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msmetadata.effexposuretime - Function

1.3.2 Get the effective exposure (on-source integration time)


Description

Get the effective exposure time (equivalent to what might be more commonly known as total integration time or total sample time) is calculated by summing over all rows in the main MS table, excluding autocorrelations or rows where FLAG_ROW is false, thusly:

sum[over i] (exposure[i]*sum[over j](UFBW[i, j])/ncorrelations[i] )/ nmaxbaselines

where exposure[i] is the value of EXPOSURE for the ith row, the inner sum is performed over each correlation for that row, UFBW is the unflagged fractional bandwidth is determined by summing all the widths of the unflagged channels for that correlation and dividing by the total bandwidth of all spectral windows observed at the timestamp of row i, ncorrelations is the number of correlations determined by the number of rows in the FLAG matrix for MS row i, and nmaxbaselines is the maximum number of antenna pairs, nantennas*(nantennas-1)/2, where nantennas is the number of antennas in the ANTENNA table. This method returns a quantity (a dictionary having a numerical value and a string unit).

Arguments





Returns
record

Example

 
    msmd.open("my.ms")  
    # get the effective exposure time.  
    exposure_time = msmd.effexposuretime()  
    msmd.done()  

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