Hubble Space Telescope
What is Hubble Space Telescope?
Probes & telescopes· Launched 1990-04-24 – operating for 36 years. Humanity's first great optical telescope above the atmosphere. Since 1990 it has measured the age of the universe, revealed accelerating expansion, and photographed the nebulae and galaxies you see across this index.
Mission timeline
Spacecraft specs
| Launch | 1990-04-24 |
|---|---|
| Orbit altitude | ~520 km |
| Mirror | 2.4 m |
| Status | operating (five shuttle servicing missions) |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- When did Hubble Space Telescope launch?
- 1990-04-24.
- What is the status of Hubble Space Telescope now?
- operating (five shuttle servicing missions).
- In one line, what is Hubble Space Telescope?
- Probes & telescopes — Humanity's first great optical telescope above the atmosphere.
A sinking orbit — re-entry and the reboost debate
Hubble has no propulsion. Its orbit at about 520 km sinks slowly under the drag of the thin upper atmosphere, and the last time a shuttle raised it was 2009. In years of strong solar activity the atmosphere swells and the decay speeds up; on current trends re-entry is calculated for the mid-to-late 2030s, and because some large components could survive to the ground NASA has studied a controlled re-entry.
In 2022 NASA and SpaceX jointly studied docking a Dragon spacecraft to Hubble to raise its orbit. It would add more than a decade of life, but the risk of grappling a telescope built without a docking fixture, and the cost, led NASA in 2024 to set the idea aside for now. Hubble switched to a one-gyroscope mode in 2024 with a modest loss of efficiency, and plans to continue science observations into the 2030s.
The mission in depth
The Hubble Space Telescope is a 2.4-metre reflector launched aboard the shuttle Discovery on 24 April 1990 into low Earth orbit, about 520 km up. Observing above the turbulent atmosphere gives it far sharper images than ground telescopes and access to ultraviolet light. A flawed mirror blurred its early pictures, but the first servicing mission in 1993 installed corrective optics, and four more visits kept it at the front line of astronomy for more than three decades.
Hubble changed more than the pictures. Its Cepheid measurements pinned the Hubble constant and the age of the universe near 13.8 billion years, and its distant supernova observations were decisive in establishing that cosmic expansion is accelerating — work recognised with the 2011 Nobel Prize. The Hubble Deep Field showed thousands of galaxies hiding in an apparently empty patch of sky, and Hubble found protoplanetary discs in the Orion Nebula and new moons of Pluto.
Because Hubble circles Earth every 96 minutes, it is not drawn in the orbit view of this simulator, but many nebula, galaxy and black-hole entries in this index use its photographs. Unlike its successor, the James Webb Space Telescope, Hubble sees in visible light — comparing the two telescopes' images of the same object shows how differently the sky looks at different wavelengths.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.