Friday, November 9, 2012

Astronomy Capital of the World?!

If you Google "Astronomy Capital of the World", you will learn that the Tucson area holds that distinction (also known as "Optics Valley" because of telescopes and startup optics-related companies here.  Not that you can believe everything you read on the Internet!  Not only is it home to Kitt Peak National Observatory, but there are also major observatories on Mount Graham, Mount Hopkins and Mount Lemmon, all within 60 air miles of Tucson.

But on Hawaii's "Big Island", stands Mauna Kea, certainly the largest concentration of big telescopes on one peak!  The Keck Observatory, the center two domes in the above image, when working together, would be considered the largest telescope in the world.  Fortunately, I have a friend who works there, Andrew Cooper, who gladly volunteered a tour when we visited a week and a half ago.  A tour is not without difficulty - at 14,000 feet elevation, there is only about half the oxygen available at sea level.  In addition, a high-clearance or 4-wheel drive vehicle is required to access the peak - rental cars are expressly prohibited from going there in the rental agreements!  Fortunately, the road to the 9,000+ foot level visitor center is very good, though very steep, and Andrew drove us up in his personal vehicle from there.

The Observatory is located near the center of the Big Island, on the tallest of the five shield volcanoes that dominate the Island.  It is accessed from the "Saddle Road" which can be seen running between Mauna Kea and Mauna Loa in the shortcut between the east and west sides of the Island.  Recent improvements make the trip to Hilo from the west arid side with the many resorts very pleasant.  The turnoff from the Saddle Road, while not unmarked, belie the significance of the activities atop the mountain. 

Of course, we had to stop for a few pictures!  While Mauna Kea is considered dormant, last erupting 4,600 years ago, there are many nearby "fresh" lava flows from adjacent Mauna Loa, which last erupted for a month in 1984 (as opposed to Kiluea, which has been continuously erupting for 30 years).  The flows shown here next to the turnoff are from Mauna Loa flows from 1935.  Even with the "new" lava surface, plant life can exist - it is part of the rehabbing of the surface, breaking up the rock to form new soil.  The smoothed-surface lava here is known as pahoehoe, as opposed to a'a lava which is very rough in texture, of which we also saw plenty.

Heading up the hill, the road ascended very quickly - few switchbacks in these lower sections - the road almost goes directly up the slope!  Just about when you think it can't get any steeper and you must be coming to the top, you crest a hill and see the peak still well ahead and fortunately, a flattish area with a visitor center, as well as support buildings for the various observatories - dormitories, dining halls and the like.  Staff and astronomers staying on the mountain can't sleep at 14,000 feet elevation, but rather at the lower elevation of Hale Pohaku.  Public visitors, staff and astronomers alike that ascend the mountain are supposed to spend at least 30 minutes to an hour to help their bodies acclimate to the change in elevation.  We don't think much of driving up Kitt Peak, Mount Lemmon or even the nearly 11,000 vertical feet of Mount Graham, but most all of those enjoy a base elevation of about 3,000 feet.  On Hawaii, you can drive from sea level to the 14,000 feet atop Mauna Kea in just over an hour, something your body would likely complain about!  The visitor center, by the way, shown at left here, is very nice - there is a very small seating area where a video is always playing describing various aspects of the observatories or mountaintop, static displays and exhibits, and also a very nice little store with great souvenirs.  They do a tremendous about with the limited space.  In addition to all that, they have free telescope viewing every night!  As you can imagine, they enjoy remarkable conditions from the small plaza, not only with the center's telescopes, but those sizable ones that amateurs bring up and volunteer.  Many tour companies take advantage of these offerings, and I did too on my first trip there 20 years ago.

Andrew arrived promptly shortly after we arrived at noon, and he talked up the place as we acclimated before we headed up for our 1pm tour.  His truck normally seats 4 plus the drive, but we had 5, so was a bit like a sardine can, but only for the 15 minute drive up the last leg of the trip.  It was a beautiful day - a perfect blue sky, made darker by the high altitude.  We sat in the staff area a bit while he checked in with the weekend staff, and found out what the work schedule was and where we could and couldn't go.  I was impressed with the company-supplied snack table, and I admit I took advantage of the dried mango - tasty stuff!

He led us through the room full of electronics and computers that he was intimately familiar with, since he works with those details every day.  It was all sort of a blur to me, but an impressive amount of wiring and blinking lights!  The next room over was the control room, where the telescope and instrumentation are controlled for the night's observing.  Giving everyone a chance to sit in the operators chair, it looks at left like Shannon thinks she broke something!  Among the displays were of the telescope position, weather conditions,  and telescope and mirror temperatures inside the dome, shown on the right.

Finally we made it out into the telescope enclosure.  The building looks small compared to the telescope - not a lot of space in the dome, including getting a wide-angle view of the scope.  I took some panorama shots of the scope, but my software has difficulty putting them together without bending the tubes of the telescope truss!  I'm still working on them...  At left Andrew shows us the Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE - I want the job that comes up with these acronyms!), a Cassegrain instrument that was not in use.  It is stored on the rails here near the edge of the dome, and when it is needed, the telescope points to the horizon away from the instrument, and it slides forward on the rails to mount to the rear of the telescope.  A cool way to do it!  At right is a wide view of the telescope.  The empty rails in the foreground likely belong to the instrument that is currently installed.

The telescope is quite different in basic design than the scopes that the University of Arizona help build.  This telescope, pioneered by Jerry Nelson back in the 80s, uses hexagonal segments that fit together to form the curved surface collecting area.  At the Mirror Lab we use a single mirror substrate of large diameter to collect the light.  Each design has their pros and cons - but they provide the best two examples of methods of making large modern telescopes.  In the image at left, you can see the very small gap (2 millimeters) between the hexagonal segments, each of which is about 1.6 meters across the hexagon.  The edges between adjoining segments have electronic detectors that monitor and control the positioning of the segments to maintain a continuous mirror surface.  The net result is a collecting surface that is about 10 meters in diameter.  While the Large Binocular Telescope, here in Arizona has two 8.4 meter mirrors, some instruments utilize both mirrors, which are equivalent to about 12 meter effective aperture.  Similarly, The Keck telescopes (there are actually 2 identical telescopes), has some instrumentation that use both scopes simultaneously, so total area would be larger than the LBT...  It is sometimes difficult to justify which is the largest telescope in the world!  Also in the left image is the tertiary mirror in the central assembly.  This third mirror in the optical train (after the segmented primary and smaller secondary mirrors) directs the light out to the Nasmyth Focus to the left in this image.  The image at right shows the azimuth hydrostatic (oil pad) bearings - the entire structure floats on a thin layer of pressurized oil.  Also seen at the center is the cable wrap up which provides electronic connections as the telescope rotates.  Also at far left is the tiny "monkey cage", a public viewing gallery where the public is welcome to check out the scope. 

While taking our tour, the staffers on duty moved the telescope and dome for us.  It was cool seeing it come alive!  I took some images for a time-lapse, we'll see if they get to be part of this post or another...

A our tour wound down, the girls warmed up in the staff area (it was pretty cold, near freezing in the dome), while Andrew showed me a couple items normally not part of even the "behind the scene tour".  Most impressive to me was the "mirror garage" - a semi-clean room (thus we weren't allowed in, but could peer through a cracked door) where the spare segments are kept.  The Keck Telescope has 36 segments, and because they occupy different parts of the mirror curve, there are actually 12 different shaped segments that can be swapped into place with short notice.  So there are 12 spares for the telescope, most in the garage, for substituting when a segment needs to come out for coating or other maintenance.  It was incredible to see them "standing at attention" like an army of little robots waiting to be put into use.  The other item I got to see was the aluminizing chamber (shown at right), about 2 meters in diameter, where they reapply a fresh aluminum coating after the old coating is removed.  The aluminum surface, exposed to weather and volcanic dust, is cleaned regularly (using a CO2 process), but eventually degrades and needs recoating every year or so.

Finally we were finished and walked out the back door and we got to "tour the mountain" as we walked around the building.  Andrew pointed out the new site where the "Thirty Meter Telescope" is currently designed to go.  Like Keck, it will have a segmented mirror, but much larger than Keck.  I took a panorama of the scopes on the east ridge, shown here at left.  from left is the NASA Infrared Telescope Facility (IRTF), the  Canada-France-Hawaii Telescope (CFHT), Gemini North Telescope, and the University of Hawaii 2.2 meter Telescope.  Interestingly, the last mirror was made by my buddy Bob Goff!

After a short drive up the hill in the above picture, we looked back towards the Keck Observatory.  As is normal, in the far distance between the domes is a view of the next Hawaiian island over, Maui, with the 10,000 foot tall mountain Haleakala, about 80 miles distant.  To the left of the Kecks is the Japanese National Telescope, also called the Subaru Telescope (Japanese for the Pleiades star cluster).  On the right is the IRTF again.  Down in the valley to the left are a number of radio telescopes.  From the small dome at left is the Caltech Submillimeter Telescope (CSO), the James Clerk Maxwell Telescope (JCMT), and the Submillimeter Array (SMA).  In all, there are 13 operational telescopes on Mauna Kea, about half the number of scopes at Kitt Peak, but the total area of scopes has a huge advantage for Hawaii.

Oh - and the time lapse?  Yes, I finally finished it, though I'm not completely happy with it - varying light levels (when am I going to learn to put exposure in MANUAL?!), needed to use wider lens, etc, etc...  Always easy to find fault - oh, and needs music too, but then, nearly all my time lapse clips need music!  For a REAL video of the inner workings of the Keck Observatory, check out Andrew Cooper's own spectacular version of behind-the-scene views!  He also has a blog post with some of the details.  Click the links and be amazed!  Oh, and Andrew - thanks for the Tour!

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