A Little Snow in the Forecast

It was a gorgeous day when we arrived on the summit. A deep blue sky above brilliant white snow covering the slopes. It was difficult to put much faith in a forecast calling for truly dire weather. I could see nothing to the southwest, the direction this weather was approaching from, just the blue Pacific stretching to the horizon.

Snow
A little fresh snow on the summit of Mauna Kea
Oh yeah… The car is still there. It is a truly sad sight to see, the car halfway down the slope. Rumor had it that a tow truck was to come up today to remove the vehicle, but the car was still on the slope when we left.

Not a bad day, I accomplished everything on my to-do list for the day. Some work in AO to check for any stray light, removing some old servers to make way for a new system, locating and labeling some optical fibers that are already in place for this same system. Everything went well, except the lunch time cribbage game, I lost badly.

The weather was degrading all day, first the clouds loomed overhead, then they descended as a heavy fog while the temperature dropped. It did indeed begin to look like the forecasts might have a bit of truth. The prediction is for heavy snow, as much as 6-10 inches. Not sure if that will materialize, it would be nice, we have not had any real snowfall this winter. I will just have to check the webcams tomorrow morning.

It was beginning to snow when we pulled out.

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!

Keck Observations Reveal Complex Face of Uranus

UC Berkeley press release

The planet Uranus, known since Voyager’s 1986 flyby as a bland, featureless blue-green orb, is beginning to show its face.

By using a new technique with the telescopes of the Keck Observatory, astronomers have created the most richly detailed, highest-resolution images ever taken of the giant ice planet in the near infrared, revealing an incredible array of atmospheric detail and more complex weather.

The planet, in fact, looks like many of the solar system’s other large planets — the gas giants Jupiter and Saturn, and the ice giant Neptune — said Imke de Pater, professor and chair of astronomy at the University of California, Berkeley, and one of the team members. The planet has bands of circulating clouds, massive swirling hurricanes and an unusual swarm of convective features at its north pole.

“This ‘popcorn’ appearance of Uranus’s pole reminds me very much of a Cassini image of Saturn’s south pole,” said de Pater.

Uranus with Keck AO
The two faces of Uranus as seen through the adaptive optics on the near-infrared camera of the Keck II telescope in Hawaii. Credit: Lawrence Sromovsky, Pat Fry, Heidi Hammel, Imke de Pater.

Saturn’s south pole is characterized by a polar vortex or hurricane, surrounded by numerous small cloud features that are indicative of strong convection and analogous to the heavily precipitating clouds encircling the eye of terrestrial hurricanes. De Pater’s group suggested that a similar phenomenon would be present on Neptune, based upon Keck observations of that planet.

“Perhaps we will also see a vortex at Uranus’ pole when the pole comes in full view,” she said.

The study was led by Larry Sromovsky, a planetary scientist at the University of Wisconsin, Madison. In addition to de Pater, other team members are Pat Fry of the University of Wisconsin and Heidi Hammel of the Association of Universities for Research in Astronomy. The team will report the details of their observations Oct. 17 at a meeting of the American Astronomical Society’s Division of Planetary Sciences in Reno, Nev.

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How bad is it?

One of the miscellaneous systems in the observatory that I have inherited is the weather station. A critical set of gear that has been neglected far too long. Neglected to the point our telescope operators had been complaining, loudly, about a system that frequently gives erroneous data or provides wildly oscillating readings.

Weather mast covered with several inches of ice
The Keck weather mast covered with several inches of ice
The weather station is critical in protecting the all important optical surfaces of the telescope. The mirrors that gather light from distant galaxies depend on a thin coating of aluminum that is easily damaged. Snow, ice, fog or even simple dew can damage the coating and require the mirror segments to go through a laborious re-coating process. Thus the operators monitor the weather closely, when fog and humidity roll in, alarms go off, and the great shutters are closed to protect the telescope.

The first part I have replaced is the humidity and dew point sensor. In many ways the most important part of the system. The new unit is a modern sensor with a direct ethernet interface, simple to link into the observatory network. This is the same sensor used by the National Weather Service in their remote weather stations. All I had to do was spend a little money, and spend a day hanging off the weather tower on the observatory roof installing it. It was a beautiful, warm, sunny day up there, I got the job done, and got a slight sunburn in the process.

Continue reading “How bad is it?”

Atop the Weather Mast

I got lucky.

Weather Mast
The author working on the Keck weather mast
I had expected it to be a day of 20mph winds and freezing temperatures. What I got was a balmy 11°C (52°F) and just a gentle breeze. All for the good as I planned to spend several hours hanging off the weather mast installing wiring to improve the new dew point sensor. A cold wind can quickly turn the roof of the observatory into a miserable place.

The original sensor housing had proved to be vulnerable to heavy icing. The new housing should be more resilient, as well as providing better daytime temperature readings. This is due to changing to a different shelter design that uses a fan to move air through the housing past the sensor. I also modified the housing with the addition of a heating element to allow de-icing.

Weather mast covered with several inches of ice
The Keck weather mast covered with several inches of ice
To make the heating element I needed heavy nichrome wire. Not having any on hand I took a trip to the thrift shop. There I bought a used toaster for a couple dollars and spent an hour dismantling the toaster to remove the heating elements. I took the wire and wrapped it through the interior of the instrument housing, creating a heating element that should work quite nicely with a 12V supply, gently warming the housing and melting any ice.

A beautiful day on the summit, nice to spend a few hours atop the roof, hanging in a safety harness from the weather mast. I even remembered to put on some sunscreen to avoid frying in the high altitude sunlight. A new cable pulled through the conduit, the instrument shelter replaced, a little further wiring inside and the job was done. I will have to await another round of bad weather to see if the changes work, but given the trend this winter, I will not have to wait long.