PRF

The actual pulse repetition frequency (PRF) is computed based on the data in the SLC leader file. However, the 'actual' value, as read from the leader file, is used (after private communications with ESA helpdesk). It is defined as:

$${\rm PRF} = \frac{Nl-1}{\,dt_a}$$ (D31)

Where:
PRF is the pulse repetition frequency in Hz.
Nl is the total number of lines (lastline - firstline).
$\,dt_a$ is the azimuth time of the last line minus the azimuth time of the first line, or the acquisition time of the image.
This equation, and the following, can be easily verified by substitution of the values for the first/last line/pixel.