South Pole Diaries 2000/01

   

   


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