PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM LABEL_REVISION_NOTE = "20090629, L. Gaddis - Initial Version 20101001 C. Isbell - post review" OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "LO3" INSTRUMENT_ID = {"80MM_FLC","610MM_FLC"} OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = {"80-MM FOCAL LENGTH CAMERA", "610-MM FOCAL LENGTH CAMERA"} INSTRUMENT_TYPE = "DUAL LENS CAMERA" INSTRUMENT_DESC = " LUNAR ORBITER III PHOTOGRAPHIC SYSTEM OVERVIEW ============================================== Much of the information in this document was abstracted from Kosofsky and El- Baz, 1970; Hansen, 1970; and Bowker and Hughes, 1971]. See references cited for more detail. The Lunar Orbiter photographic system included the spacecraft's photographic subsystem; the ground reconstruction electronics (GRE); and the communications system. The five Lunar Orbiter missions used a dual-lens camera system a 610-mm narrow angle high-resolution (HR) lens and an 80-mm wide-angle medium resolution (MR) lens [e.g., Boeing Company, 1967, 1968a, b; Hansen, 1970; Kosofsky and El-Baz, 1970; Bowker and Hughes, 1971; Byers, 1977]. Both lenses placed their frame exposures on a single roll of 70 mm film. The axes of the two cameras were coincident so the areas imaged in the HR frames were centered within the MR frame areas. The telephoto lens provided coverage equivalent to 1 meter from an altitude of 46 kilometers and the wide-angle lens an 8 meter object from the same altitude. Oblique angle photography enhanced interpretation of topographic features to provide photographs of areas beyond the field of view of a vertical camera orientation, and to investigate photometric characteristics of the lunar surface. Six of the 12 primary sites to be photographed by Lunar Orbiter III were selected for convergent telephoto stereo coverage with the remaining sites photographed by near-vertical or cross track tilt of the camera axis. With convergent stereo photography, one sequence of photographs was taken with the camera axis near vertical to obtain maximum resolution of the area. The camera axis was tilted on the other pass the amount necessary for coincident coverage. The film was moved during exposure to compensate for the spacecraft velocity, which was estimated by an electric-optical sensor. The film was then processed, scanned, and the images transmitted back to Earth. The system also had a film processing unit, a readout scanner, and a film handling apparatus. Scientific Objectives --------------------- The primary objective of the five Lunar Orbiter missions was to locate smooth, level areas on the Moon's nearside and to confirm their suitability as manned landing sites for the Apollo program. This required photographic coverage at a ground resolution of 1 meter within 5 degrees of the equator between longitudes 45 degrees E and 45 degrees W. Lunar Orbiter III re- photographed 12 of the most promising 20 potential landing sites initially photographed by Lunar Orbiters 1 and 2. This was essentially completed by the end of the third mission, leaving the fourth and fifth missions to explore broader scientific objectives. The second objective of Lunar Orbiter III was to collect selenodetic, radiation intensity, and micrometeoroid impact data. THE LUNAR ORBITER III PHOTOGRAPHIC SUBSYSTEM ============================================ The Lunar Orbiter photographic subsystem was designed to photograph the lunar surface, process the exposed film, scan the processed film with a flying spot scanner and provide video signals to the communications subsystem for transmission to Earth [e.g., Beeler and Michlovitz, 1969; Boeing Company, 1968a, b; Hansen, 1970; Anderson and Miller, 1971]. The system comprised a dual camera, a film processing unit, a readout scanner, and film-handling apparatus. The photo subsystem simultaneously exposes two pictures at a time, processes the film and converts the information to an electrical signal for transmission to Earth. Dual Cameras ------------ The two cameras, one with a high resolution (HR) lens and one with a medium resolution (MR) lens, operated simultaneously, placing two discrete frame exposures on a common roll of 70-mm film. The high-resolution frame was exposed through a 610-mm narrow-angle lens and a focal plane shutter. The medium-resolution frame was exposed through an 80-mm wide-angle lens and a between-the-lens shutter. The 80-mm focal-length lens provided an angular coverage of 44.4 degrees by 38 degrees; the 610-mm focal-length lens had an angular coverage of 20.4 degrees by 5.16 degrees. The two camera axes were coincident so that coverage of the HR-frame was centered within the coverage of the MR-frame. Each camera operated at a fixed f/5.6 lens aperture, at shutter speeds of either 1/25, 1/50, or 1/100 second. Exposure times were recorded in digital form on the film alongside the M-frames. Image-motion compensation (IMC) was provided to minimize smear. An electric- optical sensor viewed the lunar surface through a portion of the 610-mm lens to determine the spacecraft's velocity to height (V/H) ratio. This was used for direct drive of the camera platens and film at the proper rate to ensure IMC during exposure and also for controlling the spacing of exposures during multiple exposure sequences. Calibration ----------- Tests and calibrations performed on the photographic subsystem included lens- film characteristics, exposure calibration and control, image motion compensation, camera alignment, readout quality, and photogrammetric distortion calibration of the 80-mm camera. Film ---- The Kodak special high definition 70-mm film aerial film, type SO-243 with a recording capability of 450 lines/mm met the resolution requirement of approximately 76 lines/mm and low enough speed to make it relatively insensitive to space environment radiation. Camera Film Advance -------------------- The average camera film advance was 11.70 inches or 130+-1 edge numbers. Film advance through the camera was quite accurate and any errors were due to film set. An inadvertent pre-countdown film advance resulted in 10 frames being available rather than 11. Approximately three-fourths of the film supply of the first three missions was used to photograph areas of interest to the Apollo program. The remainder could not be used for such areas because of operational film-handling requirements; i.e., the film could not remain stationary in the camera for long periods of time lest it deteriorate. Photographs taken when the areas of primary interest were not in view, referred to as film-set frames, were expended in different ways for different missions. Filters ------- The photo subsystem was equipped with a 0.21+-0.02 neutral-density filter in front of the 80-mm lens, which resulted in a transmissivity of 59%. The 610- mm lens transmissivity was 65%. The neutral-density filter in the wide-angle camera equalized the two cameras satisfactorily, with observed density differences of less than 0.1 except for marginal exposures. Exposure -------- The difference in light transmission between the wide-angle and telephoto lenses was successfully balanced by the installation of the 0.21+-0.02 neutral-density filter. The photometric characteristics of the target area were first estimated by using Earth-based observations and then by evaluation of photography from the previous two missions. Changes were made during the course of the mission using data gathered on the mission; approximately one- third of the exposures were changed from those originally planned. Resolution ---------- The requirement for resolution for the Lunar Orbiter missions was that the photograph could detect a 1-meter object with the telephoto lens and an 8- meter object with the wide-angle lens from an altitude of 46 kilometers. This required a resolution of 76 lines per millimeter on the spacecraft film or 10 lines per millimeter on the GRE record. The resolution requirement was equivalent to detection f objects with images spanning four scan lines. Resolution requirements on the mission were met or slightly exceeded. PATTERNS OF PHOTOGRAPHIC COVERAGE ================================= A single exposure of the dual-frame camera produced nested ground coverage. The ground coverage could be expanded in the direction of flight by sequential exposures and in the perpendicular direction by photographing from successive orbits. Automatic sequences of 1, 4, 8, or 16 photos could be obtained with a slow or fast repetition rate. Successive exposures were automatically determined by the T / H sensor. Exposures overlapped by 52 percent, providing continuous stereo coverage over nearly the full length of the strip. At an altitude of 55 km, which was approximately the perilune height, the HR system photographed a 4.15- by 16.6-km area of the lunar surface, which was centered on the 31.6- by 37.4-km area photographed by the MR system. Resolutions were 1 and 8-m, respectively. At apolune, on the Moon's farside at about 1850-km altitude, the areas photographed were correspondingly larger. Film Processing --------------- Prior to being placed onboard the spacecraft, the photographic film was soaked in a monobath processing solution to develop the exposed portions to a negative image, with exposed with strip numbers, a nine-level grayscale bar, resolving power chart, and reseau marks. After exposure, film-processing took place on board the spacecraft by the Kodak Bimat diffusion transfer technique. The average processor rate was 2.42 inches per minute, below specified. At least two frames were processed each orbit to minimize Bimat dryout effects. The undeveloped silver ions were transferred to the processing web, where they were reduced to form a positive image. The negative film went through the drying section, and then the film went through the readout scanner to its takeup spool. Film Readout ------------ Film density readout was accomplished by a high-intensity light beam focused to a 6.5-micron-diameter spot from a linescan tube, which converted the photographic images into electrical signals. The flying spot scanner swept 2.67 mm in the long dimension of the spacecraft film. This special cathode- ray tube whose phosphor layer was coated on a rotating cylindrical metal anode put out a bright spot of light that repetitively traced a line across the phosphor drum. The scanner lens focused a 0.005-mm spot of light on the film. The electrical scan of the spot traced a line 2.68-mm long on the film in the direction parallel to the film edge. One traverse of the scanner lens required 22 seconds, during which time the electrical scan was repeated over 17,000 times. The scanning of a complete dual exposure took 43 minutes. The resulting sections of spacecraft film scanned in this manner, referred to as framelets, are the basic units eventually used for the ground reassembly. The intensity of light reaching the photomultiplier tube was modulated by the density of the image on the film. An electrical signal proportional to the intensity of the transmitted light was generated, amplified, and fed to the spacecraft communications subsystem. The raster signal received at the ground station was recorded on magnetic tape and also fed to ground reconstruction equipment (GRE). A total of 422 HR and MR photographs were taken of the 12 primary and 31 secondary sites planned for Lunar Orbiter III. A failure of the film advance motor occurred and caused premature termination of final readout for some frames [e.g., Boeing Company, 1968b, p. 100]. This failure occurred after 275 HR and MR photos of the 422 taken had been read out. Fifty one of the remaining photos were read out in whole or in part during the priority read- out phase. This failure was the only event that resulted in loss of any of the mission data acquired by Lunar Orbiter III. TRANSMISSION AND RECONSTRUCTION OF PHOTOGRAPHS ============================================== Original film strip photographs were transmitted to Earth as analog data. Photographic prints from the film strips were hand mosaicked into sub-frame (for HR data) and full-frame (for MR data) views and widely distributed. The video data coming from the photographic subsystem occupied a frequency spectrum from 0 to 230 kilohertz. This signal was modulated on a 310-kHz subcarrier (single sideband, suppressed carrier). The video signal, telemetry signals, and a 38.75-kHz pilot tone were summed, and the resulting composite signal phase-modulated the S-band (2295-MHz) carrier. A 10-watt traveling- wave tube amplifier and a 92-cm parabolic antenna transmitted the signal to Earth, where it was received at one of the three deep space stations (DSS) [Bundick et al., 1965]. The 10-MHz intermediate frequency of the DSS receiver, containing the composite signal, was recorded on magnetic tape for permanent storage. At the same time, it was passed to the ground communications equipment which recovered the telemetry and video. The video signal was fed to the GRE where it was converted into an intensity modulated line on the face of a cathode-ray tube. In a continuous motion camera, 35-mm film was pulled past the image of this line, recording each readout framelet at 7.18 times the spacecraft's image size. The recording film was cut up into framelets, which were then reassembled into enlarged replicas of the original spacecraft frames. The M-frames were reassembled in complete form, while the H-frames, which would be about 1.5 meters long if fully reassembled, were reassembled into three component sections. These products contained anomalies such as 'venetian blind' striping, missing or duplicated data, and frequent saturation effects that hampered their use." END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "ANDERSON&MILLER1971" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "BEELER&MICHLOVITZ1969" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "BOEINGCO1967" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "BOEINGCO1968A" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "BOEINGCO1968B" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "BOWKER&HUGHES1971" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "BUNDICKETAL1965" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "BYERS1977" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "HANSEN1970" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "KOSOFSKY&ELBAZ1970" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END