Double act on the Moon

Thursday 18 June 2009, this evening NASA is to send two probes to the Moon in preparation for the astronauts’ return.

 

The Lunar Reconnaissance Orbiter probe: a robotic scout for the return of astronauts to the Moon. Credit : NASA

Update : the 18 June launch of LRO and LCROSS is a success.

Having been neglected by the space exploration programme for a while, the Moon has, over recent years, become a major objective once again. Not so very long ago, 3 probes were orbiting our natural satellite at the same time: the Chinese Chang’e 1, the Japanese Kaguya and the Indian Chandrayaan 1. The first two recently completed their missions by means of a controlled crash on to the Moon’s surface (1 March 2009 for Chang’e 1 and 10 June for Kaguya – read this Enjoy Space article).

LRO: the Hitchhiker’s guide to the Moon
However, the Indian probe is not going to be alone for very long as this evening at 17:12, Florida time (21:12 UTC, Greenwich Mean Time - 23:12, Paris time), an Atlas V booster rocket is to blast off from the Kennedy Space Center and launch the dual LRO and LCROSS mission to the Moon.
Let us take a look, first of all, at the LRO or Lunar Reconnaissance Orbiter. This 1.9 tonne probe is going to study our natural satellite from a polar orbit at an altitude of only 50 km. NASA has clearly drawn up the priorities of this mission: to select safe landing sites, to identify lunar resources and to assess the effects of the radiation as regards the health of future explorers. In short, where to go, how to stay there and under what conditions. A genuine hitchhiker’s guide to the Moon, except that we are not talking about holidays, but about setting up scientific expeditions! Moreover, 4 out of the 7 onboard instruments (see Find out more), are directly dedicated to the search for water, probably in the form of ice deposits in the lunar soil or subsoil in permanently shadowed regions (certain craters at the poles). An essential resource that would greatly facilitate missions lasting several weeks or months, as it would then avoid us having to take the precious liquid needed by the astronauts with us from Earth. LRO will also draw up a map of the lunar relief using a laser altimeter whilst its camera of the utmost quality examines the ground with a precision of 1 meter! This means that we will be able to identify the different pieces of equipment left behind during Apollo missions when it flies over the sites in question (however, only 10% of the Moon is to be photographed with the highest resolution). Rather like getting back to basics so as to hand the baton over to future generations of moonwalkers.

The Shepherding probe observes the last stage of the Atlas V booster rocket as it crashes on to the Moon. The impact is scheduled for October, providing the lift-off takes place before 21 June. Credit : NASA

LCROSS: double impact
Although LRO has been given at least a year to carry out its scouting role, its partner probe from the LCROSS (Lunar CRater Observation and Sensing Satellite) mission, does not have as much time as it is to crash on to the Moon in October 2009 and only has a few minutes in which to achieve its primary aim! Once the LRO has been launched and released, the last stage of the rocket, topped by a small 891 kg probe named Shepherding, will follow a slightly different trajectory. Four months later, Shepherding will break away so that it can observe the 2.3 tonne rocket stage crash on to the Moon at approx. 9,000 km/h. Shepherding’s instruments will then analyse not only the luminous flash, but also the plume of dust spewed out to an estimated height of 10 km. This should confirm whether or not water is contained in the permanently shadowed polar craters; we come back to this quest for water for future human space flight missions. 4 minutes later, Shepherding will then suffer the same fate as the rocket stage by crashing in turn on to the surface of our natural satellite. LRO’s partner, therefore, has but a few minutes to gather the much awaited precious data and transmit it to Earth.
If the lift-off takes place this evening or before the 21 June, the LCROSS mission will target the south lunar pole (the exact crater will be selected at a later date) for a double impact between 7 and 11 October.

Published on 18 June 2009