(NASA) The partial lunar eclipse of July 28, 1999 poses a last-minute obstacle to Lunar Prospector, which is scheduled to crash into the Moon three days later.

This Wednesday, July 28, sky watchers in the Americas, east Asia and the Pacific have a chance to view the last lunar eclipse before the year 2000 when the full moon passes through Earth's umbral shadow for over 2 hours. This eclipse will be a partial
one. At maximum approximately 40% of the Moon will be covered by the darkest part of Earth's shadow giving the moon an eerie, orange-colored glow.

Lunar eclipses are fairly common -- they happen about once every 6 months, on average -- but there's something uncommon about this one. It could mark the premature end of NASA's Lunar Prospector mission.