Apollo Sites from LRO Options

[kenny]

I did this a couple of years ago without the benefit of Phil's lovely book. It is a frame from the A14 descent movie showing an oblique view towards the western EVA traverse areas planned for A13. I think I have Star correct, and you can see from this angle why apparently it was so named, given its brightness. The white line beyong Doublet is the rim of Sunrise.

[jmknapp]

I wonder if they plan to image the sites where Saturn IVB/IU stages impacted the Moon? That kind of encounter would have a big footprint I imagine. For example the SIVB/IU from Apollo 17 impacted at 4.23S 12.36W according to post-flight reports.

[Phil Stooke]

The Apollo 13 and 14 SIVB impact craters and ejecta were imaged back at the time, so we know what to look for. I can confirm that all these types of site are LROC targets.

Phil

[volcanopele]

I assume that is so they can get a handle on what a very fresh, small impact crater looks like on the moon?

[dvandorn]

Actually, the impacts from known hardware are useful to observe. We can calculate pretty accurately the mass of the impactor, the speed of the impactor at time of impact, and the trajectory.

Remember, our theories on impact processes are based primarily on theoretical physics, with experimental results limited to very small impactors in laboratory conditions. Exacting measurements and analyses of relatively large-scale impacts (at least, larger than can be achieved in a lab setting) are valuable to the testing and verification of our theories on how impact processes actually work.

-the other Doug

[jmknapp]

Actually, the impacts from known hardware are useful to observe. We can calculate pretty accurately the mass of the impactor, the speed of the impactor at time of impact, and the trajectory.

Should be interesting to see. The info I have is that the Apollo 17 Saturn IVB hit at an angle of 34 degrees from the vertical and a speed of 2.5 km/sec, with a mass of 12,900 kg empty. A quick calculation gives 4*10^10 J of kinetic energy or about 10 tons of TNT. As they say on Mythbusters, that's what I'm talkin' about!

LCROSS is due to hit at a similar speed but with less mass (2,366 kg), about 5x less. More bang for the buck hopefully though, in terms of scientific payoff.

[As old as Voyage...]

The impact crater left by the ascent stage of the Apollo 17 LM should be visible up on the (south?) massif near the landing site. That'd be cool to see. Has anyone identified it yet? Such a shame the rover didn't get to see the actual impact.

[Phil Stooke]

I have searched for this in Clementine, HST and Earth-based radar images, and seen nothing. There were no Apollo 17 images of the landing site after the impact, unfortunately. The first Taurus-Littrow LROC image doesn't show the area (it's off the west edge and would probably be in shadow anyway). The Taurus-Littrow stereo image released after the first landing site image might be far enough west but we don't have the full version of that yet.

I suspect that the LM ascent stage did not impact exactly where it was predicted to, but who knows? Finding this and other impact sites is a high priority for me.

Phil

[dvandorn]

Well, we have a lot of Apollo 15 and Apollo 17 pan camera high-resolution imagery of the Taurus-Littrow site, so we ought to be able to identify any new crater in the LRO images.

This might be a good situation for doing a photographic subtraction in Photoshop. If you can get roughly similar sun angles, a subtraction of the LRO image from an A15 or A17 image of the same area would highlight any major changes to the terrain. In fact, that's something we want to do in a variety of areas, I think -- it will let us get good empirical data on the cratering rate (down to sub-meter cratering events) over a period of nearly 40 years.

-the other Doug

[jmknapp]

I suspect that the LM ascent stage did not impact exactly where it was predicted to, but who knows?

They had direct measurements from tracking stations, and they figured an accuracy of 3km in the impact point. According to the post-flight report:

The final lunar impact point is 4.23 degrees south latitude and 12.36 degrees west longitude. The accuracy of the impact coordinates is conservatively estimated at +/- 0.09 degree latitude and +/- 0.05 degree latitude. These accuracies are based upon the variations in latitude and longitude resulting from a large number of lunar impact solutions and on the quality of the late PTC trajectory solution. In particular, the range-rate and range residuals from five tracking stations observing the vehicle just prior to impact are excellent (see Figures 3-18 and 3-19).

Apollo/Saturn V Postflight Lunar Impact Trajectory -- AS-512 S-IVB/IU, April 11, 1973


PTC stands for passive thermal control, referring to when they set the S-IVB tumbling on three axes after the last propulsive maneuver 12 hours after liftoff.

EDIT: Oops, you were talking about the LM ascent stage, never mind.

[kenny]

Anyone have any intelligence on when the Apollo 12/Surveyor 3 site was due to be imaged? LRO must have passed over it in daylight by now. At low sun angles (sunrise and sunset) Surveyor is invisible in the crater shadow, but the LM descent stage should be vsiible in any lighting conditions.

[Phil Stooke]

Surveyor 3 will not be in shadow because the sun is coming from the west in images at the moment, and higher above the horizon than in the first images. I think we have to wait a week or so to get another attempt.

Phil

[Guest_Zvezdichko_*]

http://lroc.sese.asu.edu/news/index.php?/a...-Fra-Mauro.html

LRO successfully photographed Apollo 14 site again. ALSEP and the trails are visible.

[John Moore]

The change in lighting conditions.

Left: July 17 2009 Right: A month later

John

[ElkGroveDan]

I'd do an a anaglyph with those two, but I'm rushing off early right now. Stu?