Working the Weather

One of the little side jobs I have gotten assigned at Keck is updating the weather station. This involves replacing all of the weather monitoring equipment that allows the operators to keep an eye on conditions around the telescopes. This gear is absolutely critical, giving the operators the data they need to protect our equipment, including the irreplaceable mirrors.

Keck Weather Mast
The weather mast atop the Keck observatory building
As a side job it has been fun. A simple job that can be completed with a minimum of complications and the usual folderol that surrounds larger engineering projects. Just come up with a plan, put some numbers on the plan, buy the gear and install it. As budget has allowed I have worked my way through the plan, replacing bits of gear one item at a time.

It has been fun to learn about measuring temperature, humidity, dew point and more. It seems so simple at first, but the complications of getting a good reading are subtle. Passive instrument shelters, active ventilation, instrument positioning, calibration and more. Issues that can make a good instrument give bad data.

Barometric Sensor
A barometric sensor installed in the Keck weather mast
Likewise the severity of the weather at the 13,600ft elevation of the observatory is a real challenge. How do you get a good reading in 70mph blowing snow? What do you do about 8 inches of ice that has formed over every vertical surface. That one was a challenge, the first shelter I put up for the temperature and humidity partially collapsed under the weight of the ice on the sensor cables.

Last week I installed a new barometric sensor. This was the last part of the existing weather instrument suite that needed to be replaced. I got lucky, it was a great day on the summit, sunny with just a modest breeze. Just the day to spend a couple hours hanging off the weather mast in a climbing harness rewiring a junction box for the new cables. A few holes to drill, a few bolts, a couple cables… done!

My next item is to install an anemometer. We have not had an operational anemometer in many years and our observing staff has made it abundantly clear that they want an anemometer. Not that this one will be easy, it is a bit of a challenge to get a decent wind reading anywhere near a 100ft diameter dome. This challenge will be a bit more involved, and involve some good engineering fun. Time to learn about measuring wind-speed and how to do it right. Looking forward to the next part of the plan!

Author: Andrew

An electrical engineer, amateur astronomer, and diver, living and working on Mauna Kea, Hawai'i.

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