Anisotropy measurements of the cosmic microwave background (CMB) are a very effective tool for testing and
constraining models of cosmic structure formation. With the
discovery of large angular anisotropy by COBE (Smoot et al.1992), there has been an increased interest in characterizing
anisotropy on degree angular scales. Although all CMB measurements have to overcome a long list of systematic effects
and foreground contaminants (Wilkinson 1994), they have the potential to constrain many of the global parameters of the
universe and thus discriminate among the plethora of cosmic structure formation models. Over the past 6 years, we have
traveled to the South Pole 3 times to perform these degree-scale anisotropy measurements. The results from our
1988-1989 measurements are detailed in Meinhold & Lubin (1991) (SP89a) and Meinhold et al. (1993) (SP89b), while the results
from the 1990-1991 measurements are detailed in Gaier et al. (1992) (SP91a) and Schuster et al. (1993) (SP91b). The results
from these measurements and the five balloon-borne Millimeter-wave Anisotropy Experiment (MAX) are summarized in Lubin (1994).
In order to obtain additional sky coverage and frequency coverage, we returned to the Amundsen-Scott South Pole Station
during the austral summer 1993-1994 (SP94).
We present results from the two observations of the cosmic background (CMB) performed from the South Pole during the 1993-1994 austral summer. Each observation employed a 3 degree peak-to-peak sinusoidal, single difference chop and consisted of a 20 degree x 1 degree strip on the sky. The first observation used a receiver which operates in three channels between 38 and 45 GHz (Q-band) with a FWHM beam which varies from 1 degree to 1.15 degrees. The second observation overlapped the first observation and used a reciever which operates in four channels between 26 and 36 GHz (Ka-band) with a FWHM beam which varies from 1.5 degrees to 1.7 degrees. Significant correlated structure is observed in all channels for each observation. The spectrum of the structure is consistant with a CMB spectrum and is formally inconsistant with a diffuse synchrotron and free-free emission at the 5level. The amplitude of the structure is inconsistant with 20 K interstellar dust; however, the data do not discriminate against flat or inverted spectrum point sources. The root mean square amplitude
of the combined (Ka + Q) data is
for an average window function which has a peak value of 0.97 at
and drops to
of the peak value at
A band power estimate of the CMB power spectrum,
Gaier, T., et al. 1992, ApJ, 398, LI.
Lubin, P. M. 1994, Proc. IAU Symp. 168, ed. M. Kafatos & Y. Kondo (Dordrecht: Kluwer), in press.
Meinhold, P., & Lubin, P. 1991, ApJ, 370, LI I.
Meinhold, P., et al. 1993, ApJ, 406,12.
Schuster, J., et al. 1993, ApJ, 412, L47.
Smoot, G. F., et al. 1992, ApJ, 396, LI.
Steinhardt, P. J. 1994, private communication.
Wilkinson, D. 1994, Proc. 9th Lake Louise Winter Institute, Particle Physics and Cosmology, (Singapore: World Scientific), in press.
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