A2708 freqSw galactic OH lines

Intro:

• Looking at 1720,1665,1667 oh lines as well as HI
• The freq switch is done by using two velocities for the same source: 7.5 AND 58.384 Km/sec
• The interim correlator is used in full stokes mode with 2048 channels over .78125 MHz bandwidth.

• Set 7.5 km vel
  
• adjust power, doppler shift
• 10 sec calon
• 240sec data
  
• 10 sec calon
• 240sec data
• set 58.384 km/sec velocity
• doppler shift (we are using velocity to shift the freq rather than a fixed freq freq. so each board gets a different shift)
• The doppler shift includes the source velocity as well as the change in the user projected velocity into the lsr system.
• 10sec calon
• 240sec caloff
• 10 sec calon
• 240sec caloff

• I through together some idl code to look at the data.
  
• The full processing should eventually be done with carl's routines.
  
• find all of the 7.5 km/sec (freqOn) data as well as the 58.3384 km/sec (freqOff) scans
• Use corstokes() to process each scan
• Create calOff by averaging 10 sec of the datascan
• bpc
  
• compute calDif=calOn-caloff spectra
  
• then do a linear fit to calDif (exclude edges and lines)
• Use this for the bandpass correction
• phase rotate with caldeflection
• No mueller matrix correction is applied
  
• FreqSwitch processing
• Let a set be:
• freqOn,freqOn, freqOff,freqOff .. this is 240secs*4 seconds of data
• process the first freqOn with the first freqOff of each set and the 2nd freqOn with the 2nd freqOff
  
• compute fsw1=freqOn - freqOff spectra
• make a copy of fsw (fsw2) and shift it by  df=(velOn-velOff)/c * cfrEach band
• do an integral shift
• then do an  interpolation for the fraction portion of the shift
• Compute fsw=(fsw1 - fswSh2)*.5
• do a linear fit about the line (excluding the lines) to get rid of standing waves.
• Average fsw over each day.
• currently unit weighting is done (should use 1/sigma^2 eventually)
• There is currently no gain correction (we only have point source gains).
• Average all days done (scale each day by the number of scans that day)

Plotting the data

• The plots show  the average of 8 days of data (.ps) (.pdf)
• Colors:
• red=stokesI
• green:stokesQ
• blue: stokesU
• black: stokesV
• Units:
• The horizontal scale is lsr km/scal
• The vertical scale is deg Kelvins
• I've left the factor of 2 in (so Tsys is 60 Kelvin, not 30 Kelvin)
• No gain correction has been applied
• the Relative line strength label is the peak line strength divided by the 1667 Line, and then multiplied by 9.
  
• Page 1:
  
• Top: 1720 line
• middle: 1665 line
• bottom: 1667 line
• Page 2:
• A blowup showing the q,u,v power.

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