The validation check for the TimeCOA polynomial doesn't take into account negative numbers, [This](https://github.com/ngageoint/sarpy/blob/master/sarpy/io/complex/sicd_elements/validation_checks.py#L408) line should become ```if timecoa_poly.shape == (1, 1) or numpy.all(numpy.abs(timecoa_poly.flatten()[1:]) < 1e-6)```
