The ESA Planck Surveyor Mission
Since the discovery of the cosmic microwave background radiation (CMBR) by Penzias and Wilson in 1965, the phenomenon has been studied intensively. By measuring intensity fluctuations in the CMBR, we can obtain unique information on the physical conditions in the early Universe. Just after Big Bang these physical conditions were very extreme, but the expansion of the Universe caused the temperature and density to decrease rapidly. The matter was completely ionised, and, due to the Thomson scattering by the free electrons, the Universe was completely opaque to electromagnetic radiation. Approx. 300.000 years after Big Bang, the temperature has decreased to about 3.000 K. The nuclei (mostly protons) and the free electrons re-combined to form neutral atoms and the Universe were suddenly completely transparent to photons. All these photons have travelled undisturbed through the Universe ever since and are now seen as the cosmic microwave background radiation.
The study of the early evolution of the Universe is a high-priority scientific area in Denmark. In order to combine both the theoretical and the observational efforts, a co-operation between DSRI, Theoretical Astrophysics Center (TAC) and the Niels Bohr Institute for Astronomy, Physics and Geophysics (NBIfAFG) was formed in 1995. As the first observational project, DSRI engaged itself in the US balloon experiment TopHat, described in section 2.5.1 below.
In April 1996, the Planck Surveyor mission was selected as the next ESA medium size mission. The main scientific objective is to study the CMBR with unprecedented sensitivity and angular resolution. DSRI has participated in the preparation of the Planck Surveyor mission since the early phases of the project. As a part of the preparation an appropriation from the Danish Ministry of Research was given to produce a carbon fibre test mirror, in order to demonstrate the Danish capability to produce the optical elements of the required quality. The test mirror was produced by Terma Industries, Grenaa.
The test mirror has been carefully tested. It has been demonstrated that the mirror fulfils the requirements concerning deviations from the optimal surface (rms. <>
Planck Surveyor is defined as a "principal investigator" mission, implying that only the parties responsible for the delivery of scientific instrumentation will have access to the scientific data during the long period from the time the data are collected and analysed, till the final maps are delivered to the general astronomical community. In this case, the mirror system is considered a scientific instrument. An agreement on the delivery of the mirror system has been signed between DSRI and ESA. The final approval by the ESA Council was given at the June 2000 meeting. ESA has decided to combine the Planck Surveyor mission and the FIRST missions on the same ARIANE 5 launch, planned for the first quarter of 2007.
A Danish Planck consortium with 3 member institutes as those taking part in the TopHat project has been established. The consortium is led by a steering committee with 2 representatives from each institute. Support has been obtained from the Danish Natural Science Research Council and the Danish Committee for ESA-related research.
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