A dataset provided by the European Space Agency

Mission GIOTTO
URL ftp://npsa01.esac.esa.int/pub/mirror/GIOTTO/OPE/GIO-C-OPE-3-RDR-HALLEY-V1.0
DOI https://doi.org/10.5270/esa-2qm622x
Abstract The GIO-C-OPE-RDR-HALLEY-V1.0 data set contains the phase measurements of the optical probe photopolarimeter on board of the GIOTTO spacecraft of the European Space Agency. The data were obtained during the GIOTTO flyby on comet Halley in March 1986
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 2.09 Green 576 10 0.88 Red 718 4 4.40 OH 310 6 16.81 CN 387 4 8.20 CO+ 424 4 1.34 C2 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 ...
Instrument OPE
Temporal Coverage 1986-03-13T23:16:10Z/1986-03-14T00:02:49Z
Version V1.0
Mission Description Mission Overview In 1978,ESA was invited by NASA to plan a joint mission consisting of a comet Halley fly-by in November 1985 and a rendezvous with comet Tempel 2 in 1988. The mission comprised an American main spacecraft which would carry a European probe. The main spacecraft, with its array of sophisticated cameras and experiments, would complete a fly-by of comet Halley at a safe distance. Shortly before fly-by, the probe would be released towards the nucleus to make detailed in-situ observations in the innermost coma. In January 1980, however, it became clear that financial support for the Halley Fly-by/Tempel 2 Rendezvous mission could not be secured in the USA. By that time the interest of European scientists had built up such momentum that ESA considered the possibility of a purely European mission. The support for a fly-by mission was strong in Europe and went far beyond the small section of scientists specialised in cometary research. A fly-by of comet Halley was suggested to ESA by the scientific community in February 1980. Rather than having the American spacecraft deliver the probe to the comet as in the earlier concept, the Europeans proposed that the capabilities of the small probe be increased by building an independent, self-sufficient spacecraft to be launched using the European Ariane rocket. The limited time available for development and the small financial resources made it advisable to use a spin-stabilised spacecraft derived from the European Earth orbiting spacecraft Geos. This proposal was studied by ESA in the first half of 1980. The European mission to comet Halley was named Giotto after the Italian painter Giotto di Bondone who depicted comet Halley as the `Star of Bethlehem' in one of his frescoes in the Scrovegni chapel in Padua in 1304. The Giotto mission was finally approved as ESA's first interplanetary mission on 7 July 1980. An Announcement of Opportunity was issued ...
Date Published 1992-04-30
Publisher And Registrant European Space Agency
Credit Guidelines European Space Agency, 1992-04-30, GIO-C-OPE-3-RDR-HALLEY, V1.0. https://doi.org/10.5270/esa-2qm622x