The shuttle Columbia sat poised late tonight for blastoff early Tuesday the 30th anniversary of the Apollo 11 moon landing ready to carry a $1.6 billion X-ray telescope into orbit in the first shuttle flight commanded by a woman.

With Hillary Rodham Clinton, the world champion U.S. women s soccer team and Sally Ride, America s first female astronaut, looking on, commander Eileen Collins and her four crewmates were scheduled for launch at 12:36 a.m. from Pad 39B at the Kennedy Space Center.

A veteran of two shuttle flights, Collins is the first female space commander since Soviet cosmonaut Valentina Tereshkova in 1963 and the first with major responsibility.

It s a role she clearly relishes. I wish that we could have had women in the space program a lot sooner, said Collins, a former test pilot, Air Force Academy math instructor and mother of a three-year-old girl. But that s just the way our society worked and that s just the way it was. We can t change that now, but we can make it better in the future.

The goal of the flight is the planned deployment Tuesday morning of NASA s Chandra X-ray observatory, a Hubble-class telescope designed to study radiation emitted by some of the most violent objects in the universe.

The telescope and its two-stage rocket booster stretch 57 feet in Columbia s 60-foot-long cargo bay and tip the scales at 50,162 pounds, the heaviest payload ever carried by a space shuttle. Columbia is NASA s oldest and heaviest shuttle, and the only one without a cargo bay space station airlock. Thus it has room to carry Chandra. To enable the orbiter to lift its load, unneeded equipment was removed and now-outdated but lighter main engines were installed, cutting the shuttle s weight by about 7,000 pounds.

We put Columbia on a strict diet to get to this mission, said Grant Cates, the engineer in charge of Columbia s ground processing. Unlike visible light, X-rays from deep space are almost totally absorbed by Earth s atmosphere and can only be studied from space. Chandra is the most sophisticated X-ray telescope ever built. It is the Hubble of X-ray astronomy, a factor of 10 better than anything done before, said Edward Weiler, NASA s associate administrator for space science.

Unlike Hubble, however, Chandra cannot be repaired in orbit if anything goes wrong. In a bid to cut costs, it was designed to operate in an orbit with a high point of 87,000 miles and a low point of 6,000 miles, well above the shuttle s maximum altitude. NASA managers are confident the hugeinstrument will work as advertised.

But we are launching a space shuttle, we re going into space with the largest civilian payload ever launched on the shuttle, it s high-tech stuff, and there are always risks, Weiler said. The flight plan called for Chandra and its two-stage solid-fuel booster to be ejected seven hours and 17 minutes after launch. One hour later, the inertial upper stage booster was scheduled to fire, boosting Chandra into an initial orbit with a far point of 46,000 miles and a near point of 755 miles.

An onboard rocket system is scheduled to fire five times over the next 10 days to boost the telescope to its final orbit. The first test images are expected in about three weeks.

The Hubble revealed the visible side of the universe, said theorist Michael Turner. But most of the universe does not emit visible light. It s only visible by other means, in particular the X-rays. So Chandra will give us the same clarity of vision as Hubble does, but for the dark side of the universe. . . . The discovery capabilities are immense.