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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 |