Will amateur astronomers really be able to see anything?
"It's doubtful," says Lunar Prospector's principal investigator Dr. Alan Binder, "but I would encourage anyone to try."
Although amateurs won't be able to see the tenuous vapor cloud -- ultraviolet and infrared spectrometers are required for that -- there's a slim chance that a plume of lunar soil and spacecraft debris might be visible through amateur telescopes just after Lunar Prospector slams into the Moon. If the debris makes it over the crater's obscuring rim, the plume would briefly shine by means of reflected sunlight (just like the rest of the Moon) and it could persist for as long as several minutes glowing faintly against the black sky just above the lunar limb.
Undaunted by the slim prospects, hundreds of amateur astronomers plan to monitor the Moon for signs of impact. The Association of Lunar and Planetary Observers (ALPO), the American Association of Variable Star Observers (AAVSO), and members of the International Occultation Timing Association (IOTA) are participating in the observing campaign. If a unexpectedly bright plume arises, amateurs somewhere will almost certainly record it.
Dry air observing sites are best. If the air is humid it will scatter the moonlight, greatly increasing the brightness of the sky and making a faint plume that much more difficult to see. The moment of impact was chosen so that the Moon would be visible at night from Hawaii and Texas where important telescopes are located. The best potential viewing sites for the collision range eastward from the mid-Pacific to central North America. The table below
"If an impact plume is detectable by amateurs, I suspect that it will be recorded by those equipped with astro-video equipment," says Bill Dembowski, the ALPO Coordinator for Lunar Topographical Studies. "Not only are these cameras quite sensitive, but they allow the recording of hundreds of images in a short space of time which can later be searched and enhanced to show very faint details."
Mission scientists emphasize that the failure to observe a plume, by professionals or amateurs, does not signify a lack of water on the Moon.
According to the UT Austin Lunar Prospector Impact Web Site: "A negative result will tell us nothing one way or the other about potential lunar water resources. The spacecraft could miss the crater entirely; it could impact high up the inner rim; it could miss a water deposit. Many things could go wrong. Still, it is befitting of this extremely productive little spacecraft that, even in its final act, Lunar Prospector may serve yet once more as a source of knowledge about our Moon."
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