Iii. Radio Astronomy Academic and Research Staff A. Very Long Baseline Interferometric Study of the Water-vapor Emission Regions in Orion A

The H20 line emission (rest frequency equal to 22235. 08 MHz) regions in W49 and Orion A were measured during June 1970, at three radio astronomical receiving stations: the 120 ft antenna of the Haystack Observatory in Tyngsboro, Massachusetts, and the 140 ft and 36 ft antennas of the National Radio Astronomy Observatory at Green Bank, West Virginia, and Kitt Peak, Arizona. The Haystack-Green Bank baseline was 845 km (6. 3 X 107 wavelengths), the Green Bank-Kitt Peak baseline was 2940 km (2. 2 X 10 8 wavelengths), and the Haystack-Kitt Peak baseline was 3659 km (2.7 X 108 wavelengths). The maximum fringe spacings for these baselines were 01'0033, 0.'00094, and 0."00076. The portion of the results relating to the angular distribution of radiation in W49 has been reported by Johnston et al. In this report we shall review the results on the structure of Orion A.