'Snowtrack'

When it began to rain during lunch down in the valley, I suspected we might be in for a somewhat colder version of precipitation at the CARMA Cedar Flat site, elevation ~8000 feet. We were briefed on the snow policy for the telescope, and headed back up the mountain to watch over the antennas during the snow storm and for the duration of the weekend.

The first task in a snow storm is to divide the antennas into sub-arrays, one which included the larger antennas (10-meter, which collect the most snow), one for the central (6-m) antennas which have a possibility of colliding, and a third sub-array comprised of the smallest (3.5-m) antennas.  For the 10-m antennas, we issue the command 'snowtrack', which measures the wind direction and points the antennas with their back to the wind, minimizing the accumulation of snow on the collecting area of the antennas.  We then 'stow' the 6-m antennas, pointing towards the zenith (straight up).  For the 3.5-m antennas, we keep them tracking a source in the sky that never sets.

That's the easy, and warm (done from the control room), part of our responsibilities during the recent ~24 hour snowstorm.  During that time, we monitor the snow-fall rate, and any time more than 2 inches of snow accumulates on the 10-m antennas, we trek out to the array and begin clearing snow.  Now, I'll reiterate that the antennas are 10-m in diameter, so we can really only reach the bottom half, even with long extend-able squeegees.  The other part we didn't consider is that when you start clearing snow from over your head, the only place the snow will go is... down... on top of us!  The second time we went to clear snow, we suited up in fully waterproof overalls and parkas, what we deemed our "spacesuits".  The third time, we suited up with even more layers, and much to our relief, the snowfall had lightened and the snow was no longer sticking to the antennas.  The command 'snowtrack' had done its job so that we didn't have to do ours! 

Hiking out to the array with the squeegees, around 6 pm, the first of our trips to clear snow.

We continued to monitor the snowfall rate, and in the morning pointed the telescopes toward the sun to dry them out.  In all, we had about 6 inches of snow, coming down at 0.25-1 inch per hour over about 24 hours.  At some point, feeling cooped up, with icy roads and no where to go, we decided to try out the bikes on the snowy paths nearby, and my co-observer spotted the perfect sledding hill.  In our spacesuits, we cleared a luge and enjoyed a few sledding runs down the hill, soaking in some of the Saturday afternoon sun.  Then, when the telescopes appeared clear, it was back to science and business as usual.