Pick up to 4 telescopes to compare side-by-side. State lives in the URL — share the link and the comparison loads exactly as you left it.
Space telescope data has underpinned 1.5 million+ scientific papers since 1990.
| Attribute | Fermi Gamma-ray Space Telescope NASA/DOE/international · 🇺🇸 Active · Last updated 2026-06-01Trust: Agency-primaryⓘ Last verified Remove × | Chandra X-ray Observatory (CXO) NASA · 🇺🇸 Active · Last updated 2026-06-01Trust: Agency-primaryⓘ Last verified Remove × | |
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| Agency | NASA | NASA/DOE/international | NASA |
| Status | Retired | Active | Active |
| Wavelength band | optical | gamma-ray | x-ray |
| Launch year | 2009 – 2018 | 2008 | 1999 |
| Orbit | Earth-trailing heliocentric orbit | Low Earth Orbit (LEO) ~550 km, 25.6° inclination | Highly elliptical (perigee 10,000 km / apogee 140,000 km) |
| Mirror / aperture | 1.4 mas of [1] ↑ Largest | — | 1.2 mas of [1]Four pairs of nested grazing-incidence mirrors; effective aperture 0.04 m² |
| Mass | 1,052 kgas of [1] | 4,303 kgas of [1] | 4,800 kgas of [1]Including HRMA mirror assembly ↑ Heaviest |
| Wavelength range | 0.43–0.89 μm (optical) | 20 MeV – 300 GeV (LAT); 8 keV – 40 MeV (GBM) | 0.1–10 keV (soft to medium X-ray) |
| Key missions |
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| Summary | The mission that proved planets are abundant throughout the galaxy. Kepler monitored 150,000+ stars continuously for 4 years, finding that most stars host planets. A reaction wheel failure in 2013 ended the primary mission; the repurposed K2 mission (2014–2018) found 1,000+ additional planets before fuel ran out. | The most sensitive gamma-ray telescope ever flown. Fermi's Large Area Telescope (LAT) has detected over 6,000 gamma-ray sources — pulsars, blazars, gamma-ray bursts, and potentially dark matter annihilation signals. Its GBM instrument records ~300 gamma-ray bursts per year. | NASA's flagship X-ray telescope and one of the Great Observatories. Chandra's angular resolution is 100× better than previous X-ray telescopes, enabling detailed imaging of supernovae remnants, galaxy clusters, and the region around supermassive black holes. Still operating after 25+ years despite being designed for a 5-year mission. |
All 9 major space telescopes with primary-source citations from NASA, ESA, STScI, and JPL. Pure URL state — bookmark or share the link and the comparison reproduces exactly.