PSLV C-58 and POEM

The Polar Satellite Launch Vehicle (PSLV) flew for its sixtieth flight to carry a special X-ray astronomy satellite, XPoSat to orbit. The vehicle reused the fourth stage to move to a different orbit to test experimental payloads.

I have not understood the X-ray polarimetry science despite reading several articles on it that XPoSat will conduct.

So, this is a stand-in post.