| [1689] | 1 | import os
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| 2 | import math
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| 3 | from asap import scantable
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| 4 | from asap import merge
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| 5 | from asap import fitter
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| 6 | from asap import selector
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| 7 | from asap import rcParams
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| 8 |
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| 9 | def _import_data(data):
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| 10 | if not hasattr(data, "__len__"):
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| 11 | if isinstance(data, scantable):
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| 12 | return data
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| 13 | elif isinstance(data, str):
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| 14 | return scantable(data)
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| 15 | tables = []
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| 16 | for d in data:
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| 17 | if isinstance(d, scantable):
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| 18 | tables.append(d)
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| 19 | elif isinstance(d, str):
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| 20 | if os.path.exists(d):
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| 21 | tables.append(scantable(d))
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| 22 | else:
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| 23 | raise IOError("Data file doesn't exists")
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| 24 | else:
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| 25 | raise TypeError("data is not a scantable or valid file")
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| 26 | return merge(tables)
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| 27 |
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| 28 | def skydip(data, averagepol=True, tsky=300., plot=False):
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| 29 | """Determine the opacity from a set of 'skydip' obervations.
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| 30 | This can be any set of observations over a range of elevations,
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| 31 | but will ususally be a dedicated (set of) scan(s).
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| 32 | Return a list of 'n' opacities for 'n' IFs. In case of averagepol
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| 33 | being 'False' a list of 'n*m' elements where 'm' is the number of
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| 34 | polarisations, e.g.
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| 35 | nIF = 3, nPol = 2 => [if0pol0, if0pol1, if1pol0, if1pol1, if2pol0, if2pol1]
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| 36 |
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| 37 | The opacity is determined by fitting a first order polynomial to:
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| 38 |
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| 39 |
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| 40 | Tsys(airmass) = p0 + airmass*p1
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| 41 |
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| 42 | where
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| 43 |
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| 44 | airmass = 1/sin(elevation)
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| 45 |
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| 46 | tau = p1/Tsky
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| 47 |
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| 48 | Parameters:
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| 49 | data: a list of file names or scantables or a single
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| 50 | file name or scantable.
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| 51 | averagepol: Return the average of the opacities for the polarisations
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| 52 | This might be useful to set to 'False' if one polarisation
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| 53 | is corrupted (Mopra). If set to 'False', an opacity value
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| 54 | per polarisation is returned.
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| 55 | tksy: The sky temperature (default 300.0K). This might
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| 56 | be read from the data in the future.
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| 57 | plot: Plot each fit (airmass vs. Tsys). Default is 'False'
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| 58 | """
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| 59 | scan = _import_data(data)
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| 60 | f = fitter()
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| 61 | f.set_function(poly=1)
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| 62 | sel = selector()
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| 63 | basesel = scan.get_selection()
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| 64 | inos = scan.getifnos()
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| 65 | pnos = scan.getpolnos()
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| 66 | opacities = []
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| 67 | for ino in inos:
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| 68 | sel.set_ifs(ino)
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| 69 | opacity = []
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| 70 | for pno in pnos:
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| 71 | sel.set_polarisations(pno)
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| 72 | scan.set_selection(basesel+sel)
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| 73 | tsys = scan.get_tsys()
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| 74 | elev = scan.get_elevation()
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| 75 | airmass = [ 1./math.sin(i) for i in elev ]
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| 76 | f.set_data(airmass, tsys)
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| 77 | f.fit()
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| 78 | if plot:
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| 79 | f.plot(residual=True, plotparms=True)
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| 80 | raw_input("Hit <return> for next fit...")
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| 81 | params = f.get_parameters()["params"]
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| 82 | opacity.append(params[1]/tsky)
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| 83 | if averagepol:
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| 84 | opacities.append(sum(opacity)/len(opacity))
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| 85 | else:
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| 86 | opacities += opacity
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| 87 | sel.reset()
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| 88 | scan.set_selection(basesel)
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| 89 | return opacities
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