Tuesday, 5 February 2013

Exploring the Summit

View of the telescopes taken from a helicopter
from the north-east, CFHT closest, IRTF & Keck on the right
http://www.ifa.hawaii.edu/images/aerial-tour/aerial-tour.html
The summit of Mauna Kea is host to thirteen telescopes right now, ranging in flavour from the radio to the sub-millimetre and infrared.  They're clustered together in loose groups - five telescopes sit on summit ridge on the eastern side (the Canada-France-Hawaii telescope, or CFHT; Gemini-North; the University of Hawaii 2.2-m telescope; the United Kingdom Infrared Telescope, UKIRT; and an educational telescope for the University of Hawaii).  Driving from east to west, you then come to the Infrared Telescope Facility (IRTF), the twin Keck domes and the Japanese Subaru telescope.  Then lower down from the summit we find the James Clerk Maxwell Telescope (JCMT), the Caltech Sub-Millimetre Observatory (CSO) and the Sub-Millimetre Array (SMA).

Over the last few years we (i.e., outer planet observers) have used several of these observatories, in addition to the IRTF which has been our major workhorse:

Gemini-North and CFHT in the background,
at sunset on Feb 4th 2013
Gemini North features an 8.1-m primary mirror and has been running since 2000, but the UK sadly pulled out of the Gemini science partnership as of the end of last year.  Sometimes the ALTAIR adaptive optics system can be seen using a laser guide star, a beam of light high overhead that allows the telescope to correct for the turbulence of the Earth's atmosphere.  We've used the NIFS instrument in the past to study the clouds of Uranus and Neptune in the near-infrared (e.g., Irwin et al., 2012, http://dx.doi.org/10.1016/j.icarus.2012.05.017), and the MICHELLE mid-infrared instrument to analyse the 2009 impact event on Jupiter (e.g., de Pater et al., 2010, http://dx.doi.org/10.1016/j.icarus.2010.07.010).  Much of these observations are conducted remotely, generating observing routines in large software programs which are then submitted to the night astronomers for execution.

Subaru (left) and the twin Keck telescopes at sunrise
on February 4th 2013.
Subaru is a Japanese 8.2-m telescope that has been operating since 1999, just next to the twin Keck telescopes, and run by the National Astronomical Observatory of Japan.  I've been lucky enough to visit Subaru twice, where the observations are conducted from an office building right next to the dome, but you don't really get to see inside properly.  We've used the mid-infrared instrument Subaru/COMICS (Cooled Mid Infrared Camera and Spectrometer) to track the evolution of giant vortices on Jupiter (e.g., Fletcher et al., 2010, http://dx.doi.org/10.1016/j.icarus.2010.01.005) and the changing polar atmosphere of Neptune (e.g., Orton et al., 2012, http://dx.doi.org/10.1016/j.pss.2011.06.013).

I've never used the twin Keck telescopes directly, but I did get a guided tour back in 2005.  These two domes have the largest mirrors on the summit at 10-m diameter.  Each mirror consists of 36 hexagonal segments which can all move to correct for the atmospheric distortion. There are delay lines in the building between the two domes that allow the two telescopes to be combined to form an interferometer.  I've helped analyse data from the LWS (Long Wave Spectrometer), which was taken off the telescope before I started observing, but my US colleagues have used LWS to detect polar hotspots on Saturn (Orton and Yanamandra-Fisher, 2005, http://dx.doi.org/10.1126/science.1105730) and to get images and spectra of Neptune (de Pater et al., in prep.).
UKIRT at sunset on February 4th 2013

Oxford colleagues have used the 3.8-m UKIRT on several occasions for all four gas giant planets, but that era is sadly coming to an end after the UK shuts down this facility at the end of this year.  UKIRT has been operational since 1979, but since 2010 the telescope has been operating remotely, conducting a deep sky survey (UKIDSS) with the WFCAM instrument (a wide field imager).  Just before it switched to this mode, we used WFCAM to observe the interaction of Jupiter's Oval BA and Great Red Spot in September 2010.  Oxford colleagues Irwin et al. (2010, http://dx.doi.org/10.1016/j.icarus.2010.03.017) had previously used the UIST instrument (0.8-5 ┬Ám spectrometer) to study the clouds of Uranus between September 2006 and July 2008, either side of the 2007 equinox.



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