source: branches/asap-3.x/tutorials/tutorial_2.rst@ 2067

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Tutorial 2 – Data Reduction for multiple spectra

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Tutorial 2 – Data Reduction for multiple spectra
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.. sectionauthor:: Kate Brooks

Main goal: Handle multiple Spectral windows (IFs) and plot spectral-line catalogues

Files

  • 2006-07-09_1431-M168.rpf Data file (63 Mb)
  • 3mm.txt Emission line catalogue
  • QuickData.py Data Reduction GUI (by Cormac Purcell)

Data Log

  • ON-OFF-OFF-ON Position switching mode with Mopra
  • 4 Scans (2 OFF and 2 ON)
  • 4 x 2-GH bands (IF 0, 1, 2, 3)

Instructions

  1. Work through the list of commands given in the text file to calibrate data taken with the Mopra telescope and identify the emission lines. Commands should be typed line-by-line into ASAP. Seek help from the tutors if there are any commands you don’t understand.
  2. The commands given in the text file are for 1 Mopra frequency band only (IF0). Now work on the other 3 bands and make a final plot showing all four frequency bands stitched together.
  3. Now repeat the calibration steps using the Mopra Data Reduction GUI. This GUI has been created via a python script (QuickData.py).

Commands

# Load data into memory and display short description
s = scantable('2006-07-09_1431-M168.rpf')
print s
# Set the plotting mode
plotter.set_mode(stacking='i', panelling='t')
plotter.set_histogram()
plotter.set_colours('black')
plotter.set_linestyles('solid')
# Plot all the raw data
plotter.plot(s)
# Form the quotient spectra
q = s.auto_quotient()
# Average all scans in time, weighting according to Tsys value
av = q.average_time(weight='tsys')
# Average the two polarisations together, weighting according to Tsys value
iav = av.average_pol(weight='tsys')
### Work on IF0 only
# Define a selector
sel1 = selector()
# Select the first IF for scantable 'iav'
sel1.set_ifs(0)
iav.set_selection(sel1)
# Plot the first IF with x-axis in channel number
iav.set_unit('channel')
plotter.plot(iav)
# Flag out the end channels
msk1 = iav.create_mask([0,120])
iav.flag(msk1)
msk1 = iav.create_mask([7900,8200])
iav.flag(msk1)
# Redo the plot
plotter.plot(iav)
# Identify emission lines
iav.set_unit('GHz')
plotter.plot(iav)
# Load in catalogue of emission lines and overlay on plot
lc3 = linecatalog('3mm.txt')
plotter.plot_lines(lc3,location='top',rotate=90,doppler=-45)
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