A Millimeter/Submillimeter Search for the Sunyaev-Zel'dovich Effect in   the Coma Cluster
  Observations from the first flight of the Medium Scale Anisotropy Measurement (MSAM1-92) are analyzed to search for the Sunyaev-Zel'dovich (SZ) effect towards the Coma cluster. This balloon-borne instrument uses a $28\arcmin$ FWHM beam and a three position chopping pattern with a throw of $\pm40\arcmin$. With spectral channels at 5.7, 9.3, 16.5, and 22.6~\icm, the observations simultaneously sample the frequency range where the SZ spectral distortion in the intensity transitions from a decrement to an increment and where the fractional intensity change is substantially larger than in the Rayleigh-Jeans region. We set limits on the Comptonization parameter integrated over our antenna pattern, $\Delta y \leq 8.0 \times 10^{-5}$($2 \sigma$). For a spherically symmetric isothermal model, this implies a central Comptonization parameter, $y_o \leq 2.0 \times 10^{-4}$, or a central electron density, $n_o \leq 5.8 \times10^{-3}$cm$^{-3}h_{50}$, a result consistent with central densities implied by X-ray brightness measurements and central Comptonization estimates from lower frequency observations of the SZ effect. 
R.F. Silverberg, E.S. Cheng, D.A. Cottingham, D.J. Fixsen, C.A. Inman,   M.S. Kowitt, S.S. Meyer, L.A. Page, J.L. Puchalla, ...