PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM LABEL_REVISION_NOTE = " 2004-08-25 S.McLaughlin Created; 2005-02-10 S.McLaughlin Resolved liens from Oct 2004 thermal-vac review; 2006-05-18 DI:S.McLaughlin Resolved liens from Apr 2006 peer review; 2006-10-02 DI:S.McLaughlin Corrected FOV characteristics; 2006-12-07 DI:S.McLaughlin Resolved liens from Nov 2006 peer review; 2007-05-30 DI:S.McLaughlin Added reference id KLAASENETAL2005; " OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "DIF" INSTRUMENT_ID = "MRI" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = " DEEP IMPACT MEDIUM RESOLUTION INSTRUMENT - VISIBLE CCD" INSTRUMENT_TYPE = "CCD CAMERA" INSTRUMENT_DESC = " Instrument Overview =================== The Medium Resolution Imager consisted of an f/17.5 Cassegrain telescope followed by a filter wheel feeding directly onto a CCD for direct, optical imaging. The MRI telescope was a classical Cassegrain design with the following parameters: Primary aperture : 12.0 cm diameter, round Primary focal ratio : 3.75 Secondary Obscuration : 6.6 cm diameter, round Secondary magnification : 4.75x (net Cassegrain focal length 210 cm) Back focal distance : 30.0 cm The filter wheel contained two clear apertures and eight filters. The filters included duplicates of some of the medium-band filters in the High Resolution Instrument and narrow-band filters that isolate OH, CN, and C2 as well as the green and violet continuum. These narrow-band filters were designed to match the Hale-Bopp filter sets used for ground-based programs since 1996. The longest wavelength filter was actually a long-pass filter that used the CCD response to define the long-wavelength cutoff at about 960 nanometers. The detector was a 1024 x 1024 split-frame, frame-transfer CCD with 21-micron-square pixels. The electronics allowed readout of centered sub-frames in multiples of 2: 64x64, 128x128, and so on, with or without rows of overscan. Transfer time, to move the two halves of the image from the exposing area to the two shielded areas, was about 5.2 milliseconds. There are readout amplifiers in each of the four quadrants. Readout time for a full frame was 1.8 seconds. Net pixel scale was 10 microradians/pixel (2 arcseconds/pixel). The MRI instrument in full-frame 1024 x 1024 mode had the following field-of-view characteristics: Pixel Size : 21 micrometers Pixel FOV : 10.0 microradians Instrument FOV : 10.0 milliradians or 0.587 degrees Surface Scale : 7 meters/pixel at 700 kilometers The three instruments on the flyby spacecraft, MRI, HRII (High- Resolution IR Imaging Spectrometer), HRIV (High-Resolution Visible CCD), were mounted on a separate instrument platform together with the star trackers. The three instruments were nominally co-aligned. For a detailed discussion of the instrument, see Hampton, et al. (2005) [HAMPTONETAL2005]. This instrument overview was provided by Dr. Michael A'Hearn, the principal investigator for the Deep Impact mission. Instrument Calibration ====================== The MRI instrument was calibrated by using in-flight data as well as pre-launch data taken during a thermal-vacuum test (TV4) performed in 2003. The calibration of the MRI instrument was discussed in the 'Deep Impact Instrument Calibration' paper by Klaasen, et al. (2006) [KLAASENETAL2006]. There is a 1/3-pixel, horizontal gap for a clocking phase between the upper and lower halves of the CCD. It was inserted by the manufacturer to facilitate the simultaneous upward and downward reading of the upper and lower quadrants. The gap causes a 10 percent reduction in the sensitivity of the two central rows (i.e., one row immediately above the gap and one below it). Flight Performance ================== The MRI instrument generally performed as expected during flight. " END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "HAMPTONETAL2005" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "KLAASENETAL2005" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "KLAASENETAL2006" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END