Please tell me the difference between Radiometers, Spectrometers, and Spectroradiometers?

Question

i can readily understand your answer if you could tell me in a remote sensing perspective

Answer 1

Hi. If you put a radiometer at the focus of a telescope, it would measure total radiation being received. If you put a spectrometer at there it would measure the spectrum (for instance all absorption and emission lines of the received light). If you put a spectroradiometer there you could measure any PARTICULAR frequency or range.