What information do astronomers obtain by studying radiation by comets,meteoroids,asteroids?
Definition. By “radiation” you mean light. If you are fortunate enough to have an asteroid pass in front of a star, you can line up a series of cameras and time when the light of the star winks out and reappears. This can give you the shape of the asteroid. Three or more observations with carefully noted position and time can be used to compute the orbit of comets and asteroids. Spectrum information can be used to determine what any of these objects are made from. Elements and molecules. Meteoroids are objects passing through our atmosphere. So you have to work fast to get anything from them. Sometimes you can trace them back and figure out what their orbit must have been. Often you can easily trace them back to one of several well studied meteor showers.