A lot of today was spent on SUMMIT. With the new filter installed, we were anxious to check that everything still worked. A suitable stand was constructed from an upturned rubbish tin, the Redhat Linux manual, and a primer on PERL. (This is probably the first time we've actually found the Linux manual useful.) After the usual mistakes, false starts, incorrect assumptions and other foolishness, SUMMIT was coaxed into life and made the first ever observations at 200 microns at Dome C. To be fair, the observations were of the inside of the AASTINO, but it's a start.

We also made a rough check of how well SUMMIT was working by showing it a lump of snow to see if it could tell the difference between that and room temperature. It passed with flying colours, and so will find itself back on the roof tomorrow.

Installing the calcium hydride desiccant in SUMMIT proved more complicated than expected, as do most things involving calcium hydride. First, it's now clear that the containers we place our dessicant in do not permit sufficient air circulation to allow the drying process to work. Second, the previous container design resulted in calcium hydride going all over the place. Gathering it up and dumping it into a beaker of water rendered it safe, albeit with lots of fizzles and pops. OK, the MSDS says not to do this in case it explodes, but it seemed the least of the available evils. We used expensive imported Italian mineral water, so it was probably all right.

I've previously mentioned the dramas that we had getting hold of the calcium hydride in the first place. In the end it was the generosity of Bill Leck from the School of Chemical and Physical Sciences, Victoria University of Wellington, that enabled us to get sufficient quantity in time. Thanks Bill!

When we write up the paper describing the SUMMIT 200 micron experiment, a section of it will go something like this:

"To prevent the calcium hydride from clumping, it was mixed in equal quantities with molecular sieve. The sieve had previously been dried by heating to approximately 200C in a dry atmosphere. The sieve and dessicant were placed in a small container and retained by 500 micron nylon mesh. Assembly took place in a cold-room at a temperature below zero. The instrument was then baked at +30C for 18 hours to remove all traces of moisture."

What really happened was this. The molecular sieve (which are tiny little balls of clay-like stuff) was emptied into the upturned lid of the rubbish tin (boy these rubbish tins are useful!) We then took it outside to where it's -36 C and the humidity more or less zero, and blasted it with the heat gun until it started to smell. Since it was clearly planning to go everywhere again as soon as SUMMIT was sealed up, we glued a piece of nylon insect screen across the top of the container. (Please don't tell Michael Ashley where the piece of insect screen came from. There’s plenty more left on the tent anyway, and in any case the mozzies don't bother us much here.) Then we put the whole thing together in the tent which, despite our efforts to the contrary was still far too cold for comfort, and lugged it in to the AASTINO to warm it up overnight before we put it on the roof.

Additional drama occurred today when I suddenly heard the engine note change on Sid, who has been running faultlessly for the past few days. I looked up to see the batteries discharging at 40 amps, with presumably another 20 amps or so being provided by the now-straining Sid. This is a serious amount of power (1500 watts) disappearing into what presumably was a catastrophic fault somewhere in the system. I did an instant mental survey of possible fault conditions that could absorb such a massive current, and decided that virtually all of them would be irreparable in our remaining week.

Just as panic and despair were about to completely engulf me, I looked up to see Jon cheerily warming up some heat-shrink tubing with the heat-gun. Like me, he had completely forgotten that we'd switched from Station power across to our own inverter, in order to power our computer screens and other small items while the Station power was down. So, congratulations to our little 750 watt inverter for putting its shoulder to the wheel when duty called. However, I’ll have to have a word to the 32 Amp circuit breaker which, after sitting there for two years doing nothing finally had a chance to leap into action, but appears to have been off with fairies at the crucial moment.

And finally, an experiment everyone can participate in. At most existing observatories recoating the telescope mirrors on an annual basis is a costly and time-consuming process. Having the cleanest air in the world, Dome C might allow telescope mirrors to last forever without recoating, which would be a major bonus. Last January we set up a simple test: four small mirrors were coated with an identical reflective coating. Two are safely stored in the lab at UNSW, the other two were placed on a post at Dome C (on the horizontal arm halfway up the weather station pole in the photo COBBER.jpg). Eventually we’ll take them back to UNSW and compare them with the 'unexposed' mirrors.

Meanwhile, MirrorTest.jpg shows a photo of the sky, and the sky reflected in the mirror. Assume the sky varies in a completely uniform way as you go away from the zenith (this is Dome C, after all), and that the photographer has taken care to place the sun in the plane of the mirror. The ratio of the brightness of the sky to its reflection gives the reflectivity of the mirror.
- John