The Planck Satellite
The Planck satellite was launched in 2009 with the mission of precise mapping of the Cosmic Microwave Background (CMB) radiation that pervades the universe. It follows the earlier work of the COBE and WMAP satellites. It collected data for 4.5 years, ending it's mission on 23 October, 2013. Like the WMAP satellite, it made use of the L2 Lagrange point during its operational lifetime, but was moved into a stable orbit around the Sun at the end of its mission.
The WMAP mission has provided the first detailed full-sky map of the microwave background radiation in the universe. The map produced is characterized as a map of the effective temperature of the microwave background radiation as depicted below. This is a synopsis of the description of the mission from the WMAP mission report on the NASA website. The illustrations are NASA graphics.
Note that the temperature variation on the Earth covers about 100°C while those measured by WMAP range only over about 0.0004 °C, a smaller range by a factor of a quarter of a million.
The synopsis of the implications of WMAP as summarized in the mission report includes the following quote from the WMAP site:
The positioning of the WMAP satellite made use of the Lagrange point L2 which permitted it to be kept in place with a minimum expenditure of fuel and always keep its sensors pointed away from both the Earth and the Sun.
WMAP home page
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