The Orpheus Aerial Reconnaissance System

The Orpheus Aerial Reconnaissance System

The Orpheus pod originates from close cooperation in 1966 between De Oude Delft Optical Industry, the National Aerospace Laboratory (NLR) and Fokker. The cameras and the necessary electronics were supplied by Oude Delft. These were five daylight cameras and one InfraRed Line Scanner (IRLS). The light-metal gondola has been developed by Fokker in collaboration with NLR.
The 306 photo reconnaissance squadron (September 17, 1954 to October 2010)) uses the Orpheus pod underneath the RF-104G Starfighter and the (R)F-16A Falcon.

The Orpheus pod
The pod has a total weight of approximately 350 kg. and a length of 3.75 meters with a diameter of 0.47 meter. Inside the pod placed from front to rear are: five TA-8M daylight cameras, the IRLS-5 InfraRed Line Scanner and the Coupler Control Unit (CCU) which consist most of the control electronics.

The complete pod is hung under the centerline rack of the aircraft, using two hooks and is connected to the aircraft by two connectors. The system operates fully automatically when the pilot operates the cameras and / or the scanner with a control panel in the cockpit.

The Orpheus pod has been developed for aerial reconnaissance at low altitude and at high speed. The temperature limits for the system are between -54 and +71 degrees Celsius.

The flying speeds at which this all happens are between 500 and 1,100 km / h and  optimum results are achieved between 30 and 500 meters flying altitude.

The daylight cameras
The front camera and first left and right cameras are equipped with 70 mm lenses. The aft left and right cameras has interchangeable lenses of 70, 100 and 150 mm. The film exposure times varies between 1/376 and 1/7500 second and the diaphragm is automatically adjusted for each camera. The film speed is controlled by the ratio between ground speed and radio altitude for optimum imaging results.

The InfraRed Line Scanner (IRLS)
This system works with infra-red radiation from the earth surface (temperature differences) that is recorded on a black & white film using an ingenious optical and electronic system. The sensitivity is such that differences of 0.1 degree Celsius are registered which makes it possible to take photographs under the most challenging conditions. We have to see this “taking pictures” of the IRLS as “writing lines” to the film. The rotor of the scanner, which consist of three mirrors, rotates at a speed of 12000 revolutions per minute. This means that three lines are written on the film per rotation of the rotor. After shooting the image by the IRLS, the picture consists of a large number of adjacent lines.

Both the daylight cameras and the IRLS have a cassette with 45 meters of film of which about 4 meters are used per target. The exposed film is cut off in a dark room so that the remaining unexposed part can be reused.

The Orpheus pod has its own temperature management system. When the internal temperature exceeds 44 degrees Celsius, the cooling system will automatically start.

The pod has a water tank from which demineralised water is sprayed in the cooling air. Due to the evaporation of the water the temperature in the pod decreases. Depending on the height of the temperature, the intensity of spraying can be increased so that a guaranteed maximum temperature in the pod is not exceeded. If the temperature drops below 10 degrees Celsius, electric heating elements are switched on to prevent condensation on the glass panes and lenses of the cameras. Both systems, cooling and heating, are built in to protect the electronics. In addition, at high temperatures the development value of the film deteriorates and at low temperatures the chance of breaking off the film arises. As a result of high-quality maintenance by excellent trained specialists, a high degree of employability is achieved.