STS-31: The Space Shuttle Mission That Put Hubble in Orbit

On April 24, 1990, Space Shuttle Discovery roared off Pad 39B at Kennedy Space Center. The crew was five astronauts: Loren Shriver, Charles Bolden, Bruce McCandless II, Steven Hawley, and Kathryn Sullivan. Their payload was the Hubble Space Telescope. A 24,500-pound observatory packed into the cargo bay. It was 43 feet long and 14 feet wide. Getting it to orbit was not just another satellite deployment. It was the reason the shuttle existed.

NASA designed the shuttle to carry big things and people at the same time. Hubble needed both. It needed a crew to deploy it, check it, and be ready to fix problems. It needed a vehicle that could reach an altitude higher than most shuttle flights. Hubble had to go above the thick part of Earth’s atmosphere. That meant Discovery had to fly to about 380 miles up. At the time, that was the highest shuttle orbit ever attempted. Higher orbit means less atmospheric drag, but it also means less margin if something goes wrong. The crew had to nail it.

Before launch, the mission had already been delayed. Hubble was supposed to fly in 1986, but the Challenger disaster grounded the shuttle fleet. When flights resumed, the telescope had to wait for a slot. That delay gave engineers time to upgrade Hubble, but it also raised the pressure. By 1990, the telescope was years late and over budget. Everyone knew the shuttle was the only ride. If Discovery failed to reach the right orbit, Hubble would be stuck too low. The atmosphere would drag it down faster. Its science would be limited. The crew spent months practicing the deployment in simulators. They ran through failures: stuck solar arrays, broken antennas, communication dropouts. They had to be ready for anything.

The deployment itself was tense. Hubble was too big and complex to just push out. The crew used the shuttle’s robotic arm to lift the telescope out of the payload bay. Then they waited. Hubble’s solar arrays had to roll out. Its high-gain antenna had to deploy. If those mechanisms failed, the telescope would be useless. McCandless and Sullivan had trained for a contingency spacewalk. They were ready to go outside and manually crank the arrays open. That would have been a brutal EVA, but they were prepared. In the end, they did not need it. Hubble’s systems worked. On April 25, 1990, Discovery released the telescope. It floated free for the first time.

That moment is why STS-31 belongs in the shuttle’s greatest hits. The shuttle did not just launch a satellite. It launched a scientific revolution. Hubble was not the first telescope in space, but it was the first big one designed to be serviced by astronauts. That was the shuttle’s superpower. It could go up, grab a spacecraft, and fix it. No other vehicle at the time could do that. Hubble would later need that service. Its primary mirror was ground wrong by a tiny amount, about one fiftieth of the width of a human hair. The images came back blurry. NASA looked like it had blown a billion-dollar mission. But the shuttle gave them a second chance. In 1993, astronauts on Endeavour installed corrective optics. Hubble became the telescope everyone remembers.

STS-31 was the first step. It put Hubble in orbit. It proved the shuttle could deploy a flagship observatory. It also showed how risky that work was. The crew had to back away safely. Hubble had to power up. The ground had to confirm everything. Discovery landed at Edwards Air Force Base on April 29, 1990, after 80 orbits. The mission lasted five days, one hour, and sixteen minutes. It was a clean success. But the real payoff came later. Hubble’s deep field images showed thousands of galaxies in a speck of sky. It helped pin down the age of the universe. It found evidence of dark energy. It studied exoplanet atmospheres. None of that happens if STS-31 fails.

The shuttle program had plenty of hard days. It also had missions like this. STS-31 was not flashy because of a spacewalk or a rescue. It was a delivery run with the stakes of a moonshot. Discovery’s crew put the most productive telescope in history into orbit. Then the shuttle kept it alive for decades. That is a greatest hit by any measure.