Antarctic Astronomy Diaries 2003/04

   

   
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Tuesday, November 18, 2003

And your bird can sing...

We started the day with a tour of Gerhard's precipitation monitor, which measures the amount of snow falling by shining a light beam through the air and looking at how much of the light is scattered. It's a very nicely made instrument from the Vaisala company in Finland. It has a second monitor that simply looks at how much snow falls on a flat surface a few cm square, the surface being heated to ensure the snow steadily sublimes. The flat surface is surrounded by sharp spikes to prevent birds from sitting on it, which presumably could lead to some pretty bizarre results - especially if they were emus.

If we can find a way to connect Gerhard's experiment to the AASTINO, he will be able to take data all winter long instead of just during the summer time when the station is open. This could finally resolve some interesting questions that still puzzle climate modellers: for example does the wintertime snow on the Antarctic plateau come in one or two big storms, or does it just fall lightly most of the time?

On the way back we dropped in at the EPICA ice-core drilling tent. The Dome C ice-core is an extraordinary undertaking, drilled straight down for 3,200 metres. Last year I greatly enjoyed talking to the various scientists about the amazing things you can learn from ice cores. The Dome C ice core preserves a record of the earth's climate, and much more, going back over the past 800,000 years or so. Today, the person who does the actual drilling, Laurent, was able to explain to us the technology that makes it all happen. The drill is really a brilliant piece of engineering, lowered the 3,200 metres at 1.5 metres/second and then manoeuvred with millimetre precision as it does the actually drilling. The drill shaft is filled with kerosene to prevent it collapsing in on itself, so the drill itself has to operate under enormous hydrostatic pressure.

Gerhard was also able to explain the work he does looking at crystal structure of the cores. Apparently when the earth's climate is colder, the ice forms smaller crystals than when it is warm. The reason for this is rather neat - when the earth is colder it is also drier, and hence dustier, and the tiny particles of dust in the air pin the crystal boundaries and prevent the crystals from growing larger. If I wasn't an astronomer I think I'd like to drill ice cores.

Just before lunch we switched on the sodar (acoustic radar) and were amazed to find that it worked perfectly. It even produced sensible-looking results, which is a good start for any instrument. The sodar works by sending out very loud pulses of sound, then listening for the incredibly faint echoes that come back from the turbulence in the air. In this way it can measure where the turbulence is located and how strong it is. If it is very close to the ground, then that is very good for astronomy because its effects can then be easily corrected for.

The sodar emits a series of musical notes that could be heard all over the Station. It's not an unpleasant noise, being rather reminiscent of a bird singing - hence the title of today's diary, borrowed from a Beatles song.

Our second science instrument, Summit, measures the transparency of the atmosphere at sub-millimetre wavelengths. At most locations on earth, water vapour in the earth's atmosphere renders the sky totally opaque to these waves. This is a shame, as they carry a lot of useful information about how the universe began, how galaxies formed, and other things that would make our lives more satisfying if only we knew the answer to them. The incredible dryness of the Antarctic atmosphere makes it the best place on earth for sub-millimetre astronomy; Summit will tell us just how good Dome C really is.

Summit gave some good results earlier this year, but has recently begun behaving rather strangely. In fact, we couldn't get any sense out of it at all this morning. This was sufficiently frustrating to inspire us to ring Jon L. back at UNSW on the Iridium phone. Jon was able to sort out a lot of our problems instantly, and we soon had Summit working like a champ. Unfortunately, Anna has discovered that there appears to have been some kind of a relationship breakdown between Summit and the Supervisor computer - something we will try to resolve tomorrow. Anna has also started exploring the log files that tell us everything the Supervisor did since we closed the door to the AASTINO last February, and is piecing together a plausible picture of what happened.

The email link to the outside world from Dome C continues to be rather tenuous, with the result that we don't yet have answers to many of the questions we've been firing back to the team at UNSW. To make matters worse, the School of Physics computer at UNSW collapsed in a big heap today, so we weren't even able to make contact via Iridium. If things don't improve tomorrow my next diary entry will continue the Beatles theme by being titled "No reply".

We're currently running everything in the AASTINO (except for the fan heaters) from the two solar panels. They're providing more than enough power to keep the batteries fully charged. Solar panels are just superb in Antarctica, and work even better here than they do in temperate climates. First, the solar cells are considerably more efficient when they are really cold. Second, there is a lot of reflection off the snow, so the panels receive a lot more light. Third, we're very high here and the atmosphere is extraordinarily clear, which of course lets even more sunlight through. With the sun in front of the panels we are getting nearly 400 watts (not bad for two 150 watt panels); even with the sun behind the panels we get around 75 watts!

Today I finally got rid of the cracked batteries and all the lead-contaminated paper towel. Yesterday I'd given everything that the battery acid had spilled on a good wash with Virgin Kiwi brand mineral water, which just happened to be on hand. I wrapped everything up in plastic bags, threw it onto the back of a snowmobile and carted it back to the Station. Disposing of the lead made me feel a lot better about working in the AASTINO - lead is right up there with cigarette smoke as a dangerous environmental pollutant.

Around about mid afternoon, Gerhard dropped in to talk about interfacing issues and software and power considerations for his precipitation monitor. We were immersed in conversation when I first smelled, then saw, smoke rising from the sodar. Smoke is not generally considered a good sign where electronic things are concerned, and is considered an even worse sign when those electronics are sitting on top of a fuel tank. (We sit a lot of things on the fuel tanks because there's not much space in the AASTINO that isn't fuel tanks. We do, however, try to choose things that are not known for spontaneously bursting into flames.)

Dashing across the room I unplugged the sodar, which stopped singing in mid-chirp like a bird that had just fallen out of its tree. It turned out that the smoke was coming from the sodar power supply that had been hastily assembled in January when the original sodar power supply blew up (see 2002 - 3 diaries). We're not having a lot of luck here. Amazingly, it was not an electronic component that had blown, but the circuit board itself had decided to burn. I've never seen this before...

Gerhard was very understanding but, as he left, I could see he was calculating just how far away he could place his precious instrument from the AASTINO and still be electrically connected to it.

We had our final group of visitors to the AASTINO in the late afternoon, when three of the Station crew turned up to check things out. Fortunately most of the smoke had dissipated by then. I gave them a good tour and Anna took a photo of Chiara, the most photogenic of the trio, with the web camera. The AASTINO is becoming a major tourist attraction at Dome C, and I expect that the Lonely Planet will soon have an appropriate entry for it.

Jean-Louis is now up to speed and is wowing everyone with his cooking. The sight of Jean Louis emerging from the kitchen, proudly bearing a tray of his latest creation and beaming with anticipation of the pleasure of his diners, is enough to stir even the most finicky appetite.

John

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