A Cosmic Cartographer; The Once and Future Cosmos; Special Editions; by Charles L. Bennett, Gary F. Hinshaw and Lyman Page; 2 Page(s)

On June 30, 2001, NASA launched a Delta 2 rocket carrying an 840-kilogram, four-meter-high spacecraft. Over the next three months the Microwave Anisotropy Probe (MAP) maneuvered into its orbit around the sun, 1.5 million kilometers beyond Earth's orbit. MAP is now observing the cosmic microwave background (CMB) radiation in exquisite detail over the entire sky. Because this radiation was emitted nearly 15 billion years ago and has not interacted significantly with anything since then, getting a clear picture of the CMB is equivalent to seeing a map of the early universe. By studying this map, scientists can learn the composition, geometry and history of the cosmos.

MAP is designed to measure the anisotropy of the CMB-the minuscule variations in the temperature of the radiation coming from different parts of the sky. MAP can record fluctuations as small as 20 millionths of a kelvin from the radiation's average temperature of 2.73 kelvins. What is more, the probe can detect hot and cold spots that subtend less than 0.23 degree across the sky, yielding a total of about one million measurements. Thus, MAP's observations of the CMB will be far more detailed than the previous full-sky map, produced in the early 1990s by the Cosmic Background Explorer (COBE), which was limited to a seven-degree angular resolution.