Hubble, Chandra, XMM-Newton, Kepler,... I can name a few off of the top of my head, but how many space telescopes are there in all?


  • $\begingroup$ Kepler is already out of service, isn't it? $\endgroup$
    – B--rian
    Mar 30 '21 at 15:31
  • 1
    $\begingroup$ It's an ambiguous question, because there is no clear distinction between space telescopes and narrow-angle cameras on deep space probes. For example, the LORRI imager on the New Horizons spacecraft is now being used to observe distant bodies - does it make it a space telescope? $\endgroup$
    – cuckoo
    Mar 31 '21 at 0:02
  • $\begingroup$ @cuckoo If you follow the Wikipedia page I linked in my answer, "space-telescope" looks pretty well-defined as "dedicated astronomy space-missions", (my definition). I agree that strictly speaking, the term "space telescope" probably refers to all non-terrestrial observing equipment. $\endgroup$
    – B--rian
    Mar 31 '21 at 6:44
  • $\begingroup$ But you listed the Lunar-based ultraviolet telescope (which is not a dedicated telescope mission), and any telescope mounted on the ISS isn't a dedicated mission either. $\endgroup$
    – cuckoo
    Mar 31 '21 at 10:51
  • $\begingroup$ I answered following my own, wider definition "all extraterrestrial telescopes (I am aware of)". I am happy to add the telescopes you mentioned. $\endgroup$
    – B--rian
    Mar 31 '21 at 11:12

More than 20 if the Wikipedia's List of Space Telescopes is accurate. I extracted the active ones, and removed duplicates (to the best of my knowledge):

  1. Swift Gamma Ray Burst Explorer
  2. AGILE
  3. FGST
  5. NuSTAR
  6. Astrosat
  7. Insight (Chinese: 慧眼)
  8. Спектр-РГ (Spektr-RG)
  9. The famous Hubble Space Telescope, HST, see
  10. STSat-1
  11. IRIS
  12. Hisaki
  13. Lunar-based ultraviolet telescope
  14. BRITE
  15. NEOSSat
  16. TESS, see
  17. CHEOPS, see
  18. Odin
  19. IBEX
  20. AMS-02
  21. DMPE
  22. Chandra, see
  23. XMM Newton, see
  24. NICER (Mounted on the ISS).

Interestingly, the majority is satellite based, but there is e.g. also a moon-based one.

In addition to that, there are space crafts whose Instruments have been temporarily or permanently been repurposed to astronomy. For instance, you could look at the Moon with METEOSAT.

  • 1
    $\begingroup$ Alas, Spektr-R the radiotelescope mission is over. I didn't know about Spectr-RG until just now! $\endgroup$
    – uhoh
    Mar 30 '21 at 14:28
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    $\begingroup$ SOHO with EIT and Lassco? $\endgroup$
    – Dr Chuck
    Apr 4 '21 at 16:15

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