This data book has been prepared by the National Reconnaissance Office with the assistance of the National Photographic Interpretation Center to provide general technical information pertinent to the reduction of data obtained by the KH-4B camera system.
The KH-4B camera system is expected to be operational in the fall of 1967. This photographic system is a continuation of the KH-4 series with modifications to provide adjustable exposure control, selectable filters, and a change in the mechanism which provides image motion compensation as well as a 3 inch focal length terrain camera.
TABLE OF CONTENTS
This data book incorporates the latest modication to die basic KHA camera system. The KH-4B camera system consists of 2 main panoramic cameras, a stellar/index camera and 4horizon cameras (Fig 1). The payload consists of 2 recoverable sub-systems, each containing approximately 16,000 ft of film (8,000 ft of film per camera). The 2 recoverable sub-systems are designated mission part 1 and mission part 2. The system may be used to meet either reconnaissance or cartographic objectives. lle camera (Fig 1) is oriented so that the forward camera in the vehicle is the aft looking, and the aft camera is the forward looking.
Each panoramic camera is mounted in the photographic vehicle at a 15 degree angle from the vertical, thus forming a 30 degree convergence angle. The cameras are designated as forwardlooking and aft-looking.Panoramc Camera Data
Table 1. Panoramic Camera Data
|Lens||Petzval f/3.5 T 3.8|
|Focal Length||609.602mm (24.0 in)|
|Scan Angle||70 deg +/- 35 deg from track)|
|Field of View||5.12 deg (along track)|
|Usable Format||29.323" X 2.147"|
|Slit Widths||Variable-- from 0.17 in to 0.30 in|
|Film Load||1. 70mm Wide|
|2. 8,000 ft per recovrable sub-system (part 1 or 2 of a mission) for each camera|
|3. 16,000 ft per recoverable sub-system|
|4. 16,000 ft per camera per mission|
|5. 32,000 ft total load for both cameras for a mission (part 1 and 2)|
|Image Motion Compensation (IMC)||Camera nods proportional to velocity/height (V/H) ratio|
|Stereo Angle||30.46 degrees|
|Filter||Variable -2 position commandable|
|Film Type||3404, Estar Base|
Binary Values in Milliseconds
|Least Significant Bit nearest the Takeup end of the format.||1|
|Most Significant Bit Nearest the Supply end of the format.||268435456|
Figure 2 is a complete record of the format for the forward looking and aft looking panoramic cameras. The following is a description of the various items on the film.
1. Camera Serial Number -- An imaged record of the camera manufacturer's serial number. An even number indicates the aft looking camera. An odd number indicates the forward looking camera.
2. Binary Time Word -- A recording of vehicle clock time to the nearest millisecond. The time word contains 29 bits plus a parity bit. There are six columns of 32 bits available, but only three columns of 30 binary bits are presently used as shown in Figure 3. The column nearest the film edge is column number one, and all 30 bits are illuminated to provide a registration for mechanical readout. Column two presents the time word in rows 1 through 29 with the 30th being the parity bit. Column three presents reciprocated time, again with the 30th bit being the parity bit. The data block is located outside the platen area on the taketip side. This me= that any time readout, as seen on the film, is associated with the following (next higher number) frame, or conversely, when ascertaining the time a particular frame was taken, it is necessary to look at the data block on the previous or lower numbered frame.
3. Titling Data -- The title is affixed crossway on the film between frames and consists of a pass number, frame number, an arrow (indicates frame to which title applies), mode (S for stereo, M for mono, or MS for mixed), date, mission number, camera (fwd or aft-looking), and classification. The letters D, A, and M, preceeding the pass number have the following meanings:a. D The pass is descending from north to south.
4. Panoramic Geometry Traces -- lines on either side of the format which aid in determining the locus of principal points of the lens.
5. A nod angle calibration system which, by means of a xenon flash triggered by an optical encoder mounted on the nod axis, images a series of small dots along the edge of the format.
6. Pan Geometry Fiducial Marks -- An image of the 73 holes through the film guide rails. Each hole is approximately 40 microns in diameter spaced at 1 centimeter intervals with a double hole at the center of format.
7. Time Track -- An image of a 200 cycle per second light pulse which records the camera lens scan rate.
8. Slur Time Pulse -- A stretched pulse which occurs immediately after the dock is interrogated in order to show the relation between the time marks and the clock time. This should permit the determination of the time at which a point on the format was exposed with accuracy of 2.5 milliseconds (3 sigma).
9. Start of Operation Indicator -- A cross imaged near the camera serial number on the last frame of the previous camera operation.
Table 2. Panoramic Camera Calibration
|Main Lens||Equivalent Focal Length||25 Microns|
|Main Lens||Radial Distortion||1 Micron|
|Main Lens||Convergence||60 ARC Seconds|
|Horizon Optics||Equivalent Focal Length||25 Microns|
|Horizon Optics||Principal Point to Fiducial Intersection||10 Microns|
|All Lens||Alignment Horizon to Pan and Pan to Pan||60 ARC Seconds|
|Not dot encoder||Nod Angle position||One dot every 19.78 arc sec of nod shat rotation|
Figure 4 shows the angles covered by the several cameras. Figure 5 shows the typical terrain coverage expected and lists the coverage for vanous altitudes. Figure 6 is a conversion chart to determine photographic scale at different distances from the format center over the altitude range from 80 to 120 nautical miles.Camera Calibration
The panoramic camera lenses and horizon cameras are individually calibrated prior to being mounted on the panoramic camera. This individual calibration consists of determining the principal point of autocollimation and the equivalent focal length, and checking the lens distortion characteristics. Subsequent to this, each camera system is calibrated to determine the position of the horizontal cameras in relation to their respective panoramic camera lens. The accuracy of these calibrations is shown in Table 2.
Two horizon cameras are associated with each panoramic camera. The imagery from the horizon cameras is used to determine the attitude (pitch and roll) of the main panoramic cameras. The paired horizon cameras will operate simultaneously on altemate panoramic frames. The horizon camera formats are exposed adjacent to the main panoramic frames (Figure 2).Horizon Camera Data
Table 3. Horizon Camera Data
|Depression Angle||15 deg|
|Filter||Wratten 25 plus Commandable Attenuator|
|Film Type||Same as in main panoramic cameras|
|Angular Field of View||Approximately 51 deg 44 min by 23 deg 28 min|
|Usable Format||2.1X 0.9 in|
|Aperture||f/6.8 or f/8.0 -- varies according to which cameras are primarily pointing toward or away from the sun|
|Frame forward cover (n.m.)||7.7||8.2||8.6||9.1||9.6||10.1||10.6||11.00||11.5|
|Frame width cover (n.m.)||117.0||124.0||131.0||139.0||146.0||154.0||161.0||168.0||176.0|
|Area pr. fr. (sq. n.m.x 10'2||8.9||10.0||11.3||12.5||13.9||15.3||16.8||18.4||20.0|
|Mission stero cover sq. n.m. x 10'6||4.9||5.6||6.2||7.0||7.7||8.5||9.3||10.2||11.1|
|Side dimension of ground patttern (n.m.)||120.6||135.6||150.7||165.8||180.8|
|Area coverage pr. fr. - sp. n.m. X 10'4(n.m.)||1.45||1.84||2.27||2.75||3.27|
|Overlap - % 9.375 sec/cycle||68.0||71.6||74.4||76.7||78.7|
|Mission stero cover sq. n.m. x 10'6||57.4||62.1||65.9||69.0||71.6|
The horizon camera photographs have no specific scale associated with them, nor do they have an independent frame number. They arereferred to as the port or starboard exposures associated with the forward looking or aft looking panoramic camera frame. Port is defined as the left side of the vehicle as the observer faces in the direction of flight and starboard is the right side.INDEX (TERRAIN) CAMERA
The index camera is a frame camera which provides vertical small-scale photography. It may be used for rapid correlation and indexing of main panoramic photography. The index camera also provides conjugate imagery for a relative orientation between the index and main panoramic cameras. This is necessary for eventual adjustment of attitude data (pitch, roll, and yaw) between the stellar and main panoramic cameras. The index camera is preset to operate at 9.375, 12.5, 15.625, or 18.75 seconds per cycle; based on the planned camera altitude, it can be programmed to operate independently from the panoramic cameras.
The terrain format is shown in Figure 7. Figure 8 shows the data block details and the start of operation marks.
Table 4. Index Camera Data
|Lens||f.4.5 T/6.75 AWAT|
|Focal Lengh||3 Inches|
|Field Angle||74 deg|
|Format Size||4.5 by 4.5 inches|
|Film Load||5 in by 2000 feet|
|Reseau||Glass plate with 2.5 mm interval grid|
|Shutter Speeds||1/250, 1/500|
|Shutter Type||Rotary, Efficiency 57¢|
|Overlap||68 to 80 percent between 80-120 nm for 9.375 sec/cycle|
|Cycle Period||9.375 sec/cycle|
|>||15.625 sec/cycle or|
|Scale||1/2,432,000 at 100 nm Altitude|
|Coverage||22,700 sq/nm per frame at 100 nm altitude; 30x 10¹ sq /nm per mission|
Present plans call for titling each frame sequentially from 1 thru n for any given pass. Frame count would then start at 1 for the first frame of the next pass. Mitling data would consist of mission number, pass number, frame number, date and classification.
The reseau grid forms a calibrated array of points on the photograph which may be used as an aid in correcting the eflects; of film shrinkage, lens distortion, and atmospheric refraction.STELLAR CAMERA
Stellar photography provides a means forvery accurate determination of pitch, roll, and yaw during operational cycles. One stellar photograph is pointed out either side with the optical axis 10' above the horizontal. A reseau is provided to correct for image distortion and to recover geometric orientation.
Table 5. Stellar Camera Data
|Focal Lengh||3 Inches|
|Field Angle||Approximately 23.5°|
|Format Size||1.25 inch diamter with flats|
|Film Load||35mm by 2000 feet|
|Reseau||Glass plate with 2.5 mm interval grid|
|Max Distortion||15 microns (R) 5 microns (T)|
Either of the stellar cameras can be capped if a light source (which could degrade the imagery from the other camera) shines directly into the lens.
The stellar camera cycle period is 3.125 seconds, while the terrain camera is operating in the dependent mode. When the terrain camera is operating independently, the stellar camera operates once for each terrain exposure. The lens serial number for each stellar camera is exposed on the format (see Figure 9). The time word is exposed adjacent to the port serial number. Ihe port serial number is further identified by a "P" after the number. Start of operation marks are exposed adjacent to the time word as shown in Figure 11.
Although the stellar imagery is originally produced on unperforated 35mrn film, it is customarily reproduced on 70 mm duplicate positives for case of handling by specified users as shown in Figure 9.
Present plans call for tiding each port and starboard frame sequentially from 1 thru n for each recoverable subsystem of a mission. Each port frame number is preceded by a P and each starboard frame number is preceded by a S. On the leader of the stellar film is a listing of the passes and their corresponding frames.