Antarctic Astronomy Diaries 2002/03

   

   
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17 February 2003

Thursday, January 16, 2003

A diary holiday

Things are a bit hectic here at present. We're all flat out getting the
actual science instruments up and running (which is why we're here,
after all). At the same time, our physical limitations are catching up
with us, as minor frostbite, skin rashes caused by the dryness,
decomposing feet and other little ailments slow us down. For me,
cracked fingers and thumbs are making typing (and everything else, for
that matter) a bit difficult.

Please rest assured that we are forging ahead. However, we ask for your
understanding if details of today's activities have to wait until
tomorrow.

A serious setback

Today should have been the day that our acoustic radar burst into song.
Instead, it burst into flames (well, lots of smoke anyway).

It was like this...

The acoustic radar (also called a SODAR) had been working just fine at
UNSW, running off the mains. Prior to that, we'd run it off 24 Volts DC
for several years, at UNSW, South Pole and at Calerne Observatory in
France. Then, it went back to the factory to have the calibration of
the antenna checked, and to have a new Linux operating system installed.
And, unbeknown to us, while it was at the factory they...

...opened up the case and replaced the 24 Volt amplifier with a 12 Volt
one...

...which would have been fine, had they told us, and especially if they
had removed the sticker that says "Input voltage 19 - 35 Volts".

Actually, even a little hint would have been nice - something like
"Surprise!!!" written on the outside of the case.

When we first switched it on it popped the 1 Amp circuit breaker. Now,
we know it draws a bit more than an Amp, so this was not too unusual,
but I was perhaps unwise to have "commented out" the circuit breaker
with a short length of wire. This left only our main 32 Amp instrument
circuit breaker in the line, and this was more than happy to provide the
30 Amps that the SODAR had suddenly acquired a taste for.

We removed the obviously exploded electrolytic capacitors, but it's
still a dead short from input supply to ground.

Since the SODAR is an important part of Tony's PhD thesis work, he is
understandably a bit put out. He's taking it well though, and we're now
frantically trying to get a new power amplifier (and a 24 Volt to 12
Volt converter) flown in from Christchurch. It might just be possible
in the three weeks left before the Station closes.

Rather better news surrounds the Stirling engines. Sid is running
continuously - so far without a problem - while we have been
deliberately stopping and starting Nancy to learn more about the
start-up behaviour. We can now set the AASTINO to any temperature we
like, using a Eurotherm PID temperature controller to suck cold outside
air into the building in exactly the quantities required. We set the
temperature to +30C for a couple of hours, just for the pure pleasure of
being truly warm for a change.

One of the great mysteries of this trip has been what happened to all of
our electronics spares. We had quite a good kit together, including a
full range of resistors. The whole lot has, quite simply, vanished.
It's possible that the aliens feel they have now abducted plenty of
people, but are running short of resistors. If so, I can sympathise
with them. Dome C is along way from the nearest Dick Smith store.

This morning I put together a shopping list of resistors and also some
Schottky diodes (see below). This afternoon, they arrived, via Twin
Otter, from Terra Nova Bay! It was just like Internet shopping only
better - delivered to our door and we don't even get a bill. This is
just one example of the kind of pleasant things that occur surprisingly
often in Antarctica. Another example was when there was a knock on the
door of the AASTINO earlier today, and one of the Station crew presented
me with two boxes of resistors, resplendent in their gaudy colour codes,
and covering every possibility we could wish for.

(A Schottky diode, by the way, is like a normal diode in that it
conducts electricity in only one direction. However, it switches much
faster, and imposes less of a penalty in terms of reducing the voltage.
We use them a lot for two purposes. One is to prevent the voltage on
any line from going higher than it should, and thereby blowing things
up. The other purpose is similar - to prevent static electricity from
destroying the computer and other instruments. Static electricity is a
menace of plague proportions in Antarctica. Schottky diodes are the
antibiotic pill of the electronics world.)

During the course of the day we also installed our second instrument,
SUMMIT, on the roof of the AASTINO. This required a bulldozer fitted
with a crane. I never fail to be impressed by the precision and
delicacy with which an experienced crane driver can manoeuvre tonnes of
material around. (On the other hand, when he arrived he did run the
bulldozer into the side of the AASTINO. I think it was just to save
having to get out and knock on the door.)

Prior to installation, we fitted SUMMIT with a canister of calcium
hydride. Readers of diaries from previous years will know that calcium
hydride is the stand-out champion at sucking up water vapour. We put it
in many of our instruments to prevent ice forming on the inside of
optical windows. Tony also sealed up ICECAM (again with some CaH2), and
put in on the roof of the little orange building over the crypt.
Finally, COBBER, an instrument to measure clouds at infrared
wavelengths, was tested and readied for installation.

The day finished on a good note. The same Twin Otter that brought some
resistors and Schottky diodes for us also brought a new SIM card for our
Iridium phone and, best of all, fresh vegetables.

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