COsmic Background Explorer


NASA's COBE (Cosmic Bakground Explorer) satellite was developed to measure the diffuxe infrared and cosmic microwave background radiation from the early Universe to the limits set by our astrophysical environment. COBE was launched on November 18, 1989 and carried three instruments: DIRBE (the Diffuse InfraRed Experiment) to search for and measure the cosmic infrared background radiation, DMR (Differential Microwave Radiometers) to map the cosmic microwave background radiation precisely, and FIRAS (Far-InfaRed Absolute Spectrophotometer) to compare the spectrum of the cosmic microwave background radiation with that from a precise blackbody.

Data from the full four years of COBE observations continue to be analyzed. Student and post doctoral opportunities exist.

A large number of people were involved at various stages in the COBE project.

DIRBE (Diffuse Infrared Background Experiment)

DIRBE has mapped the absolute sky brightness in 10 wavelength bands ranging from 1.25 microns to 240 microns. These data contain the signal from the cosmic infrared background and the foreground emissions from extragalactic sources, our Galaxy, and dust and other sources in our solar system. Work is in progress on separating and modeling the varios components. Significantly improved limits on the cosmic infrared background exist and future progress is possible and likely. A significant amount of work involves study of the astrophysics of the interesting foreground sources. There is a very rich data base on the infrared emission from the Galaxy and the interplanetary dust.
Galactic plane emission: bands 1-5

Galactic plane emission: bands 6-10

DMR (Differential Microwave Radiomters)

The COBE DMR ( Smoot et al. 1992 ) has found anisotropies in the cosmic microwave background on all scales from the nominal beam size of 7-degrees up to the full sky at a typical level of one part in 100,000 to a few parts per million. These anisotropies are interpreted as imprints of the seeds that eventually grew under the influence of gravity to galaxies, clusters of galaxies, and clusters of clusters of galaxies. They also indicate that we should eventually expect to find even larger scale structures. They also give us a clue to how the Universe originated - i.e. how space and time and all the other contents of the Universe came into being. Two of the four years of the COBE DMR data have been released. Data processing of all four years are in progress and the full four year data were released in January 1996. The DMR team had a large number of memembers over the years in addition to those from the COBE science working group that participated.

DMR Schematic

CMB Fluctuations (2 years of data)

CMB Fluctuations (galaxy removed)

DMR Four Year DMR images of the Cosmic Microwave Background Fluctuations.

FIRAS (Far Infrared Absolute Spectrophotometer)

FIRAS has shown that the cosmic microwave background spectrum matches that of a blackbody of temperature 2.726K with a precision of 0.03% of the peak intensity over a wavelength range 0.1 to 5 mm. Longer wavelength measurements, though not nearly as precise, conducted by Smoot's group at LBL and collaborators and by other groups, show that the CMB spectrum is well-described by a single temperature blackbody. See figure [attach Intensity and Temperature plots] of spectrum measurements. These measurements limit possible alternative models to the Big Bang extremely strongly and limit potential energy releases in the early Universe, typically to less than 0.1% to 0.01%.

More Information

Extensive information about the COBE mission, including much information about the three experiments on board, is available by clicking on more COBE information or through the NASA's NSSDC & Goddard Space Flight Center maintained COBE Home Page. More photographs related to and of COBE. NASA was responsibile for the development of the COBE satellite and mission operations. Scientific Guidance was provided by the COBE Science Working Group.

Return to the Smoot Group page for a complete description of Dr. Smoot's group's research activities.

Revised 9 February 1997;