List of proposed space telescopes
This list contains proposals for space telescopes, space-based (situated in space) astronomical observatories.  It is a list of past and present space observatory plans, concepts, and proposals.  For observatories in orbit, see list of space telescopes.  Unlike that list, this one includes concepts and proposals that are unlikely ever to be launched, as they may have been cancelled or were only proposals.

Space observatories under development

Merged, cancelled, or superseded space observatories

Additional examples and non-space telescopes 
For launch in the 2030s, NASA is evaluating four possible designs:  the Origins Space Telescope, Lynx X-ray Observatory, Habitable Exoplanets Observatory (HabEx), and Large UV Optical Infrared Surveyor (LUVOIR).

Balloon-borne telescopes have been in use since the 1950s. A 20–30 meter balloon telescope has been suggested. The balloon would be transparent on one side, and have a circular reflecting mirror on the other side. There are two main designs using this principle.
Large Balloon Reflector (LBR) (sub-orbital version)
Space-based Large Balloon Reflector (LBR) 
TeraHertz Space Telescope (TST)

Additional examples     
     
     
 Advanced Telescope for High Energy Astrophysics (ATHENA)
 Big Bang Observer
 Cosmological Advanced Survey Telescope for Optical and UV Research (CASTOR)
 Deci-hertz Interferometer Gravitational wave Observatory (DECIGO)
 EChO
 Fast Infrared Exoplanet Spectroscopy Survey Explorer (FINESSE)
 Gravity and Extreme Magnetism Small Explorer (GEMS) 
Habitable Exoplanets Observatory (HabEx), a large UV to NIR focused design, 4 meter mirror 
 LOFT - Large Observatory For X-ray Timing 
 Large Ultraviolet Optical Infrared Surveyor
 Large Interferometer For Exoplanets
 Nautilus Deep Space Observatory
 Near-Earth Object Surveillance Mission (formerly Near-Earth Object Camera (NEOcam))
 PEGASE
 Planetary Dynamics Explorer
 Space Infrared Telescope for Cosmology and Astrophysics (SPICA)
 Telescope for Habitable Exoplanets and Interstellar/Intergalactic Astronomy (THEIA)
 THESEUS
 Waypoint-1 Space Telescope, visible light, UV and hyper-spectral imaging for astrophysical research and ground observation
 Whipple, proposed transit telescope for KBO and Oort objects
 ZEBRA, Zodiacal dust, Extragalactic Background and Reionization Apparatus  A small infrared observatory sent out to 10 AU by NASA

See also
 Lists of telescopes
 Lists of spacecraft

References

External links
 Video (86:49) – "Search for Life in the Universe" – NASA (July 14, 2014).

space observatories
space observatories
space observatories