Goddard Space Flight Center
Greenbelt, MD
November 1999
GODDARD COBE TEAM’S HISTORIC MISSION OPENED A WINDOW ON CREATION
Thanks to Goddard’s Cosmic Background Explorer (COBE) team, crucial evidence for the theory that the Universe was
created abruptly in a primordial explosion was discovered — a result that astrophysicist Stephen Hawking termed, “the
discovery of the century, if not of all time.” Goddard celebrates the tenth anniversary of the COBE mission Nov. 18.
“The Goddard COBE team can be extremely proud of its heroic effort,” said Dr. John Mather, COBE project scientist. “The
spacecraft and its three instruments were all designed, assembled and operated at
Goddard. Goddard takes great pride in COBE because it worked so
well — its results are a historic confirmation of our ideas about the origin of the Universe and are included in every
modern textbook on astronomy.”
The idea that the Universe was born in a cosmic explosion, called the Big Bang theory, predicts that the original fireball
can still be detected anywhere you look in distant space, glowing at a
characteristic temperature. Just like a piece of hot metal changes color as it cools, the multi-trillion degree Big Bang
fireball cooled to barely above absolute zero as the Universe expanded, and has
changed color so that it is not visible to the human eye. It now only whispers its fury to us with the faint hiss of
microwaves, part of the static between radio stations.
Big Bang theory predicts that a graph of this Cosmic Microwave
Background (CMB) radiation displaying its intensity at different energies should have a special shape, resembling a
smooth, round mountain. The Far Infrared Absolute Spectrophotometer (FIRAS)
instrument on COBE made observations that agreed with that
prediction to within 50 parts per million.
“The remarkably close fit between our observation and the Big Bang prediction was a stunning confirmation, and
engendered the only
standing ovation I’ve ever seen for the presentation of a scientific result,” said Mather, also the Principal Investigator
for FIRAS.
The Big Bang was uniform in all directions — almost. If it had been absolutely uniform, we would not be here. Tiny
variations in its density became gravitational seeds that allowed stars and galaxies (and planets and us) to form. A record
of these density variations is imprinted on the Big Bang radiation as tiny fluctuations in its temperature across the sky.
Denser regions are ever so slightly
cooler; by one part in 100,000. The greater density of these regions endowed them with a stronger gravitational field,
which stretched out the microwave radiation to slightly less energetic (cooler) types. The Differential Microwave
Radiometer (DMR) on COBE measured these incredibly small differences for the first time. Dr. George Smoot of Berkeley
and Goddard’s Dr. Chuck Bennett were the Principal
Investigator and Deputy Principal Investigator, respectively, for this instrument.
“It was a tremendous accomplishment to measure this,” says Mather. “Chuck Bennett made it happen on a daily basis. He
is also the Principal Investigator for a new mission to measure these temperature variations in greater detail, called the
Microwave Anisotropy Probe (MAP) mission. It was another great success for Goddard to win the competition to build
MAP, which will enable us to understand the conditions in the first instant of the Big Bang that gave rise to the density
fluctuations in the first place.”
Dust warmed by all the stars that have existed since the beginning of time casts a background infrared glow across the
sky, which was detected for the first time by COBE’s Diffuse Infrared Background Experiment (DIRBE). Infrared light is
also invisible to the human eye, but we perceive some types as heat. Dr. Michael Hauser, a Goddard alumnus now Deputy
Director of the Space Telescope Science Institute, was Principal Investigator for this instrument.
“The infrared background was unexpectedly bright; brighter than all the light from all other known objects in the
Universe,” said Mather. “DIRBE created a new branch of astronomy by telling us that at great distances, there are
cosmically significant things that are a big surprise.”
COBE was proposed in 1974, with mission studies beginning in 1976. Goddard was chosen to develop a plan for the COBE
mission in 1977, and in 1982, it was selected to build the spacecraft with complete in-house support. Roger Mattson
(deceased) was the Project Manager, and the Deputy Project Manager was Dennis McCarthy, now the Far
Ultraviolet Spectroscopic Explorer Project Manager at the Johns
Hopkins University. A team of more than 1500 people, including
contractors, was assembled to work on the project at its peak. COBE was originally designed to be launched on the space
shuttle, but the Challenger explosion in 1986 necessitated a redesign so that it could be carried to orbit on a Delta
rocket.
COBE was launched Nov. 18, 1989, from Vandenberg Air Force Base, Lompoc, Calif. COBE scientific operations spanned
four years, then it was transferred to the Goddard Flight Operations Team for training and experimentation. All data are
on-line at Goddard’s National Space Science Data Center, and are accessible from the COBE website.
For more information about COBE, visit:
http://www.gsfc.nasa.gov/astro/cobe/
Readers who wish to know more about the struggles and triumphs of COBE can consult “The Very First Light — The True
Inside Story of the Scientific Journey Back to the Dawn of the Universe,” by John C. Mather and John Boslough (Basic
Books 1996) at the Goddard Library or a nearby public library.
For more about the Big Bang theory and the MAP mission, visit:
