A family of optical instruments used for precise time-correlated observation of distant airplanes, missiles, and artificial satellites, all of which travel at apparent velocities much greater than those of most astronomical objects. The instruments supply permanent engineering records for the determination of spatial position, missile attitude, structural behavior, and performance of specific mechanisms. These observations enable engineers to correct design, improve performance, and collect scientific data from missiles and satellites at extreme distances and altitudes.
Optical tracking instruments were used initially for photographic recording of distant engineering events and for the determination of their spatial position. Tracking telescopes were the basic engineering event-recording systems, while cinetheodolites and ballistic cameras were used for precise spatial position. Electrooptical sensors and computer developments have expanded the family of optical tracking instruments to include television and laser detection and tracking of objects out to geosynchronous orbits. The proliferation of sensors has led to the development of flexible optical tracking instruments (see illustration) capable of accommodating a variety of photographic and electrooptical sensors. These sensors have been combined with computer controllers to develop automatic tracking instruments offering both event and position functions in one instrument. The further addition of laser ranging capability permits single-station position solutions along with tracking telescope engineering event recording.
KINETO Model 433 Tracking Mount shown with 100- and 200-in. focal-length (2.5- and 5.1-m) motion picture cameras, both with 12-in. (30-cm) aperture, and a 40–240-in. focal-length (1.0–6.1-m), 6-in.-aperture (15-cm) television camera. The fourth platform is reserved for either a laser ranger or a thermal imaging system. (Contraves Goerz Corp.)
Spatial position determination can be considered the determination of the position of a moving target using dynamic adaptions of the methods of civil surveying. The classical techniques utilize a minimum of four instruments on precisely measured baselines to locate a moving target. Each instrument records the data for computing the direction of the line of sight to the target for each instant of time. This information, in the form of analog or digital elevation and azimuth angles, the times of observation, and the known location of each instrument, is used to triangulate for the location of the missile as a function of time. See also Surveying.
Cinetheodolites
Most of the spatial position work is performed by cinetheodolites, which are surveying theodolites having 35-mm motion picture cameras with 45–120-in. focal-length (1.2–3-m) lenses substituted for the surveyor's eye and telescope. The system of cameras is synchronized up to a maximum of 30 frames per second from a master control station for simultaneous exposure as the cinetheodolites follow the moving missile. Each photograph records the elevation angle, the azimuth angle, the missile image, and the reticle lines which define the instrumental axis.
Ballistic cameras
These are fixed-axis, wide-angle, photographic-plate cameras capable of more precise spatial position determination by recording on one plate multiple exposures of the missile against a stellar background. Use of a static system and precisely cataloged star positions decreases the necessity for long-term mechanical stability and accuracy, allowing ballistic cameras to achieve 2–5 seconds' angular accuracy. Pyrotechnic flares of electronic stroboscopic lamps at the missile are used to indicate the missile positions against the night sky.
Tracking telescopes
These are long-focal-length telescopes mounted to track missiles in flight precisely while collecting missile performance data. The first systems were crude attempts to track manually with 35-mm cameras of 12–24-in. (30–60-cm) focal length. Increased focal length led to the use of geared, manually driven naval gun mounts and variable-speed, belt-driven machine gun mounts with the telescopes substituted for the armament. In all such systems, the tracking operator observes the missile through an optical sight while controlling the orientation of the telescope to ensure that the missile remains within its field. The advent of computer control and electrooptical automatic tracking systems has resulted in the adaption of direct-drive torque motor systems to replace the electrohydraulic systems.
Satellite optical tracking
Satellites equipped with retroflectors have been placed in orbits at altitudes which minimize gravitational and atmospheric anomalies. Satellites, such as Lageos with a 3700-mi (6000-km) orbit, are the basis of laser ranging measurements which require precise optical tracking to be effective.
The orbit of the satellite becomes the basis of measurements because of its regularity. Operation requires that the optical tracking systems must direct a 10-arc-second laser beam along the predicated laser path. Hundreds of laser ranging measurements are then made from two locations. The satellite ephemeris then becomes the yardstick for measuring the location relative to other measured points. This technique is used for geodetic and geophysical studies of polar motion, Earth rotation, gravimetric and tide models, and precise geoid determination. See also Astronomical photography; Camera; Geodesy; Laser; Lens (optics); Satellite (spacecraft).
