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.