Let's have a little mental exercise, shall we?

[thewayne]

We're all astronomers. Smart people, highly educated. We work at or have visited a particular observatory that is at high altitude, for sake of discussion said observatory is in southern New Mexico at 9200' (almost 2800 meters), and you know it gets cold up there. In fact, starting in November, it routinely gets below freezing (32f/0c) and regularly snows. In fact, when it gets down to 0f, or if it's particularly windy and below freezing, they'll close down because the lubricants are stiffer and it makes the motors work harder, increasing wear.

Very cold work environment up at the telescope level, fortunately the control rooms are inside a nice office environment.

Now, we're a special kind of astronomer. We're instrument scientists. We design infrared camera systems, we design spectrographs, things like that. And they have to work at these temperatures because the telescope's dome is open to the elements and our instruments attach directly to the telescope to capture information from distant stars and objects.

On top of this, the place where the instruments are built is at a university in, say, Seattle, where snow is also a known element. Maybe not in the immediate area, but a snowy Mount Rainier overlooks the area and there are snow sports not far away.

So we're going to build a new instrument. Doesn't matter if it's a camera or a spectrograph, it's going to require a shutter, very similar in design and operation to the shutter in a camera. And said instrument is going to said observatory in southern New Mexico. But it doesn't really matter where it goes because most observatories are at high altitude and get pretty darn cold in their winters, whichever hemisphere they're in.


Now, the question for the class:

Are you going to order a shutter that operates at temperatures down to below freezing, or only in temperatures above freezing?

Write down your answer, fold your paper in half, and pass it to the front of the class.

Looking at your papers, it seems that most of you chose a shutter that would work in below freezing temperatures. Very good.


The last two instruments sent to my wife's observatory had shutters rated for only above freezing temperatures.


I kid you not.

The first shutter was able to be software reconfigured to work at below-freezing temperatures. It has a slight bounce problem at those temperatures which would be an issue on a camera-type instrument, but on a spectrograph, it isn't much of a problem. It stabilizes in a couple of milliseconds.

The newest instrument? *sigh* A replacement shutter is going to have to be ordered, and the instrument is going to have to be taken apart as it is buried in the guts. Which means the instrument can't be used in cold weather. WELL, GOOD THING THERE'S NO COLD WEATHER COMING UP! It's already frozen up once and had other problems, and this particular instrument is a replacement for the observatory's oldest and most venerable instrument, DISS: the Dual-Imaging Spectrograph, it's not like there's any demand for it (aside from everyone wants to use the new hotness. DISS has two spectrographs and can simultaneously shoot spectra in both red and blue wavelengths! But it is so far past its retirement date that it isn't funny. Honestly I don't know what's special about the new one, but apparently it's pretty good. Except the software is a big problem.

And somebody didn't pay attention to the specs of the shutter that they slapped into the new instrument, and now that it's here and running, it won't be usable on cold nights, and it will have to be taken out of service for a few days to be taken apart, replace the shutter, put back together, then vacuum-pumped back down.

There's a reason why there's a bunch of parkas with the observatory's name all over the place up there, ya know?!

Comments

[dewline]

See Snoopy for reaction cues.

[thewayne]

Yep. You wouldn't believe the disbelief when we found out that the stupid shutter was only rated to 10f, but it was much akin to Snoopy's. I think it was louder, was also four letters, but not to be printed in the funny pages.

[kathmandu]

I would want the shutters and all other parts rated down to at least thirty below (celsius). Astronomy is the kind of thing where if there's a freak weather event, and it stops you from observing one particular night, that opportunity may not come around again ever, or at least not for a whole human lifetime.

Yes, that does sound like severe lack of planning in the instrument-procurement process.

[thewayne]

While these people aren't through-and-through licensed engineers, they know the conditions at the observatories, they know electronics, etc.  I'm not sure the telescope can operate at -30 because of the lubricant problem as described above: it puts a lot of strain on the motors because of the precise movements of the telescope when it is operating at such cold temperatures, even if there isn't any wind load.  We had a cold snap of -28c for three days back about a decade ago, that's when they learned about this problem with the lubes.  They routinely get into single-digit below freezing (F) temperatures in the winter at night and things are fine as long as the wind isn't too high, it changes the shut-down parameters and they have to keep an eye on the wind load (direction and speed of the wind vs the direction and altitude the telescope is pointing).  But when the temp starts pushing -25c, it's pretty much automatic shutdown.  Damage to the motors just can't be risked because it can be a multi-week shutdown if one fails, and winter is the longest nights for observing!

[warriorsavant]

Sounds like you actually expected the people who custom build your instruments to actually understand how they are used.

[thewayne]

You'd think that since they are astronomers, and actually spent time using the telescope in the process of earning their degree, that they would have learned something.  Is that too much to ask?  Apparently so!  As the saying goes, common sense ain't too common!

[warriorsavant]

I know. I’m so naive.

[silveradept]

Was this the decision of the people who know the instrument to order this thing, or did someone farther along the chain decide that the thing being asked for was too expensive and this much cheaper item would fit just as well, not understanding that the thing requested was requested for specific reasons?

[thewayne]

The parts for the instrument are ordered at the departmental level, so I wouldn't think that's an issue.  That approval is done by people who know the field, but that approval also may not occur with minute scrutiny, trusting that the scrutiny and approval had occurred elsewhere.  It could slip by that something is out of spec, trusting that the people who specified the part ordered it with the correct tolerances.

[silveradept]

That makes sense. It seems like a grand case of incompetence somewhere, but I want going aware where it might have been found. Goodness knows there are a lot of administrators not actually in a field who would do substitutions like that for fiscal reasons without understanding.