From 280 miles high, Atlantis' crew took time out Saturday to chat with schoolchildren, a diversion from the detailed testing of a huge scientific observatory the astronauts will release Sunday.

"Can you see Oklahoma from where you are?" asked 7-year-old Steven Soby, one of the pint-size interrogators in an amateur radio experiment."Stand by, I'll get to a window," replied pilot Ken Cameron, a ham radio operator who did most of the talking. He couldn't see Oklahoma because the space shuttle was orbiting too far north, he explained.

A child in Illinois asked: "How hard is it eating up there?"

"Well, I just finished my lunch," said Jay Apt, who will be a space walker come Monday. "I had a little chicken soup. The noodles float right up and they are gooey enough, they'll adhere to the spoon. But even if they don't, you can chase them down with your mouth."

Most of the day's activities were directed toward preparing for release of the Gamma Ray Observatory from the shuttle's cargo bay Sunday morning. The 31-foot-long observatory will circle Earth for at least two years recording radiation that is the most energetic in the universe but invisible from Earth.

"The Gamma Ray Observatory is healthy, and it's ready to be deployed," Shaw said.

He said 1,074 computer commands were sent to the observatory during Saturday's testing.

Apt and Jerry Ross will be in space suits, ready to go to the rescue, should anything go wrong during the satellite's release. The observatory will be lifted from the cargo bay with the shuttle's robot arm and tested from the ground with nearly 5,000 commands before it's set free.

If all goes as planned, Apt and Ross will go into the empty cargo bay on Monday to practice techniques for assembling a space station some time in the future.

Theirs will be the first space walk in more than five years.

The observatory is designed to undertake a systematic survey of gamma rays, the energetic radiation produced by the collision of nuclei and the annihilation of matter in the presence of antimatter. The rays flow from quasars and supernovas, from pulsars and neutron stars and from black holes.