PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM LABEL_REVISION_NOTE = " 2004-08-25 S.McLaughlin Created 2005-02-04 S.McLaughlin Resolved liens from Oct 2004 thermal-vac review; 2006-05-22 DI:McLaughlin Resolved liens from Apr 2006 peer review; 2007-05-30 DI:McLaughlin Added RECORD_TYPE, reference id LINDLERETAL2007; 2009-01-02 EPOXI:McLaughlin Updated for EPOXI mission. 2009-05-22 EPOXI:McLaughlin Additional updates for EPOXI. 2009-08-19 EPOXI:McLaughlin Lien resolution for 23 Jul 2009 peer review. 2011-05-08 EPOXI:McLaughlin Improved array characteristics regarding binned and unbinned modes; noted that binning *averages* pixels. 2011-08-24 EPOXI:McLaughlin Resolved liens from the Aug 2011 peer review: fixed outdated wording; added reference KLAASENETAL2011. 2013-03-08 EPOXI:McLaughlin Resolved liens from Mar 2013 peer review: Changed pub date for KLAASENETAL2011. " OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "DIF" INSTRUMENT_ID = "HRII" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = " DEEP IMPACT HIGH RESOLUTION INSTRUMENT - IR SPECTROMETER" INSTRUMENT_TYPE = "INFRARED SPECTROMETER" INSTRUMENT_DESC = " Instrument Overview =================== The High Resolution Imager (HRI) consists of a long-focal-length telescope with a dichroic beam splitter, located in front of the focal plane, 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 (High Resolution Visible CCD) and HRII (High Resolution IR spectrometer), 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 cm) Back focal distance : 30.0 cm The dichroic beam-splitter has equal transmission and reflection occurring at about 1.05 microns and is placed in front of the telescope focal plane. The spectrometer is a 2-prism design, one of calcium fluoride (CaF_2) and one of zinc selenide (ZnSe) to maximize etendue and minimize problems with order separation. The camera and collimator lead to a net demagnification of 3x, for an effective focal ratio of f/12 and effective focal length of 360 cm in the final beam. The entrance slit subtends on the sky 2.53 milliradians by 10 microradians (0.145 degrees by 2 arcseconds), filling the 512-pixel height of the IR array. The slit width of 10 microradians matches the binned pixel (2x2) mode used for most observations. The near-infrared detector is a 1024 (wavelength) x 512 (spatial) pixel mercury cadmium telluride (HgCdTe) device manufactured by Rockwell using the multiplexer originally developed under contract from the University of Hawaii for use in the WFC3 on HST. Physically, it is a 1024 x 1024 device, but only half of the device is active. Pixels are 18 microns square and normal operations include 2x2 binning (post-readout; pixels are averaged together). Spectral resolving power, because of the 2-prism design, varies from greater than 740 at 1.04 microns down to 210 at 2.6 microns, and back up to 385 at 4.8 microns. Due to saturation problems in warm areas of a cometary nucleus, the central quarter of the detector is covered with a neutral density filter, which is also called the anti-saturation filter. When operated in the 512 x 256 pixel, 2x2 binning mode, the HRII instrument has the following field-of-view characteristics: Spatial ------- Physical Pixel Size : 36 micrometers Effective Pixel FOV : 10.0 microradians or 2.06265 arcseconds Effective FOV : 2.5 milliradians or 0.15 degrees Spectral -------- Effective Pixel FOV : 10.0 microradians Effective FOV : 10.0 microradians (slit width) Note: For unbinned modes, pixels are 5 microradians wide in the spatial dimension and the slit width remains fixed at 10.0 microradians. Therefore an unbinned pixel subtends 10 microradians x 5 microradians or 5x10^-11 steradians on the sky while a binned pixel subtends 10 microradians x 10 microradians or 1x10^-10 steradians. The spectrometer includes an internal stimulator lamp for calibrating between the two quadrants of the spectrometer (i.e., not as a standard calibrator). However the lamp was broken during one of the ground thermal-vacuum tests and was not replaced. Therefore this lamp was never used during the Deep Impact and EPOXI missions. The three instruments on the flyby spacecraft, HRII, HRIV (High- Resolution Visible CCD) and MRI (Medium-Resolution Visible CCD), are mounted on a separate instrument platform together with the star trackers. The three instruments are nominally co-aligned as described by by Klaasen, et al. (2008) [KLAASENETAL2006]. For a detailed discussion of the instrument and how it was used during the Deep Impact mission, see Hampton, et al. (2005) [HAMPTONETAL2005] and Klaasen, et al. (2005) [KLAASENETAL2005]. For the EPOXI mission, the HRII instrument imaged Earth and Mars as remotely-sensed planets and comet 103P/Hartley 2. Instrument Calibration ====================== The HRII instrument was originally calibrated by using in-flight data acquired during Deep Impact as well as pre-launch data taken during thermal-vacuum tests (TV1, TV2, and TV4) performed in 2002 and 2003. In-flight calibrations continued through the EPOXI mission to monitor performance and to provide additional data for refining the calibration pipeline. Instrument calibration for Deep Impact is discussed by Klaasen, et al. (2008) [KLAASENETAL2006]; instrument calibration for EPOXI is discussed by Klaasen, et al. (2013) [KLAASENETAL2011]. Flight Performance ================== The HRII instrument generally performed as expected during flight. During Deep Impact, small changes in instrumental temperatures affected the dark current more than expected from ground thermal-vacuum tests. This effect continued for EPOXI and is discussed in the Deep Impact instrument calibration paper by Klaasen, et al. (2008) [KLAASENETAL2006]. Calibration data acquired throughout EPOXI showed changes to the linearity constants and increases to the numbers of bad pixels. Also a new flat field that corrected for the anti-saturation filter was constructed. Therefore new calibration files and constants were incorporated into the calibration pipeline for EPOXI processing; additional improvements such as the timing for certain imaging modes are discussed by Klaasen, et al. (2013) [KLAASENETAL2011]. During the Deep Impact mission, early images of stars acquired by the HRIV CCD indicated the HRI telescope was out of focus. An analysis showed the focus was forward of the HRIV CCD, so bakeouts were performed in late February and early March 2005 to improve the focus. The bakeouts reduced the defocus from 1.0 cm to 0.6 cm, which caused the width of star images to decrease from about 12 pixels to about 9 pixels in a HRIV frame. This focus problem had only a nominal effect on the HRII instrument. For a detailed discussion about the focus of the HRI telescope, please see Klaasen, et al. (2008) [KLAASENETAL2006] and Lindler, et al. (2007) [LINDLERETAL2007]. This instrument description was originally provided by Dr. Michael A'Hearn for the Deep Impact mission, then updated as the EPOXI mission progressed. " 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 OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "KLAASENETAL2011" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "LINDLERETAL2007" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "LINDLERETAL2013" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END