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cso:instruments:heterodyne:observing [2014-01-22 18:54]
sradford
cso:instruments:heterodyne:observing [2014-01-29 00:16] (current)
sradford
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 +====== Heterodyne Observations ======
  
 +This is a brief introduction to heterodyne observing at the CSO. 
 +It continues from the general [[.:​..:​..:​observing:​operating]].
 +
 +  * [[#Quick Start]]
 +  * [[#After Observing]]
 +
 +  * Preparation
 +    * [[heterodyne]] systems description
 +    * [[obstime]] calculation
 +    * Source and line [[cso:​telescope:​uip:​catalog|catalog]] preparation
 +    * Planning for [[wideband]]
 +      * [[http://​cso.caltech.edu/​atm/​tuning.html|Receiver tuning diagram]]
 +    * Tuning [[.tuning:​sidecab|narrow band]] and [[.tuning:​barney]] receivers
 +  * Types of Observations
 +    * [[chop]]
 +    * [[onoff]]
 +    * [[pointing]]
 +    * [[fswitch]]
 +    * [[mapping|Mapping]]
 +    * [[otfmap]]
 +  * [[calibration]]
 +    * [[#Sideband Identification]]
 +  * [[analysis]]
 +  * [[#​Troubleshooting]]
 +
 +
 +
 +
 +===== Quick Start =====
 +
 +This guide outlines a common observing scenario, simultaneous [[chop]] observations of [[wideband#​example_1|three CO isotopologues]] in the (2-1) lines. There are many possible variations.
 +
 +  - [[cso:​observing:​remoteobs#​connect_to_the_vnc_desktop|Connect]] to the VNC desktops. Two desktops are used, one for the UIP and the other for the spectrometer displays. (This is more flexible than one large desktop.) \\ ''​mycomp>​ ** csovnc.pl -C -l //user// uip ** ''​ \\ ''​mycomp>​ ** csovnc.pl -C -l //user// spectro ** ''​
 +    * In the UIP desktop, there are two xterms on the right side:
 +      - The upper one displays the telescope status, updated once per second.
 +      - The lower one is for the UIP. 
 +  - In the UIP xterm, log into your account then start UIP. \\  ''​kilauea% **ssh //​user//​@kilauea**''​ \\ ''​kilauea% **uip**''​
 +  - If necessary, enable control mode. \\ ''​UIP>​ **pundit true**''​
 +  - Open the [[cso:​telescope:​shutter|shutter]]. Avoid the sun. When remote observing, wait until one hour after sunset. \\ ''​__UIP__>​ **shutter /open** ''​
 +  - Create a data file. \\ ''​__UIP__>​ **data //​yyyy-mm-dd//​**''​
 +  - Open source and line [[cso:​telescope:​uip:​catalog]],​ if necessary. \\ ''​__UIP__>​ **catalog //​sources//​**''​ \\ ''​__UIP__>​ **catalog //lines// /​line**''​
 +  - Start the [[cso:​telescope:​secondary]] wobbler for [[chop]]. Tuning the servo takes about 5 min. For example, 120 arcsec amplitude at 0.534 Hz. \\ ''​__UIP__>​ **secondary 120 0.534**''​
 +    * Check the status of the servo tuning. \\ ''​__UIP__>​ **secondary** '' ​
 +  - Select the receiver and verify the teritary mirror position. ​
 +    * For the sidecab receivers, first place the telescope at 25° zenith angle. \\ ''​__UIP__>​ **za 25** ''​ \\ ''​__UIP__>​ **instrument [RX230 | RX345 | RX460 | RX690]**''​ \\ ''​__UIP__>​ **tertiary /​sidecab**'' ​
 +    * For the Cassegrain receivers, first remove the mirror covers and manually rotate the tertiary mirror. \\ ''​__UIP__>​ **instrument [RX345X | RX805]**''​ \\ ''​__UIP__>​ **tertiary /​cassegrain**'' ​
 +  - If necessary, load the appropriate pointing file. \\ ''​__UIP__>​ **point //​rx_name//​**''​
 +  - Tune the receiver. For example, the standard tuning for [[wideband#​example_1|three CO isotopologues]]. \\ ''​__UIP__>​ **lo 12co2-1 /side up /if 5.28**''​ \\ Older receivers require manual tuning.
 +    * [[.tuning:​sidecab]]
 +    * [[.tuning:​barney]]
 +  - Configure the spectrometers ([[ffts1|FFTS1]],​ [[ffts2|FFTS2]],​ [[aos5|AOS5]]). \\ ''​__UIP__>​ **spec 2 /ffts2 /ffts1w 5.28 /res ** ''​
 +    * For the older narrow band receivers, turn on the [[aos5#IF processor]] {{ifprocswitch.jpg?​linkonly|switch}} in the [[aos5|AOS5]] {{aos5rack.jpg?​linkonly|rack}}.
 +  - [[calibration|Calibrate]] and measure the system temperature. \\ ''​__UIP__>​ **cal**''​
 +  - Measure the [[pointing]] with [[chop]]. \\ ''​__UIP__>​ ** spec /base 2500 3500 4700 5700 **''​ \\ ''​__UIP__>​ **five 20 /ffts1 /range 4000 4200 ** ''​
 +    * Use the [[cso:​telescope:​orrery]] to select pointing sources. ​
 +  - Take a reference spectrum of the pointing source with [[chop]]. \\ ''​__UIP__>​ **chop 2**''​
 +    * Maybe useful as a [[calibration]] reference.
 +  - Track the target source. \\ ''​__UIP__>​ **obs //​target//​**''​
 +  - [[calibration|Calibrate]] and measure the system temperature. \\ ''​__UIP__>​ **cal**''​
 +  - Set the integration time. \\ ''​__UIP__>​ **spec 10**''​
 +  - Observe the target.
 +    * With [[chop]]. \\ ''​__UIP__>​ **chop 10**''​
 +    * For [[onoff]], first stop the [[cso:​telescope:​secondary]] wobbler. \\ ''​__UIP__>​ **secondary /stop **''​ \\ ''​__UIP__>​ **oo 10**''​
 +
 +===== After observing =====
 +
 +  - Close the [[cso:​telescope:​shutter|shutter]]. This takes 10-15 min. When remote observing, please close one hour before sunrise. \\ ''​__UIP__>​ **shutter /​close**'' ​
 +    * If the shutter doesn'​t close, follow these [[cso:​telescope:​shutter#​troubleshooting|instructions]]. Please report problems to the staff. ​
 +  - Stow the telescope \\ ''​__UIP__>​ **stow**''​ \\ After sunrise, wait until the shutter is no more than 15% open before using the ''​**stow**''​ command. Please do //not// let the Sun directly illuminate any part of the telescope structure. Check the [[http://​www.cso.caltech.edu/​webcams.html|CSO webcams]]. ​
 +  - Stop the secondary wobbler \\ ''​__UIP__>​ **sec /​stop**''​
 +  - Turn off the [[aos5#​if_processor|IF processor]] in the [[aos5|AOS5]] rack.
 +  - Turn off the receiver.
 +    * For the 230/460 GHz receiver: ​ \\ ''​__UIP__>​ **lo /​off**''​
 +    * For the older receivers: [[cso:​instruments:​heterodyne:​tuning:​sidecab#​shutdown]] procedure
 +    * For Barney: [[cso:​instruments:​heterodyne:​tuning:​barney#​shutdown]] procedure
 +  - Replace the Cassegrain mirror covers.
 +  - Exit from the UIP. \\ ''​__UIP__>​ **exit**''​
 +  - Exit from your account but please do not close the UIP xterm in the VNC desktop. ​
 +  - Stow any ladders or other equipment.
 +  - Return the pointing log book to the shelf. \\ Heterodyne observers please add your nightly pointing sheet to the end the log book and return the book to the bookshelf. ​
 +  - Please submit an [[cso:​observing:​obsreport]].
 +  - Logout from kilauea and other computers.
 +  - Turn off all the lights and heaters in the building. ​ Lock both entry doors. ​   ​
 +
 + // Drive safely! ​ //   
 +
 +===== Sideband Identification =====
 +
 +The CSO has DSB receivers with equal gain in the two sidebands. ​
 +To determine if specific lines are in the upper or the lower side band, change the LO frequency. ​
 +Lines in the two sidebands will shift in opposite directions.
 +Lines in the image sideband will shift twice as far as lines in the signal sideband. ​
 +
 +  * To change the LO by 5 MHz, \\ ''​__UIP__>​ **lo /f_off 0.005**''​
 +
 +If the atmospheric transmission in the two sidebands is different, [[calibration]] correction will be necessary. ​
 +
 +===== Troubleshooting =====
 +
 +  * If the system temperature is unreasonably high for the [[http://​www.cso.caltech.edu/​tau|optical depth]] (//τ//) or [[cso:​weather:​weather|weather]] conditions.
 +    * Is the [[aos5#​if_processor|IF processor]] in the [[aos5|AOS5]] rack on?
 +    * Is there a warm load or something else in the beam?
 +    * Are the cassegrain mirrors uncovered?
 +    * Is the position of the tertiary mirror correct?
 +    * Are the sidecab mirror positions correct? To reposition them, \\ ''​__UIP__>​ **za 25**''​ \\ ''​__UIP__>​ **lo //line// /receiver //rx_name// /force** ''​
 +    * Is the line frequency close to an atmospheric line? \\ Check the [[http://​www.submm.caltech.edu/​cso/​weather/​atplot.shtml|atmospheric transmission]]. ​
 +    * Is the [[cso:​telescope:​shutter|shutter]] closed? ​
 +    * Is the [[http://​www.cso.caltech.edu/​tau|optical depth]] (//τ//) high and the zenith angle large?\\ Wait for the source to rise. 
 +    * Is the [[cso:​weather:​weather|weather]] worse than you thought?
 +    * Is the [[.tuning:​sidecab#​345ghz|345 GHz sidecab receiver]] tuned to the fifth harmonic? ​
 +
 +  * If there'​s no line even though the system temperature is reasonable and the source should have a bright line.
 +    * Is the correct pointing model displayed on the antenna status monitor?  ​
 +    * Is the pointing good?
 +    * Is the frequency correct? Check the catalog.
 +    * Is the receiver tuned properly?
 +
 +  * If the spectrometer stops, restart it (specify the backend). \\ ''​__UIP__>​ **spectrometer /​restart ​ /ffts2 ...**'' ​
 +
 +=== ===
 +
 +These older documents may contain obsolete information. Use with caution.
 +
 +  * {{cookbook.pdf|Cookbook}} 2011-06-22
 +  * {{checklist.pdf|Checklist}} 2011-06-22
 
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