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We report measurements of the Jupiter brightness spectrum in the 850-[[micro]meter]and 1100-[[micro]meter] atmospheric windows with a spectral resolution of 125 MHz,obtained with a Fourier transform spectrometer on the James Clerk MaxwellTelescope. Three results were obtained. First, the predicted absorption featuresdue to the rotational lines of HCN at 266 and 354 GHz were not detected within ourerror limits of less than 1%. We establish new upper limits for the HCN abundancein the jovian troposphere for five assumed abundance distributions and for twoassumed [NH.sub.3] abundances. The upper limits are 1.7 to 13 times smaller thanthe abundance value obtained in the only reported detection of HCN in Jupiter priorto the impact of ShoemakerLevy 9. Second, the continuum brightness temperaturespectrum at 850 [[micro]meter] was determined and is in agreement with previousmeasurements, but has large error bars due to uncertainties in the photometriccalibration. We estimate the ammonia abundance in the 1-2 bar region to be 1.7times solar, but this result is tentative since scattering by [NH.sub.3] cloudparticles and absorption by gaseous [H.sub.2]S were neglected in our atmosphericmodel. Finally, the first rotational line of [PH.sub.3] at 267 GHz was notdetected, a result which we demonstrate is consistent with the statistical noiselevel in these measurements, with current values of the spectroscopic parameters,and with phosphine measurements at other wavelengths. Key Words: abundances, atmospheres; atmospheres, composition; data reductiontechniques; Jupiter; Jupiter, atmosphere; radiative transfer; spectroscopy.

The near-millimeter brightness temperatures of Uranus and Neptune are obtained accurately by photometric measurements. Smoothly varying spectrum in the region of 0.35 and 2.0 millimeter is exhibited by both the planets. No strong unresolved spectral feature is exhibited by the planets, indicating the absence of molecular transitions. The presence of depression in the spectrum of Uranus which was reported in earlier observations is absent in the present observations. An empirical formula is obtained for the temperature in Uranus using the Martian temperature system as the standard.