South Pole Diaries 2000/01    

   


Saturday 9th December 2000

From John Storey.....

Today was the day of the zig-zags. After the initial excitement of making our first ever measurements at Dome C began to fade, we had to confess to each other that the data did look a bit on the weird side. Instead of the signal from the sky smoothly increasing as we looked at ever greater angles from the zenith, it was jumping up and down in a completely regular but nevertheless inexplicable pattern. Naturally we had lots of theories as to what might be going wrong, but as the day wore on we seemed to be making little progress. Finally we tracked it down to the stepper motor that drives our rotator mirror. We were running a small current through its windings to keep the mirror rigidly fixed at each position where we took data. This current was interfering with our extremely sensitive detector, and basically messing everything up. Switching off the current solved the problem completely.

I have never been a fan of stepper motors, as their deceptive simplicity hides a capacity for pure evil. Today's experience has done little to change that opinion. In fact, I may go so far as to write a glossary entry on stepper motors.

With that problem solved a new one has emerged; namely that our signal becomes very noisy at one particular elevation angle. At first we thought it was just the sun getting into our beam, but then the sun moved on the way it does and the noise was still there.

Jean-MIchael and Karim launch a weather ballon at Dome CJust after breakfast a Twin Otter arrived with Karim and Jean-Michel from the University of Nice. They are here to perform a series of balloon launches to measure the microthermal turbulence of the atmosphere as a function of altitude. This will complement the work done a few years ago at the South Pole by the late Rodney Marks, in collaboration with Jean Vernin.

This is the first Twin Otter we've had for a few days, and it was good to see several boxes of fresh fruit and vegies being unloaded as well.

After lunch I spent some time discussing my impending departure from Dome C and return to Sydney. It will involve a Twin Otter flight to McMurdo, then a flight in a US C130 back to Christchurch. We called McMurdo on the HF SSB rig, and with any luck they are now organising a seat on a Hercules for me.

Tomorrow I have been asked to give the inaugural Dome C Science Talk in the Free-time Tent. As there are no A/V facilities I will have to just stand up and speak, and maybe get Paolo to do some street theatre to accompany the talk.

John

New glossary entry!

Stepper Motor. An electromechanical device which is very simple in concept yet surprisingly complicated in detail. Failure to appreciate this has been one of the greatest sources of human misery since the invention of Lotto. Were it not for the fact that they are extraordinarily useful little devices I would have nothing to do with them.

 

Coming Soon!