The ITEK Panoramic Camera

The Mission

As part of NASAÂ’s Apollo J-Series experiments for the scientific exploration of the Moon, the Itek Optical Systems Division of Lexington, Massachusetts supplied a 24-inch-focal-length optical bar panoramic camera, based on it's KA-80A photo reconnaissance camera in use by the United States Air Force. The panoramic camera was installed in the Scientific Instrument Module (SIM), bay 1 of the Apollo Service Module. The optical bar cameraÂ’s role in the mission was to provide high quality stereo photography of a large area of the lunar surface to aid in selection of potential landing sites and future exploration areas, and to provide selected detailed information to support the selenodetic and cartographic goals of the experiments. Additionally the photography will establish the vehicle landing constraints related to the selected landing sites and aid in defining the design parameters of future mobility units and ground support facilities.

Operated in orbit 69 miles above the lunar surface, the optical bar panoramic camera produced stereo photography covering about 1.9 million square miles, or about 15 percent of the MoonÂ’s surface. Each photographic frame recorded an area 211 miles wide by 13.5 miles long with such fine detail that an object smaller than 6 feet (2m) in size can be examined and its position pinpointed.

The Concept

In the optical bar system, the lens continuously rotates 360 degrees, with the imagery being recorded a specified number of degrees on either side of vertical. Although film motion across the image plane is intermittent, the film supply and take-up spools revolve continuously. Continuous rotation of the lens and films spools reduces operating power and eliminates stop-start perturbations that would degrade photography.

The lens is formed in the shape of an elongated N (see diagram above), the optical path being bent by two folding mirrors located at the pivot points of the N. This provides for the longest possible focal length consistent with the size of the camera compartment.

The Camera

The camera is a completely self-contained package, with all mechanical assemblies, electronic circuits, and sensor systems housed within a two-piece cover that serves as a thermal blanket. Camera operation is fully automatic, the correct exposure and cycle rate being automatically controlled by sensor systems that continuously monitor the apparent ground speed and the average scene brightness. The camera is activated by the astronaut in the Apollo Command Module. Command Module panel 230 was added for the 'J' missions, to activate the various experiments including the panoramic camera, and a power switch to turn on the scientific data system information collection and processing equipment. Another switch activates the remote checkout of the scientific data system frequency generating equipment by the ground.

In addition to receiving operating and temperature control power from the Apollo Service Module, the camera is connected to the vehicle telemetry circuits, to the experiment equipment control panel in the Apollo Command Module, and to the vehicle central timing equipment.

The camera comprises three major assemblies: (1) the roll frame assembly, which basically provides the platform for the rotating lens system, (2) the gimbal structure assembly, which rocks the roll frame assembly back and forth to provide for the stereo photography and to compensate for the forward motion of the vehicle, and (3) the main frame assembly, which attaches to the vehicle and provides a platform for the film transport system as well as the roll frame and gimbal structure assemblies.

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The above image shows the panoramic camera without its thermal shield prior to mounting in the SIM bay.

Panoramic camera as seen from the Apollo 17 Lunar Module Challenger.

Roll Frame Assembly

The roll frame assembly includes the lens system, a circular cage of rollers that supports the film, a variable slit assembly, and a capping shutter. The lens is an eight-element, field-flattened Petzval type, polished to within a surface accuracy of one-millionth of an inch. Two mirrors fold the 24-inch (610mm) focal length into a more compact configuration by introducing two angles in the optical path. The camera has a relative aperture of f/3.5 and a field of view of 10 degrees 46 minutes. The individual picture size is 45.24 inches (1,149 mm) long and 4.5 inches (114.9 mm) wide. Resolution of approximately 135 lines per millimetre is achieved on 80 percent of the imagery, with no imagery being below 108 lines per millimetre at low contrast.

During the operation of the camera, the lens is rotated about an axis which is parallel to the Apollo Command Module at a rate related to the apparent ground speed. A capping shutter opens during the time the lens passes through a 108° arc below the vehicle.

Light entering the lens during this scan period is focused onto the film through a variable width slit located at the rear of the lens system next to the film. The slit is continuously variable (governed by signals from a light sensor and V/H sensor) from a minimum opening of 0.015 inch (0.381 mm) to a maximum opening of 0.300 inch (7.62 mm). The width of the scanning slit at any particular time combined with the scanning rate (the rate of rotation of the lens) establishes the photographic exposure time.

Gimbal Structure Assembly

The gimbal structure assembly, to which the roll frame assembly is attached, provides for both forward motion compensation and stereo coverage by rocking forward and aft (up and down) along the axis of vehicle travel. For forward motion compensation, the gimbal structure moves in the direction of the apparent ground motion at the exact rate necessary to Â“freezeÂ” the image during exposure. This avoids blurring which otherwise would occur when photographs are taken from a fast moving vehicle. See diagrams below.

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Pan camera in the SIM bay.

When the camera operates in the stereo mode, the gimbal structure automatically pitches alternately from a position 12.5° forward to 12.5° aft of the vertical between successive exposures. That is, one exposure will begin with the gimbal structure in a position 12.5° forward of vertical, the next exposure will begin with the structure at a position 12.5° aft of vertical, and for the next it will shift to the 12.5° forward position once again. The cycle rate of the camera is set so that a 100 percent overlap between stereo pairs is maintained. When properly viewed, the two photographs of the same ground area thus taken from different angles provide a 25-degree convergent stereo image (see diagram below).

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The diagram above shows the geometry of how exposures taken with the roll frame rocked forward & aft by 12.5° in each direction. The two heavy solid lines that converge on a common point on the surface at an angle of 25° indicate how the convergent stereoscopic coverage is obtained with every fifth frame, in this case, with frames 1 & 6, and also 3 & 8.

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The above map shows an example of the Panoramic Camera's Â‘footprintÂ’ on the lunar surface. Note the forward and aft looking frames to create the 25° convergent stereo images. This example is of part of the Apollo 15 coverage.

A velocity to height ratio (V/H) sensor and an incremental shaft angle encoder control the camera operating cycle. The V/H sensor continuously determines the rate of apparent motion of the ground scene, and controls both the motion of the gimbal structure for forward motion compensation and the speed of the rotation of the lens system (the optical bar). The speed of the film across the roller cage is, in turn, controlled by the rotation of the optical bar. A light sensor determines the degree of the ground brightness. This information is combined with the information from the V/h sensor in the exposure control assembly, which adjusts the film. The incremental shaft angle encoder, in combination with a cycle control assembly, provides the timing and synchronization for the operating subsystems of the camera.

Main Frame Assembly

The main frame assembly is mounted to the vehicle and supports the gimbal structure and all other components, including the film supply and take-up mechanisms.

The film metering roller continuously moves film from the supply cassette to a supply shuttle (a system of fixed and suspended rollers which stores a surplus of film ready for use). At a rate synchronized with the cycle rate, a framing roller intermittently draws film across the revolving roller cage in the direction opposite to that of the lens rotation, through the focal plane, and then into a take-up shuttle. The supply shuttle is refilled during that portion of the cycle when the film remains stationary over the roll cage. Film in the take-up shuttle is continuously drawn into the take-up cassette. It takes approximately 2 seconds for each complete exposure during which time 1.2m of film is passed over the roller cage and past the exposure slit. Consecutive frames were exposed every 6 seconds. The surplus film which is intermittently entering and leaving the supply and take-up shuttles provides the flexibility required to maintain constant film tension throughout the system while the gimbal assembly tilts through its stereo and forward motion compensation cycle.

Because the camera lens rotates at a distance from the image surface (the radius of the roller cage) which is not equal to the focal length of the lens, lateral image motions could be introduced. During the exposure cycle, the film is moved across the roller cage in a direction opposite to the lens rotation to compensate for these image motions. The rate of film transport is proportional to the rotation rate of the lens.

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Above is a diagram of the film transport mechanism.

The film take-up cassette is removed from the camera by an astronaut during an extravehicular activity (EVA) and stored aboard the Apollo Command Module for return to Earth.

Below are examples of the photography produced by the panoramic camera.

The frame shown is AS15-9377. Area shown is Hadley-Appenines adjacent to the Apollo 15 landing site. Click on the frame above to see an enlarged version.

The frame shown is AS15-9554. Area shown is Taurus-Littrow. Click on the frame above to see an enlarged version.

Below is the centre segment from the panoramic frames AS17-2309 & AS17-2314 of the valley of Taurus-Littrow. They represent a 25° convergent stereoscopic pair.

By merging the image the stereo effect becomes apparent. When used in conjunction with an analytical stereoplotter, highly detailed topographic maps can be produced at high scales, as illustrated below.

Below are examples of the topographic mapping products that were produced using imagery from the panoramic camera.

Click the above maps to enlarge.

The map shown at top is a Lunar Photomap, chart 41B4S4 (25) produced at a scale of 1:25,000 showing the Apollo 15 traverses. The map in the centre is part of a Lunar Topophotomap produced at a scale of 1:50,000, showing part of the crater Brackett on the southern boundary of Mare Serenitatis. The map at the bottom is part of a Lunar Topophotomap produced at a scale of 1:50,000, showing the Apollo 17 landing area. This map was produced using Apollo 17 Panoramic camera frames AS17-2748, 2750 & 2752.

These maps were produced for NASA by the Defense Mapping Agency, Topographic Center, Washington, D.C.

Copies of the photographs taken by the Panoramic Camera and maps derived from it's imagery can be obtained from the National Space Science Data Center at http://nssdc.gsfc.nasa.gov/

General Specifications

Lens	24-inch (610-mm), f/3.5, Petzval
Resolution	135 lines per millimetre, over 80 percent of the detail, no detail less than 108 lines per millimetre at low contrast
Field of view along track	10 degrees 46 minutes (13.5 miles at 69-mile altitude)
Field of view, crosstrack	108 degrees (211 miles at 69-mile altitude)
Overlap	Consecutive forward frames and consecutive aft frames overlap 10 percent; stereo pairs overlap 100 percent.
Shutter type	Scanning slit
Slit width	0.015 to 0.300 inch (0.381 to 7.62 mm)
Film type	3400, 3414, SO-230, or any other thin base material.
Film width	5 inches (127 mm)
Film thickness	0.003 inch (0.076 mm) or less.
Format	45.24 by 4.5 inches (1,149 x 114.3 mm)
Exposure control	Automatic with variable slit
V/H Range	0.010 to 0.019 radians per second
Operating modes	Monographic or 25° convergent stereo at autocyle of 4.7 to 8.0 seconds per cycle.
Film Length	6,500 feet (2,005 metres)
Exposures	1,650 total
Weight (camera with film)	336 pounds
Weight (Take-up cassette with film)	73 pounds
Power Requirements	115VAC, 27.5VDC, 234 watts average, 340 watts peak

Sources

ITEK Optical Systems Division - Technical Bulletin, PFR-71-106, 1971

Apollo 15 CM Software - Delco Electronics, 1971

Apollo 15 Press Kit - NASA 71-119K, July 1971

Apollo 15 Mission Report - NASA MSC-05161, December 1971

On the Moon with Apollo 16, Gene Simmons - NASA EP-95, 1972

On the Moon with Apollo 17, Gene Simmons - NASA EP-101, 1972

Apollo over the Moon, Harold Masursky, G. W. Colton, Farouk El-Baz - NASA SP-362, 1978

North American Rockwell - Space Division, Fact Sheet SP-29, 1972

Chariots for Apollo: A History of Manned Lunar Spacecraft. C. G. Brooks, J. M. Grimwood, L. S. Swenson jnr - NASA SP-4205, 1979

Where No Man Has Gone Before: A History of Apollo Lunar Exploration Missions. William Crompton - NASA SP-4214, 1989

National Space Science Data Center

Last update: 2017-02-17


The Fairchild Lunar Mapping Camera	Return to SIM Bay Cameras	Apollo 17 Photographic Task Requirements