Tuesday, October 13, 2009

LCROSS – What Happened?

Last week, the Lunar Crater Observation and Sensing Satellite, or LCROSS, completed its 113-day mission by crashing into the surface of the moon. Preceding the satellite was the bus-sized Centaur booster stage that accompanied it most of the way. Many of you knew this was going to happen from the day it was launched piggyback with the Lunar Reconnaissance Orbiter on June 18. NASA predicted the impact would raise a could of debris 10 meters in altitude, rising over the limb of the moon, that would be visible to telescopes on earth.

I was at my telescopes eyepiece watching – a long shot to see anything as those of us on the east coast were already in daylight, but I was hoping the scientists had underestimated the effect of the impact. I remembered reading about the monks in 1178 AD who witnessed “two horns of light” while looking at the moon, which some astronomers speculate was the creation of crater Giordano Bruno. I thought if they could see that with the unaided eye, I might get to see something with my scope.

The time came, and went. Nothing to be seen. Did I miss it? Was I looking in the right place? Did I mess up the time? I went inside to check NASA TV and used the DVR to rewind back to impact time. Nothing there either. Meanwhile, I hear the scientist say that it was successful with data returned to earth. The bombing of the moon that had been trumpeted in the news was a fizzle.

This is one of the difficulties in communicating science to others. Predictions are made – most conscientious scientists will be conservative in their predictions, but often excitement tends to cause over speculation. We really did not know what would happen when the Centaur and LCROSS impacted the moon, although we did have a precedent. In1971, the Saturn V S-IVB third stage of the Apollo 14 mission slammed into the moon at 2.54 km/sec. It left a crater 35 m in diameter, ejecting debris for 1.5 km. Although smaller, the Centaur was traveling faster, and was predicted to evacuate a larger crater and produce a much larger plume. In fact, both of these events occurred, observed by LCROSS and LRO, just not from earth.

Sometimes science can produce a wonderful show that helps to motivate and interest the general public, and sometimes we get disappointed. Nature is fickle. There is a difference between what you see on a tour at Kennedy Space Center and what you see on the Jungle Cruise at the Magic Kingdom. The important thing is not the show, but the data returned. And in that respect, LCROSS was very successful.

1 comment:

  1. Great post Jim... I have had a lot of questions about this event and many of them are anxious to learn what was observed. Also, I think a lot of people are wanting to know the answer now. and I mean NOW!!! In this twitter status rt update world it is sometimes difficult to accept that, on occassion, science takes time. If I can get approved for a new credit card in 30 seconds, why does it take NASA a few weeks to tell us what happened with LCROSS... Although, didn't NASA recently "Tweet" from their last shuttle mission??? Great stuff Jim.