SOLAR-RADIATION (190-230 NM) IN THE STRATOSPHERE - IMPLICATIONS FOR PHOTOELECTRIC EMISSIONS FROM INSTRUMENTATION AT BALLOON ALTITUDES

Photoelectric contamination of conductivity measurements using the relaxation time method and electric field measurements using double-probe systems have been observed well below maximum baloon altitudes. We employ a photocurrent model to investigate the contamination of the relaxation time measruements. The model result shows that the solar flux in the range of 190-230 nm is more than sufficient to account for our conductivity observations. In the double-probe measurements of electric fields, the photoelectric effects appear as perturbations to the probe potentials. On the basis of our analysis, we recommend that the surfaces of double-probe instruments in the stratosphere be coated with a material of highly uniform work function in the optimum range of 4.6-5.4 eV. -from Authors