In this answer to Why is the hot part of Webb's MIRI cryocooler in the 300K area? and comments below discusses the helium refrigerator used for cooling JWST's Mid-Infrared Instrument or MIRI.

A comment there talks about the disadvantages of using a dewar or reservoir of helium that performed passive cooling by a slow boil-off. Advantages are that it doesn't fail like a compressor would nor does it vibrate (though it can slosh). Disadvantage is that it runs out, which might come a lot sooner than a(n extremely well-designed) compressor failure would.

...what the 'dewar flask' cooling is... a flask of liquid helium provides liquid helium to locations needing cooling where the liquid absorbs heat, turns to gas which is then vented to space. Long service life would mean a very large, very heavy amount of helium. It would also mean an absolute hard limit to useable lifetime.

That "hard limit" sounds familiar, though I think the limit was softened by limited operation at shorter wavelengths. In any event, I'd like to ask:

Question: Which (if any) space telescope would have worked longer if it hadn't simply run out of helium?


2 Answers 2


Past infrared telescopes (IRAS, Spitzer, others I can't remember) in space have generally used expendable liquid He. They either ceased operation or lost a large part of their capability when the He ran out.

Also there were failures caused by design errors in the difficult-to-test cryogenic systems. WIRE lost its cryogen store (hydrogen, not He) when its aperture cover came off prematurely. The x-ray quantum calorimeter on Suzaku lost its He due to a thermal runaway caused by inadequate venting.

  • 1
    $\begingroup$ Yes, Spitzer and specifically the "Spitzer Warm Mission" is what I was trying to remember, thanks! $\endgroup$
    – uhoh
    Sep 4, 2022 at 18:49

The Herschel infrared telescope is another recent telescope that stopped working once it ran out of Helium for its coolant.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .