POWER/TSA                                15-SEPT-1992 A.Schwarzenberg-Czerny
    
Purpose:  
           Compute discrete power spectrum for uneven sampling by slow method.
           This command is recommended as departure point for the analysis
           of sampling (spectral window) and signal. However, since the power
           spectrum has no well defined statistical properties we recommend
           use of AOV/TSA and/or SCARGLE/TSA for assessing the significance
           of features in the periodogrammes.
Syntax:
           POWER/TSA intab outima start step nsteps
           intab  = name of input table, it must contain columns :TIME and 
                    :VALUE in DOUBLE PRECISION. For numerical reasons it is
                    advisable to subtract mean from :VALUE, except for window 
                    function calculation.
           outtab = name of output image; its first row contains the power  
                    spectrum and second row contains the window function. 
           start  = start frequency of the periodogramme, in inverse
                    units of :TIME 
           step   = frequency step of the periodogramme, in inverse
                    units of :TIME 
           nsteps = number of frequencies of the periodogramme, in inverse
                    units of :TIME 
See also:
           SHOW/TSA, AOV/TSA, SCARGLE/TSA
Note: 
           By default 'intab', 'outtab', 'start', 'step' and  'nsteps'
           retain their values from the last use of TSA commands, unless 
           explicitly specified.
           For detection of smooth signals use SCARGLE/TSA.
           Sensitivity of power spectrum to signals with  sharp features is 
           poor, use AOV/TSA instead. 
Examples:
           POWER/TSA LCURVE PERIODG 0.01 0.01 100 
           POWER/TSA ? ? 0.2 0.0001
           You may run this second command after the first example to inspect 
           the frequency range 0.2 to 0.21 at higher resolution.