Two of the three sensors find guide stars around the target within their respective fields of view.

Once found, they lock onto the guide stars and send information to the flight computer to keep the guide stars within their field of view.

The second is to acquire pre-selected guide stars.

During acquisition, a guide star is first centred in an 8 x 8 pixel window.

Most modern professional telescopes use a guide star.

Instead, one can create an artificial guide star by shining a laser into the atmosphere.

But the Air Force has created and tested a laser system that projects an artificial "guide star" high above the ground.

"Painted Stick has taken his fix on the guide star."

So astronomers are experimenting with guide stars created artificially by laser light.

It took mission members about 29 hours to recover and transfer back to the nominal state, with the guide star locked in.