The Naval Research Laboratory far ultraviolet experiment on board the OGO 4 satellite accidentally detected hydrogen Lyman &agr; emission following the passage of missiles through the upper atmosphere. The deposition of hydrogenous exhaust products above 100 km results in a local enhancement of hydrogen, which resonantly scatters Lyman &agr; radiation from the Sun and from the geocorona, and produces a far ultraviolet contrail. The observed local enhancement of radiation was as much as 37% above the natural background. All event detections took place at time intervals of 6 min to 10 hours following the passage of a missile or spacecraft. There was no opportunity to observe prompt emissions. We describe the observations of this unusual phenomenon and the implications for hydrogen production mechanisms. ¿ 1999 American Geophysical Union