This Week in Rocket History, we’re going back 31 years to one of the most important missions of the Space Shuttle program.

On April 24, 1990, at 12:33 UTC, the Space Shuttle Discovery launched from the Kennedy Space Center in Florida. It was crewed by Loren Shriver, Charles Bolden Jr., Bruce McCandless, Steven Hawley, and Kathryn Sullivan. This was the 35th Space Shuttle mission, titled STS-31, and it was originally supposed to go up on April 10, but it had to be scrubbed at T-minus four minutes due to a faulty valve and was subsequently rescheduled for April 24.

Discovery went up to an altitude of around 617 kilometers, the highest orbit ever achieved by any space shuttle mission at that point.

The next day, astronaut Steven Hawley took control of the “Remote Manipulation System”, also known as RMS or the “Canadarm”, and used it to pull their primary cargo out of the cargo bay and into space – and thus began the still continuing mission of the Hubble Space Telescope.

The 13-meter long space telescope then deployed its antennas and was supposed to deploy and unfurl its solar arrays, except that one of the solar arrays failed to unfurl. This was a huge problem since Hubble’s batteries could only keep it alive for a couple of hours with one solar panel extended. If it couldn’t be extended in time, an extra-vehicular activity, or EVA, had to be performed in order to deploy the array manually.

The crew of Discovery was ready for such contingency, as astronauts McCandless and Sullivan were already suited up in their EVA suits and ready with repair kits and tools. McCandless thought the problem was in the software responsible for deploying the solar array and preventing it from over-extending. Moments before they would have exited the airlock, an engineer on the ground confirmed McCandless’s theory and found a workaround that allowed the second solar array to be unfurled all the way. Unfortunately for McCandless and Sullivan, this meant that they didn’t get to observe the deployment of the space telescope in person.

After the space telescope was successfully deployed with both solar panels functioning properly, Discovery lowered its orbit slightly and continued its secondary mission: a series of experiments mostly relating to radiation, taking advantage of the high altitude they were in.

As with almost every U.S. space mission since Gemini, NASA transmitted songs over the radio to wake up the astronauts on the mornings of multi-day missions, and the songs used in this mission, in order, are “Space is our World” by The Private Numbers – which was an original song written specifically for this mission, “Shout” by Otis Day and the Knights, “Kokomo” by the Beach Boys, “Cosmos” by Frank Hayes – also written specifically for this mission, and finally “Rise and Shine” by Raffi and Ken Whiteley.

Discovery landed safely on April 29, 1990, at Edwards Airforce Base in California, but Hubble’s story was just beginning.

In early May of 1990, the first images started coming down from the telescope, and as many of you probably know, they weren’t great. Granted, they were still better than anything taken by ground telescopes, but it was nowhere near the level of detail and clarity the engineers were expecting to receive. It was clear that something had gone wrong with the $4.7-billion telescope.

It was later discovered that the company responsible for manufacturing one of Hubble’s mirrors had a misaligned measurement unit called a Reflective Null Corrector, which caused them to carve the mirror with the wrong curvature by 2200 nanometers, which is about 40 times thinner than a human hair, but enough to cause 1.7 waves of spherical aberration, severe enough to affect image clarity. A second Reflective Null Corrector unit did actually find the problem during manufacturing, but technicians assumed it was a false positive and chose to rely on the data coming in from the faulty unit instead of from that of the secondary one. 

It would be three more years and several more billions of dollars before the first servicing mission would go up and a device functioning basically as glasses would be installed on Hubble and turn it into one of the most prolific and recognizable scientific instruments to date, but that’s a story for another time.

More Information

Launch video

PDF: Mission Safety Evaluation Report (NASA)

PDF: Space Shuttle Missions Summary (NASA)

Somebody Get a Camera: Remembering the Deployment of Hubble, OTD in 1990 (AmericaSpace)

PDF: Chronology of Wakeup Calls (NASA)

What was wrong with Hubble’s mirror, and how was it fixed? (Sky at Night)