The commander of the Discovery shuttle mission says the Hubble Space Telescope his crew will put into orbit should help scientists unlock mysteries of the heavens.

The powerful $1.5 billion astronomical observatory, the most expensive unmanned spacecraft ever built, will be put in orbit 370 miles above the Earth where it can provide scientists a clearer view of space, unhindered by atmospheric distortion.If all goes according to plan, Hubble will be deployed a day after Discovery and its five crew members blast into space from Cape Canaveral, Fla., on April 12.

"We're getting very excited," Discovery commander Loren J. Shriver said Thursday at the crew's final news conference before the mission. "We've been training for a long time. This is a major milestone . . . We're glad to be finally this close to launch."

The 25,000-pound, 43-foot-long telescope originally was scheduled for launch in late 1983, but technical problems postponed liftoff until 1986. The Challenger accident on Jan. 28, 1986, delayed the mission until 1989, and concern over the shuttle's solid rocket boosters pushed it back yet again.

It has been a long wait for the scientists waiting to use the telescope.

"They're beaming with pride at the prospect of finally getting the space telescope that they've worked with for so long . . . to finally see it getting so close and producing results in the near future," said Shriver, an Air Force colonel commanding his first shuttle flight.

Hubble will allow astronomers to study stars and galaxies so distant that their light has been traveling toward Earth for 14 billion years - meaning that scientists will see what the objects looked at the creation of the universe, an estimated 15 billion years ago.

The telescope's location above Earth's atmosphere will enable it to detect light of all wavelengths, including ultraviolet, before it is absorbed or distorted by the atmosphere.

It will look seven times more deeply into space and detect objects 50 times fainter and with 10 times greater clarity than the best ground-based observatory. Its 8-foot primary optical mirror is the most precise ever made.