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SPACE/ Mission accomplished for one of Planck’s two “eyes”

Marco Bersanelli comments on the completion of one of the parts of the Planck mission to study the Big Bang by observing the first light of the universe and the formation of galaxies.

Planck   (Credits ESA - C. Carreau) Planck (Credits ESA - C. Carreau)

While keenly awaiting the new discoveries that are expected to be announced at an international conference in Bologna this month, the European Space Agency’s Planck mission has completed an important step. On January 14, one of the two scientific instruments that make up the mission, the HFI (High Frequency Instrument) completed its work. Ilsussidiario.net talked to Marco Bersanelli, an astrophysicist at the University of Milan and the Deputy Principal investigator of the other instrument, the LFI (Low Frequency Instrument), about this milestone.

So, a part of the mission has already been completed?
Yes, and in perfect agreement with predictions. The dilution refrigerator has exhausted its supply of Helium 3 and Helium 4, the combination of which kept the temperature of the HFI bolometers to 103 thousandths of a degree above absolute zero (-273 ° C) for thirty consecutive months with amazing stability.

How have the two instruments worked all this time?
The Planck satellite was launched on May 14, 2009 in an orbit 1.5 million kilometers from Earth, four times more distant than the Moon. The two instruments on board, the French-led HFI (high frequency) and the Italian-led LFI (low frequency) have collected data, together and continuously, with unprecedented accuracy. At the time of the launch, the minimum duration of the mission was fifteen months, but the in-flight performance of the equipment exceeded all expectations by doubling the duration of the exploration.

What do you foresee for the other part?
We expect the LFI, which requires a temperature of "only" 269 degrees Celsius below zero, to continue its observations until the summer of 2012 and perhaps beyond. All of this will allow us to gather more valuable information both in order to increase the sensitivity of the final maps (which are proportional to the square root of the observation time), and in order to improve the calibration of instruments and the suppression of systematic interference effects.

What are your objectives in this research?
The purpose of this research is to collect observations of the cosmic microwave background (CMB), the first light of the universe, with extreme sensitivity (a few millionths of a Kelvin) and high angular resolution (10 arcmin). The CMB photons uniformly fill every corner of the universe (there are exactly 441 in each cubic centimeter of space) and they reach us after a journey of 14 billion years, allowing us to listen, so to speak, to the first stirrings of the cosmos, emitted long before the formation of galaxies, stars and any other structures.

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