MAP science mission
NASA FACT SHEET
Posted: June 27, 2001
In 1992, NASA's Cosmic Background Explorer (COBE) satellite detected tiny fluctuations, or "anisotropy," in the cosmic microwave background. It found, for example, one part of the sky has a temperature of 2.7251 kelvins, while another part of the sky has a temperature of 2.7250 kelvins. (kelvin, is a unit of temperature: 0 kelvin is the complete absence of heat, called "absolute zero," and 273 kelvins is the same as 0 degrees Celsius). These fluctuations are related to fluctuations in the density of matter in the early Universe and thus carry information about the initial conditions for the formation of cosmic structures such as galaxies, clusters, and voids.
If viewed from afar, we would see the Earth as a uniform sphere. When viewed with improved resolution, we would see blurry images of the continents and oceans. With yet better resolution, the rich features of the Earth --deserts, mountains and forests -- would become visible. The first observations of the microwave background revealed only a uniform sky. The smallest features that COBE could distinguish were about 7 degrees wide on the sky, so COBE made the equivalent of the first detection of continents and oceans. Over the past few years, balloon-borne and ground-based experiments have made high-resolution images of small portions of the sky. MAP will make a high-resolution image of the whole sky. Analysis of the new information revealed by the MAP observations will help cosmologists to answer several key questions, such as: What is the density of atoms in the Universe? What is the density of exotic dark matter in the Universe? How old is the Universe? How did structures such as galaxies and clusters of galaxies form in the Universe? When did the first such structures form?
For the first 400,000 years or so after the Big Bang, the Universe was a seething cauldron of matter (electrons, protons, neutrons, and a small percentage of heavier atomic nuclei), and light (photons). Since photons scatter or bounce off electrons, the universe was opaque. As space expanded, the Universe cooled and the electrons combined with the protons (and other atomic nuclei) to create the first atoms, primarily hydrogen. The first light of creation could finally be freed from its pinball-like interactions with the electrons at which point the Universe became transparent.
Since this time, this light has effectively moved through the cosmos unimpeded and brings to us an image of the infant Universe. It is the oldest light that can be detected. Cosmologists studying the first light from the Big Bang, called the "cosmic microwave background" (CMB) radiation, look back through time and space to about 400,000 years after the Big Bang, when the Universe was opaque.
One of the most fascinating things about the Universe is its mystery. It seems that every question that is answered with some certainty gives rise to ten more. The data collected from MAP should help to answer some of the most fundamental questions before astronomers today.
Science observations and data collection
During the phasing loops and until MAP is past the Moon, MAP communicates with Earth with the use of its transponders and two omni antennas located at the top and bottom of the spacecraft. On the way to L2, MAP will switch to use of the Medium Gain Antennas located at the bottom of the spacecraft. Data is transmitted to Earth once per day from L2. On orbit operations are conducted at NASA's Goddard Space Flight Center.
Control of scientific measurement errors
New technology associated with MAP
The MAP receivers split the incoming microwaves into separate paths, each with their own independent amplification. Any differences in these signals are due to instrumental changes, while common signals are from the sky. This automatically neutralizes the adverse affects that would otherwise occur due to naturally occurring changes of receiver gain.
This MAP receiver approach was enabled by the creation of amplifiers (which are only a little bigger than a box of matches) that were custom designed by Marian Pospieszalski and built for MAP by the National Radio Astronomy Observatory in Charlottesville, Virginia. The MAP receivers contain 80 of these amplifiers.
The microwaves are directly amplified, even at MAP's highest frequency (about 100 GHz) with high sensitivity over a 20 percent wide range of frequencies. In the past, it would have been necessary to convert the microwave signals to lower frequencies in a process that resulted in a considerable loss of sensitivity and which often introduced other problems. The MAP receivers also preserve the polarization information of the original signal, which provides additional constraints on cosmology.
Flight Data File
Vehicle: Delta 2 (7425)
Launch date: June 30, 2001
Launch time: 3:46:46 p.m. EDT (1946:46 GMT)
Launch site: SLC-17B, Cape Canaveral, Florida
Satellite broadcast: GE-2, Trans. 9, C-band
Launch timeline - Chart with times and descriptions of events to occur during the launch.
Ground track - Trace the Delta rocket's trek during launch.
Restricted zone - Map outlining the Launch Hazard Area where mariners should remain clear for the liftoff.
Delta 2 rocket - Overview of the Delta 2 7425-model rocket used to launch MAP.
Microwave Anisotropy Probe - Technical look at the spacecraft and its systems.
Delta directory - See our coverage of preview Delta rocket flights.
MISSION STATUS CENTER