The Doppler centroid frequency (azimuth) is computed as a second degree polynomial:
Xtrack_f_DC_constant (Hz, early edge): 117.3210000 Xtrack_f_DC_linear (Hz/s, early edge): 72338.0000000 Xtrack_f_DC_quadratic (Hz/s/s, early edge): -455000000.00000
This frequency is used in the azimuth filtering, and in the resampling. It should also be used if the complex SLC data is harmonically oversampled (as is done in the range filtering routine), but we did not implement this yet. But, for Hz this should not have any effect (assuming PRF-ABW=300Hz).
Since for a signal f(t) with Fourier transform F()
The azimuth spectrum of a SLC image processed on a certain Doppler frequency (spectrum shifted to this frequency) can be shifted back to zero by multiplication in the space domain by the term