Weird! I’d never heard of this, whether it’s a rumor or not. But there are at least two places for oils of some kind: inside the “reaction wheels” and gyroscopes. The reaction wheels are wheels that are used for slewing the telescope around. Rather than using a rocket motor, we have massive wheels with electric motors on them. Turn the wheel one way, and thanks to Newton’s 3rd Law, the spacecraft spins the other way. I don’t know whether these have any kind of oil in them, but I’d imagine they do at some level.
The gyroscopes definitely do. In fact, we had a MAJOR problem with them until this last Servicing Mission. As I recall, the oil being used to lubricate them was slightly corrosive, and it wound up eating away at some part of the gyroscope. In the end, we were down to just two functioning gyros, out of a total of 6! (One for each axis, plus one back-up for each axis)
So there are two places you might find whale oil used. Now, as far as what kind of oil… Well, it wouldn’t be put in the HST User’s Manual. Too hardware-specific. It might be in a technical report, which can be searched here:
http://ntrs.nasa.gov/search.jsp?N=0&Ns=HarvestDate|1
I looked for reports on “hubble” (or “HST”) and “gyroscope,” but the one that might talk most specifically about gyroscope design is from 1988 and is only available in paper copies:
http://ntrs.nasa.gov/search.jsp?R=1045361&id=10&as=false&or=false&qs=No%3D20%26Ntt%3Dhst%257cgyroscope%26Ntk%3Dall%257call%26Ntx%3Dmode%2Bmatchall%257cmode%2Bmatchall%26Ns%3DHarvestDate%257c1%26N%3D0
Looking around, the source of the rumor seems to be a book called Whale, reviewed in the L.A. Times here:
http://articles.latimes.com/2010/feb/25/entertainment/la-et-book25-2010feb25/2
I looked in the book itself (via Amazon) and found only a vague, unsourced statement about the Hubble:
http://www.amazon.com/Whale-Search-Giants-Sea/dp/0061976210/ref=sr_1_1?ie=UTF8&s=books&qid=1273449803&sr=8-1
No references, no quote. Seems to be a theater-focused writer, so I’m not sure how reliable a writer he is on history and science. The LA Times is critical of him on some minor points, and I could pick out a factual error in a brief quote they made. (The American buffalo did NOT become extinct!)
So anyway, it’s entirely possible that Hoare’s claim that sperm whale oil is so good at very low temps that it’s used for spacecraft, and that somewhere there are aging stockpiles of whale oil from a half century ago that the gyroscope builders could tap into.
But then again, the Hubble isn’t all that low a temperature (direct sunlight half the time!), and you’ve got to have cryogenics in it to keep the IR systems working.
In fact, the more I think about it, the more skeptical I am, just because the HST isn’t at extreme cold.