[X] My Assistant

[tolis]

Hi All,

I am not sure whether this is of interest to the community, but next year will see three
rather significant 50th anniversaries in unmanned lunar and interplanetary spaceflight,
those of Luna-1, the first probe to escape the gravitational field of the Earth (lunar impact intended),
Luna-2, the first probe to actually hit the Moon and Luna 3, the first probe to image the Moon's far side.

Luna-1 was launched on 2nd January 1959 and flew by the Moon on the 4th of the same month at a
distance of 6000 km on its way to heliocentric orbit.

http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=1959-012A

Luna-2 was launched on the 12th of September of the same year, hitting the Moon on the 14th in
the Palus Putredinus region (0 degrees longitude, 29 degrees N latitude) near the crater Archimedes.

http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=1959-014A

Luna-3 was launched less than a month later on 4th October (the second anniversary of Sputnik-1),
swung around the Moon to image the far side on the 7th and transmittted its data to
the Earth by the 18th.

http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=1959-008A

I don't know about you but I'm thinking of raising a glass of champagne a day later
than New Year's Day in honour of Korolev and his merry band of pioneers.

Happy Holidays to All,

Tolis.

[dvandorn]

I just realized I mis-stated something. At the time of ascent/descent stage separation, Snoopy was actually in an orbit of roughly 300 by 10 miles, not 70 by 10. For reasons of aligning the craft properly to simulate a Constant Delta Height rendezvous sequence after two low passes over the landing site, they had to enlarge the orbit between passes to place the LM and CSM in the proper locations.

This impacts this discussion in that a 300 by 10 mile orbit might have taken longer to decay than a 70 by 10 orbit. Depending on how the mascons affected the descent stage, the dynamic may well have raised the periselene a bit before dropping it back down again.

I do know that NASA wasn't at all concerned that this piece of space flotsam might be yet in orbit when they launched Apollo 11 into an almost identical orbit two months later, though. So, the descent stage must have been assumed to have impacted by then. Of course, with no electronic tracking (and skin tracking being nearly impossible at that distance), and with no seismometers emplaced as of yet, it would be nearly impossible to figure out where and when it actually impacted. Same with Apollo 11's ascent stage, the impact of which was never observed on the EASEP seismometer.

The impact speeds were indeed not incredibly high, especially for the orbital assets like the Apollo 10 descent stage and all of the ascent stages from the landing missions. The materials would be broken up a lot but not vaporized. Many small but recognizable pieces of terrestrial technology are scattered around the lunar surface in a variety of locations; some impact sites will likely only be found when someone on the surface runs across one of these pieces.

But truly, is it certain that artificial craters are necessarily indistinguishable from natural ones? The images I've seen from known spacecraft/booster impacts tend to have dark haloes -- at least I recall this from at least two of the S-IVB impact craters and at least one of the Ranger impacts. It was speculated at the time that this might be due to the interaction of remnant volatiles within the impactors with the lunar ejecta, an effect that was most obvious with the S-IVB impacts but still noticeable in some other impacts, including one of the Ranger impacts, if my memory isn't fooling me again...

I know dark haloes are not a definite or ubiquitous trait of spacecraft impact craters, but wouldn't a look through the existing imagery of the "target" areas in question for fresh-looking dark halo craters be something worthwhile to try?

-the other Doug