ANISOTROPY IN THE COSMIC MICROWAVE BACKGROUND AT DEGREE ANGULAR SCALES

Observations of the microwave sky using the Python telescope in its fifth season of operation at the Amundsen-Scott South Pole Station in Antarctica are presented. The system consists of a 0.75 m offaxis telescope instrumented with a HEMT amplifier-based radiometer having continuum sensitivity from 37-45 GHz in two frequency bands. With a 0.91 ◦ × 1.02 ◦ beam the instrument fully sampled 598 deg 2 of sky, including fields measured during the previous four seasons of Python observations. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background, we place constraints on the angular power spectrum of fluctuations in eight multipole bands up to l � 260. The observed spectrum is consistent with both the COBE experiment and previous Python results. There is no significant contamination from known foregrounds. The results show a discernible rise in the angular power spectrum from large (l � 40) to small (l � 200) angular scales. The shape of the observed power spectrum is not a simple linear rise but has a sharply increasing slope starting at l � 150. Subject headings: cosmic microwave background - cosmology: observations