This measurement of the large-scale cosmic microwave background radiation (CMBR) anisotropy places the most stringent constraints to date on fluctuations in the CMBR on angular scales greater than ∼4°. Using a four-channel bolometric radiometer operating at 1.8, 1.1, 0.63, and 0.44 mm, the diffuse sky brightness over half of the northern hemisphere has been mapped with an angular resolution of 3°.8. Analysis of the sky map at the longest wavelength for Galactic latitudes \b\ ≥ 15° yields a 95% confidence level upper limit on fluctuations of the CMBR at ΔT/T ≤ 1.6 × 10-5 with a statistical power of 92% for Gaussian fluctuations at a correlation angle of 13°. Between 3° and 22°, the upper limit of fluctuations is ΔT/T ≤ 4.0 × 10-5 (95% confidence level). An anisotropy is detected in the map, but it cannot yet be attributed to primordial sources. The ultimate sensitivity for this experiment is ΔT/T ∼ 7 × 10-6 (95% confidence level) over this angular range for Gaussian fluctuations.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
- Cosmic background radiation