Keck – Page 45 – A Darker View

Laser Launch Telescope

A big milestone arrived this week. The launch telescope arrived from the manufacturer. It is an impressive instrument itself, a half meter aperture, an extraordinarily short focal length, made to very exacting precisions, even for optics. It is a cassegrain design with an focal ratio of f/1. The primary is coated with a custom coating designed for maximum reflectance at the 589nm sodium D line, where the laser will operate. This gives the primary a notably orange cast that is quite beautiful. The entire telescope is enclosed in an airtight aluminum shell with the optics supported on a carbon fiber frame within.

This is one of the key components in creating a laser for the Keck 1 adaptive optics system. An enormous amount of work has gone into preparing for the laser… modifications to the structure of the Keck 1 telescope, cabling, electrical power and liquid cooling plumbing. An insulated room built on the side of the telescope to house the laser and a safety system to comply with laser safety regulations. All of this in preparation for the arrival of two key components, the laser itself and the launch telescope that will focus this light into a clean beam rising into the night sky over Mauna Kea.

The entire assembly will mount behind the secondary of K1. This is different than the current laser in Keck 2 that is emitted from a launch telescope along the side of the main telescope. Having the laser on the side creates some problems for the AO wavefront controller, the artificial guidestar can be elongated by parallax when seen from the other side of a ten meter telescope. Having the laser launched from the center of the main telescope is a far more optimal solution. But doing that takes a far more difficult to design and build launch telescope as it has to be extraordinarily compact.

We expect delivery of the laser itself in May. Our laser engineer has been working with the laser manufacturer to insure it meets all specifications. Reports indicate it is not only meeting those specifications, but surpassing them. When we take delivery there will be a period of testing before the equipment is trucked to the mountain for installation in its final position.

The coming week will be fun, need to string a new set of cables to the Keck 1 secondary mirror. This means 150 feet of cabling from the Nasmyth Deck, up the tubular structure of the telescope and across the spider to the secondary. On a ten meter telescope this means a lot of high work from the personnel bucket of the jib crane among the girders of the telescope. This is going to be fun!

Shoveling Snow

Monday I spent the day on the summit, I often choose Mondays, if I have a choice, as we often have a smaller crew and getting access to the various parts of the telescope is easier. There are fewer people trying to do fewer things at once. Monday turned out to be very good choice indeed, the first clear day at the summit since Christmas. We arrived at the summit to deep blue skies over a landscape of white. Poli’ahu has again blessed the summit of the White Mountain with deep snow.

Snow Day — Looking across at the Keck 1 dome from the top of Keck 2 with Mauna Loa in the background

A small crew does have a disadvantage as well, the chance of being drafted into whatever job needs being done. Not that I was unwilling, the job in this case was clearing snow and ice from the domes. This meant climbing to the top, one place in the facility I had not yet had a chance to go.

So after rigging myself in full safety harness I climbed the dome with the crew. The view from the top is stunning! A full 360 degree view of the summit on a perfectly clear sunny day. The entire summit is blanketed in a beautiful white coat of snow, one of the most dramatic scenes I have ever witnessed. The small Canon G9 camera fit in a breast pocket, small enough not to interfere. I began filling my memory card with many images of the view from the top, reveling in the spectacular vista.

Not that it was all sightseeing, there was work to do, shoveling snow and chipping ice from the areas where it could interfere with operation of the telescope. Ice and snow coated the upper sections of the dome. Several inches of ice needed to be hammered free of the steelwork and drifts of snow, up to two meters (six feet) deep were packed into any corner and along the side of the shutter. Blocks of ice and shovelfuls of snow flew, crashing to the ground 30m (100ft) below. A crew worked each side of both domes for several hours to complete the task, made all that more difficult by the extreme altitude.

In the thin air there is only so much you can do before you are short of breath. Put down the shovel for a few moments and take a few more pictures. I have material from which to assemble a full panorama as well as dozens of individual images.

After much of the snow and ice had been cleared by hand there was one more step to accomplish. Clear the large drift of snow from the back of the shutter by using the shutter itself as a snowplow. This drift is many tons of snow, over 2m (6ft) thick at the top and about 12m (40ft) wide. When it came down it becomes an artificial avalanche, with huge blocks of snow falling to the ground far below.

Avalanche from Andrew Cooper on Vimeo.

Two Moonrises

I enjoyed moonrise tonight on the way home, and then enjoyed it again. The first was just after leaving Waimea, a golden full Moon rose over a band of clouds, a beautiful sight as I drove home from work. My drive then takes me deep into the shadow of Mauna Kea, the Moon disappearing behind the bulk of the mountain. A second moonrise found me about ten miles further down the road, with that golden orb rising over the summit. Two beautiful moonrises to grace the end of a long day.

Venus was visible in the golden glow of sunset, mercury right below if you knew to look for it. I saw no sign of Saturn which should have been a ways below the other two, it was probably hidden by a band of clouds that occupied the right spot.

Yes, I did say I was driving home from work on a Saturday. One of the guys on the crew is out with a bad back, and I worked a couple more days on the summit to cover. I was performing some procedures I had never done before, optical alignments in preparation for using the interferometer that night. As a result I will have spent five out of seven days on the summit, quite a bit more than my usual two days a week. I get a day off tomorrow, then back at it Monday. Even tomorrow will not be completely a day off, with an interferometer run in progress there will be some work I need to do from home to check the systems and insure they are ready for the night.

Hopefully the phone stays silent through the night.