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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