Live: satellite, Centaur to separate for moon strikes

Update, 9:55 p.m.: NASA's LCROSS spacecraft has successfully separated from the Centaur rocket stage, setting the stage for both to crash into the moon Friday morning at 7:31 a.m. and 7:35 a.m.

A NASA satellite is approaching a critical separation maneuver from a rocket stage necessary before both can smash into the moon as planned Friday morning.

At 9:50 p.m. EDT, the $79-million Lunar Crater Observation and Sensing Satellite, or LCROSS, is set to release from the upper stage of a United Launch Alliance Atlas V rocket, called a Centaur.

Click here to watch the live animations starting at 9:40 p.m. Low-resolution pictures beamed back from the spacecraft are expected to begin playing at 9:55 p.m.

This will be the first time a spacecraft commands separation from a Centaur; it's usually the other way around. And spacecraft normally separate within hours after launch, not after 112 days like LCROSS.

"That was a risk that we had identified very early in the development of this mission," said Dan Andrews, the mission project manager, in a news conference today. "Most separation systems are not expected to hang around and wait to do their thing as long as we have."

It's been 112 days since LCROSS launched on June 18 from Cape Canaveral Air Force Station, along with NASA's Lunar Reconnaissance Orbiter.

But Andrews said the separation system had been tested under more extreme temperature conditions that it has experienced so far in space.

"We're actually pretty confident it will work as advertized," he said.

If the separation is successful, the satellite will execute a braking burn at 10:30 p.m. to create space between it and the spent rocket motor before both collide with the lunar south pole crater Cabeus.

The Centaur is scheduled to strike at 7:31 a.m. Friday, the spacecraft four minutes later.

The mission is an effort to look for water ice in the moon's permanently shadowed polar craters. Scientists expect the rocket stage to kick up a high plume of debris and vapor that LCROSS instruments will analyze for evidence of water.

For more background on the mission, check out this fact sheet and press kit.

Here's a link to the mission flight director's blog.

And follow mission Twitter updates here.

IMAGES: Above, image of the centaur separation as viewed from the visible light camera. Credit: NASA. Below, an artist's rendering of the Lunar Crater Observation and Sensing Satellite just after separation. Credit: NASA.