RADIOMETER FOR THE MEASUREMENT OF WATER-VAPOR IN THE UPPER-ATMOSPHEREFROM SPACE

We describe the design, the development, and the calibration of a radi ometer to measure water vapor abundance in the middle atmosphere, usin g the solar occultation technique from an orbiting platform. The use o f gas cells containing water vapor and carbon dioxide leads to a relat ively simple, but sensitive, design. This radiometer is shown to be ca pable of detecting water vapor in the mesosphere, where, because of di ssociation by the Sun, the amounts are very small, of the order of 1 p art per 10(6) or less. A flight version of the instrument will be laun ched in 1992 on board the European Retrievable Carrier space platform, and the data will be employed for a better understanding of the Earth 's water budget.