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--- cso:instruments:heterodyne:analysis [2013-11-10 04:07]
sradford
+++ cso:instruments:heterodyne:analysis [2014-11-18 01:08] (current)
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@@ Line 1: / Line 1: @@
+====== Heterodyne Data Analysis ======
+[[http://www.iram.fr/IRAMFR/GILDAS/doc/html/class-html/class.html|CLASS]] is used at the CSO for analysis of heterodyne data. CLASS is part of the [[http://www.iram.fr|IRAM]] [[http://www.iram.fr/IRAMFR/GILDAS|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.
+=== Getting started ===
+  - Connect to kilauea with X window transport \\ ''mycomp> **ssh -X //user//@kilauea.caltech.edu**''
+    * Not necessary if you have installed GILDAS and transferred the data to your computer.
+  - Move to your data directory \\ ''kilauea> **cd //data_directory//**''
+  - Start CLASS \\ ''kilauea> **class**''
+  - Open a graphics window, if necessary \\ ''LAS> **device image** ''
+  - Open the data file \\ ''LAS> **file in //mydata//.cso** ''
+  - List the contents  \\ ''LAS> **list in** ''
+  - Choose a spectrum \\ ''LAS> **get //N//** ''
+  - Plot the spectrum \\ ''LAS> **plot** ''
+=== Data access ===
+  - Access the CSO computer \\ ''mycomp> **sftp //user//@kilauea.caltech.edu**''
+  - Move to your data directory \\ ''sftp> **cd //data_directory//**''
+  - Transfer data to your computer \\ ''sftp> **get //mydata//.cso**''
+  - End sftp session \\ ''sftp> **exit**''
+=== Example ===
+Analyse simultaneous observations of <sup>12</sup>CO, <sup>13</sup>CO, and C<sup>18</sup>CO in IRC 40540, an evolved star, made on 2114-11-16. During the observations, the receiver was tuned for <sup>12</sup>CO(2-1) but a tuning shift was deliberately introduced between between the first spectrum and the others. For the receiver tuning, see [[wideband]], [[wideband#example1|Example 1]].
+  * Data overview
+    * Notice the strong <sup>12</sup>CO(2-1) line in the center and weaker <sup>13</sup>CO(2-1) line on the left edge. C<sup>18</sup>CO(2-1) is not obvious.
+    * Notice the shift of the <sup>12</sup>CO(2-1) line.
+<code>
+file in 2014-11-16.cso                      ! open data file
+list in                                     ! list contents
+find /source IRC40540 /tel "CSO FFTS 1W"    ! select FFTS1 data
+stamp /scan
+</code>
+{{irc40540-stamp.png?800}}
+  * Analyse <sup>12</sup>CO(2-1)
+    * Because the receiver was tuned for <sup>12</sup>CO(2-1), the sideband and reference information is correct for all four spectra. Hence the spectra may be averaged directly.
+<code>
+file in 2014-11-16.cso                      ! open data file
+list in                                     ! list contents
+find /source IRC40540 /tel "CSO FFTS 1W"    ! select FFTS1 data
+set align v i                               ! select velocity alignment, intersect region
+average /resample                           ! average the spectra
+set unit v f                                ! set the display axes, velocity (bottom) and frequency (top)
+set mode x -67 33                           ! set the display limits [km/s]
+plot
+</code>
+{{irc40540-12co.png?800}}
+  * Analyse <sup>13</sup>CO(2-1)
+    * Because <sup>13</sup>CO(2-1) is in the image sideband, the reference information must be updated before the spectra may be averaged. This requires an intermediate, scratch file.
+<code>
+file in 2014-11-16.cso                      ! open data file
+list in                                     ! list contents
+find /source IRC40540 /tel "CSO FFTS 1W"    ! select FFTS1 data
+set variable spectro write                  ! enable modification of reference information
+set variable calibration write
+file out scratch1.cso multiple              ! open scratch file
+for i 1 to found                            ! modify each spectrum
+  get next
+  let r%head%spe%line 13CO2-1               ! set line name
+  @swap_sidebands 220398.6765               ! set reference info for 13CO(2-1)
+  write
+next
+file in scratch1.cso                        ! open scratch file
+list in                                     ! list contents
+find /source IRC40540 /tel "CSO FFTS 1W"    ! select FFTS1 data
+set align v i                               ! select velocity alignment, intersect region
+average /resample                           ! average the spectra
+set unit v f                                ! set the display axes, velocity (bottom) and frequency (top)
+set mode x -67 33                           ! set the display limits [km/s]
+plot
+</code>
+{{irc40540-13co.png?800}}
+  * Analyse C<sup>18</sup>O(2-1)
+    * Because C<sup>18</sup>O(2-1) is also in the image sideband, the reference information must be updated before the spectra may be averaged. This requires an intermediate, scratch file. Moreover, C18O is only barely detected so the spectral resolution must be reduced to see the line.
+<code>
+file in 2014-11-16.cso                      ! open data file
+list in                                     ! list contents
+find /source IRC40540 /tel "CSO FFTS 1W"    ! select FFTS1 data
+set variable spectro write                  ! enable modification of reference information
+set variable calibration write
+file out scratch2.cso multiple              ! open scratch file
+for i 1 to found                            ! modify each spectrum
+  get next
+  let r%head%spe%line C18O2-1               ! set line name
+  @swap_sidebands 219560.3568               ! set reference info for C18O(2-1)
+  write
+next
+file in scratch2.cso                        ! open scratch file
+list in                                     ! list contents
+find /source IRC40540 /tel "CSO FFTS 1W"    ! select FFTS1 data
+set align v i                               ! select velocity alignment, intersect region
+average /resample                           ! average the spectra
+set unit v f                                ! set the display axes, velocity (bottom) and frequency (top)
+set mode x -67 33                           ! set the display limits [km/s]
+smooth                                      ! reduce spectral resolution by 2^6 = 64
+smooth
+smooth
+smooth
+smooth
+smooth
+plot
+</code>
+{{irc40540-c18o.png?800}}