Data Set Information
DATA_SET_NAME GIOTTO OPTICAL PROBE PHASE MEASUREMENTS V1.0
DATA_SET_ID GIO-C-OPE-3-RDR-HALLEY-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : The OPE photopolarimeter was designed to measure the polarized components of the light in seven bandpasses or channels, ranging from the near ultraviolet to the near infrared. Three channels (so- called blue, green and red) were devoted to the observation of the scattering of solar light by cometary dust grains, in emission-free countinuum bands. Four other channels (so called OH, CN, CO+, C2) were devoted to the observation of light emitted by cometary gases. The imaging of a mosaic of interference filters (placed in front of the objective lens and organized into a mosaic to compensate for the chromatic effects) onto a microchannel plate allowed the spectral discrimination to be achieved. A polaroid analyzer, placed in front of each filter, except the CO+ one, allowed the polarization to be determined by the rotation of the analyzer with the spin of the spacecraft. During a spin period (of approximately 4 seconds), eight consecutive measurements of the polarized intensity, Ii, Ii+1, Ii+2, etc, (of approximately half a second each), were performed in the seven channels at eight so-called clock angles. Absolute calibration Due to the reduced amount of time available for calibrations after the flight detector was available, the absolute-radiance sensitivity of the instrument had been inferred by considering the individual spectral transmission of each optical component, the field of view of the instrument, the photocathode spectral sensitivity and the total responsivity of the microchannel plate photomultiplier (Giovane, 1991). The results were the following: Channel Wavelength Bandpass Responsivity nm 50% peak,nm 10-7 Wm-2sr-1mm-1ct-1 Blue 442 5 2.09Green 576 10 0.88Red 718 4 4.40OH 310 6 16.81CN 387 4 8.20CO+ 424 4 1.34C2 514 4 3.75 The on-board calibration tritium-phosphor source (mounted on the back of the baffle cover), which allowed the instrument to be tested during the pre-Halley-encounter cruise, was released with the baffle cover prior to Halley encounter. The data for Optical Probe Experiment was submitted by Andrew Weisenberger for the Frank Giovane at the Space Astronomy Laboratory, Univ of Florida. The data are grouped by 'phases' into tabular form; the first four columns of the table are calibrated fluxes identified as P2, P3, P4, and CO+ (no contribution or only a very weak one, not separable from the underlying continuum exists for that gas channel). No time is specifically given but rather the last column lists cometocentric distance ranging from 192041 to 947 km. Each table corresponds to a specific phase. Fluxes are collected at 500 ms intervals, one phase after another but are listed in each table at 4 s intervals (at every rotation of the spacecraft or about every 274 km along the spacecraft trajectory). Data for the gas are not given. Three phases gave non usable data and are thus not provided here. In all tables, the geometry relative to the comet is the same. The distance to the nucleus can be used as a clock to identify the phase at which the observations were taken.
DATA_SET_RELEASE_DATE 3000-01-01T00:00:00.000Z
START_TIME 1986-03-13T11:16:10.000Z
STOP_TIME 1986-03-14T12:02:49.000Z
MISSION_NAME GIOTTO
MISSION_START_DATE 1985-07-02T12:00:00.000Z
MISSION_STOP_DATE 1992-07-10T12:00:00.000Z
TARGET_NAME HALLEY
TARGET_TYPE COMET
INSTRUMENT_HOST_ID GIO
INSTRUMENT_NAME OPTICAL PROBE EXPERIMENT
INSTRUMENT_ID OPE
INSTRUMENT_TYPE PHOTOPOLARIMETER
NODE_NAME Small Bodies
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : N/A
CITATION_DESCRIPTION Levasseur- Regourd, A. C., Giovane, F., M. A'Hearn, E. Grayzeck, and A.C. Raugh, GIOTTO OPTICAL PROBE PHASE MEASUREMENTS V1.0, GIO-C-OPE-3-RDR-HALLEY-V1.0, NASA Planetary Data System, 1989.
ABSTRACT_TEXT The OPE photopolarimeter was designed to measure the polarized components of the light in seven bandpasses or channels, ranging from the near ultraviolet to the near infrared. Three channels (so- called blue, green and red) were devoted to the observation of the scattering of solar light by cometary dust grains, in emission-free countinuum bands. Four other channels (so called OH, CN, CO+, C2) were devoted to the observation of light emitted by cometary gases.
PRODUCER_FULL_NAME INTERNATIONAL HALLEY WATCH
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