
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.


Planck is an ESA satellite developed with national agencies, especially CNES and CNRS (INSU and IN2P3) for the HFI, and ASI and INAF for the LFI. Credits are available in this pdf document on the International Participation in Herschel and Planck.