The Planck satellite is in good shape. The First Light Survey, performed to demonstrate the stability of the instruments and the ability to calibrate them over long periods, indicate that the data quality is excellent. This bodes well for the full sky survey that has just begun and will take about six months.
Figure 1 : La bande du ciel observée par Planck est représentée ici en fausses couleurs sur une image complète du ciel où on peut voir notre Galaxie. Crédits : ESA, LFI et HFI consortia (Planck), image de fond : Axel Mellinger. Cliquer sur l’image pour l’agrandir [en]Figure 1 : Artist’s view of the satellite PLANCK. Planck will be launched on an Ariane-5 from the Guiana Space Centre, Kourou, French Guiana, at the end of July 2008. It will be launched together with ESA’s Herschel spacecraft, in a dual launch configuration. About 2.5 hours after launch, Planck separates from Herschel, and then starts its cruise to L2 (second Lagrangian point in space), its destination, where it will arrive in less than 6 months. Credit ESA Click on the image to enlarge it
Following launch on 14 May 2009, check-outs of the satellite’s subsystems were started in parallel with the cool-down of the instruments’ detectors. The detectors are looking for variations in the temperature of the CMB that are about a million times smaller than one degree. a feat comparable to measuring from Earth the body heat of a rabbit sitting on the Moon. To achieve this, Planck’s detectors must be cooled to extremely low temperatures, some very close to absolute zero (-273.15°C, or 0 K). A team from LERMA, reinforced by visitors from Caltech and JPL, has performed the delicate tuning of the bolometer of the High Frequency Instrument. The HFI and the Low Frequency Instrument have demonstrated excellent characteristics so far, fulfilling expectations from ground tests. In preparation for routine scientific operations, their long-term stability has been verified by conducting a first ’trial’ survey. the First Light Survey.
The First Light Survey, which began on 13 August 2009, covers a two-week period during which Planck surveyed the sky continuously. It was carried out to verify the stability of the instruments and the ability to calibrate them over long periods to the exquisite accuracy needed. The satellite rotates around its axis, surveying the entire sky over time and in the process measuring tiny fluctuations in the temperature of the Cosmic Microwave Background (CMB). Each map is a ring about 15 degrees wide, stretching across the full sky. Preliminary analysis indicates that the quality of the data is excellent. The first Light survey was completed on 27 August, yielding maps of a strip of the sky, one for each of Planck.s nine frequencies. The maps are taken in 9 bands at frequencies ranging from 30 GHz to 1000 GHz, i.e. wavelengths from 0.3 mm to 1 cm.
Figure 2 : On peut voir un agrandissement (20°x20°) de la galaxie observée dans les neuf bandes de Planck. Cette mosaïque montre que les bandes centrales (à 100,143 et 217 GHz), où l’émission de la Galaxie est la moins importante, sont privilégiées pour l’observation du fond cosmologique. Crédits : ESA, LFI et HFI consortia (Planck) Cliquer sur l’image pour l’agrandir [en]Figure 2 : George F.Smoot, Nobel Prize for Physics in 2006, views the Planck satellite in the Alcatel Alenia Space facilities in Cannes, France, on 1 February 2007. Smoot, from the Lawrence Berkeley National Lab., Univ of California, shares the Nobel prize with John C. Mather (NASA) for the discovery of the blackbody form and anisotropy of the Cosmic Background Radiation - Planck’s object of study. The telescope has an effective diameter of 1.5m and will be cooled passively down to about 40 Kelvin. The Planck satellite can be seen in the background. It can be contained in a volume of 64 cubic meter. Credit ESA, S. Corvaja Click on the image to enlarge it
Figure 3 : La figure représente une région du ciel (10°x10°) observée avec la bande à 70 GHz de l’instrument basses fréquences (LFI) et la bande à 100 GHz de l’instrument hautes fréquences (HFI). On y voit l’univers tel qu’il était il y a 13,7 milliards d’années dans cette direction du ciel. Cette lumière a voyagé jusqu’à nous tout ce temps et nous révèle des petits écarts de température, tels qu’ils étaient seulement 400 000 ans après le Big Bang, mais qui seront à l’origine de la formation de grandes structures, comme les galaxies et les amas de galaxies que nous pouvons observer aujourd’hui. Crédits : ESA, LFI et HFI consortia (Planck). Cliquer sur l’image pour l’agrandir
