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PLANCK -- UNLOCKING THE SECRETS OF THE UNIVERSE
A. LЁ teenmЁ 1 , M. Tornikoski1 , J. Aatrokoski1 , E. Valtao ja ah aki
1 2

MetsЁ vi Radio Observatory, Helsinki University of Technology aho MetsЁ vintie 114, 02540 KylmЁ a, Finland aho alЁ alien@kurp.tkk.fi
2

Tuorla Observatory, University of Turku, Finland

The Planck satellite is a Europ ean Space Agency ESA's mission capable of mapping the whole sky at several radio wavelengths. The ultimate purp ose of the satellite is to measure, with a high resolution, the cosmic microwave background (CMB) anisotropy pattern, and thus define the geometry and content of our Universe. At the same time all foreground radio sources in the sky, including extragalactic radio sources, will b e measured, to o. The bypro ducts of the CMB map cleaning pro cess, the foreground source maps, will b ecome useful scientific results in themselves. Hence the task is two-fold. First, to provide the cosmologists with to ols for cleaning the CMB maps, and second, to extract scientific information out of the high radio frequency all-sky foreground source catalogs. One of the most imp ortant goals of our Planck pro ject is the acquisition of complete sky surveys at several high radio frequencies --an unprecedented event that should solve at least some of the op en questions regarding active galactic nuclei (AGNs). Even though we do have a general idea of the basic structure and nature of AGNs, the detailed structure and precise physical pro cesses at work are not yet well understo o d. AGNs emit at all electromagnetic frequencies from the radio to the gamma-ray region, and all these frequencies are connected, each frequency adding to the complete picture. The future of the AGN research is in multifrequency studies p erformed with sophisticated ground-based and space-b orne instruments or instrument networks, and Planck will b e a significant contributor to this work. The MetsЁ vi and Tuorla Planck team has develop ed a sp ecial software called the aho Quick Detection System (QDS), that will b e used for detecting strong, p ossibly flaring, radio sources in the time-ordered data stream of the Planck satellite within one week from the time of observation. This is essential for follow-up observations since the actual data pro duct of the satellite will not b e available until after two years after the mission has started, and even the Early Release Compact Source Catalog (ERCSC) will b e available only approximately nine months after the first full sky observation cycle has b een completed. The QDS will give us a unique opp ortunity to get our hands on the Planck foreground data months b efore anyb o dy else, to trigger virtually simultaneous follow-up observations of interesting events, and also help monitor the quality of the satellite data at an early stage. QDS will b e op erated in the Planck Low Frequency Instrument (LFI) Data Pro cessing Centre (DPC) in Trieste, Italy, by our team. The launch date of the Planck satellite is currently set for early 2008, and the op eration of the QDS will start as so on as the test p erio d of the satellite has b een completed. In this pap er we describ e the Planck mission; the instruments and the science it has b een designed to study. A sp ecial emphasis will b e made on the Finnish participation in the pro ject. This includes, for example, the 70 GHz receivers that were designed and build in Finland, and many asp ects of the science we are currently involved in.