Incorrect Calculation of peak RCS

[JensReimann]

The calculation of the peak RCS in the file python/packages/isce3/cal/radar_cross_section.py::measure_target_rcs() is missing a scaling factor.

This issue has been resolved at

https://github.com/JensReimann/isce3/tree/peak_RCS_fix

but I'm not permitted to open a pull request for it. Please manually pull the changes.

A more detailed description of the problem can be found in the commit. Comments explaining the rationale for the change have been included in the source code.

[bhawkins]

I don't think we intended to restrict opening pull requests. Are you able to open one using the "compare across forks" feature as below?