LCROSS Adjusts its Aim

Do you remember NASA's Deep Impact mission of July 4, 2005, which punched a spectacular hole in Comet Temple 1 in order to see what was inside? Well, as Yankee's great Yogi Berra would say, its “déjà vu all over again.” Only this time the target is a lovely crater at the South Pole of the Moon.

The mission is NASA's Lunar CRater Observation and Sensing Satellite, or LCROSS for short. The mission objectives of LCROSS include confirming the presence or absence of water ice in a permanently shadowed—and therefore always cold--crater at the Moon’s South Pole. As mentioned here a few days ago with the Chandrayaan-1 announcement, the identification of water is very important to the future of human activities on the Moon. LCROSS will excavate the permanently dark floor of one of the Moon’s polar craters with two heavy impactors to test the theory that ancient ice lies buried there. The impact will eject material from the crater’s surface to create a plume that specialized instruments will be able to analyze for the presence of water (in the forms of ice and vapor), hydrocarbons and hydrated materials.

Like on Earth, water is a crucial resource on the Moon and it won't be practical for humans to carry with them all of the water they will need. It is critical to find natural resources, such as water, on the Moon. The LCROSS mission will begin NASA's direct search for water, leveraging the information that was learned from NASA'S Clementine and Lunar Prospector missions.

By going first to the Moon and staying there for extended periods of time, astronauts can search for resources and learn how to work safely in a harsh environment before moving out to other bodies in our solar system. In addition, a close up and extended study of the Moon can offer scientists insight to the time when the planets were formed.

A sister mission working with LCROSS is NASA's Lunar Reconnaissance Orbiter, or LRO. From lunar orbit, LRO will scout for safe and compelling landing sites for future missions, locate potential resources (with special attention to the possibility of water ice) and characterize the effects of prolonged exposure to the lunar radiation environment. In addition to its exploration mission, LRO will also return rich scientific data that will help us to better understand the moon’s topography and composition.

Back on June 18, LCROSS and LRO began their mission from Launch Complex 41 at Cape Canaveral Air Force Station, aboard an Atlas V first stage with a Centaur upper stage. Since then, the mission teams have been using their returning data, along with data from current and past lunar missions (those previously noted as well as ISRO's Chandrayaan-1 and JAXA's Kaguya spacecraft), to refine the South Pole target for the LCROSS impactors.

Until recently the target was crater Cabeus A, a companion to crater Cabeus (proper). Then on Monday the LCROSS mission announced it was shifting the target to Cabeus (proper). The latest data now seems to show that Cabeus has the highest hydrogen concentrations at the South Pole. Also, the latest terrain models show a small valley in an otherwise tall Cabeus perimeter ridge, which will better allow sunlight to illuminate the ejecta cloud—the stuff flying out from the impact—on October 9, which is the scheduled date for the event. While this target change means that the ejecta will have to fly a little higher before it is visible to ground-based and Earth-orbital telescopes, a shadow cast by a large hill along the Cabeus ridge, will provide an excellent, high-contrast, back drop for ejecta and vapor measurements. The first impactor will be the Centaur upper stage, which has been guided by the LCROSS spacecraft. Following its observations of the first impact, LCROSS itself will then dive in, creating the second impact.

The exact time of the impact is early Friday morning, October 9, at 7:30 a.m. EDT/4:30 a.m. PDT. As the date gets closer, mission teams will continue to refine the target, choosing the exact point of impact within Cabeus crater in order to avoid rough spots, and to maximize solar illumination of the expected debris plume and Earth observations. Scientific benefits aside, it looks to be a great show. If you happen to be at a location where the Moon is visible at that time, and if you have a telescope with a 10” to 12” aperture, you might want to gather some friends for a LCROSS impact party. It should be fun. Just be sure to observe and party responsibly.

To keep current on the missions as they progress, stay tuned to these sites:

NASA's Lunar CRater Observation and Sensing Satellite (LCROSS) Mission
www.nasa.gov/lcross/

NASA's Lunar Reconnaissance Orbiter (LRO) Mission
http://www.nasa.gov/mission_pages/LRO/main/index.html

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