Hubble vs James Webb
Webb is often called Hubble's replacement, but the two see different universes. Hubble observes mostly visible and ultraviolet light from low Earth orbit; Webb observes infrared from deep space, letting it see the earliest galaxies and inside dust clouds that Hubble cannot penetrate.
Missions4 min
Hubble Space Telescope
The Hubble Space Telescope, launched April 24, 1990, has made nearly 1.7 million observations and still operates in one-gyroscope mode after 36 years.
Missions4 min
James Webb Space Telescope
The James Webb Space Telescope is a 6.5-meter infrared observatory launched December 25, 2021. It observes the earliest galaxies and exoplanet atmospheres.
Key differences
- Wavelengths: Hubble covers ultraviolet through near-infrared; Webb is optimized for infrared, where the most distant (redshifted) objects shine.
- Mirror: Webb's segmented 6.5 m mirror collects about six times the light of Hubble's 2.4 m mirror.
- Location: Hubble orbits about 520 km up and was serviced five times by astronauts; Webb sits 1.5 million km away at L2 and cannot be serviced.
- Complementarity: they routinely observe the same targets together, Hubble in visible light and Webb in infrared, which is why NASA operates both.
Side-by-side specifications
| Hubble Space Telescope | James Webb Space Telescope | |
|---|---|---|
| Operators | NASA and ESA | - |
| Launch date | April 24, 1990 | December 25, 2021 |
| Launch vehicle | Space Shuttle Discovery, STS-31 | Ariane 5 ECA |
| Orbit | Low Earth orbit, roughly 520 km | Halo orbit around Sun-Earth L2, about 1.5 million km from Earth |
| Primary mirror | 2.4 m | 6.5 m, 18 gold-coated beryllium segments |
| Servicing missions | Five (1993, 1997, 1999, 2002, 2009) | - |
| Observations | Nearly 1.7 million as of April 2025 | - |
| Status | Operational in one-gyroscope mode | Operational; Cycle 5 science began July 1, 2026 |
| Operator | - | NASA with ESA and CSA |
| Sunshield | - | 21.2 m x 14.2 m, five layers |
| Instruments | - | NIRCam, NIRSpec, MIRI, FGS/NIRISS |
| Development cost | - | About $10 billion (NASA share) |
Figures come from each article's infobox; see the articles for sources and context.