Apparent temperature of Jupiter at a wave length of 10 cm.

Abstract

Thirty-three measurements of the apparent temperature of Jupiter were made between June 10 and August 20, 1958 at wave lengths of 10.2 and 10.3 centimeters using the Naval Research Laboratory, 84-foot diameter, paraboloidal antenna. Each measurement consisted of the point by point average of from 4 to 8 right- ascension scans of the antenna beam thru the position of Jupiter at the sidereal rate. The measured apparent blackbody temperatures ranged from 3000K to IoIo0K about a mean of 6400K + 8~0K estimated standard error. The high value of apparent temperature was unexpected, because it was higher by factors of 3 to 4 than apparent temperatures previously measured in the centimeter wave length region of the spectrum, at wave lengths between 3.15 cm and 3.75 cm, which were in reasonable agreement with temperatures measured in the infra-red. The present measurements give a roughly normal distribution of apparent temperature with a standard deviation of 1900K. On the basis of the estimated measurement errors, the expected standard deviation is about 1450K, which is in reasonably good agreement with the observed scatter, but does not preclude the possibility of a variable component in the intensity of the radiation. The measured temperatures show no long-time trends over the 71 day measurement interval, but show a suggestion of a cyclical variation of about 30 per cent correlated with a rotation rate between 40 seconds and 2 minutes longer than the rotation period of System II. U. S. Naval Research Laboratory Washington, D. C.