MEASUREMENTS OF THE MILLIMETER-WAVE SPECTRUM OF INTERSTELLAR DUST EMISSION

We report measurements of the differential brightness of interstellar dust emission near the Galactic plane and at high Galactic latitudes. The data were obtained as part of a program to measure anisotropy in t he cosmic microwave background (CMB). The measurements were made with a 0.degrees 5 beam size and a 1.degrees 3 p-p sinusoidal chop, in broa d bands (Delta nu/nu similar to 0.3) centered near frequencies of 6, 9 , and 12 cm-l. A measurement made toward the Galactic plane, at longit ude l = 23.degrees 7, is compared with the contrast observed in the 10 0 mu m IRAS data. Assuming the dust emission has a brightness I-nu pro portional to nu(n)B(nu)(T-d), where B-nu is the Planck function, a bes t fit yields n = 1.6 +/- 0.4, T-d = 24 +/- 5 K. In a region near the s tar mu Pegasi (mu PEG l = 91 degrees, b = -31 degrees), the comparison of our data with the 100 mu m IRAS data yields n = 1.4 +/- 0.4, and T -d = 18 +/- 3 K. In a second region near the star gamma Ursa Minoris ( GUM l = 108 degrees, b = 41 degrees), an upper limit is placed on cont rast in dust emission. This upper limit is consistent with the spectru m measured at mu PEG and the IRAS 100 mu m emission contrast at GUM, w hich is similar to 8 times lower than mu PEG.