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User Documentation |
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./contrib getps_v2.pro
| getps_v2 |
procedure getps_v2, scan, [ifnum=integer], [intnum=integer], [plnum=integer], [fdnum=integer], [tau=float], [tsys=float], [ap_eff=float], [smthoff=integer], [units=string], [eqweight=flag], [calscan=integer], [ifile=string], [caltype=string] |
This procedure retrieves and calibrates a total power position switched scan pair, which is followed by a on+off observation of a noise diode. If the third or first scan in the sequence is not a noise diode observation, the users must give the scan number for the noise diode observation, using the "cal=" option. The data must be taken with the "OnOff" or "OffOn" procedures. This procedure will reject data not taken with one of those two procedures. The routine produces a spectrum calibrated in Ta (K). Other recognized units are 'Ta*' and 'Jy'.
The only required parameter is the scan number. This can be either scan in the sequence of two total power scans, and the paired scan is determined from the header. Arguments to identify the IF number, polarization number and feed number are optional. The program calculates Tsys based on the Tcal values, and cal_on/cal_off observations. However, a median tsys for the spectra is applied, as we do not have any gain versus frequency information available. The tcal value comes from the gbt_tsys routine. The user can override this calculation by entering a system temperature. The procedure will NOT correct the Tsys for the observed elevation. If the data are calibrated to Ta* or Jy, then additional parameters are used. A tau value may be specified, and an aperture efficiency may be specified. The user is *strongly* encouraged to enter values for these calibration parameters, but they will be estimated if none is provided.
A parameter called smthoff can be used to smooth the reference spectrum prior to calibration. In certain cases this can improve the signal to noise ratio, but it may degrade baseline shapes and artificially emphasize spectrometer glitches. Use with care. A value of smthoff=16 is often a good choice.
By default, internal averaging of integrations is weighted by Tsys. To give all integrations equal weight instead, use the /eqweight flag.
NOTE: the procedure assumes you are firing a high cal (preferred for this type of observation). if you are not, you must say so, as this information is NOT recorded in the sdfits files.
Contributed By: Karen O'Neil, NRAO-GB
| Parameters | |
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scan |
M&C scan number |