Arrival of the Hubble Space Telescope

When the Space Shuttle Discovery released Hubble into orbit on April 24, 1990, you were witnessing the end of a 44-year journey. Discovery climbed to 380 miles above Earth, the highest shuttle altitude since Apollo, to deploy the 24,000-pound telescope. The mission cost $1.175 billion and survived budget cuts, redesigns, and the 1986 Challenger disaster before launch day arrived. There's even more to this incredible story you won't want to miss.

Key Takeaways

• Discovery reached the highest shuttle altitude since Apollo, orbiting at 380 miles above Earth during Hubble's deployment mission.
• The OMS engines burned 50% of available propellant during a five-minute burn to achieve the correct insertion orbit.
• The 43-foot, 24,000-pound Hubble Space Telescope was successfully deployed using the shuttle's robotic arm system.
• Crew members aboard Discovery witnessed Earth's full curvature for the first time during the historic mission.
• Discovery shadowed Hubble for two days after deployment as a precautionary safety measure before departing.

The 1962 Idea That First Proposed the Hubble Space Telescope

Long before the Hubble Space Telescope became one of humanity's greatest scientific achievements, astrophysicist Lyman Spitzer planted its seed in 1946 by proposing an orbital observatory free from Earth's atmospheric interference. His vision specified a telescope mirror design featuring a primary mirror three meters in diameter—three times larger than any existing ground-based telescope.

The concept stayed largely theoretical until the 1960s, when scientific community support began solidifying. In 1962, the National Academy of Sciences formally proposed a large three-meter lens telescope at an official meeting. That same year, NASA launched the Orbiting Solar Observatory, proving space-based observation was viable. By 1965, the National Academy of Sciences officially endorsed the space telescope concept, transforming Spitzer's bold idea into a serious scientific and engineering pursuit you can trace directly to today's Hubble. Nancy Roman played a critical role in bridging the gap between engineers and scientists to help turn this ambitious concept into a practical reality.

Operation Stargazer, launched by the U.S. Air Force in 1962, contributed meaningfully to this growing momentum by demonstrating that upper atmosphere observations could yield far more accurate scientific measurements than those taken from the ground, helping build the case for an observatory beyond Earth's atmosphere entirely.

How Hubble Got Its Name and a Smaller Mirror

As the 1960s transformed Spitzer's vision into a serious scientific pursuit, engineers and administrators faced equally important decisions about what the telescope would be called and how big it would actually get.

In 1977, NASA named it after Edwin Hubble, the astronomer who proved galaxies exist beyond the Milky Way and reshaped humanity's understanding of the Universe. Originally designed with a 3-meter mirror, budget downsides forced engineers to downsize it to 2.4 meters.

They completed the precision-ground primary mirror in 1981, finishing the full spacecraft by 1985. Unfortunately, mirror grind flaws introduced spherical aberration that compromised image quality after the 1990 launch, costing $6 million monthly in operational delays until the 1993 servicing mission installed corrective optics and restored the telescope's intended capabilities. The project had first received NASA and ESA backing in the 1970s, marking a pivotal moment of international cooperation that made the telescope's construction financially viable.

The telescope's scientific objectives were so complex that Instrument Definition Teams were established to translate specific research goals into the actual devices that would fly aboard the spacecraft.

How the 1986 Challenger Explosion Set Hubble Back Four Years

The explosion reshaped NASA's priorities:

Solid Rocket Booster joints were redesigned for temperature resilience

Civilian spaceflights were shelved until 2007

Satellites shifted to expendable rockets

Safety protocols replaced NASA's unsustainable launch culture

The Rogers Commission was created by President Reagan to investigate the accident and criticized NASA's organizational culture and decision-making processes. The disaster claimed the lives of all 7 astronauts aboard, including Christa McAuliffe, the first schoolteacher selected to fly into space.

Why Hubble's Launch Was Delayed by Seven Years

Hubble's journey to orbit wasn't a smooth one — it faced nearly a decade of funding battles, political pressures, and engineering setbacks before it ever left the ground. Originally targeting a 1983 launch, the project encountered political funding challenges almost immediately. Congress slashed the entire budget in 1974, forcing astronomers nationwide to lobby just to restore half the funding. Downsizing followed, shrinking the primary mirror from 120 to 94 inches.

Unexpected technical roadblocks compounded these struggles. Perkin-Elmer's Optical Telescope Assembly repeatedly ran over budget and behind schedule, slipping roughly one month every quarter. Scientific instruments required costly redesigns, and underestimated engineering demands pushed the launch date repeatedly. By mid-1986, total costs had ballooned to $1.175 billion — and Hubble still hadn't reached space. To help offset the financial burden, NASA entered into a partnership with the European Space Agency, which contributed funding and instruments in exchange for guaranteed telescope observation time.

Even after reaching orbit, Hubble was not without its troubles, as a malfunction in the Control Unit/Science Data Formatter disrupted the storage and transmittal of science data to Earth, requiring the spacecraft computer to safe the payload computer and science instruments when errors were detected.

What Actually Happened on Launch Day, April 24, 1990

After years of delays and cost overruns, launch day finally arrived on April 24, 1990, when Space Shuttle Discovery lifted off from Pad 39B at Kennedy Space Center at 8:33 a.m. EDT. Despite unusual APU glitches scrubbing the April 10 attempt, the crew pushed forward.

A brief hold at T-31 seconds occurred when software failed to close liquid oxygen valves, but technicians corrected it quickly, enabling perfect orbital insertion.

Here's what made this launch remarkable:

1. Discovery reached 380 miles — the highest shuttle altitude since Apollo
2. OMS engines burned five minutes, consuming 50% of available propellant
3. Crew witnessed Earth's full curvature for the first time
4. Hubble's 43-foot payload was successfully deployed, opening a new astronomy era

The five-member crew included mission specialists Kathy Sullivan and Bruce McCandless, who trained extensively for the mission's unique challenges and hazards alongside Commander Loren Shriver, Pilot Charlie Bolden, and Steve Hawley.

The successful deployment marked a triumphant milestone, especially considering that funding for Hubble had only been approved by Congress just thirteen years earlier in 1977.

How Steven Hawley Deployed Hubble Into Orbit

On April 25, 1990, Mission Specialist Steven Hawley took control of the Canadian-built Remote Manipulator System (RMS) arm to begin Hubble's deployment. Through precise robotic arm control, he lifted the telescope from Discovery's cargo bay and suspended it approximately 332 nautical miles above Earth.

Before releasing Hubble, the crew completed critical telescope deployment preparations. They activated Hubble's internal power, unfurled its solar arrays to recharge the six onboard batteries, and deployed the high-gain antennas. NASA Goddard's Space Telescope Operations Control Center monitored every system throughout the process.

Once each system passed verification testing, Hawley released the RMS arm's hold, setting Hubble free to orbit Earth independently. Discovery then backed into a parallel orbit, shadowing Hubble for two days in case corrective action became necessary. At the time of launch, Hubble weighed 24,000 pounds, making its precise handling by the robotic arm a critical and carefully executed operation. The STS-31 mission was the tenth launch of shuttle Discovery, marking a historic milestone in the storied legacy of the orbiter.

What Went Wrong With Hubble's Primary Mirror?

When NASA announced Hubble's flaw on June 27, 1990, just two months after launch, the news stunned the scientific community. The causes of mirror manufacturing error traced back to a misaligned null corrector device, while flaws in quality control procedures allowed the mistake to go undetected. The primary mirror's outer edge was ground too flat, resulting in spherical aberration that compromised the telescope's performance. The error in the primary mirror measured just 0.002 millimeters, yet its impact on image quality was catastrophic.

Here's what went wrong:

1. Incorrect lens spacing — The null corrector's lens was off by 1.3 millimeters, guiding polishing equipment to the wrong curvature.
2. Overruled warning — A refractive null corrector identified the error, but technicians dismissed it.
3. No verification — Nobody rechecked the reflective null corrector's dimensions after assembly.
4. Devastating impact — Every imaging camera suffered blurred images, while the High Speed Photometer was virtually crippled.

How the 1993 Endeavour Mission Fixed Hubble's Blurred Vision

NASA's embarrassing mirror flaw demanded a bold fix, and on December 2, 1993, Space Shuttle Endeavour launched the STS-61 mission to deliver it. Seven astronauts completed five spacewalks totaling 21 hours, executing precise instrument swaps inside Hubble's crowded bays.

They installed the Wide Field and Planetary Camera 2, which used nickel-sized corrective mirrors to restore light concentration from 10-15% back to 70%. COSTAR replaced the High-Speed Photometer, deploying five curved mirrors that acted like eyeglasses for three additional instruments. Solar array installation replaced the degraded originals, ensuring reliable power. The primary mirror's defect, known as spherical aberration, had been traced back to a misplaced washer inside the null corrector used during the mirror's grinding process.

Following the servicing mission, subsequent instruments built for Hubble included their own internal optical corrections, eventually eliminating the need for COSTAR entirely and freeing up space for new scientific equipment.

How Hubble's Observations Reshaped Our Understanding of the Universe

With Hubble's vision restored, the telescope began delivering discoveries that permanently changed how we comprehend the cosmos. Combined with cosmic microwave background data, Hubble's findings advanced galaxy formation studies, revealing how structures evolved across billions of years.

1. Universe Age – Precise Cepheid measurements confirmed the universe is 13.8 billion years old.
2. Accelerating Expansion – Supernova observations proved expansion is speeding up, uncovering dark energy comprising 74% of the universe.
3. Deep Field Imaging – A single moon-sized sky patch revealed over 3,000 galaxies, some dating back 800 million years post-Big Bang.
4. Black Hole Confirmation – Supermassive black holes were confirmed at the center of virtually every galaxy containing a central star bulge. The eXtreme Deep Field image further pushed these boundaries, capturing approximately 5,500 galaxies, including the faintest ever observed by humanity.
5. Hubble Constant – The telescope provided precise measurements of the Hubble Constant, the rate of cosmic expansion, with astronomer Wendy Freedman playing a key role in refining this critical value.

When Will Hubble Space Telescope Finally Retire?

After more than three decades of groundbreaking science, Hubble's clock is ticking. It launched at 600 km in 1990, but it's now fallen below 500 km, with solar activity accelerating its descent. Without a reboost, you're looking at reentry as early as 2028, with a median prediction of 2033.

NASA explored potential satellite rescue methods through a 2022 SpaceX partnership, but no reboost mission has been approved. Funding availability for future reboosts remains uncertain, with Hubble's budget down 30% in inflation-adjusted terms. Jared Isaacman's 2022 reboost proposal was ultimately rejected.

If solar flux stays elevated, reentry could happen by 2029. Best-case projections extend survival to 2040, but Hubble needs external intervention soon before its trajectory becomes unrecoverable. Once Hubble descends to 248 miles altitude, it is expected to have less than a year remaining before reentry.

Hubble has also faced significant hardware challenges in recent years, having already lost three gyros with a fourth showing degradation. In 2024, the observatory transitioned to single-gyro mode in an effort to eke out a few more years of operational life.