<p>Past infrared telescopes (<a href="https://en.wikipedia.org/wiki/IRAS" rel="noreferrer">IRAS</a>, <a href="https://en.wikipedia.org/wiki/Spitzer_Space_Telescope" rel="noreferrer">Spitzer</a>, 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.</p>
<p>Also there were failures caused by design errors in the difficult-to-test cryogenic systems. <a href="https://en.wikipedia.org/wiki/Wide_Field_Infrared_Explorer" rel="noreferrer">WIRE</a> lost its cryogen store (hydrogen, not He) when its aperture cover came off prematurely. The x-ray quantum calorimeter on <a href="https://en.wikipedia.org/wiki/Suzaku_(satellite)" rel="noreferrer">Suzaku</a> lost its He due to a thermal runaway caused by inadequate venting.</p>

CC BY-SA 4.0
2022-09-04T18:49:19.440Z
Yes, Spitzer and specifically the "[Spitzer Warm Mission](https://en.wikipedia.org/wiki/Spitzer_Space_Telescope#Warm_mission_and_end_of_mission)" is what I was trying to remember, thanks!
uhoh
CC BY-SA 4.0
2022-09-04T14:54:40.567Z
2022-09-04T15:04:24.197Z
2022-09-04T15:04:24.197Z
John Doty
<p>The <a href="https://en.wikipedia.org/wiki/Herschel_Space_Observatory" rel="noreferrer">Herschel</a> infrared telescope is another recent telescope that stopped working once it ran out of Helium for its coolant.</p>

CC BY-SA 4.0
2022-09-04T16:31:38.133Z
2022-09-04T16:31:38.133Z
Rob
<p>In <a href="https://space.stackexchange.com/a/60209/12102">this answer to <em>Why is the hot part of Webb's MIRI cryocooler in the 300K area?</em></a> and comments below discusses the helium refrigerator used for cooling JWST's <a href="https://en.wikipedia.org/wiki/MIRI_(Mid-Infrared_Instrument)" rel="noreferrer">Mid-Infrared Instrument</a> or MIRI.</p>
<p>A <a href="https://space.stackexchange.com/questions/60202/why-is-the-hot-part-of-webbs-miri-cryocooler-in-the-300k-area#comment199277_60209">comment there</a> 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.</p>
<blockquote>
<p>...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.</p>
</blockquote>
<p>That &quot;hard limit&quot; sounds familiar, though I think the limit was softened by limited operation at shorter wavelengths. In any event, I'd like to ask:</p>
<p><strong>Question:</strong> Which (if any) space telescope would have worked longer if it hadn't simply run out of helium?</p>

<observational-astronomy><space-telescope><infrared>
Which (if any) space telescope would have worked longer if it hadn't simply run out of helium?
uhoh
# Which (if any) space telescope would have worked longer if it hadn't simply run out of helium?

(Asked by: username_0 on 2022-09-04)

In [this answer to *Why is the hot part of Webb's MIRI cryocooler in the 300K area?*](https://space.stackexchange.com/a/60209/12102) and comments below discusses the helium refrigerator used for cooling JWST's [Mid-Infrared Instrument](https://en.wikipedia.org/wiki/MIRI_(Mid-Infrared_Instrument)) or MIRI.

A [comment there](https://space.stackexchange.com/questions/60202/why-is-the-hot-part-of-webbs-miri-cryocooler-in-the-300k-area#comment199277_60209) 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?

**Tags:** observational-astronomy, space-telescope, infrared

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## 2 answers

### Answer by username_1 on 2022-09-04. Score: 20

Past infrared telescopes ([IRAS](https://en.wikipedia.org/wiki/IRAS), [Spitzer](https://en.wikipedia.org/wiki/Spitzer_Space_Telescope), 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](https://en.wikipedia.org/wiki/Wide_Field_Infrared_Explorer) lost its cryogen store (hydrogen, not He) when its aperture cover came off prematurely. The x-ray quantum calorimeter on [Suzaku](https://en.wikipedia.org/wiki/Suzaku_(satellite)) lost its He due to a thermal runaway caused by inadequate venting.

> **Comments:**
> **username_0**: Yes, Spitzer and specifically the "[Spitzer Warm Mission](https://en.wikipedia.org/wiki/Spitzer_Space_Telescope#Warm_mission_and_end_of_mission)" is what I was trying to remember, thanks!  

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### Answer by username_2 on 2022-09-04. Score: 18

The [Herschel](https://en.wikipedia.org/wiki/Herschel_Space_Observatory) infrared telescope is another recent telescope that stopped working once it ran out of Helium for its coolant.


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