PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = " 2004-08-25 S.McLaughlin Created 2005-02-09 S.McLaughlin Resolved liens " OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "DIF" INSTRUMENT_ID = "HRIV" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = " DEEP IMPACT HIGH RESOLUTION INSTRUMENT - VISIBLE CCD" INSTRUMENT_TYPE = "CCD CAMERA" INSTRUMENT_DESC = " The instrument overview was provided by Dr. Michael A'Hearn, the principal investigator for the Deep Impact mission. For a detailed discussion of the instrument, see Hampton, et al. (2005) [HAMPTONETAL2005]. Instrument Overview =================== The High Resolution Imager (HRI) consists of a long-focal-length telescope followed by a dichroic beam splitter that reflects visible (0.3 to 1.0 microns) light through a filter wheel to a CCD for direct, optical imaging. The beam splitter transmits the near-infrared light (1 to 5 microns) to a 2-prism spectrometer. For convenience, we consider these as two separate instruments, HRIV and HRII, sharing the telescope since the two focal planes operate in parallel asynchronously. The HRI telescope is a classical Cassegrain design with the following parameters: Primary aperture : 30.0 cm diameter, round Primary focal ratio : 4.5 Secondary Obscuration : 9.7 cm diameter, round Secondary magnification : 7.8x (net Cassegrain focal length 1050 m) Back focal distance : 30.0 cm The beam-splitter is a dichroic with equal transmission and reflection occurring at about 1.05 microns and it is placed in front of the telescope focal plane. The filter wheel contains two clear apertures and 7 filters. Five of the filters are roughly 100 nanometers in bandwidth, centered at 450, 550, 650, 750, and 850 nanometers. The shortest-wavelength filter is effectively a short-wavelength pass filter starting at 400 nanometers and limited to about 340 nanometers on the short end by the rapid decline in beamsplitter reflectivity. The longest wavelength filter is actually a long-pass filter starting at 900 nanometers that uses the CCD response to define the long-wavelength cutoff at about 960 nanometers. The visual detector is a 1024 x 1024 split frame-transfer CCD with 21-micron-square pixels, with each quadrant read out through a separate amplifier. The electronics allow 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 is about 5.2 milliseconds. Readout time for a full frame is 1.8 seconds. The HRIV instrument in full-frame 1024 x 1024 mode has the following field-of-view characteristics: Pixel Size : 21 micrometers Pixel FOV : 2.0 microradians Instrument FOV : 2.5 milliradians or 0.118 degrees Surface Scale : 1.4 meters/pixel at 700 kilometers The three instruments on the flyby spacecraft, HRII, HRIV and MRI, are mounted on a separate instrument platform together with the star trackers. The three instruments are nominally co-aligned. " END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "HAMPTONETAL2005" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END