Apollo Sites from LRO Options

[Paolo]

How big is the retro rocket?

my sources say a sphere 94 cm (3 ft) across

[mcaplinger]

How big is the retro rocket?

I'm pretty sure Surveyor used an early version of the Star-37 -- http://www.astronautix.com/s/star37.html -- so 0.66 meters in diameter.

[GoneToPlaid]

This is my interpretation of the field of view of the Apollo image AS12-46-6759. First a rough perspective view of the image to help identify features near the horizon.

[attachment=41144:AS12_46_...rsp_post.jpg]

And a broader LROC view of the area:


[attachment=41146:AS12_46_...iew_post.jpg]

The prominent crater with a little crater on its near rim (A) is not the larger one near the retro-rocket impact - B. If B is visible at all it is the one barely visible near the right edge and horizon. I don't thing the retro-rocket casing would be visible at all, given the poor focus and the distance. In particular it's not the nice round object just beyond A.

Phil

A in your reprojected view of AS12-46-6749 really is B as labeled in your LRO overhead view. The terrain towards the Surveyor III retro rocket impact site actually is somewhat up-slope from the landing site -- just a bit more than enough up-slope to counter the local curvature of the lunar surface when looking towards the retro rocket impact site from near the lunar module. Although you postulated that the retro rocket might be resting on the lip of its created crater, to me and in my deconvolved images the retro rocket appears to be resting at the center of the crater. The nozzle is perhaps casting a very fine yet distinct shadow within the crater. The lip on the crater appears to be just that -- a crater lip and not the retro rocket itself.

AS12-46-6738 also appears to show the Surveyor III retro rocket impact site. I will post enhanced photos of this particular image.

[Phil Stooke]

It's very difficult to match points between surface and overhead views, and I have certainly made many mistakes in the past. That's why I like to stretch out the image in a reprojection. But in this case I think my matching features were correct.

Here is a direct comparison between the roughly projected view and a greatly enlarged LROC NAC image (M162466771L). Over 20 points of correspondence can be mapped. Number 15 is my previous crater A. Out at the edge, beyond my points 14 and 21, the surface drops into a shallow crater, and my previous crater B is seen where its far rim rises up again, twice as far away, but still short of the retro-rocket.

Phil

[GoneToPlaid]

It's very difficult to match points between surface and overhead views, and I have certainly made many mistakes in the past. That's why I like to stretch out the image in a reprojection. But in this case I think my matching features were correct.

Here is a direct comparison between the roughly projected view and a greatly enlarged LROC NAC image (M162466771L). Over 20 points of correspondence can be mapped. Number 15 is my previous crater A. Out at the edge, beyond my points 14 and 21, the surface drops into a shallow crater, and my previous crater B is seen where its far rim rises up again, twice as far away, but still short of the retro-rocket.

Phil

That matching is spot on!

[wildespace]

I do not understand how you can see it is "clearly visible". For one thing, do we know where the antenna is? Is it on its side to cast a thick shadow or what?

I would need to calculate the length of the flag shadow (not including the pole) for the shallowest sun elevation images to confirm this is likely a flag shadow. It did not jump out at me at the time as being obvious, but maybe I was wrong.

In the Flip Book (which is indeed an excellent and fun way to analyse the terrain and Apollo stuff on the ground), around the 9:00 to 11:00 time marks, I can see the flag's shadow clearly. It appears to be detached from the ground, which is what a flag's shadow does because it's on a pole, at some elevation from the ground:



A darkish area appears on the image at around 8:20 time mark, indicated here in an enhanced image:



I believe this is the actual location of the flag, showing the disturbed lunar soil:



The antenna doesn't really cast much of a shadow, it looks very pale in LROC images:






And MET's shadow stays attached to it, as it's sitting directly on the ground. It is visible earlier in the morning (if you move the slider from right to left), before the flag's shadow becomes clearly visible.

[wildespace]

In my site map I show a 'dark spot'. I am having trouble figuring out what it is. We have good images of the area from the LM window and nothing obvious shows up.

Phil

I have overlayed your schematic over a couple of LROC images at different sun angles (only your arrows, etc. remain, the background is now from different images).

The first one, where a PLSS is clearly visible:


It looks like the dark spot is just a subtle part of landscape, either some soil that was kicked up by the PLSS, or just a quirk of terrain (it's inside a very shallow crater)

Here's a second image, where that area is more directly illuminated by the rising Sun:

[Phil Stooke]

Nice images! The dark spot puzzles me because it doesn't seem to move with changing sun height, so it is on the surface, but there is absolutely nothing there in the images from the LM window after EVA 2. I have wondered if it was a bit of material thrown there during the LM liftoff, though usually when we see that it is bright, not dark (e.g around Apollo 11 in LRO images).

Phil

[wildespace]

Nice images! The dark spot puzzles me because it doesn't seem to move with changing sun height, so it is on the surface, but there is absolutely nothing there in the images from the LM window after EVA 2. I have wondered if it was a bit of material thrown there during the LM liftoff, though usually when we see that it is bright, not dark (e.g around Apollo 11 in LRO images).

Phil

The "dark spot" only shows up clearly in high sun angle NAC images, suggesting that it's simly rougher soil that doesn't reflect as much sunlight directly upwards as the surrounding area (same as with astronauts' foot tracks and other disturbed soil areas (however, the roughness in this case might be completely natural)). This roughness and the effect it produces wouldn't be obvious from a shallow-angle Apollo photo from the LM.

These are all just my musings, of course, based on what I see in the images.

[Phil Stooke]

These are two Apollo 14 images taken from the LM windows:

Pre-EVA 1:

https://www.hq.nasa.gov/alsj/a14/AS14-65-9204HR.jpg (lower left corner)


Post-EVA 2:

https://www.hq.nasa.gov/alsj/a14/AS14-66-9338HR.jpg (left of centre, just beyond the flag shadow)


I just find it surprising that there is not something more obvious at that location. A little crater might contribute a bit, but it's very small. I mentioned the possibility of a bit of LM descent stage material blown off by the ascent stage during launch, and it occurs to me now that an item like that might have scuffed the surface before being blown further away, creating disturbed soil after the last surface image was taken.

Phil