Cosmic Background Explorer

12/23/93: NASA ENDS COSMIC BACKGROUND EXPLORER SCIENCE OPERATIONS





Donald L. Savage


Headquarters, Washington, D.C.                December 23, 1993





Michael Finneran


Goddard Space Flight Center, Greenbelt, Md.





RELEASE:  93-228








     The final operational instrument on NASA's first spacecraft


to explore the origins of the universe will be turned off today


after completing 4 years of landmark research, including


confirmation of the Big Bang theory that says the universe was


created in a single momentous explosion.





     The Cosmic Background Explorer (COBE) spacecraft, built and


managed by the Goddard Space Flight Center (GSFC), Greenbelt,


Md., will be used as an engineering training and test satellite


by NASA's Wallops Flight Facility, Wallops Island, Va. beginning


in January after Goddard spacecraft controllers conclude


engineering operations.





     "COBE has more than achieved its technical goals," said Dr.


John Mather, Project Scientist at GSFC.  "It has observed the


universe as it was at its birth.  It's done everything we asked


it to do, and it's a proud day for us to declare our flight


operations complete."





     Launched on Nov. 9, 1989, on a Delta rocket, COBE's primary


science mission requirement called for one year of observations.


Near the end of its first year the liquid helium coolant needed


by two of the three instruments was exhausted, leaving one


instrument and some channels of a second instrument operational.





     COBE was the first space mission to address basic questions


of modern cosmology, such as how the universe began, how it


evolved to its present state and what forces govern this


evolution.  According to the Big Bang theory, the universe was


created about 15 billion years ago in a violent cosmic explosion


that hurled primeval matter in all directions.   COBE became well


known for its very precise measurements confirming the Big Bang


theory and for its detection of the largest and oldest objects


ever discovered.





     Scientists styudying the mysterious conditions present in


the early universe and how it evolved into stars and galaxies


used precise measurements from three COBE instruments:





        *   The Far Infrared Absolute Spectrophotometer (FIRAS),


designed to measure the spectrum of the Cosmic Microwave


Background to great accuracy.





        *   The Differential Microwave Radiometers (DMR), designed


to measure the "lumpiness," or anisotropies, in the universe that


existed just 300,000 years after the Big Bang.





        *   The Diffuse Infrared Background Experiment (DIRBE),


designed to search for the glow from the first stars and galaxies


in the universe.





     The FIRAS instrument measured the spectrum of the Cosmic


Microwave Background radiation with unprecedented accuracy,


showing that it is the same as the spectrum predicted by the Big


Bang theory.  Since the COBE measurements show no deviations from


the spectrum predicted by the Big Bang, it is known now that


99.97 percent of the energy of the universe was released within


the first year after the Big Bang itself.





 


     The FIRAS also showed that the temperature of the afterglow


of the radiation from the Big Bang some 15 billion years ago has


cooled to 2.726 degrees above absolute zero, with an uncertainty


of only 0.01 degrees.  At the moment of the Big Bang, the


temperature of the universe was trillions upon trillions of


degrees.





     The DMR instrument detected the primordial hot and cold


spots in the Big Bang radiation.  The cold spots show denser


matter that could condense into huge clouds of galaxies.  Hot


spots were thinner regions that eventually contained no galaxies.


Scientists hailed these findings because this first detection of


primordial seeds will form the basis of scientist's understanding


of how matter was able to form into galaxies, clusters of


galaxies and superclusters of galaxies and huge empty spaces


devoid of galaxies.





     The hot and cold spots found by COBE are only 30-millionths


of a degree -- one part in 100,000 -- warmer or colder than the


regions next to them.  The COBE results show that these seeds are


truly primordial and were present just 300,000 years after the


Big Bang.