Wednesday, January 13, 2016

A New Life for an Old Friend!

If you can have favorite telescope, mine would likely be the 2.1-Meter Telescope atop Kitt Peak. Dedicated and brought on-line in 1964, it is a beautiful, classical, equatorial fork-mounted telescope. When I worked there back in the early 80s, it was a favorite of mine - beautiful, easy to work on and change instruments, simple and elegant in design. The mechanicals were built by Willamette Iron and Steel from Portland, Oregon, normally making ocean-going ships and large steam boilers. The mirror was polished in the basement of the NOAO offices optics shop on Cherry Street, from a Pyrex disk cast at Corning Glass. Shown at left, the white telescope moves north-south inside the fork, which rotates east-west to allow access to all parts of the sky. Once an object is aligned, a simple rotation of the fork will keep it centered, since the fork axis is aligned to the Earth's axis. In the rear at ground level is the console room, from which it is operated (built on my watch in 1980!), and the ever-present white spot used to calibrate CCD detectors. The instrument shown here at left is Phoenix, an IR spectrometer.

The past few decades, the National Science Foundation (NSF) has slowly been divesting itself of support of the telescopes at Kitt Peak as budgets get tight. Back in the 80s, the staff supported 9 stellar telescopes, all of which could be used by astronomers around the country if their research was deemed important enough. Kitt Peak is no longer so much a National Observatory, as a collection of private, consortium-operated telescopes as various groups have stepped in to operate them. Only the WIYN and 4-meter have any time available for access, and that is severely restricted to a few blocks of time, or administered thru NASA (for WIYN). It was sad to see the announcement nearly 2 years ago when new tenants for the 2.1 were sought.

Courtesy Robo-AO and Caltech
There were four serious candidates, and finally this last September, it was announced that California Institute of Technology's (Caltech) Robo-AO program would take over the facility. There was some word of an adaptive-optics (AO) program, but details were not quickly forthcoming. AO is exciting stuff - a product of "Star Wars" technology of the late 80s that use deformable mirrors to correct the blurring effects of the Earth's atmosphere. It has been the goal of many astronomer teams to get images similar in sharpness to that of the Space Telescope, from within this ocean of air we live in, with various amounts of success.

Laser Projector, dome lights on, off. 
Courtesy Robo-AO, Caltech
I didn't know much about the Caltech program, but last night I scored an invite to a lecture by one of the scientists from the program - Reed Riddle talked to the Kitt Peak docents about the program and some of their results. Shown at left is the dome of the 2.1 meter telescope, now in use by Robo-AO, since they moved in early November! The image is misleading - the instrument uses a laser to create an artificial guide star, but it emits a beam in the ultraviolet that is invisible to the eye. Shown here is an image from a camera that has been modified - the UV blocking filter has been removed and the laser is now visible by UV leaks in the bayer filter matrix, now visible to the sensor, but still not to the eye.

Otherwise the system is similar to others. Because the laser works in the UV, it has the benefit that it does not bother pilots or airplanes, so the FAA has no objections to its use. Also because of the short wavelength used, corrections can be made in the visible part of the spectrum. Most artificial guide stars use visible light, so would interfere with visible applications. Most of these systems do their science in the near infrared wavelengths. The 10 watt laser is diverged to about 15cm before projecting, and is precisely aligned with the telescope view. Focused about 10km altitude (6 miles up), it makes an artificial guide star about 2cm diameter visible from Rayleigh scattering. While not quite at the top of the atmosphere, it can be used to correct much of the effects of atmospheric turbulence. The artificial star is imaged by the telescope, and run through a Schack-Hartmann sensor which controls a 140-segment flexible mirror in a feedback loop to correct for turbulence.

You can't argue with the results! Shown here is a video of Saturn from their early results with the Palomar 60" - the first half of the clip is without the AO turned on, the second half shows the results when turned on:

They literally walked into the facility 2 months ago and are really still getting things working, but early results are encouraging. Reed showed us star images that readily showed diffraction rings, and you can't really do better than that! They have extensive programs in observing Kepler objects that show exoplanets, as well as a number of high-resolution imaging including planetary disks, multiple stars and centers of star clusters. They are still looking for observing ideas, since instead of a week or two of observing time, they will now have unlimited telescope use at the 2.1 meter. Lucky them!

If you are interested in the gritty details of their instrument, check out this 10 minute video, or if you are really hardcore, you can watch this hour-long Caltech Astronomy Colloquium presentation... I'm just glad one of my lil' beauties is enjoying a new life!

ADDENDUM: I had an e-mail discussion with one of the administrators at Kitt Peak, about my concerns it was really no longer a "National Observatory", since most of the telescopes have been transitioned to private control. He correctly pointed out that the 4-Meter Mayall, the 3.2 Meter WIYN and the 2.1 Meter, now controlled by the Caltech Robo-AO are all promising a percentage of their time to competively-awarded research projects. In addition, many of the major projects these large telescopes are transitioning to will have data publicly-available, so able to be widely used by the astronomical community. So while directly-assigned telescope time is continues to be a rarity, the treasure-trove of data that will become available to the public could still qualify it as a true National Observatory!

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