LCROSS Pre-Impact Briefing Notes

Currently, spacecraft is GO for Impact

Target chosen: Cabeus Crater

(Image: Showng the Cabeus Crater. Credit: APOD)
The Cabeus Crater is a 3.5 to 4 kilometers deep crater in the Southern polar region of the Moon. It is 100 kms wide and about 100 kms from the Lunar South pole. Therefore, there were worries on whether the ejecta could be seen from Earth. However, new topography data obtained by LRO's LOLA instrument and Kaguya's altimeter data showed that there was a gap in the rim which would enable us to see the ejecta.

Earth and Space-based Observatories observations

Earth and Space-based observatories are going to watch the LCROSS impact. On 7th October 2009, a rehersal was done which included the Keck, CFHT, Gemini, IRTF and Haleakale observatories in Hawaii and MMT, Kitt Peak and Palomar facilities in South West United States rehearsed the observation and tested the communication infrastructure successfully. The impact will also be witnessed by space-based observatories like Hubble.

What is happening now?
Image: A picture showing the current location of the LCROSS spacecraft at 19:36 hrs UTC on October 8, 2009. LCROSS has been made bigger than its actual size. Credit: NASA

Ground and lunar orbital based observation of the Cabeus crater is now under way. Recent data from Chandrayaan and LRO have re-confirmed that there is hydrogen in the crater. The LCROSS and Centaur stage are currently in orbit around Earth-Moon system and heading towards the impact target.

Ground based Observations
NASA scientists say that there will be nothing dramatic in the ground based observations. With the black background, the ejecta will be seen as a reduction in the blackness.

Impact!
Centaur Upper Stage Impact: Centaur will be seen drifting away from LCROSS spacecraft. As the Centaur upper stage heads for impact, 5 cameras will watch the spacecraft. At the time of impact, a near-infrared camera will watch the spacecraft. After the impact, as the impact plume from the Centaur upper stage rises normal cameras will be switched on.

LCROSS Spacecraft Impact: Four minutes after the Centaur upper stage impacts the Moon, the LCROSS spacecraft will also impact the Moon 3 to 4 kilometers away in a region known to be rich in water ice. The second impact will add to the vapour cloud rising higher than the dust plume and thus can be seen by ground based observers.

Will the Impact affect our Moon?
We have explained the answer to this question thoroughly in this post. NASA scientists add that impacts of such energy happen atleast four times a month on the Moon. So, there is no danger to our Moon.