INFRARED IMAGING OF VENUS FROM IRTF PROTOCAM OBSERVATIONS IN 1991/

Infrared observations of Venus' night-side between 3 and 5 mu m provid e a valuable means to study the upper cloud structure (at approximatel y 68 km) and the thermal structure above the clouds. New observations between 3.67 and 5.08 mu m, concerning spectral images of Venus obtain ed in October 1991 with the Proto CAM/IRTF and a Circular Variable Fil ter, are presented. A cloud particle scale height for the upper clouds of 3.9 +/- 1 km is retrieved from limb darkening measuremets which is in good agreement with measurements from both space probes and Earth- based observatories. The observations show an increase in temperature from the centre towards the poles when sounding altitudes above 72 km. This, along at cloud top levels, implies isothermal profiles between 68 and 74 km at high latitudes. Copyright (C) 1996 Elsevier Science Lt d