Instrument Information
INSTRUMENT_ID LORRI
INSTRUMENT_NAME LONG RANGE RECONNAISSANCE IMAGER
INSTRUMENT_TYPE IMAGER
INSTRUMENT_HOST_ID NH
INSTRUMENT_DESC
########################################################################      
########################################################################      
REQUIRED READING:                                                             
- Cheng et al. (2008) [CHENGETAL2008]                                         
- Conard et al. (2005) [CONARDETAL2005]                                       
########################################################################      
########################################################################      
                                                                              
      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.                                                                 
                                                                              
    N.B. In calibrated images, radiance is stored as 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 the SOC Instrument Interface Control Document        
    (ICD) for more detail.
REFERENCE_DESCRIPTION