DopplervsPixel and other attributes in crop.py

[Carolinah23]

Hello all,

I am a little confused about the parameters used by crop.py to crop the data. It uses this line coeff = frame._dopplerVsPixel which in my case results in coeff=None and creates an error later.

I assume this case is similar to this problem where unpackFrame_ENV.py only works by changing some lines that refer to the doppler Coeffs #488 (comment). This solution worked for me but it would be nice to be able to crop the data to facilitate the rest of the process.

This attribute frame._dopplerVsPixel is available just for some satellites/data types? I am working with Envisat