title: Optical instrumentation for tracking high altitude vapor releases by day.
abstract: High altitude chemical vapor trails may not be photographed by day because of the intense background light of the sky. A comparison of several possible emission line detectors is given. An instrument incorporating an ultra-narrow interference filter in a differential radiometer is described and the results of a successful field test are given.
authors.forename: G T
authors.initials: GT
authors.lastname: Best