The invention provides in one aspect a fast digital light source tracker aboard a moving ground-based or airborne platform. The tracker consists of two rotating mirrors, a lens, an imaging camera, and a motion compensation system that provides the Euler angles of the mobile platform in real time. The tracker can be simultaneously coupled to UV-Vis and FTIR spectrometers, making it a versatile tool to measure the absorption of trace gases using the light source's incoming radiation.

Scanning apparatus includes a base and a gimbal, including a shaft that fits into rotational bearings in the base and is configured to rotate through 360 about a gimbal axis relative to the base. A mirror assembly, fixed to the gimbal, includes a mirror, which is positioned on the gimbal axis and is configured to rotate about a mirror axis perpendicular to the gimbal axis. A transmitter directs pulses of optical radiation toward the mirror, which directs the optical radiation toward a scene. A receiver, receives, via the mirror, the optical radiation reflected from the scene and outputs signals in response to the received radiation. Control circuitry drives the gimbal to rotate about the gimbal axis and the mirror to rotate about the mirror axis, and processes the signals output by the receiver in order to generate a three-dimensional map of the scanned area.

A method for detecting azimuthal angle of a heat source includes a preparing step and a detecting step. The preparing step includes: detecting a unit period (Tc) by rotating a target positioning portion through one circle, and aligning the target positioning portion with an aligning member. The detecting step includes: driving the target positioning portion to rotate. The position of the aligning member defines an initial azimuthal position. When an infrared signal emitted from the external heat source is transmitted into an infrared sensor via the target positioning portion, a transmitting time is defined as a time point (Ts) of the heat source, and an angle between the target positioning portion and the initial azimuthal position is defined as an azimuthal angle (x) of the heat source, in which x=(Ts/Tc)360.