Astronaut Push-Starts $617-Million Machine : Space: Antenna on orbiting observatory jams. Crew leaves shuttle to free it. Scientific mission begins.
The $617-million Gamma Ray Observatory, designed to study the most powerful radiation emitted by the most violent events in the universe, required the gentle nudge of a human hand Sunday to begin its historic assignment.
When the observatory’s antenna ignored orders from Mission Control to swing out on the end of its five-foot boom, astronauts Jerry L. Ross and Jay Apt donned space suits, left the relative safety of the space shuttle Atlantis and fixed it.
It was only the second unscheduled spacewalk in the history of the shuttle program.
As the Atlantis sped along at 17,500 miles an hour 280 miles above the Earth, Ross, 43, literally shook the mechanical arm holding the huge observatory and the antenna broke free of a stubborn latch.
“It’s free! It’s free!” a jubilant Ross shouted. “I can see it move.”
“Far out,” answered Apt, 41. “Good work.”
Told by Houston that the maneuver had brought loud applause in mission control, Ross answered: “That made my day.”
The repair operation was accomplished so quickly that the two men began doing some of the experiments that were scheduled for today’s planned spacewalk. They are expected to spend several hours today trying out various devices that could help astronauts assemble the Space Station Freedom later this decade.
Earlier in the day, the Gamma Ray Observatory was lifted out of the shuttle’s cargo bay by astronaut Linda M. Godwin, 38, who gently maneuvered the 35,000-pound satellite with a mechanical arm that is so fragile it cannot lift its own weight when the shuttle is on the ground.
She kept the observatory dangling on the end of the arm until all its systems could be checked out, a strategy that proved wise when the antenna that is to provide the primary communications link refused to budge.
The observatory passed its first milestone when its two solar panels slowly unfurled from its sides like the flexing wings of a prehistoric bird. The solar panels supply the energy to keep the satellite’s batteries charged, and without them its sophisticated instruments would not be able to operate.
The sight of the huge observatory--the heaviest civilian satellite NASA has ever launched from the shuttle--brought words of praise from Apt.
“Boy, this is sure a pretty sight,” he said as he gazed at the observatory, suspended between the shuttle and a blue and white Earth. “It’s just a gorgeous spacecraft they’ve got here, with these beautiful black wings. It’s just a beautiful spaceship.”
The balky antenna proved to be only a minor problem for the two astronauts, and the observatory was finally set free to be bombarded by fierce radiation from some of the most violent events in the universe. Its job, simply stated, is to catch gamma rays.
Gamma rays are created when atoms are ripped apart in a process so violent that nearly all the matter is converted to pure energy.
Gamma rays are of profound interest to scientists because they are produced when stars collide, or explode, or a black hole gobbles up nearby matter--or in ways as yet unknown. The most powerful form of radiation, gamma rays occupy the top of the electromagnetic spectrum that ranges down to radio waves, the weaklings of the universe.
They are so energetic that they are extremely difficult to study.
The Gamma Ray Observatory is not a telescope, and it does not even have a mirror because gamma rays would pass right through it. Instead, the observatory must literally capture the gamma rays in a process that produces bursts of light, or sparks, that can be detected.
The observatory consists of four instruments, each about the size of a compact car. They have to be that large because gamma rays are much rarer than visible light, so it takes a large “bucket” to capture enough rays to study.
Gamma rays are produced in many ways.
Black holes, which cannot be seen because they are so dense that even light cannot escape their gravity, are believed to produce gamma rays when material is literally ripped apart on the atomic level as it spirals into the black hole. Scientists hope the observatory will reveal that process, thus further confirming the existence of black holes.
There are many mysterious sources in the sky that seem to explode with massive bursts of gamma rays. No one knows why, and the observatory could solve that riddle, according to Gerald Fishman, a lead scientist on the project.
A single burst can be so powerful that it outshines all other sources of gamma rays combined. One burst, detected by a small research satellite in 1979, released in one-tenth of a second more energy in gamma rays than the total energy the sun will emit over the next 1,000 years.
“Most believe the bursts are associated with neutron stars,” Fishman said.
Neutron stars are so dense that a chunk the size of a sugar cube would weigh hundreds of millions of tons on Earth. They are so dense that matter on a neutron star is quite different from matter on Earth, consisting of tightly compacted subatomic particles.
Fishman said there are several competing theories for the source of the gamma ray bursts. One leading theory is that the bursts may be thermonuclear explosions on the surface of neutron stars.
“It would be like a billion hydrogen bombs exploding on the surface,” he said.
The bursts could also be created by a tiny object the size of a marble crashing into a neutron star and having its atoms ripped apart by the star’s gravity as it drew closer. Or the bursts could have been caused by a violent rupture in the surface of the star--a star quake.
The Gamma Ray Observatory should allow scientists to determine which of those three candidates caused the burst, Fishman said.
But that is only one of many riddles the observatory might solve.
Scientists believe that gamma rays were also produced by the “Big Bang” and have been traveling through the universe ever since. The Gamma Ray Observatory should capture some of those, and they will be priceless packets of information that have been traveling through space since the beginning of time.
Those are among the many questions the observatory will address, but scientists say the most exciting discoveries will probably be things they have not even thought of.
It will be more than a month before the observatory will be ready to begin observations. The observatory, built by TRW Inc. of Redondo Beach, will be controlled by the Goddard Space Flight Center in Greenbelt, Md.
The Atlantis is to land at Edwards Air Force Base in Southern California on Wednesday at 7:34 a.m., PDT.
