STS-93

STS-93 carried Eileen Collins into a role no woman had held before. Collins had already made history in 1995 as the first woman to pilot a Space Shuttle, and four years later she returned to Kennedy Space Center as commander of Columbia, the first woman ever entrusted with command of an American spaceflight.

The mission's primary payload was equally historic in its own field: the Chandra X-ray Observatory, one of NASA's most powerful space telescopes, designed to observe X-ray emissions from some of the most extreme environments in the universe, including black holes, neutron stars, and the aftermath of exploding stars. At more than 22 tons, Chandra was the heaviest payload the Shuttle had ever launched to that point.

Launch on July 23, 1999, did not go entirely to plan. During ascent, a short circuit knocked out two of Columbia's main engine controllers just seconds after liftoff, and separately, a small hydrogen leak caused the main engines to burn slightly less efficiently than planned, leaving Columbia in a lower orbit than intended. Collins and her crew managed the anomalies calmly, and the minor shortfall did not prevent the mission's central objective.

The crew successfully deployed Chandra using the Shuttle's robotic arm, sending it toward an unusually high, elliptical orbit that would let it operate for decades. Columbia returned safely to Kennedy Space Center on July 27, and Collins's calm handling of the in-flight anomalies alongside her historic command reinforced her reputation as one of the most skilled astronauts of her generation, a reputation she would draw on again six years later commanding the Shuttle program's first Return to Flight mission after the Columbia disaster.

STS-93 marked a milestone in American spaceflight leadership, with Eileen Collins's command proving that women could hold the highest positions of responsibility aboard NASA's most complex spacecraft.

Collins's calm handling of the in-flight electrical and propulsion anomalies during ascent reinforced her reputation for skill under pressure, a reputation NASA would rely on again just six years later when it selected her to command the critical STS-114 Return to Flight mission after the Columbia disaster.

The mission's deployment of Chandra also delivered lasting scientific value, giving astronomers a powerful new tool for studying the universe's most extreme environments, contributions that have continued for decades and cemented Chandra's place alongside Hubble as one of NASA's most important space telescopes.