The spectral results of the far-infrared absolute spectrophotometer instrument on COBE

The cosmic microwave background (CMB) spectral results of the Far-Infrared Absolute Spectrophotometer (FIRAS) instrument are summarized. Some questions that have been raised about the calibration accuracy are also addressed. Finally, we comment on the potential for major improvements with new measurement approaches. The measurement of the deviation of the CMB spectrum from a 2.725 +/- 0.001 K blackbody form made by the COBE-FIRAS could be improved by nearly 2 orders of magnitude.