Sentence:  The measurements made with the NRL 50 - foot reflector , which is altitude azimuth mounted , would have shown a systematic <WSD>change</WSD> with local hour angle in the measured intensities of Venus and Jupiter if a substantial part of the radiation had been linearly polarized . 
Meaning of the word marked with <WSD> tags:  a relational difference between states; especially between states before and after some event