PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2003-09-30 Cornell:carcich" OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = CON INSTRUMENT_ID = CFI OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "CONTOUR FORWARD IMAGER" INSTRUMENT_TYPE = "IMAGER" INSTRUMENT_DESC = " CFI is the CONTOUR Forward Imager, designed for high sensitivity and responsivity to ultraviolet wavelengths. CFI will perform its measurements while CONTOUR is approaching the nucleus and at a range of >2000 kilometers, so it looks out the front side of the spacecraft through an opening in the protective dust shield. Its main functions are: * to locate the target comet against the star background days to weeks before an encounter * to take color images of the nucleus, any gas or dust jets, and other features in the inner coma * to image the inner coma in wavelengths sensitive to major species of ionized gas CFI Vital Statistics Telescope aperture 60 mm Telescope focal length 300 mm Field-of-view 2.5deg x 2.5deg Pixel field-of-view 43 mrad (0.002deg) Wavelength range 308-920 nm Spectral channels 10 Detector type Marconi 47-20 Pixels per image 1024 x 1024 Typical exposure times 90 ms to 10 sec CFI is optimized for low-light and short-wavelength imaging of a comet during CONTOUR's approach to it, including early detection for optical navigation, imaging of the coma, and imaging of emissions from ionized gases. CFI's reflective telescope focuses light through one of ten selectable filters mounted in a filter wheel, of which one is for broadband ('clear' filter) optical navigation images, three are for imaging in narrow wavelength bands emitted by ionized gases in the coma, and six are for multispectral imaging of the nucleus and coma. The digital image is captured by a high-efficiency, back-illuminated charge-coupled device (CCD) manufactured by Marconi. This is similar to the detector used in a standard video camera, except that CFIs CCD is black and white only (with color obtained using different filters) and it is manufactured to achieve higher sensitivity especially at ultraviolet wavelengths (as short as 308 nm for coma emission band imaging). The field of view is 2.5deg x 2.5deg, 1024 x 1024 pixels. Instead of looking directly at a comet and into the oncoming stream of impacting dust, CFI's telescope looks at one of four mirrors mounted onto the side of a rotatable cube. Only one mirror is exposed at a time to the oncoming dust, and a fresh mirror is put in place before each comet encounter by rotating the cube. The most important CFI measurements at each comet are for optical navigation and broad scale nucleus/coma imaging, and these are made at distances of tens to hundreds of thousands of kilometers before the mirror could be seriously damaged by oncoming dust particles. CFI Camera Filters Wavelength FWHM1 Purpose 'Clear' 350 Navigation / tracking 309.0 6.0 OH emissions 344.8 8.4 OH, CN continuum 387.0 6.2 CN emissions 445 10 Geology, 'blue' 514.1 11.8 C2 emissions 526 5 C2 continuum, 'green' 620 4 Geology, 'red' 840 9 Geology / near-IR 1 920 13 Geology / near-IR 2 FWHM = full width of the wavelength range passed by the filter at greater than half intensity CONTOUR's highest-velocity comet encounter (28 kilometers per second) will be with Comet Encke in November 2003. During the days before the enounter, every six hours a group of clear-filter images will be taken for spacecraft navigation and downlinked to Earth. These show the comet's position against a background of stars as dim as 11th magnitude, and will be analyzed to refine targeting of the encounter. Science imaging of the coma begins 5 hours before closest approach to the nucleus, with regular monitoring of activity in the inner coma. The prime CFI science imaging begins only six minutes out and continues through about 70 seconds before closest approach, with detailed imaging of the inner coma and color imaging of the nucleus. The narrow emission band filters are sensitive to hydroxyl (OH) from dissociated water and to cyanide and carbon (CN and C2) from dissociated dust, and will show the locations of jets of gas and dust driven off the nucleus by sublimating ices. The last color images will show details on the nucleus surface as small as 85 meters across. After this, the nucleus passes out of CFI's field-of-view and is no longer observable. From http://www.contour2002.org/instruments4.html Copyright 2002 NASA Discovery Program Used by Permission " END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "CONARDETAL2003" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END