/* IMAGING SCIENCE SUBSYSTEM - NARROW ANGLE */ OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = VG2 INSTRUMENT_ID = ISSN OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "IMAGING SCIENCE SUBSYSTEM - NARROW ANGLE" INSTRUMENT_TYPE = "VIDICON CAMERA" INSTRUMENT_DESC = " INSTRUMENT: IMAGING SCIENCE SUBSYSTEM - NARROW ANGLE SPACECRAFT: VOYAGER 2 Instrument Information ====================== Instrument Id : ISSN Instrument Host Id : VG2 Pi Pds User Id : BASMITH Naif Data Set Id : UNK Instrument Name : IMAGING SCIENCE SUBSYSTEM - NARROW ANGLE Instrument Type : VIDICON CAMERA Build Date : 1976-12-17 Instrument Mass : 22.060000 Instrument Length : 0.980000 Instrument Width : 0.250000 Instrument Height : 0.250000 Instrument Serial Number : SN05 Instrument Manufacturer Name : JET PROPULSION LABORATORY Instrument Description ====================== The Voyager Imaging Science Subsystem (ISS) is a modified version of the slow scan vidicon camera designs that were used in the earlier Mariner flights. The system consists of two cameras, a high resolution Narrow Angle (NA) camera and a lower resolution, more sensitive Wide Angle (WA) camera. Unlike the other on board instruments, operation of the cameras is not autonomous, but is controlled by an imaging parameter table residing in one of the spacecraft computers, the Flight Data Subsystem (FDS) (Science and Mission Systems Handbook, 1987, JPL D-498, an internal JPL document available from JPL vellum files). The original mission was to Jupiter and Saturn. Voyager surpassed expectations and Voyager 2 went on to encounter Uranus and Neptune. As the Voyager mission progressed the objects photographed were further from the sun so they appear more faint even though longer exposures were used. As the Voyager spacecrafts' distance from the Earth increases, the telecommunications capability at each encounter decreases. The difference in capabilities from the Jupiter and Saturn encounters and that at Uranus and Neptune was considerable. The reduced telecommunications capability limits the number of data modes that imaging can use. Because of the diminished brightness of the objects being photographed, longer exposure times were used, many beyond the stated maximum of 15.360 seconds. Longer exposure times were all 48-second increments added to the maximum. In addition, the camera was slewed in order to avoid smeared imaging. The light flood state (on/off) was independent of the instrument mode. Science Objectives ================== The overall objective of this experiment is exploratory reconnaissance of Jupiter, Saturn, Uranus, Neptune and their satellites and rings. Such reconnaissance, at resolutions and phase angles unobtainable from Earth, provides much new data relevant to the atmospheric and/or surface properties of these bodies. The experiment also has the following specific objectives: observe and characterize global circulation and meteorology; determine the horizontal and vertical structure of visible clouds; characterize the nature of any colored material which may be in clouds. Operational Considerations ========================== To make full scientific use of the image collection it is necessary to understand the radiometric and geometric characteristics of the camera system and perform corrections to the data. Each Voyager camera is unique in terms of its calibrated characteristics. Each has intrinsic shading (spatially non-uniform output DNs from flat field target) and exhibits barrel distortions typical of TV cameras flown on previous planetary missions. Because of these characteristics, the cameras were calibrated before launch. The response of the pixels to known targets, illumination, exposures, etc. was measured and Calibration Files were generated to remove radiometric and geometric distortions from the flight images. These Calibration Files and detailed information on their use are available through the Imaging Node. Calibration Description ======================= The calibration program for the Voyager television cameras consisted of three parts: (1) component calibrations; ('Voyager Imaging Science Subsystem Calibration Report' July 31, 1978, M. Benesh and P. Jepsen, D-618-802) (2) subsystem calibrations; and, (3) system calibrations. In addition, provision was made for in-flight calibrations. Component calibrations were carried out prior to camera assembly. Important measurements include spectral transmittance of the lens and filters, actual exposure times and shading characteristics of the shutter, and pertinent electro-optical properties of the vidicon. After the optics and sensor were assembled it was possible to run calibrations at the camera, or subsystem, level. Particular activities accomplished during this period included radiometric calibrations, focal length measurement, determination of the modulation transfer function, measurement of the geometric distortion, and calibrations required for color reconstruction. System calibrations were conducted after the cameras were installed on the spacecraft. Important tasks included measurement of the Field-Of-View alignment and verification of the flat-field light transfer characteristics. Noise measurements were also made at the system level. A method for in-flight verification of the radiometric calibrations that were run on the ground is employed on the Narrow-Angle optics. It is very similar to the scheme used on the Wide-Angle optics except that eight lamps are required. They are located just within the field of view around the periphery of the telescope aperture. By either pulsing the lamps or leaving them on and varying the shutter exposure time a transfer curve may also be generated by using the calibration plaque. The method is identical to that described for the wide-angle optics. However, calibration data was collected but no new calibration files were generated during the Jupiter, Saturn, or Uranus encounters or their related cruise periods. Although the INSTRUMENT_PARAMETER_NAME has been provided as Radiance, the Voyager Experiment Data Record (EDR) data set has not been radiometrically corrected, and thus images do not represent radiance units. In order to convert an image from Data Number (DN) to radiance units, the image must be calibrated. Radiometric calibration files, and selected radiometrically corrected images are available through the Imaging Node. Section 'ISSN' ============== Total Fovs : 1 Sample Bits : 8 'ISSN' Detectors ---------------- ISSN 'ISSN' Electronics ------------------ ISSN 'ISSN' Filters -------------- BLUE CLEAR CLEAR GREEN GREEN ORANGE ULTRAVIOLET VIOLET 'ISSN' Section Optic IDs ------------------------ ISS-NA In modes -------- IM10 IM11 IM12 IM13 IM14 IM15 IM2 IM26 IM2A IM2C IM2W IM3 IM4 IM5 IM6 IM7 IM8 IM9 IMK IMO IMQ OC3 PB8 'ISSN' Section FOV Shape 'SQUARE' --------------------------------- Section Id : ISSN Fovs : 1 Horizontal Pixel Fov : 0.000530 Vertical Pixel Fov : 0.000530 Horizontal Fov : 0.424000 Vertical Fov : 0.424000 'ISSN' Section Parameter 'RADIANCE' ----------------------------------- Radiance is the amount of energy per time per projected area per steradian. Instrument Parameter Name : RADIANCE Sampling Parameter Name : PIXEL Instrument Parameter Unit : DIMENSIONLESS Noise Level : UNK Instrument Detector 'ISSN' ========================== Detector Type : VIDICON Detector Aspect Ratio : 1.000000 Minimum Wavelength : 0.280000 Maximum Wavelength : 0.640000 Nominal Operating Temperature : 282.000000 Description ----------- The sensor used in the Voyager - Imaging Science Subsystem (ISS) camera system is a 25-mm diameter magnetic and deflection vidicon (number B41-003, General Electro-dynamics Company). The vidicon storage surface (target) is selenium sulphur and can store a high resolution (1500 TV lines) picture for over 100 s at room temperature. The active image area on the target is 11.14 x 11.14 mm. Each frame consists of 800 lines with 800 picture elements (pixels) per line, i.e., 1 pixel =14 microns. One frame requires 48 s for electronic readout. In addition to the normal frame readout of 48 s (1:1), four extended frame-time modes of 2:1, 3:1, 5:1, and 10:1 are available by command. Following readout, light flooding is used to remove any residual image that might remain from the previous frame. At the end of light flooding, 14 erase frames are used to stabilize and prepare the vidicon target for the next exposure sequence (VGR ISS Calibration Report, 1978, an internal JPL document available from JPL vellum files). Sensitivity ----------- Calibration experiments show the gain map indicating higher sensitivity toward the top of the frame in a generally radial manner. Dark-current ratio results indicate a mean within plus-or-minus 3% of the true linearity of the light transfer function. The required accuracy of the light-transfer functions was plus-or-minus 5% of half-scale signal averaged over any randomly selected area of 10 contiguous pixels. This requirement was consistently met for all Imaging Science Subsystem (ISS) flight cameras. The radiance of the used light cannons was supposed to be plus-or-minus 5% or better of the level to produce a half-scale signal. This criterion was also met. It is not clear whether the color spatial dependence is due to the vidicon, or whether the filters have varying transmissions. In the latter case, the ratios would be independent of light level; and this has been observed to be the case for all flight cameras. Moreover, vidicons have not shown scale variations of this magnitude in the past, so that it is easier to believe that they are due to the spectral filters rather than to the vidicons. The color sensitivity is sufficient to require a separate decalibration file for each spectral filter, which has been done, but not gross enough to cause concern about the quality of the image itself (VGR ISS Calibration Report, 1978, an internal JPL document available from JPL vellum files). Instrument Electronics 'ISSN' ============================= Description ----------- The Imaging Science Subsystem (ISS) electronics consist of the vidicon support circuits and the signal chain. The vidicon support circuits are the vertical and horizontal sweep circuits, and the various power supplies for the vidicon filament, and the focus and alignment coils. The signal chain consists of the analog signal amplifiers, bandpass filters, and an eight bit analog-to-digital converter. The digital output is sent to the Flight Data Subsystem (FDS) for editing. Instrument Filter '0 - CLEAR' ============================= Filter Name : CLEAR Filter Type : ABSORPTION Minimum Wavelength : 0.280000 Maximum Wavelength : 0.640000 Center Filter Wavelength : 0.460000 Description ----------- Spectral measurements at the manufacturer were taken on Beckman spectro-photometers, and verifications at Jet Propulsion Laboratory (JPL) were made with a Cary 14 spectro-photometer. Each test scan was run from 2000 to 7000 Angstroms to check for eventual leaks outside the passband (VGR ISS Calibration Report, 1978, an internal JPL document available from JPL vellum files). For spectral information on each filter, see Danielson, E. G., et al. Radiometric Performance of the Voyager Cameras, JGR, v. 86, Sept. 1981. Instrument Filter '1 - VIOLET' ============================== Filter Name : VIOLET Filter Type : INTERFERENCE Minimum Wavelength : 0.350000 Maximum Wavelength : 0.450000 Center Filter Wavelength : 0.400000 Description ----------- Spectral measurements at the manufacturer were taken on Beckman spectro-photometers, and verifications at Jet Propulsion Laboratory (JPL) were made with a Cary 14 spectro-photometer. Each test scan was run from 2000 to 7000 Angstroms to check for eventual leaks outside the passband (VGR ISS Calibration Report, 1978, an internal JPL document available from JPL vellum files). For spectral information on each filter, see Danielson, E. G., et al. Radiometric Performance of the Voyager Cameras, JGR, v. 86, Sept. 1981. Instrument Filter '2 - BLUE' ============================ Filter Name : BLUE Filter Type : INTERFERENCE Minimum Wavelength : 0.430000 Maximum Wavelength : 0.530000 Center Filter Wavelength : 0.480000 Description ----------- Spectral measurements at the manufacturer were taken on Beckman spectro-photometers, and verifications at Jet Propulsion Laboratory (JPL) were made with a Cary 14 spectro-photometer. Each test scan was run from 2000 to 7000 Angstroms to check for eventual leaks outside the passband (VGR ISS Calibration Report, 1978, an internal JPL document available from JPL vellum files). For spectral information on each filter, see Danielson, E. G., et al. Radiometric Performance of the Voyager Cameras, JGR, v. 86, Sept. 1981. Instrument Filter '3 - ORANGE' ============================== Filter Name : ORANGE Filter Type : INTERFERENCE Minimum Wavelength : 0.590000 Maximum Wavelength : 0.640000 Center Filter Wavelength : 0.615000 Description ----------- Spectral measurements at the manufacturer were taken on Beckman spectro-photometers, and verifications at Jet Propulsion Laboratory (JPL) were made with a Cary 14 spectro-photometer. Each test scan was run from 2000 to 7000 Angstroms to check for eventual leaks outside the passband (VGR ISS Calibration Report, 1978, an internal JPL document available from JPL vellum files). For spectral information on each filter, see Danielson, E. G., et al. Radiometric Performance of the Voyager Cameras, JGR, v. 86, Sept. 1981. Instrument Filter '4 - CLEAR' ============================= Filter Name : CLEAR Filter Type : ABSORPTION Minimum Wavelength : 0.280000 Maximum Wavelength : 0.640000 Center Filter Wavelength : 0.460000 Description ----------- Spectral measurements at the manufacturer were taken on Beckman spectro-photometers, and verifications at Jet Propulsion Laboratory (JPL) were made with a Cary 14 spectro-photometer. Each test scan was run from 2000 to 7000 Angstroms to check for eventual leaks outside the passband (VGR ISS Calibration Report, 1978, an internal JPL document available from JPL vellum files). For spectral information on each filter, see Danielson, E. G., et al. Radiometric Performance of the Voyager Cameras, JGR, v. 86, Sept. 1981. Instrument Filter '5 - GREEN' ============================= Filter Name : GREEN Filter Type : INTERFERENCE Minimum Wavelength : 0.530000 Maximum Wavelength : 0.640000 Center Filter Wavelength : 0.585000 Description ----------- Spectral measurements at the manufacturer were taken on Beckman spectro-photometers, and verifications at Jet Propulsion Laboratory (JPL) were made with a Cary 14 spectro-photometer. Each test scan was run from 2000 to 7000 Angstroms to check for eventual leaks outside the passband (VGR ISS Calibration Report, 1978, an internal JPL document available from JPL vellum files). For spectral information on each filter, see Danielson, E. G., et al. Radiometric Performance of the Voyager Cameras, JGR, v. 86, Sept. 1981. Instrument Filter '6 - GREEN' ============================= Filter Name : GREEN Filter Type : INTERFERENCE Minimum Wavelength : 0.530000 Maximum Wavelength : 0.640000 Center Filter Wavelength : 0.585000 Description ----------- Spectral measurements at the manufacturer were taken on Beckman spectro-photometers, and verifications at Jet Propulsion Laboratory (JPL) were made with a Cary 14 spectro-photometer. Each test scan was run from 2000 to 7000 Angstroms to check for eventual leaks outside the passband (VGR ISS Calibration Report, 1978, an internal JPL document available from JPL vellum files). For spectral information on each filter, see Danielson, E. G., et al. Radiometric Performance of the Voyager Cameras, JGR, v. 86, Sept. 1981. Instrument Filter '7 - ULTRAVIOLET' =================================== Filter Name : ULTRAVIOLET Filter Type : INTERFERENCE Minimum Wavelength : 0.280000 Maximum Wavelength : 0.370000 Center Filter Wavelength : 0.325000 Description ----------- Spectral measurements at the manufacturer were taken on Beckman spectro-photometers, and verifications at Jet Propulsion Laboratory (JPL) were made with a Cary 14 spectro-photometer. Each test scan was run from 2000 to 7000 Angstroms to check for eventual leaks outside the passband (VGR ISS Calibration Report, 1978, an internal JPL document available from JPL vellum files). For spectral information on each filter, see Danielson, E. G., et al. Radiometric Performance of the Voyager Cameras, JGR, v. 86, Sept. 1981. Instrument Optics 'ISS-NA' ========================== Telescope Diameter : 0.176500 Telescope F Number : 8.500000 Telescope Focal Length : 1.503490 Telescope Resolution : 0.000018 Telescope Serial Number : NAO-04 Telescope T Number : 11.830000 Telescope T Number Error : 0.090000 Telescope Transmittance : 0.600000 Description ----------- The Narrow-Angle camera optics is a 150mm focal length all-spherical, catadioptric cassegrain telescope (a modified MVM 1973 design) consisting of five elements plus an additional dust lens located between the shutter and the vidicon. The f number is 8.5 (VGR ISS Calibration Report, 1978, an internal JPL document available from JPL vellum files). Instrument Mode 'IM10' ====================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 1:1, centered frame, approx. 160 pix/line (Jupiter and Saturn only) Instrument Mode 'IM11' ====================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 5:1, centered frame, 800 pix/line (Jupiter and Saturn only) Instrument Mode 'IM12' ====================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 5:1, centered frame, approx. 440 pix/line (Jupiter and Saturn only) Instrument Mode 'IM13' ====================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 10:1, centered frame, 800 pix/line (Jupiter and Saturn only) Instrument Mode 'IM14' ====================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 1:1, centered frame, approx. 80 pix/line (Jupiter and Saturn only) Instrument Mode 'IM15' ====================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 2:1, centered frame, top read out in frame #1, bottom read out in frame #2, 800 pix/line (Jupiter and Saturn only) Instrument Mode 'IM2' ===================== Data Path Type : RECORDED DATA PLAYBACK Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 1:1, full frame image, 800 pix/line (Jupiter and Saturn only) Instrument Mode 'IM26' ====================== Data Path Type : RECORDED DATA PLAYBACK Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 2:1, lines 271-536, 800 pix/line (Neptune only) Instrument Mode 'IM2A' ====================== Data Path Type : RECORDED DATA PLAYBACK Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 1:1, full frame, 800 pix/line (Uranus and Neptune only) Instrument Mode 'IM2C' ====================== Data Path Type : RECORDED DATA PLAYBACK Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 5:1, full frame, 800 pix/line, lines may be truncated (zero filled) on left or right - data dependent (Neptune only) Instrument Mode 'IM2W' ====================== Data Path Type : RECORDED DATA PLAYBACK Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 1:1, full frame, 800 pix/line, last 80 lines are zero (Neptune only) Instrument Mode 'IM3' ===================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 1:1, full frame, 800 pix/line (Jupiter and Saturn only) Instrument Mode 'IM4' ===================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 1:1, centered frame, 608 pix/line (Jupiter and Saturn only) Instrument Mode 'IM5' ===================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 2:1, Top read out in frame #1, bottom read out in frame #2, 800 pix/line (Jupiter and Saturn only) Instrument Mode 'IM6' ===================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 1:1, centered frame, 440 pix/line (Jupiter and Saturn only) Instrument Mode 'IM7' ===================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 3:1, full frame, 800 pix/line (Jupiter and Saturn only) Instrument Mode 'IM8' ===================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 1:1, centered frame, 272 pix/line (Jupiter and Saturn only) Instrument Mode 'IM9' ===================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 3:1, centered, approx. 480 pix/line (Jupiter and Saturn only) Instrument Mode 'IMK' ===================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 10:1, centered frame, 800 pix/line (Uranus and Neptune only) Instrument Mode 'IMO' ===================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 5:1, centered frame, 800 pix/line (Uranus and Neptune only) Instrument Mode 'IMQ' ===================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 5:1, centered frame (Uranus only) Instrument Mode 'OC3' ===================== Data Path Type : REALTIME Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 3:1, lines 301-510, samples 365-453 (Neptune only) Instrument Mode 'PB8' ===================== Data Path Type : RECORDED DATA PLAYBACK Gain Mode Id : LOW Instrument Power Consumption : 14.000000 In sections ----------- ISSN Description ----------- Scan rate (minor frame:line) is 5:1 or 1:1, data dependent may be IM2A, IM2C, IM2W (Uranus and Neptune only) Mounted On Platform 'SCAN PLATFORM' =================================== Cone Offset Angle : 0.000000 Cross Cone Offset Angle : 0.000000 Twist Offset Angle : 0.000000 Description ----------- The measurements recorded below are the coordinates representing the center of the Wide Angle Field Of View (FOV) in relation to the center of the Narrow Angle FOV. As of 5/26/88 the Voyager 2 scan platform offset values were updated and the removal of all extraneous offset values for VG1 and VG2 accomplished. Only the most recently input values remain in the database for each spacecraft. These values are effective for all periods of data inclusive from launch to present. (June 7, 1989). 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