The Hubble Space Telescope: What It Is and What Changed After 1990
Updated November 2, 2026.
The Hubble Space Telescope launched on April 24, 1990, aboard the space shuttle Discovery on mission STS-31. It has a mirror 7 feet 10 inches (2.4 meters) wide and has orbited Earth for more than 36 years. According to Wikipedia, it is expected to keep working until sometime between 2030 and 2040, though that is only an estimate. The James Webb telescope, launched later, observes in infrared.
The flawed mirror
Soon after launch, astronomers found a problem. It was serious. The main mirror had been ground to the wrong shape. The error caused a distortion called spherical aberration, and the images came out blurry.
The fix was slow. It came in December 1993, on the first servicing mission, STS-61. Astronauts installed corrective optics that gave the telescope its intended quality. It was a repair done in orbit. It worked.
Orbit and size
Hubble weighed 24,490 pounds (11,110 kg) at launch and circles Earth in low orbit. The Wikipedia info box lists an altitude of 470 to 475 kilometers (about 292 to 295 miles) in 2026. Another section cites about 340 miles and gives no reason for the gap.
The five servicing missions
There were five visits. Space shuttles reached the telescope over nearly 16 years. The first came in December 1993 and the last in May 2009. On each visit, astronauts swapped parts and installed new instruments. The shuttle program ended in 2011. No one has serviced Hubble since.
Cost and future
About $4.7 billion had been spent by the time of launch, in 2010 dollars adjusted for inflation. The estimated cumulative cost, not counting operations, is about $11.3 billion in 2015 dollars. The telescope’s reentry into the atmosphere is estimated for the 2030s, according to the page, and the exact date is still unknown.
This article does not cover the gyroscopes. It also leaves out plans to boost the telescope to a higher orbit, which will wait for another update when a reliable source is available.
| Date | Milestone |
|---|---|
| April 24, 1990 | Launch on Discovery, mission STS-31 |
| December 1993 | First servicing mission fixes the mirror |
| May 2009 | Last servicing mission |
| 2030 to 2040 (estimate) | Period when the telescope is expected to last |
Frequently asked questions
When did Hubble launch?
On April 24, 1990, aboard the space shuttle Discovery during mission STS-31, which placed it in orbit.
How big is Hubble’s mirror?
The main mirror is 7 feet 10 inches (2.4 meters) across, much smaller than the 21-foot mirror on the James Webb telescope.
Why did Hubble need a repair?
The main mirror was made in the wrong shape, which caused a distortion called spherical aberration. The correction was made in 1993.
How many servicing missions did Hubble have?
Five, the first in December 1993 and the last in May 2009, all flown by space shuttle crews.
How much longer will Hubble last?
Wikipedia’s estimate is 2030 to 2040, but that window is only a guess and could change over time.
Read next: NASA Explained: History, Programs and What the Agency Does Today and The James Webb Space Telescope: What It Is and How It Works.
Sources: Hubble Space Telescope, Wikipedia; James Webb Space Telescope, Wikipedia.
Featured image: Image: NASA, Public domain, via Wikimedia Commons.
.jpg){kind=link}