Rosat ( Rö ntgen' sat' ellit) was a German satellite of observation of the x-rays, launched on June 1st 1990 by a rocket Delta-II since Cap Canaveral.

Rose carried out an inventory of the whole of the sky in the field of x-rays identifier 125.000 sources with x-rays and 479 sources in the remote ultra-violet. But most of the time of observation was devoted to a limited number of sources for long, meticulous observations and exploiting the excellent resolution of the instruments.