Hello everybody. Been gone for awhile and just got back on the net. I read on here some where, that the camera for Smart-1 has a res of only 30 meters. So, I went to the Smart-1 page to see for myself. The camera has a res of 27 meters per pixel at an altitude of 300 KM. If the periapsis of the orbit can be lowered to about 20KM. what would the res be at that point? Would it be good enough to see anything at the landing sites?

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dunno- but if they took perfect pictures of all the Apollo parts on the moon, all the people who believe the landings werefaked would also think the pics were faked, as well- and they'd find some clever ways to "prove it".
altho i think a few pics of the landers and rovers and what not would be kind of neat to have.

Resolution is proportional to distance, thus if the resolution is 27 m at a distance of 300 km, than at 20 km distance the resolution would be

27 m x 20/300 = 1.8 m

The base of the LM's decent stage is 4.2 m across, so a 1.8 m resolution should be able to see it. However, this is a moot point because the spacecraft's final orbit is to be 300 km X 3,000 km with perilune over the South Pole and apolune over the North Pole. I'm reasonably confident that there is not enough propellant onboard to make such dramatic change in orbit as would be necessary to image the Apollo landing sites. Besides, it would be a great waste of resources to do so just to obtain photos that the conspiracy theorists would only dismiss as fabricated evidence.

In addition I don't think that the 1.8 m GSD would be sufficient to resolve the lander base into anything very meaningful. You can use the Johnson criteria to guestimate how many pixels that would be needed across the lander to for a human to perform different tasks. To detect the lander you'd need something like 2 pixels across, so we'd be in with a chance of detecting that there was something there, though that probably wouldn't be sufficient for the HBs. To be in with a chance of performing the recognition task, we'd need to have of the order of 8 or more pixels across it, so that means that we'd need to image it with a GSD better than 0.5 m.

Which means we would need to get within 5.5 km of the surface.

Pretty much. Anyone know how scary that would be for a lunar orbiter? (Not sure what the implications for ground clearance would be to hit a 5.5 km perilune over the Apollo landing site.)

If you were using the same camera on Smart-1, you would also have to worry about problems with along-track blurring. (If you measure the along track velocity in terms of pixels per second, then your pixel based velocity has increased by a factor of nearly 60.) There are ways to deal with this, but I don't know enough about the imaging mode of the camera on Smart-1 to say one way or the other.

What about SELENE that the Japanese will launch, will it be comparable to SMART-1 or might there be better chance of higher resolution?

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According to this NASDA Web page SELENE's terrain camera has a resolution of 10 m per pixel, although it doesn't say at what distance. I assume this is from the satellite's planned orbit of 100 km, which would give SELENE about the same angular resolution as SMART-1.

But they used a lot less fuel getting there than was anticipated. Flying over the landing sites could be done at the end of the mission if the craft still has that surplus.

And the photos would be good for publicity even outside conspiracy theory circles.

The perilune is located above the south pole. Even if they decide to lower the perilune to point a lot less than 300 km, they would still have it above the south pole. The equatorial region of the landing site will still be viewed from a great height.

If they want to shift the location of the perilune towards the equator, they would have to use even more propellant, that is not available. Plus, in order to shift the perilune, the orientation of Smart-1 would have to change (the thrust vector would have to be prependicular towards the velocity vector). Since Smart-1 uses electric propuslion, this attitude should be kept for a long time, meaning: mispointing of the scientific instruments, the communications antenna and maybe wrong geometry for the solar panels...

So, I don't actually see that "quoted" scenario taking place.

Thanks, Elias. Shifting the location of the perilune is what I had in mind when I mentioned the likely lack of propellant. Those types of maneuvers require far more propellant than simple altitude changes.