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Zpectrometer observing notes

1. Basic setup
2. Initialize for observing
3. Specify source pairs
   
4. Make flux density calibration
   
5. Specify source pair
   
6. Ppoint and focus near the target source pair.
   
7. Take a spectrum of the pointing source
   
8. Observe a target and nearby sky position
9. With a maximum time span of one hour, do another point and focus
10. Loop to step 6
11. When finished, run the shutdown procedure.
    

Basic setup

• Ask the telescope operator to configure for Ka-band observations.  This means:
  
• Ka-band receiver at the telescope focus.
• Active surface switched on.
• Your login will be "in the gateway" for telescope and system control.
  
• In another window, start CLEO by typing cleo & at the command prompt.  Use the tabs to launch the following CLEO screens:
• Launch -> Status       (brings up the status window to monitor observations)
  
• In another window, start Astrid by typing astrid & at the command prompt. 
  
• Choose to be online with control of telescope
• In the Run tab, choose
• Project: AGBT08C_073, or the appropriate session number; for the rest of the document, we assume this project
  
• Session number: keep the default, accept auto-updates
  
• Observer: as appropriate
  
• Operator: as appropriate
• In the Edit tab, choose
• Project: AGBT08C_073

Initialize for observing

• Configure for Zpectrometer observations
• Verify correct attenuator and phase cals are at the top of the zstartup script (if you don't know what these are, skip this)
• Highlight zstartup in Astrid's Observation Management 1 ->Run tab
• Hit the "submit" radio button on the screen once

Make flux density calibration

• Prepare or check the pointing script
  
• In the Astrid editor, open  zpoint
• Choose a standard flux calibrator for passband gain and flux calibration; we use 3C48 and 3C286 as primaries.  You can also use the pointing source and cross-calibrate later.
  
• Save the file
• Run  zpoint to slew to the source and point on a standard pointing source near the science source.  Commands at the beginning of the file disconnect the Zpectrometer from the IF and connect the DCR in its place.
• During auto-point
• Verify that the pointing is running well and the offsets are reasonable by looking at the data and fits by selecting Astrid's Data Display 1 -> Pointing tabs.  
• After the first pointing of the session, relax pointing heuristics with Tools -> Options -> Heuristics -> Relaxed.  Depending on the pointing source's strength, the fit may or may not converge without having relaxed heuristics.  If the fit fails but looks reasonable, ask the operator to enter the offsets manually.
• It may be necessary to select the "Raw" mode to get good fits.  In the Data Display tab, select Tools -> Options -> Data Processing, then pick the Total Power button.  If this is the case, the telescope operator may have to enter the fit results manually.  X/Left should also be selected.  
• Note down the pointing offsets for future reference; it may be useful to know that we have drifted by half a beam since the last pointing
  
• During auto-focus
• Verify that the focus offsets are reasonable by looking at the data and fits by selecting Astrid's Data Display 1 -> Focus tabs. 
  
• It may be necessary to select the "Total Power" mode to get good fits; Tools -> Options -> Data Processing, then pick the Total Power button.  If this is the case, the telescope operator may have to enter the fit results manually.
• Note the Az and El pointing offsets; check that these update in the "Status" screen.
• Write down the focus peak value and offset for future reference if only to reassure ourselves later that the gain hasn't changed significantly.
• Take two or three spectra of the calibrator source with the znod1Cal script (you will need to comment out all but the desired source in this script).  These data will be used in the reduction script to correct for passband gain variations and set the flux scale.  This script does not observe a sky position, but is reasonable as long as the calibration source flux density is much larger than the typical 30-70 mJy optical offset between nod beam positions.  
  

Specify the source pairs

• In Astrid select the Observation Management 1 -> Edit tabs and open znod2N
• Add sources to the source lists as needed, in either J2000 or B1950 coordinates.  The sources are in pairs; if the secondary source is sky, precede its name with SKY (e.g. W51, SKYW51), and give it a position about 5 arcmin away (a Dec offset is easiest).  Following the pattern in the file, comment out all other sources and add the source pair to the list.
• Select the number of pair repeats nrepc;  nrepc = 1 is good at the beginning to make sure everything is running well, and nrepc = 7 provides an hour of integration.  Leave the integration time at zpNumNodSR = 24 for standard observing.  This gives a 4 minute cycle time, as assumed by the data analysis software.  
• Save the file.

Slew to pointing source near targets, point and focus

• Prepare or check the pointing script
  
• In the Astrid editor, open  zpoint
• Add the target source to the source list if needed.
  
• Save the file.
  
• Run  zpoint to slew to the pointing source and point.  Commands at the beginning of the file disconnect the Zpectrometer from the IF and connect the DCR in its place.
• During auto-point
• Verify that the pointing is running well and the offsets are reasonable by looking at the data and fits by selecting Astrid's Data Display 1 -> Pointing tabs.  
• After the first pointing of the session (this should have happened by now), relax pointing heuristics with Tools -> Options -> Heuristics -> Relaxed.  Depending on the pointing source's strength, the fit may or may not converge without having relaxed heuristics.  If the fit fails but looks reasonable, ask the operator to enter the offsets manually.
• It may be necessary to select the "Raw" mode to get good fits.  In the Data Display tab, select Tools -> Options -> Data Processing, then pick the Total Power button.  If this is the case, the telescope operator may have to enter the fit results manually.  X/Left should also be selected.  
  
• Write down the pointing offsets for future reference; it may be useful to know that we have drifted by half a beam since the last pointing
  
• During auto-focus
• Verify that the focus offsets are reasonable by looking at the data and fits by selecting Astrid's Data Display 1 -> Focus tabs. 
  
• It may be necessary to select the "Total Power" mode to get good fits; Tools -> Options -> Data Processing, then pick the Total Power button.  If this is the case, the telescope operator may have to enter the fit results manually.
• Note the Az and El pointing offsets; check that these update in the "Status" screen.
• Write down the focus peak value and offset for future reference if only to reassure ourselves later that the gain hasn't changed significantly

Take a spectrum of the pointing source

• Edit znod1Cal to make the pointing source active.
• Run the script once or twice to get a spectrum of the pointing source.

Observe the source for one hour, maximum

• Verify that the source pair is correct in the current  znod2N script.
• Start the integration:
  
• Highlight the znod2N script in the Run window.  Seven cycles covers an hour.
  
• Hit the "submit" button.
  
• Point and focus at least once per hour!  Pointing moves the nodding secondary to ensure that its actuators are properly lubricated.  Run znod1Cal to take a spectrum of the pointing source before and after pointing; this provides a check on and some correction for optical gain drifts.

Shutdown

• Highlight and run the zshutdown script in Astrid
• The telescope operator can now remove you from the gateway
  
• Close all screens and log out