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| South Pole Diaries 2000/01 |
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Friday 8th
December 2000
From
John Storey.....
At 8 am the bulldozer arrived to take
Summit from the lab and set it up on the snow. (Actually it
was a little after 8. As Paolo explained, "8 am" translates
into Italian as "Some time after 8 we will arrive and do
what you've asked of us, plus anything else that needs doing
and we'll all have fun doing it". And so it was that the
bulldozer (a D4, for the technically minded, equipped with
forks) first levelled the snow with its forks, then poked
those same forks through the door of the lab (which was open---you
need to be careful how you specify these things where bulldozers
are concerned), gently lifted Summit up and backed it out
into the sunshine. We placed Summit on the ground, then used
a spirit level to align it. (You can use a spirit level in
Antarctica if you're quick. If you muck around too long the
bubble freezes. At this point either everything or nothing
appears to be horizontal.)
With the power cable and RS232 line
poked through a convenient cable duct into the lab, we were
taking data within 30 minutes. Once the calibration cycle
was over, the mirror in Summit turned so that it was looking
straight up through the sky. In Sydney, the instrument would
see only a few tens of meters through the dense, moist atmosphere
to record a signal corresponding to something like room temperature.
Here at Dome C the signal dropped to something like we see
in the lab when looking at liquid nitrogen. Instantly we knew
that we were seeing right through the atmosphere and looking
at the cold of interstellar space! As predicted, the cold,
dry air of Dome C, combined with its considerable altitude
(3,250 metres) endows the sky with a transparency that is
probably better than that at any other observatory site on
earth. It is that "probably" that the Summit experiment
is designed to quantify.
After making our first complete "sky-dip"
with Summit we dashed off some emails to the team back at
UNSW who had worked so hard over the past 18 months to make
Summit ready.
Next we had to look at the data to
see that they were making sense. This turned out to be surprisingly
difficult because even a quick analysis requires a well-oxygenated
brain. I believe that the maximum permissible safe altitude
for any calculation involving exponentials should be set at
about 3,000 metres. After a few false starts we concluded
that indeed the data showed the sky to be at the right temperature,
and to be about 75% transparent (ie, tau = 1.3) at our observing
wavelength of 350 microns.
A few worries remain with the instrument,
not the least being that the beautiful little Swiss-made chopper
motor sounds like it's thrown a con-rod, and that Eric (the
data-taking software process) gets bored after about 30 minutes
and just sort of stops. I suspect that the Eric problem somehow
revolves around semicolons, and that Michael Ashley will sort
it out in a flash. The chopper is more of a concern, and we
are having a spare flown out from UNSW asap.
The demise of the digital output driver
chip on our PC/104 ADC card is not proving too restricting.
The only thing that really needs to be switched off and on
automatically is the chopper motor, and that only because
it's sick and we don't want it to scatter its windings across
the snow. To solve the problem we've installed a makeshift
plug to perform this function manually (the on/off thing,
not the scattering). So, when the software says "chop on",
we have to rush out the door, open up the electronics rack,
unplug the plug, close the rack and rush inside again. It's
not as bad as it sounds, even at -40C.
In any case we have asked Andre, back
at UNSW, to send us some more of that special blue smoke that
they put into computer chips. It seems that the static electricity
spark that hit our digital driver chip caused all of its blue
smoke to leak out, and now it's not working any more. Replacing
the chip here is not really an option---it's one of those
tiny surface-mount things with a gazillion legs and the only
tools we have are a Dick Smith soldering iron and whatever
we can persuade the cook to lend us from the kitchen.
Meanwhile Paolo is stoutly maintaining
that there is nothing wrong with our chopper motor, that it
always made that noise, and it's just that it's so quiet here
you could hear a pin drop. He may be right---I notice that
the fan in the electronics rack sounds like a gas turbine
on full throttle.
In the morning I was also able to talk
briefly with Jon Everett at the South Pole via the HF SSB
radio (see glossary).
The signal was very weak and it was difficult to convey any
real information, but it was a useful experiment. The HF antennas
here are fairly basic. Given that there's no shortage of space
around here, it's tempting to imagine putting up a large rhombic
antenna. In future, this could give us an excellent, instant
communication link with the rest of our team. We also talked
to the Australian coastal station of Casey using HF. The signal
here was much stronger, but still not quite enough. Looks
like we need two rhombics.
Communication is more usually made
from Dome C via Inmarsat B, a geostationary satellite that
can handle both data and voice. An email transfer is made
twice a day, while the telephone is available 24 hours a day
for anyone with US$2.80/minute to spend. Unlike Iridium, the
Inmarsat satellites are far enough away that a largish (1-meter)
antenna is needed. Balanced against this is the fact that,
again unlike Iridium, they still actually work.
Life at Dome C continues to be very
pleasant. The waste heat from the diesel generator is used
to melt snow and heat the resulting water, so there's sufficient
available for hot showers. Perhaps the least satisfactory
aspect of Dome C is the "Free-time Tent", which is
where the sole computer for email use resides. The Free-time
Tent is a pleasant enough structure in itself, but is also
the main smoking room for the station. Australians are unused
to the level of cigarette smoke that Europeans find perfectly
normal.
Sleeping accommodation at Dome C is
mainly in large, Canadian-made "Weatherhaven" tents,
which have a rigid aluminium frame and an oil-fired heater.
They are very large and rather grand after the "Jamesway"
tents of the South Pole. The space is shared by eight people
in an open-plan arrangement, though fortunately there are
only four of us in our tent. Like the Jamesways the only real
inconvenience is the lack of acoustic shielding. It would
be an interesting project (perhaps for an undergraduate) to
calculate the minimum number of sleeping males you need to
place in one room to ensure that there is at least one person
snoring all the time.
There is a lanky Englishman visiting
Dome C as part of the EPICA ice-drilling project. When he
found he was too long for his bed the staff here quickly made
a customised bed with an extra 30cm of legroom. It seems nothing
is too much trouble to keep the scientists happy.
For the rest of the day we experimented
with different observing macros and tried to accumulate as
much data as possible. Our data are showing a funny zig-zag
pattern which I would like to get to the bottom of before
I have to leave. We have been plotting our data up using Excel
on poodle, and making attractive graphs in lots of colours.
Data always looks so much more convincing after Excel has
finished with it.
John
 
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