Toutatis. So with some luck, we can expect images four times better than those of asteroid Braille (4× more pixels across diameter of asteroid).
This is what we can expect, if everything goes well and image will be taken close to 1000 km flyby distance.

Attached image(s)

 

[Paolo]

anyway, as the camera has two linear CCDs, a forward looking and a rearward looking one I would rather expect two couples of pictures instead of two pictures

[Phil Stooke]

Machi, that is Steins, not Braille.

And Paolo - doesn't that suggest the forward camera will take one and the rearward camera will take one? Otherwise you seem to be suggesting the spacecraft reorient itself during each sequence.

And there's another new image here:

http://echo.jpl.nasa.gov/asteroids/Toutati...2_planning.html



Phil

[machi]

Machi, that is Steins, not Braille.

Yes, I know.
That is image of Steins from Rosetta used for demonstration as Toutatis may appear from CE-2.
I thought that I wrote this clearly, if not my apologies, it was lost in translation.
In fact this image was uploaded with name "Steins_as_Toutatis_from_Change2", but evidently forum system still uses some kind of thumbnail with different name even for small images.

[Paolo]

And Paolo - doesn't that suggest the forward camera will take one and the rearward camera will take one?

the camera has two parallel CCDs, one looking 8 degrees forward of the nadir (when in lunar orbit), the other 17.2 degrees to the rear. To me the most logical sequence would be one where Toutatis crosses the field of view of the first CCD almost perpendicular to it and then about one minute later (the exact timing depends on the encounter geometry, which is not known) that of the second sometime on the inbound leg. Around closest approach the probe is reoriented so that Toutatis crosses again both fields of views in the outbound leg. this gives two pairs of images.
If no reorienting is done, you get only one pair of images a few tens of seconds apart

[Paolo]

third radar picture http://echo.jpl.nasa.gov/asteroids/Toutati...32Hz.s439.b.gif
it's amazing how the quality and resolution of these images has increased since 1992

[machi]

According to this page, flyby distance will be around 300 km.
If it's true, then images from CE-2 will much better than in my simulated image (maybe 4× better).

[tasp]

I'm not thinking of any other 'rocks' imaged with ground based radar getting a nice visible light camera flyby. (It is REALLY early for me though, and no coffee yet) (we need a 'sleepy' emoticon)

Anyone recall any others?

[Paolo]

Itokawa had been imaged by radar before Hayabusa arrived

[machi]

I'm not thinking of any other 'rocks' imaged with ground based radar getting a nice visible light camera flyby...
Anyone recall any others?

Not exactly "rock", but also comet Hartley 2 was imaged by radar.
Here is article about "Radar observations of asteroid 25143 Itokawa".