Ground-based interferometers such as ALMA have enabled many discoveries. It seems like sending a fleet of small telescopes would be feasible (smaller telescopes are easier to send into space than telescopes as big as the JWST, a fleet of telescopes would be more robust, since there wouldn't be as many single points of failure) and would make it possible to do interferometry at wavelengths that can't be observed from the ground. Furthermore, the space between the furthest telescopes could be bigger that the diameter of the Earth, so the baseline of such an observatory could be even bigger than that of the EHT.

Are there any existing or planned interferometers in space? If not, why not?

I did find the Space Interferometry Mission, but it looks like it was abandoned.

I know about LISA, but my question relates to photon-collecting observatories.

  • $\begingroup$ I think the technology for space based interferometric satellites isn't quite there just yet, at least not without investing more money than places like NASA want to invest. It could very likely be done in theory right now, but the cost would be astronomical. $\endgroup$
    – zephyr
    Dec 22, 2021 at 20:46

1 Answer 1


As the Wikipedia page on VLBI interferometry points out, there have been a few spacecraft with radio antennae which have formed (along with ground based stations) part of radio interferometer networks.

The examples given are the KRT 10-m dish on the Salyut space station, and the HALCA and Spektr-R satellites. The latter was in an orbit with an apogee almost as far away as the Moon, giving VLBI using this an enormous baseline.

  • $\begingroup$ More about Spektr-R (and -RG) in Space SE and here as well. $\endgroup$
    – uhoh
    Dec 19, 2021 at 4:07
  • $\begingroup$ So there are single-dish space telescopes that were added to an interferometer. Were there any telescope fleets sent to space that were dedicated to interferometry? $\endgroup$
    – usernumber
    Dec 22, 2021 at 13:06

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