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To: Tom Swift who wrote (20931)	5/6/2004 8:22:38 PM
From: EL KABONG!!!	Read Replies (1) \| Respond to of 32907

Hello Tom, Long time, no see... It seems that the ones that make the news are spotted only days and weeks before a close pass. Absolutely true... The smaller asteroids don't reflect a lot of light. Their albedo is extremely small, smaller than even Earth-launched satellites which are sometimes highly reflective at certain angles when viewed from Earth. Without a lot of reflection, the asteroids are nearly invisible to Earth-based telescopes, and as such, we don't spot many of them unless they happen to be just at the precise angle for highest reflectivity, or perhaps their trajectory takes them a tad closer to the sun, increasing their albedo. The USA (and the European Space Agency as well, I think) will be launching orbiting satellites with powerful telescopes that will place them well outside the Earth's distorting atmosphere and will help enormously in the search for NEAs. As it is now, most NEAs are discovered not by the naked eye, but by CCD astrophotography using extremely powerful and precise telescopes. The cameras can "see" reflectivity thousands of times better than the naked human eye. I have read of another proposal in the search for NEAs, which involves sending out a radar signal randomly into space, and then reading the return echo, much the same as what a police officer does when using radar in a speed trap. The theory is that even though these things are far too small for us to see them in a telescope, or sometimes even too small and too low an albedo to even be captured on cameras, a radar beam would bounce off of them, and an image could be determined. Once identified and a trajectory/speed is determined, then ground based radio telescopes or telescopes with UV filters or IR filters, oxygen filters, etcetera could be used to study the object because we'd know exactly where it is at any given moment, and we could easily relocate it even though we couldn't actually see it. It's an exciting occupation for younger people to get into, presuming they acquire the scientific and mathematical skills necessary to earn the diploma. KJC