Flights

The Archeops experiment has already flown twice, once for a technical flight launched in Trapani (Sicily, Italy) crossing the mediterranean sea towards Spain in July 1999, producing 4 hours of night data, but with only 4 detectors. The second flight started from Esrange, a SSC (Swedish Space Corporation) base, near Kiruna (Lapland in the north of Sweden). The gondola was launched by the CNES (Centre National d'Etudes Spatiales) on January, 29$^{th}$ 2001 at 2pm (local time) and landed in Russia at Syktyvkar around midnight. The flight was shortened due to strong stratospheric winds (about 400km/h), which pushed the gondola too rapidly towards the east. We however obtained 7.5 hours of scientific data (during night and at a float altitude of 31.5 km), covering 22.7% of the sky. The cryostat remained below 100 mK during the entire flight.

Figure 7: Archeops beams (angular sensitivity distribution), projected on the sky, obtained using Jupiter's signal.

The average size of our optical beam is around 8 arcminutes, the average effective beam size is around 12 arcminutes because of the bolometers time response. Some beams are also a bit asymetric, but this only impacts the very smallest angular scales, not attainable by Archeops for this flight (see Figure 8). The quality of the data was excellent, and will allow us to compute an accurate CMB anisotropies spectrum, especially on the low $\ell$ edge of the first acoustic peak.