The brightness temperature of Venus and the absolute flux-density scale at 608 MHz

We measured the disk temperature of Venus at 608 MHz near the inferior conjunction of 1972 and obtained a value of 498 i 33 K using a nominal CKL flux-density scale. The result is consistent with earlier measurements, but has a much smaller uncertainty. Our theoretical model prediction is larger by a factor of 1.21 + 0.09. This discrepancy has been noticed previously for frequencies below 1400 MHz, but was generally disregarded because of the large observational uncertainties. We have found no way to change the model to produce agreement without causing a conflict with well-established properties of Venus. Thus we are led to suggest that the flux-density scale may require an upward revision, at least near this frequency, in excess of what has previously been considered likely. Subject headings: radio radiation, planetary - Venus