Microwave radiometer Determine the Dr. A. H. Barrett, temperature of the Massachusetts planet surface and Institute of details concerning Technology; D. E. its atmosphere Jones, JPL; Dr. J. Copeland, Army Ordnance Missile Command and Ewen-Knight Corp.; Dr. A. E. Lilley, Harvard College Observatory Infrared radiometer Determine the Dr. L. D. Kaplan, JPL structure of the and University of cloud layer and Nevada; Dr. G. temperature Neugebauer, JPL; Dr. distributions at C. Sagan, University cloud altitudes of California, Berkeley, and Harvard College Observatory Magnetometer Measure planetary and P. J. Coleman, NASA; interplanetary Dr. L. Davis, magnetic fields Caltech; Dr. E. J. Smith, JPL; Dr. C. P. Sonett, NASA Ion chamber and Measure high-energy Dr. H. R. Anderson, matched cosmic radiation JPL; Dr. H. V. Neher, Geiger-Mueller tubes Caltech Anton special-purpose Measure lower Dr. J. Van Allen and tube radiation (especially L. Frank, State near Venus) University of Iowa Cosmic dust detector Measure the flux of W. M. Alexander, cosmic dust Goddard Space Flight Center, NASA Solar plasma Measure the intensity M. Neugebauer and Dr. spectrometer of low-energy C. W. Snyder, JPL positively charged particles from the Sun Four experiments for investigation of interplanetary space and the regions near Venus employed: a magnetometer; high-energy charged particle detectors, including an ionization chamber and Geiger-Mueller radiation counters; a cosmic dust detector; and a solar plasma detector.