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Year’s First Flight Features Space Walk, Observatory Release

March 31, 1991

CAPE CANAVERAL, Fla. (AP) _ American astronauts head into orbit this week for the first space walk in more than five years to test techniques for building the biggest Tinkertoy ever, the space station.

The five-day flight of Atlantis may be short for a shuttle mission, but it promises to be long on drama. In addition to the space walk, the crew will release the heaviest civilian spacecraft ever carried by a shuttle, an astronomical observatory weighing an astronomical 17 tons.

″I expect a chorus all through the flight of people saying, ’Look at that 3/8 Oh, my gosh 3/8‴ said astronaut Jay Apt.

Atlantis is scheduled to blast off at 9:18 a.m. EST Friday. The countdown begins Tuesday morning.

The Gamma Ray Observatory will be hoisted from Atlantis’ cargo bay and set in a 279-mile-high orbit on the third day of the five-day flight. On the fourth day, Apt and Jerry Ross will spend six hours in the open bay testing tools and equipment for NASA’s planned space station Freedom.

Both men expect the excursion to be hard work but well worth the effort.

″The sense of no constraints and no bounds, the freedom that you have when you’re outside in the payload bay, is pretty overwhelming,″ Ross said. ″You have to force yourself to concentrate on the task at hand.″

It will be NASA’s 39th shuttle launch. The first one was 10 years ago this month.

Atlantis’ mission was supposed to be the second one this year. It assumed the No. 1 position when Discovery’s March military flight was delayed until late April because of cracked door hinges.

Atlantis also has hinge cracks. But they are much smaller than those on Discovery and pose no danger, officials said.

The five astronauts’ main job aboard Atlantis will be orbital delivery of the monstrous $600 million Gamma Ray Observatory, or GRO. Only military spy satellites have been heavier.

It is the second of NASA’s four so-called Great Observatories, a top-of- the-line series intended to probe every kind of electromagnetic wavelength in the heavens. The first is the Hubble Space Telescope.

″GRO’s one of a kind,″ said mission commander Steven Nagel. ″I’m excited about (the space walk), too. But GRO is unique and there won’t be another like it probably for a long time. We’re going to do a lot more space walks.″

The Gamma Ray Observatory will scrutinize pulsating and exploding stars for traces of gamma rays, the most energetic radiation known. It also will examine quasars, the most dynamic and distant objects in the universe, and what astronomers believe are black holes.

The entire sky will be canvassed during the the GRO mission, which will last at least two years. A complete gamma ray survey has never been done. And the observatory is expected to be 10 to 20 times more sensitive than previous gamma ray spacecraft, said NASA project scientist Donald Kniffen.

The observatory will be controlled from NASA’s Goddard Space Flight Center in Greenbelt, Md. Assisting in the work will be scientists from Max Planck Institute near Munich, Germany, which supplied GRO’s imaging telescope.

Unlike Hubble, which focuses mostly on visible light, the Gamma Ray Observatory has no mirrors. Hubble’s primary mirror was found to be flawed two months after the telescope was placed in orbit last April. Astronauts will go up to fix Hubble in 1993.

Nagel expects the tension in the cabin to ease once GRO is safely on its way. But he doubts he will relax until Apt and Ross are back inside Atlantis following their space walk.

It will be Ross’ third outing. He and Sherwood Spring performed NASA’s last space walk on Dec. 1, 1985.

It will be Apt’s first space walk, and he hopes not his last. His goal is to help build the $30 billion space station; the first assembly flight is scheduled for late 1995.

″Send me in, coach,″ Apt said with a grin.

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