As of 2026-07-08, LUVOIR-A tops the list with 15 m.
- #1 LUVOIR-A — 15 m
concept study of a space observatory that would be located at the Sun-Earth L2 Lagrangian point
The Large Ultraviolet Optical Infrared Surveyor, commonly known as LUVOIR, is a multi-wavelength space telescope concept being developed by NASA under the leadership of a Science and Technology Definition Team. It was one of four large astrophysics space mission concepts studied in preparation for the National Academy of Sciences 2020 Astronomy and Astrophysics Decadal Survey. Read more on Wikipedia.
Wikidata - #2 Carl Sagan Observatory — 12 m
proposed space observatory
source Wikidata - #3 Spektr-R — 10 m
Russian radio astronomy satellite
Spektr-R was a Russian scientific satellite with a 10 m (33 ft) radio telescope on board. It was launched on 18 July 2011 on a Zenit-3F launcher from Baikonur Cosmodrome, and was designed to perform research on the structure and dynamics of radio sources within and beyond the Milky Way. Together with some of the largest ground-based radio telescopes, the Spektr-R formed interferometric baselines extending up to 350,000 km (220,000 mi). Read more on Wikipedia.
Wikidata - #4 LUVOIR-B — 8.00 m
proposed UV-optical-NIR space telescope
The Large Ultraviolet Optical Infrared Surveyor, commonly known as LUVOIR, is a multi-wavelength space telescope concept being developed by NASA under the leadership of a Science and Technology Definition Team. It was one of four large astrophysics space mission concepts studied in preparation for the National Academy of Sciences 2020 Astronomy and Astrophysics Decadal Survey. Read more on Wikipedia.
Wikidata - #5 James Webb Space Telescope — 6.50 m
NASA/ESA/CSA space telescope launched in 2021
The James Webb Space Telescope (JWST) is a space telescope designed to conduct infrared astronomy. It is the largest telescope in space, and is equipped with high-resolution and high-sensitivity instruments, allowing it to view objects too old, distant, or faint for the Hubble Space Telescope. This enables investigations across many fields of astronomy and cosmology, such as observation of the first stars and the formation of the first galaxies, and detailed atmospheric characterization of... Read more on Wikipedia.
Wikidata - #6 Planck — 4.22 m
former ESA space observatory
Planck was a space observatory operated by the European Space Agency (ESA) from 2009 to 2013. The project aimed to map the anisotropies of the cosmic microwave background (CMB) at microwave and infrared frequencies, with high sensitivity and angular resolution. The mission provided data that substantially improved upon previous observations made by the NASA Wilkinson Microwave Anisotropy Probe (WMAP). Read more on Wikipedia.
Wikidata - #7 Hubble Space Telescope — 4.20 m
NASA and ESA space telescope (launched 1990)
The Hubble Space Telescope is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versatile, renowned as a vital research tool and as a public relations boon for astronomy. The Hubble Space Telescope is named after astronomer Edwin Hubble and is one of NASA's Great Observatories. The Space Telescope Science Institute (STScI) selects Hubble's targets and processes the resulting... Read more on Wikipedia.
Wikidata - #8 Euclid — 3.70 m
ESA space telescope aimed at mapping the distribution of dark matter
Euclid is a wide-angle space telescope with a 600-megapixel camera to record visible light, a near-infrared spectrometer, and photometer, to determine the redshift of detected galaxies. It was developed by the European Space Agency (ESA) and the Euclid Consortium and was launched on 1 July 2023 from Cape Canaveral in Florida. The mission is named after the ancient Greek mathematician Euclid. Read more on Wikipedia.
Wikidata - #9 SPHEREx — 3.20 m
NASA near-infrared space observatory
SPHEREx is a near-infrared space observatory that is performing an all-sky survey to measure the near-infrared spectra of approximately 450 million galaxies. In February 2019, SPHEREx was selected by NASA for its next Medium-Class Explorers mission, beating out two competing mission concepts: Arcus and FINESSE. SPHEREx launched on 11 March 2025 on a Falcon 9 Block 5 rocket alongside the PUNCH microsatellites from Vandenberg Space Force Base. The principal investigator is James Bock at... Read more on Wikipedia.
Wikidata - #10 Lazuli Space Observatory — 3.06 m
proposed private space telescope
source Wikidata