Wilkinson Microwave Anisotropy Probe

Wilkinson Microwave Anisotropy Probe ( WMAP, formerly MAP, and Explorer 80 ) was launched in 2001 is a U.S. space probe, which was in operation until 2010.

Name and Mission

"MAP " is an abbreviation for "Microwave Anisotropy Probe " and is used to study irregularities in the cosmic background radiation. From this radiation a card should be made, so it fits the abbreviation " MAP" ( Engl.: map). In December 2002, the probe was renamed " WMAP ", with the " W" for the physicist David Todd Wilkinson ( 1935-2002 ), one of the discoverers and explorers of the cosmic background radiation is.

WMAP is the successor of the COBE satellite, which by 1992 already investigated in 1989 from an Earth orbit this radiation. WMAP should create improved by a factor of 20 Map. Instruments to measure the temperature differences in the range of 20 millionths of a degree. For WMAP, a new observation site was selected: the sun facing away from the Lagrange point L2. Therefore WMAP is classified as a spacecraft and not as a satellite here. The 840 kg mass spacecraft WMAP is also classified as " Explorer 80 ".

Since August 2009, the European space probe Planck measures the radiation at three times the resolution - with better suppression of interference. However, the WMAP mission went even further until 2010.

WMAP is a collaboration between the University of Princeton ( Responsible: Lyman Page ) and the NASA Goddard Space Flight Center. Leader of the project is Charles L. Bennett.

Description of the probe

WMAP is a probe that rotates in about 129 seconds around its own axis. Its main body is about tower -shaped and bears a "pseudo - correlation radiometer " called instrument with two back to back mounted Gregory antennas of 1.4 × 1.6 m primary mirror size. The secondary mirrors are 0.9 × 1.0 m tall. It measures at the frequencies 22, 30, 40, 60 and 90 GHz. The signal components which are identical for both antennas are not registered. The remaining signal is measured. The tower stands in the center of a nearly circular, viewing hood shield, whose spokes are six solar panels, whose solar cells are mounted on the bottom. The base of the sunshade screen is constantly oriented towards the sun, so that it shields the probe from the sun. The actual probe body is thus constantly in the shade and therefore has a very low equilibrium temperature between the heat generation on board and the radiation of heat into space. The operating temperature of the pseudo - correlation radiometer is characterized noise cancellation less than 95 K ( -178.15 ° C).

Course of the mission

WMAP was launched on June 30, 2001 on a Delta II 7425-10 rocket into a highly elliptical Earth orbit, where they performed three Erdumläufe before a swing-by maneuvers carried out at the moon during the fourth round and direction L2 was thrown. In the Lissajous orbit around L2, the probe occurred on 1 October 2001. On 20 August 2010 WMAP sent for the last time scientific data and on 20 September the control jets were ignited, thereby WMAP its Lissajous orbit around L2 left and has now achieved a parking orbit around the sun. However, the NASA funded the data analysis further two years.

Results

The main task of WMAP is to measure the temperature distribution of the cosmic background radiation ( measured Planck's radiation temperature). The measurements cover the entire sky. The measured temperature fluctuations reflect the distribution of matter in the universe at the time of decoupling of radiation and matter resist a few hundred thousand years after the completed some 13.7 billion years ago the Big Bang. The total radiation is extremely homogeneous, the fluctuations relative to the average, which currently stands at about 2.7 Kelvin, will be approximately 5:10 -5. The results from WMAP are of paramount importance for cosmology:

• For the composition of the universe gives WMAP values ​​of 4.6 % conventional matter, 23 % dark matter and 72 % dark energy (in the early universe, the composition was different. )
• The data location can be on a universe with flat ( Euclidean ) close spatial geometry.
• The expansion of the universe lasts due to the significant contribution of dark energy to forever.
• The age of the universe is estimated at 13.7 billion years.
• First Stars in the Universe there was before 13.5 billion years.

Follow-up mission

A follow-up mission, the Planck space telescope was launched in May 2009 by an Ariane rocket.