Paula Cleggett-Haleim
Headquarters, Washington, D.C.                    October 5, 1989

Carter Dove
Goddard Space Flight Center, Greenbelt, Md.

RELEASE:  89-158

NASA SPACECRAFT TO LOOK OUT INTO SPACE, BACK IN TIME

     NASA will launch a spacecraft on Nov. 9, 1989, to study the 
origin and dynamics of the universe, including the theory that 
the universe began about 15 billion years ago with a cataclysmic 
explosion -- the Big Bang.

     The Cosmic Background Explorer (COBE) spacecraft will be 
boosted into an Earth polar orbit from Vandenberg Air Force Base, 
Calif., aboard the final NASA-owned, NASA-launched Delta vehicle.

     By measuring the diffuse infrared radiation (cosmic 
background) that bombards Earth from every direction, COBE's 
instruments will help clarify such matters as the nature of the 
primeval explosion -- which started the expansion of the universe 
and made it uniform -- and the processes leading to the formation 
of galaxies.

     From its orbit 559 miles above Earth, COBE will carry out 
its cosmic search using three sophisticated instruments:  the 
Differential Microwave Radiometer (DMR), Far Infrared Absolute 
Spectrophotometer (FIRAS) and Diffuse Infrared Background 
Experiment (DIRBE)

     DRM will determine whether the primeval explosion was 
equally intense in all directions.  Patchy brightness in the 
cosmic microwave background would unmask the as-yet-unknown 
"seeds" that led to the formation of such large bodies as 
galaxies, clusters of galaxies, and clusters of clusters of 
galaxies.  Measurements of equal brightness in all directions 
would mean the puzzle of how these systems could have condensed 
since the Big Bang will be even more vexing than it is today.

     To distinguish the emissions of our own Milky Way galaxy 
from the true cosmic background radiation, DMR will measure 
radiation from space at wavelengths of 3.3, 5.7 and 9.6 
millimeters.

     FIRAS, covering wavelengths from 0.1 to 10 millimeters, will 
survey the sky twice during the year-long mission to determine 
the spectrum (brightness versus wavelength) of the cosmic 
background radiation from the Big Bang.

     The spectrum that would result from a simple Big Bang can be 
calculated with great accuracy.  Such a spectrum would be smooth 
and uniform and have no significant releases of energy between 
the time of the Big Bang and the formation of galaxies.  If 
FIRAS' measurements depart from the predicted spectrum, 
scientists will know that powerful energy sources existed in the 
early universe between these times.

     These sources may include annihilation of antimatter, matter 
falling into "black holes," decay of new kinds of elementary 
particles, explosion of supermassive objects and the turbulent 
motions that may have caused the formation of galaxies.
 
     FIRAS' sensitivity will be 100 times greater than that 
achieved so far by equivalent ground-based and balloon-borne 
instruments.  Producing a spectrum for each of 1,000 parts of the 
sky, the FIRAS data will allow scientists to measure how much 
light was radiated by the Big Bang.

     DIRBE will search for the diffuse glow of the universe 
beyond our galaxy in the wavelength range from 1 to 300 
micrometers.  In the final analysis, any uniform infrared 
radiation that remains will be very rich in information about the 
early universe.  One possible source would be light from 
primordial galaxies shifted into the far infrared by the 
expansion of the universe.

     NASA's Goddard Space Flight Center, Greenbelt, Md., designed 
and built the 5,000-pound spacecraft and its three infrared- and 
microwave-measuring instruments.  Goddard also will manage the 
launch and analyze the data returned by COBE during its 1-year 
nominal mission.

     Looking out into space, back in time, the COBE spacecraft 
will undertake the esoteric task of providing new insights into 
the origin and evolution of the universe.