A Visit to the W.M. Keck HQ Visitor Centre
Aside perhaps from the distinctive Gemini North dome, the twin Keck observatories are the most prominent facility on Mauna Kea summit. They are definitely the most famous, housing two 10m telescopes that pioneered segmented mirrors and have done much of the Big Science research in astronomy over the last few decades.
The two Keck domes sit on top of a long low building that continues underground with workshops and all manner of facilities. But if you go up Mauna Kea hoping for a tour you will be disappointed. Not only canít you visit, but most of the astronomers who use Keck donít either. Thatís because, of course, most of the instruments and the scopes themselves are operated remotely.
A couple of universities in Hawaii and California have remote links to the Keck telescopes, but much of the operation and management of Keck is done from their HQ in the small town of Waimea, which lies to the north of Mauna Kea. The HQ complex has a visitor centre with some very interesting displays and exhibits; itís free and staffed by an astronomer most days. Itís an interesting side-trip if youíre holidaying on Big Island and especially for some extra context if youíve already been to the summit and seen the domes open at sunset.
†Here Iíll take a brief look at how to get there and what to see.
The little town of Waimea lies in a lush area of forest and arable land to the north of the mountain on a road connecting the east and west coasts of Big Island. Itís a fairly easy and scenic drive from Kona-Kailua to the west. The main belt road, Highway 19 north, takes you past the airport and then into barren open land running close to the ocean before taking a right turn inland to Waimea. The trip should take less than an hour. Coming from the main resort on the east coast, Hilo, will take a bit longer via Highway 19 and the scenic old town of Honokaa in the opposite direction.
Whichever way you arrive, itís an easy journey and the Keck HQ is impossible to miss Ė itís a sprawling complex of low-rise cream-coloured buildings set in spacious grounds right in the centre of town on the north side of Highway 19, just east of the main shopping mall and Walmart.
You turn in left along the main drive, park anywhere for free (plenty of space when I went) and follow the signs around to the visitor centre in the middle of the buildings. There youíll find the main entrance below a big window patterned after the segmented Keck mirrors. The visitor centre Ė small, but packed with exhibits Ė is in the main foyer.
What to See
During core hours youíre likely to be greeted by a member of staff who will offer you a free tour of the exhibits Ė this is well worth accepting, as the guy who showed me around was a professional astronomer with extensive and interesting knowledge of the scopes and their operations.
The most interesting exhibits include:
∑ Detailed cutaway models of the observatory, domes and telescopes
∑ Part of an actual Keck mirror segment made of Zerodur, a special low expansion glass also used in high-end amateur telescopes. I was astonished how thin the Keck mirrors are
∑ An early instrument, the Near Infra-Red Camera, that was used from the early days of Keck (c. 1993). This large and sophisticated instrument package, used for capturing IR spectra, was the most capable IR camera in the world at that time
∑ Lots of information boards on the telescopes, their design and plans for future instruments and research, along with various images taken with the Keck 10m telescopes
By far the most interesting thing, though, were the anecdotes from the guide, Edward.
Information from the Tour
There follow some highlights of the very informative tour, if youíre interested to learn more about the design of this giant observatory and how it operates.
The twin domes themselves are about 100ft high and 120ft across. They have walkways and gantries for inspection and frequent ice removal. The workshops lie in the long low building between the domes and are partially buried underground for protection from the harsh winter conditions at 4000m. And those conditions can be harsh indeed, Edí told us, with high winds, snow and ice a frequent problem. You might imagine the weather as agreeable all year round on Hawaii, but they did almost no work at all during February 2019 due to wind and ice.
The two telescopes were originally intended to work as an interferometer, but this proved hard to do at optical wavelengths and required a team from California. Nowadays, the adaptive optics provide excellent resolution anyway and allowing the two scopes to host different instruments (four on one, six on the other) bookable by different teams expands the work the observatory can do.
On most nights there is just a skeleton crew of two left up at the observatory to fix any problems that may arise during an observing session. The workshop facilities are apparently extensive and quite self-sufficient, including the ability to re-coat the mirror segments without transporting them off the mountain.
Although there are only 72 segments (36 per scope) in use, they actually have about 80 to allow round-robin re-coating of segments without interruption to observing. They have to handle those thin Zerodur mirror segments with extreme care as they were cast and ground thirty years ago and the equipment used no longer exists so new ones would be hard to make.
Interestingly, segmented mirrors were a completely new idea, pioneered by Keck. Each mirror is minutely controlled by actuator and computer. The number 36 represented the limit of computing power in the early nineties, but the new 30m telescope will have as many as 500 segments.
Another use of actuated mirrors and computers is the adaptive optics system fitted to each telescope. A powerful sodium laser creates an artificial star by exciting sodium ions high in the mesosphere. The measured scintillation is then cancelled in real time by a piece of optics in the beam path. To avoid interfering with aircraft, the summit is a no fly zone and liaison with NASA is required to avoid zapping passing satellites! In addition, all the observatories on Mauna Kea liaise in order to avoid laser conflicts, filling in a central log of where theyíll be pointing their beams.
One of the visitors on my tour asked why Keck doesnít produce a calendar. The answer was unexpected. Apparently, Keck mostly studies distant object using wavelengths not conducive to Ďpretty picturesí (as Edí put it). However, the nearby CHFT telescope studies closer objects and does produce a calendar every year.
The Keck HQ is well worth a visit if youíre on Big Island (plan on an hour or two). I found both the displays and talk a rich source of answers to all the questions I had after my summit tour.
Keck domes with Subaru behind.