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Date: April 18, 1996
Contact: Jacquelyn Savani (609) 258-5729
NASA Selects Princeton Team to Build Instrument to Map Cosmic Background Radiation
Princeton, N.J.--A Princeton team will build the microwave instrument for a satellite, to be constructed at Goddard Space Flight Center in Maryland. The satellite, scheduled for launch in 2001, will be propelled into space by the medium-sized rocket of NASA's new Medium-class Explorer (MIDEX) program.
NASA announced on April 10 the selection of the Microwave Anisotropy Probe (MAP) proposal for a MIDEX mission. It will map the cosmic background radiation from the earliest epoch of the universe when decoupling occurred.
According to Big Bang cosmology, billions of years ago the universe burst into being and cooled some 300,000 years later to 4,000 degrees C. Around that temperature the structure of the atom came into being as protons and electrons attracted each other and formed hydrogen atoms with a proton at the center and an electron orbiting the nucleus. And the light or photons, that had been trapped or scattered by free electrons before they settled into atoms, shines forth and streams through the millennia to us and can be detected as cosmic background radiation.
Arno Penzias and Robert Wilson won a Nobel Prize for first detecting the cosmic background radiation in 1965. They hadn't really been looking for it, but David Wilkinson, Princeton's Brackett Professor of Physics, who was an assistant professor back in the middle '60s, had built a radiometer atop Guyot Hall, for the express purpose of detecting the background radiation Penzias and Wilson found. Wilkinson's experiment yielded the results that confirmed their discovery.
Ever since, Wilkinson has been designing experiments--aboard balloons, rockets, and satellites and from desolate places on earth such as the South Pole--to get more information about the cosmic background radiation. He was one of the handful of scientists who conceived and shepherded into space the Cosmic Background Explorer (COBE) satellite.
COBE, one of NASA's most successful science missions, measured within weeks of its launch the black body spectrum--the signature of the cosmic background radiation. Another experiment aboard detected the long-sought irregularity or anisotropy in the cosmic background radiation.
As the COBE data came in, Wilkinson began thinking about how to get better data--conceiving the successor mission to COBE that is MAP.
In keeping with NASA's lean approach to space flight, MAP will cost a quarter of what COBE did, but its sensitivity will be 50 times greater.
Working with Wilkinson to build the microwave telescope at Princeton are Associate Physics Professor Lyman Page and research staff member Norman Jarosik, both veterans of conceiving, building and carrying out experiments to probe the microwave background. The other Princeton collaborator on the MAP mission is Astrophysics Associate Professor David Spergel. The physicists kept designing the experiment, and Spergel simulated via computer the results that they would get with a given design. He thereby provided feedback that enabled the physicists to improve the design.
Wilkinson has been building microwave telescopes or radiometers for 35 years. Princeton Albert Einstein Professor of Science, Emeritus Robert Dicke invented the instrument to probe the cosmic background radiation and thereby gave rise to the whole field of experimental cosmology.
MAP will consist of 20 radiometers in contrast to COBE's six--each of the 20 radiometers 50 times more sensitive than the six radiometers aboard COBE.
The anisotropy or blobs in the microwave radiation that COBE saw were so big when they formed that light couldn't make it from one side of a blob to the other, so different parts of the blobs were not in causal contact, which means the blobs could not have formed physically out of some physical process by themselves, but were built into the Big Bang as initial conditions.
MAP will look at much smaller angles of resolution and therefore be able to look at physical processes that happened at the atom-forming epoch. That information will be conveyed as a power spectrum, which should answer some of the big questions in cosmology such as:
what is the rate of expansion of the universe (Hubble's constant),
and how does that rate vary with time; which in turn answers the question,
whether there is enough matter to close the universe or not.
In addition, MAP should answer questions about Inflation, the phenomenon of explosive and colossal expansion postulated by cosmologists to have occurred soon after the initial Big Bang: whether the anisotropy detected by COBE was due to quantum fluctuations that occurred before the hypothetical inflationary epoch.
MAP should also detect the beginning of structures observed by modern astronomers, such as the great wall of galaxies and the great voids, and should therefore shed light on questions of how and when the universe evolved into the structures of galaxies and of clusters and super-clusters of galaxies that we see.
The principal investigator for MAP, Charles L. Bennett, is at Goddard. The other Goddard scientists working on MAP are John Mather (the principal architect for the COBE black-body-radiation-spectrum experiment) and Gary Hinshaw. Along with the Princeton quartet, the other principal MAP collaborators are UCLA's Edward (Ned) Wright (who analyzed the COBE data and discovered the anisotropy) and Steve Meyer, a graduate student of Wilkinson now a physicist on the University of Chicago faculty.
About $30 million of the $70 million allocated for MAP will go to Goddard to build the spacecraft which will carry MAP's telescope to orbit on the opposite side of the earth from the sun in a location known as L2.
"L2," says Wilkinson, "is a great place to do science. NASA has put a couple of probes out there and knows how to do it."
In order to get MAP to L2, it will go around the moon a few times to get precisely aligned, then on the last pass it gives the moon a close shave and is boosted out to L2, where it revolves in tandem with the earth around the sun. The idea is to have the satellite revolving with the earth around the sun and shielded from the radiation from the sun, earth, and moon. So shielded, MAP is positioned to look out into deep space and collect the feeble cosmic background radiation.
Princeton will receive about $12 million to build the microwave instrument and to test the telescope design. To achieve greater sensitivity, the telescope and instruments will be allowed to cool to about 80 degrees above absolute zero. MAP's design must accommodate these cold temperatures--about the temperature of liquid air.
The MAP team plans a strong educational component for the project. Spergel will head a $400,000 outreach effort to connect MAP with schools and the public using direct satellite links to schools, the World Wide Web, and a program at the American Museum of Natural History's Hayden Planetarium in New York City. On campus undergraduate and graduate students will be involved in the Jadwin Hall laboratories where the instrument hardware is being developed and built. "Princeton," says Wilkinson, "will offer students a rare opportunity to be directly involved in space science."
Information on the MAP mission is available on the World Wide Web at http://map.gsfc.nasa.gov.