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cso:telescope:dsos:dsos [2012-09-25 12:09]
cso:telescope:dsos:dsos [2013-08-28 08:32] (current)
sradford [Instructions]
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 +====== Dish Surface Optimization System ======
 +The CSO is one of a very few radio telescopes with an active surface correction system.
 +This Dish Surface Optimization System (DSOS) improves the telescope efficiency by
 +altering the primary mirror surface to correct for static imperfections and for changes in gravitational deformation as the telescope moves in zenith angle (elevation). ​
 +The consequent improvement in the telescope'​s aperture efficiency is significant at shorter wavelengths,​ in particular at 350 µm wavelength.
 +===== Instructions =====
 +  * [[userproc]]
 +  * {{DSOS_Test.pdf|Test procedures}} 2011-09-27
 +===== Description ===== 
 +The CSO's 10.4 m primary mirror is made up of 84 hexagonal panels with aluminum skins and honeycomb cores. ​
 +The panels are connected to the backing structure by 99 steel rod standoffs.
 +Each standoff is fitted with a (Peltier) heating/​cooling assembly so it can be elongated (heated) or contracted (cooled).
 +A controlled potential is applied to each of the 99 assemblies to adjust the shape of the primary mirror.
 +The necessary standoff lengths were determined from holography measurements of the telescope over a range of zenith angles.
 +Holography measurements indicate the DSOS improves the surface accuracy of the telescope to about 11 µm rms 
 +compared to about 25 µm rms without the system. ​
 +This would correspond to an improvement in aperture efficiency from 33% to 79% at the 350 µm wavelength.
 +The CSO's holography instrument, however, operates in the range of roughly 230 to 460 GHz.  ​
 +Additionally improvement in efficiency does not translate linearly to higher frequencies.  ​
 +As a result, of course, efficiency measurements at the 350 µm wavelength range were done. 
 +About a 71% best and 60% average improvement in peak signal power was measured.  ​
 +Which is about 56% efficiency.
 +These excellent results were measured with instruments mounted on the Cassegrain focus. ​
 +Instruments mounted on the Nasmyth focus (N2) also see marked improvements but do not benefit as much from the newer correction table. ​
 +Steps are being taken to determine the adjustments of the DSOS to best optimize performance of the telescope out to N2.
 +The DSOS has been in operation on the CSO since February 2003.  ​
 +Observers using SHARCII and the 850 GHz heterodyne receiver have been able to detect new weak and/or distant objects including with the help of this unique active optics system.
 +  * [[http://​www.cso.caltech.edu/​dsos/​DSOS_MLeong.html|Background information]]
 +===== Results ===== 
 +==== References ==== 
 +CSO Technical Briefing, Hilo, HI, October 2007
 +{{2007-leong.pdf|Update to the CSO Submillimeter Active Optics System}},\\
 +Leong, M. M., 2007, CNC/​USNC/​URSI North American Radio Science Conference, Ottawa
 +{{2006-leong.pdf|A CSO Submillimeter Active Optics System}},\\
 +Leong, M., Peng, R., Houde, M., Yoshida, H., Chamberlin, R., and Phillips, T., 2006, Proc. SPIE 6275, 62750P
 +{{2004-leong.pdf|A CSO Submillimeter Active Optics System}},​\\ ​
 +Leong, M., 2005, USNC/URSI National Radio Science Meeting, Boulder, p. 426
 +{{2003-leong.pdf|Dish Surface Optimization System: Surface Correction on a 10.4-meter Leighton Primary Mirror}},\\
 +Leong, M., Houde, M., Peng, R., Yoshida, H., Chamberlin, R., Phillips, T. G., 2003,
 +in AMOS Conference Proceedings,​ ed. P. Kervin, and J. Africano, AFRL/MEDB, Kihei, HI
 +{{2002-staff.pdf|A method for implementing the CSO surface correction hardware: Memo No. 1}},\\
 +CSO Staff (M. Leong, ​ R. A. Chamberlin, ​ M.  Houde, ​ R. Peng,  T. G. Phillips, ​ H. Yoshida), 2002 October 18
cso/telescope/dsos/dsos.txt · Last modified: 2013-08-28 08:32 by sradford
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