A SYSTEM FOR GRABBING INTEGRATED VIDEO FRAMES REMOTELY

A system for grabbing integrated video frames produced by a remote cam era is described. As part of the pointed platform in a balloon-borne e xperiment, we use a video charge-coupled-device camera to obtain wide field star images. To obtain images with a sufficient signal-to-noise ratio, integration times of up to 1 s are required. In applications wh ere the frame grabber and camera are physically close to each other, t iming the frame grabber trigger is straightforward; however, there are several advantages to locating the frame grabber not on the balloon p ayload. As a result commands issued simultaneously to the frame grabbe r on the ground and the camera on the balloon can be delayed relative to each other, resulting in failure to acquire an image. We have devel oped a system where, at the end of an integration, a tone is injected into the video field preceding the transmission of the integrated fram e; the tone is used on the ground by a decoder circuit to control the frame grabber acquisition of the integrated frame. The system has oper ated successfully in the flight of a stratospheric balloon-borne teles cope. (C) 1996 Americans Institute of Physics.