Operation Dominic. Fish Bowl Series. Project Officers Report - Project 6.11. HF Communications Experiment

One of the most sensitive measures of a change in electron content in the lowest portions of the ionosphere is the received phase of a VLF signal. Such measurements have been used for years to monitor sudden ionospheric disturbances (SID) in the lower ionosphere. Phase differences equivalent to a change of a few electrons per cubic cm or an effective ionospheric height change of less than 1 km can be detected. Project 6.11 had, as a requirement, a frequency standard with stabilities of the order of a few parts in 10 (expn 10) to be used as a time signal source at each terminal in the HF sounder program. These standards were kept on frequency by monitoring the 18-kc time-and-frequency-standard signal radiated from the U.S. Navy Transmitting Station, NBA, Balboa, Canal Zone. To synchronize the local-standard frequency with the 18-kc signal from NBA, the received phased of NBA was compared on a day-to-day basis with the local standard. Corrections to the local standard were made manually, based on several days' measurements. The system required for recording the received phase of NBA also contains data on the change in phase at the time of the Fish Bowl events. This report describes these measurements.