Techniques for tracking a straight line object by creating a detection envelope between two detections selected from temporally-discontinuous frames are discussed. The detections within the detection envelope can then be analyzed in order to determine whether they are associated with a straight line track between the outer detections of the envelope. Techniques for identifying a launch-flash are also discussed. Potential launch flashes are checked for energy duration, intensity and spectral ratio. Techniques for detecting a hostile fire based on a single-frame detection are additionally detected. Based on a frame length of the detection, it can be determined whether the detection correlates to a hostile fire.