Why were the observations made by the COBE satellite so important to cosmology?
It is through COBE that astronomers first got to see the full spectrum of CMBR which confirmed that it is a Planck spectrum which confirmed that CMBR is the remnant glow of a hot early Universe.
Before COBE attempts to trace the spectrum of Cosmic Microwave Background Radiation (CMBR) using balloon bourne experiments could not get the full spectrum. So it was not clear if it is a black body spectrum as predicted by the Standard Model of Cosmology. COBE got the full spectrum of CMBR for the first time confirming George Gamov 's hypothesis that Universe had a hot early phase.