To gain more insight into the various effects of lightning and thunderstorms on future shuttle vehicle launch and landing operations, an experiment was conducted to obtain data on the nature of electric fields in the vicinity of thunderstorms and particularly in the region of cumulonimbus cloud anvils during their various stages of build-up, maturity, and dissipation. These data supplement the airborne electric field data collected during the summer of 1975 in support of the Apollo Soyuz Test Project and the Viking launches. A Learjet aircraft was outfitted with four special electric field meters for collecting data. The onboard aircraft radar was also used to investigate cells embedded in large thunderstorm systems such as those found in frontal and squall line activities. Data were collected from 33 storm cells and used to establish a launch criteria to preclude triggering lightning during shuttle vehicle operations in close proximity to thunderstorms. Johnson Space Center NASA-TM-X-74682, JSC-12509