Instrument Information
INSTRUMENT_ID LORRI
INSTRUMENT_NAME LONG RANGE RECONNAISSANCE IMAGER
INSTRUMENT_TYPE IMAGER
INSTRUMENT_HOST_ID NH
INSTRUMENT_DESC
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REQUIRED READING:
- Cheng et al. (2008) [CHENGETAL2008]
- Conard et al. (2005) [CONARDETAL2005]
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      The LORRI description was was adapted from [CONARDETAL2005],
      [CHENGETAL2008],  and the New Horizons website.


  INSTRUMENT OVERVIEW
  ===================
    The LOng-Range Reconnaissance Imager (LORRI) is an instrument that was
    designed, fabricated, and qualified for the New Horizons mission to
    the outermost planet Pluto, its giant satellite Charon, and the Kuiper
    Belt, which is the vast belt of icy bodies extending roughly from
    Neptune's orbit out to 50 astronomical units (AU). New Horizons
    launched in January 2006 as the inaugural mission in NASA's New
    Frontiers program.


    SPECIFICATIONS
    --------------
      NAME:                    LORRI (Long-Range Reconnaissance Imager)
      DESCRIPTION:             High-resolution telescope
      PRINCIPAL INVESTIGATOR:  Hal Weaver, APL
      WAVELENGTH RANGE:        350 - 850nm
      FIELD OF VIEW:           5.06 x 5.06 milliradians (0.29 x 0.29
      degrees)
      ANGULAR RESOLUTION:      0.00494 milliradians, unbinned
      WAVELENGTH RESOLUTION:   N/A

      PRIMARY DATA FORMAT(S):  1) 1024x1024 2-D pixel array (unbinned)
                               2) 256x256 2-D pixel array (4x4 binned)

      PRIMARY MEASURED QUANTITIES:
        1) Raw data:         per-pixel brightnesses as Data Numbers (DNs)
        2) Calibrated data:  per-pixel brightnesses as calibrated DNs.
                             N.B. Calibrated image data pixels are in
                                  units of calibrated DN, with
                                  scene-dependent conversion divisors to
                                  radiance provided in the FITS headers
                                  and PDS labels.  Refer to the SOC
                                  Instrument Interface Control Document
                                  (ICD) for more detail.


    DESCRIPTION
    -----------
      LORRI is a narrow angle (field of view=0.29 deg), high resolution
      (instantaneous field of view = 4.94 urad), Ritchey-Chretien
      telescope with a 20.8 cm diameter primary mirror, a focal length of
      263 cm, and a three lens field-flattening assembly. A 1024 x 1024
      pixel (optically active region), back-thinned, backside-illuminated
      charge-coupled device (CCD) detector (model CCD 47-20 from E2V
      Technologies) is located at the telescope focal plane and is
      operated in standard frame-transfer mode. LORRI does not have any
      color filters; it provides panchromatic imaging over a wide bandpass
      that extends approximately from 350 nm to 850 nm. A unique aspect of
      LORRI is the extreme thermal environment, as the instrument is
      situated inside a near room temperature spacecraft, while pointing
      primarily at cold space. This environment forced the use of a
      silicon carbide optical system, which is designed to maintain focus
      over the operating temperature range without a focus adjustment
      mechanism. Another challenging aspect of the design is that the
      spacecraft is thruster-stabilized (no reaction wheels), which places
      stringent limits on the available exposure time and the optical
      throughput needed to accomplish the high-resolution observations
      required.  LORRI was designed and fabricated by a combined effort of
      The Johns Hopkins University Applied Physics Laboratory (APL) and
      SSG Precision Optronics Incorporated (SSG).

      LORRI has four subassemblies in close proximity connected by
      electrical harnesses. These are the optical telescope assembly
      (OTA), the aperture cover door, the associated support electronics
      (ASE), and the focal plane unit (FPU). Except for the door, all are
      mounted inside the spacecraft on its central deck; the door is
      mounted to an external spacecraft panel. LORRI is electronically
      shuttered, with no moving parts aside from the cover door. The ASE
      implements all electrical interfaces between LORRI and the
      spacecraft except for the door control, several spacecraft
      thermistors, and two decontamination heaters. [CONARDETAL2005] gives
      a detailed description of LORRI design, manufacture and test.


  Scientific Objectives
  =====================
    Hemispheric panchromatic maps of Pluto and Charon at best resolution
    exceeding 0.5 km/pixel.

    Search for atmospheric haze at a vertical resolution <5 km

    Long time base of observations, extending over 10 to 12 Pluto rotations

    Panchromatic maps of the far-side hemisphere

    High resolution panchromatic maps of the terminator region

    Panchromatic, wide phase angle coverage of Pluto, Charon, Nix, and
    Hydra

    Panchromatic stereo images of Pluto, Charon, Nix, and Hydra

    Orbital parameters, bulk parameters of Pluto, Charon, Nix, and Hydra

    Search for satellites and rings


  Calibration
  ===========
    See [CHENGETAL2008]


  Detectors
  =========
    Frame transfer CCD.  See [CHENGETAL2008] for details.

    As of late 2016, there are no known dead or hot pixels on the LORRI
    detector, so all hot and dead pixel map calibration files contain all
    zeroes.  From the current flat-field calibration file it can be seen
    that there are many pixels with relative sensitivities up to six times
    the mean (unity); those are called warm pixels.  Warm pixels are
    calibrated in the flat-field step.



  Electronics
  ===========
    LORRI electronics consist of the ASE and FPU. The ASE contains three
    printed circuit cards. These are the low voltage power supply (LVPS),
    the event processor unit (EPU), and the imager input/output (IM I/O).
    The ASE is the primary interface between the spacecraft and the FPU,
    which mounts and controls the CCD. Additional information can be found
    in [CONARDETAL2005].


  Filters
  =======
    None.


  Optics
  ======
    The LORRI OTA is a Ritchey-Chretien design, with high system
    throughput required because of the short allowed exposure time and low
    light level at Pluto. The complete LORRI OTA design was evaluated with
    a computer-aided design model including stray light analysis. Specular
    reflections and bidirectional reflectance distribution functions of
    the Aeroglaze Z-306 black paint, primary and secondary mirrors, field
    group optics and focal plane were included in the model. The primary
    and secondary baffle tubes were sized to minimize obscuration and
    suppress direct paths to the FPA's active area. The telescope
    magnification and obscuration were balanced, affecting the optical
    sensitivity and MTF, respectively. Out-of-field stray light was
    evaluated by generating point source transmittance curves with angular
    scans across the boresight in two orthogonal directions (-70 degrees
    to +70 degrees for each scan) to search for any obscured paths with
    unacceptable amplitude.

    See [CHENGETAL2008] for more details.


  Operational Modes
  =================
    LORRI high-rate image data telemetry APID definitions

             C&DH  binning
      APID   side  mode    compression type

      0x630    1    1x1    lossless
      0x631    1    1x1    packetized
      0x632    1    1x1    lossy
      0x633    1    4x4    lossless
      0x634    1    4x4    packetized
      0x635    1    4x4    lossy
      0x636    2    1x1    lossless
      0x637    2    1x1    packetized
      0x638    2    1x1    lossy
      0x639    2    4x4    lossless
      0x63A    2    4x4    packetized
      0x63B    2    4x4    lossy

    The LORRI instrument replaces the first 34 12-bit pixels of each LORRI
    image (408 bits; 51 bytes) with encoded binary header information, so
    those first 34 pixel values in the first row are not representative of
    the brightness of the imaged scene at those locations; these pixels
    are in the bottom-left corner of images displayed left-to-right and
    bottom-to-top. Furthermore, if the image was LOSSY-compressed before
    downlink (ApIDs 0x632, 0x635, 0x638, 0x63B), the header information
    corrupts the first 40 pixels of the first 8 rows of the image because
    of the Discrete Cosine Transform compression algorithm.  The SOC
    pipeline extracts these data into the FIRST34 extension of LORRI FITS
    files, which is also corrupt in LOSSY-compressed files. The SOC
    calibration pipeline also flags these pixels as bad in the QUALITY_MAP
    extension of calibrated FITS files; no such flags are available in the
    raw FITS files; the SOC pipeline did not flag the additional corrupt
    pixels beyond the first 34 in LOSSY-compressed data until the Pluto P2
    delivery late in 2016.


  Measured Parameters
  ===================
    Radiance.

    In calibrated images, radiance is stored as a combination of two items:
    calibrated DN in each pixel; scene spectrum-dependent divisors in each
    FITS header and PDS label to convert per-pixel DNs to radiances.  Refer
    to section 9.3.1.4 of the SOC Instrument Interface Control Document (ICD)
    for more detail, including a discussion of units. In the FITS headers of
    calibrated images, divisor and unit information reside in a section
    labeled 'LORRI Level 2 Absolute Calibration Parameters'.
REFERENCE_DESCRIPTION