http://cso.caltech.edu/wiki/ 2026-09-21T15:10:48+00:00 http://cso.caltech.edu/wiki/ http://cso.caltech.edu/wiki/lib/tpl/cso/images/favicon.ico text/html 2014-11-18T01:08:05+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/analysis?rev=1416272885&do=diff Heterodyne Data Analysis CLASS is used at the CSO for analysis of heterodyne data. CLASS is part of the IRAM GILDAS package. The entire package is available on the CSO computers. You may also install GILDAS on your own computer. Please refer to the GILDAS documentation for installation instructions, tutorials, etc. text/html 2015-01-29T01:20:52+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/aos5?rev=1422494452&do=diff Array Acousto Optic Spectrometer (AOS5) Developed for the CSO by the University of Köln, the Array Acousto Optic Spectrometer (AOS5) is available with the 345 GHz and 650 GHz narrow band sidecab receivers, the wide band 345 GHz receiver (Barney), and the 850 text/html 2015-01-30T01:37:08+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/calibration?rev=1422581828&do=diff Calibration For heterodyne observations, there are three types of calibrations: temperature (chopper) calibration, telescope efficiency, and (if necessary) AOS frequency calibration. It is best to calibrate regularly. * determines TA*, the antenna temperature corrected for atmospheric absorption and ambient temperature telescope losses, and measures the system temperature. text/html 2014-04-09T21:35:59+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/chop?rev=1397079359&do=diff Beam Switching Single dish observations are explicitly differential: the signal from the On position (target+sky) is compared with the signal from the Off position (sky only). Beam switching is (usually) used for observations of compact sources. The wobbling (chopping) text/html 2013-12-12T01:23:47+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/cryogenfills?rev=1386811427&do=diff Cryogen Fills All the heterodyne receivers at the CSO require periodic cryogen service. Hybrid cryostats The sidecab receivers and the 850 GHz receiver are housed in hybrid cryostats, with mechanical Gifford McMahon coolers and a liquid helium (LHe) reservoir. The CSO staff will service these receivers. text/html 2014-09-23T19:12:23+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/ffts1?rev=1411499543&do=diff Fast Fourier Transform Spectrometer (FFTS1) Developed for the CSO by the Max-Planck-Institut für Radioastronomie (MPIfR), the Fast Fourier Transform Spectrometer (FFTS1) is available with all the heterodyne receivers. This spectrometer has two modes, wide (1000 text/html 2013-12-07T05:24:00+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/ffts2?rev=1386393840&do=diff Wideband Fast Fourier Transform Spectrometer (FFTS2) Originally acquired for the CASIMIR instrument intended for SOFIA, a new FFT spectrometer (FFTS2) is now available with the wide band heterodyne receivers. At present, FFTS2 has two IF modules and four FFT modules. Each IF module divides a 4 text/html 2013-04-16T19:18:20+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/fswitch?rev=1366139900&do=diff Frequency Switched Observations Frequency switching at the CSO is implemented by switching the first LO. Observing The basic UIP command is: FSWITCH <Separation(MHz)> [<Cycles>] The two line images will be separated by twice the Separation, symmetrically offset from 0. For example, to use 3 s integrations, ±10 text/html 2014-05-07T22:54:45+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/heterodyne?rev=1399503285&do=diff Heterodyne Systems Instructions for Heterodyne Observations. Heterodyne systems at the CSO permit high resolution spectroscopy in the atmospheric windows from 177 to 920 GHz. Receivers Characteristics Receiver Range IF BW Trx Tuning Remarks Status text/html 2014-04-09T21:52:20+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/mapping?rev=1397080340&do=diff Mapping Heterodyne mapping is done by offset pointing the telescope. Especially for larger maps, OTF mapping is more efficient for larger maps because a common reference position is used for all the cells in each row. UIP commands * Point by point mapping using position switching with a specified reference position. This example uses looping commands to make a 3 x 3 map in equatorial coordinates with 15 arcsec spacing. text/html 2014-01-29T00:16:51+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/observing?rev=1390954611&do=diff Heterodyne Observations This is a brief introduction to heterodyne observing at the CSO. It continues from the general Introduction to Observing. * * * Preparation * Heterodyne Systems systems description * Observing Time calculation * Source and line catalog preparation * Planning for Wideband Observations * text/html 2014-04-15T00:05:52+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/obstime?rev=1397520352&do=diff Observing Time For heterodyne observations, estimate the sensitivity with the radiometer equation: * Trms = K Tsys (t ∆f )-1/2, where Tsys is the system temperature, t is the integration time, ∆f is the channel width, and K ≈ 2, depending on the switching scheme and observing strategy. Invert this equation to estimate the necessary observing time. Do not neglect to add overhead for setup, pointing, calibration, etc. text/html 2014-04-09T21:33:05+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/onoff?rev=1397079185&do=diff Position Switching Single dish observations are explicitly differential: the signal from the On position (target+sky) is compared with the signal from the Off position (sky only). In position switching, the telescope points back and forth between the target and a nearby blank sky position. text/html 2015-05-29T02:00:05+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/otfmap?rev=1432864805&do=diff OTF mapping During On The Fly (OTF) mapping, the data are recorded continuously while the telescope is scanning across the field. A common Off position is used for each row. Compared with point by point mapping, OTF mapping can be twice or more times as fast. text/html 2014-01-22T19:01:34+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/pointing?rev=1390417294&do=diff Pointing Point often for the first 2--3 hours after sunset because the pointing will shift as the temperature of the telescope changes (thermal pointing shifts). Repoint no later than an hour after the initial pointing. Repoint every 2.5--3 hours thereafter. Beam switching with the wobbling text/html 2014-04-16T22:23:03+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/sidecab_rxb?rev=1397686983&do=diff Wide Band Sidecab Receivers The 230 GHz and 460 GHz wide band sidecab receivers are housed in a single cryostat. They have 4 GHz bandwidths (4-8 GHz IF) and synthesized local oscillators. They were installed in 2012 May. These receivers are tuned automatically by a dedicated computer. Receiver tuning takes about a minute. For example to observe text/html 2015-07-19T03:23:19+00:00 http://cso.caltech.edu/wiki/cso/instruments/heterodyne/wideband?rev=1437276199&do=diff Wideband Observations With the wideband receivers it is possible to observe several lines simultaneously. Indeed extra lines will be there anyway in many sources so it's advantageous to tune them deliberately. At some frequencies, atmospheric absorption lines may complicate the tuning. For successful observations, some care is required for proper tuning and spectrometer setup and some additional steps are necessary during data reduction. To distinguish between lines in the two sidebands, it is …