Data Set Information
DATA_SET_TERSE_DESCRIPTION Calibrated data taken by New Horizons Alice Ultraviolet Imaging Spectrograph instrument during the PLUTO mission phase. This is VERSION 2.0 of this data set.
Data Set Overview                                                         
      This data set contains Calibrated data taken by New Horizons            
        Alice Ultraviolet Imaging Spectrograph                                
      instrument during the PLUTO mission phase.                              
      PERSI-Alice (P-ALICE; also ALICE) is a spectrograph on the New Horizons 
      spacecraft that is sensitive to extreme and far UltraViolet (UV) light  
      (520-1870 Angstroms). The ALICE instrument comprises a telescopic optics
      section and a spectrograph section that includes a diffraction grating  
      and a photosensitive two-dimensional (2-D) detector. The optics and     
      diffraction grating physical arrangement configure one detector         
      dimension as a spatial dimension and the other as spectral. ALICE has   
      two separate entrance apertures that feed light to the telescope section
      of the instrument: the AirGlow Channel (AGC) aperture; the Solar        
      Occultation Channel (SOCC) aperture. Both apertures pass light to the   
      detector through a lollipop-shaped slit comprising two contiguous       
      sections: a narrow, rectangular slit with a Field Of View (FOV) of 0.1  
      by 4.0 degrees; a fat, square slit with FOV 2.0 x 2.0 degrees. ALICE has
      two data-taking modes: pixel list mode records each detector/photon     
      event location (pixel i.e. spectral and spatial), interleaved with time 
      sequence events (hacks), allowing sub-second resolution of the photon   
      events; histogram mode summarizes the per-pixel photon event counts into
      a 2-D histogram over all detector pixels, collected over an extended    
      time which can range from a few seconds to several days. From both      
      modes, the common data product is the histogram (derived on the ground  
      in the pixel list case), which is functionally equivalent to a          
      spectral-by-spatial spectrogram (2-D image); other data products are    
      also provided and described in this data set.                           
     During the Pluto Charon Encounter mission phase starting in January,     
     2015, there were several sub-phases: three Approach sub-phases, (AP1,    
     AP2 and AP3); a CORE sequence for the Pluto flyby on 14 July, 2015 (Day  
     Of Year 195), sometimes also referred to as NEP (Near-Encounter Phase);  
     three Departure sub-phases (DP1, DP2, DP3).  For this second ALICE       
     delivery for the Pluto mission phase, this data set includes only the    
     Approach data plus a subset of the CORE and Departure sequences' data    
     that was downlinked through the end of January, 2016.  The rest of the   
     Pluto data will be delivered in future versions of this data set         
     according to the schedule worked out by the Project and NASA.            
     The first Pluto dataset delivery for the P-Alice instrument covers the   
     data on the ground between 1/15/2015 and 7/31/2015. It includes          
     functional testing and preliminary observations made during approach,    
     as well as a selected few observations from the few days up to the       
     Pluto encounter closest approach. Rho_Leo and Alice_Func are instrument  
     functional and calibration tests. PC_AIRGLOW is an observation that was  
     repeated regularly over the 2 months leading up to the CORE sequence.    
     The VISUV_MAP, Multi_Map, Airglow_Appr, and Airglow_Held observations    
     are part of the prime science data sets that meet specific objectives    
     of the mission.                                                          
     *--- Alice_Rho_Leo                                                       
     This observation points the P-Alice airglow boresight to the sky         
     location of Rho Leo to meet the following objectives:                    
     1) Quick flux sensitivity verification,                                  
     2) Airglow pointing verification,                                        
     3) Detector PHD determination.                                           
     There are the two observations included:                                 
     Unsaturated PHD observation, a single 30 second Histogram, and a         
     Rho-Leo observation, another single 300 second Histogram.                
     *--- Alice_Func_080                                                      
     This observation is the standard functional wake up Check (HK-TM,        
     Modes, Checksums and Selftest) with the following objectives:            
     1) Verify some very basic operations after the instrument has been       
     deactivated for some period of time (>month),                            
     2) Verify unchanged code (PROM and EEPROM),                              
     3) Verify successful parameter load and values,                          
     4) Verify successful completion of internal selftest,                    
     5) Verify unchanged behavior of the pixelhack problem                    
     6) Perform a standard door performance test run                          
     *--- PC_AIRGLOW    2.1-1.4                                               
     This set of observations is the P-Alice airglow observation of Pluto in  
     histogram mode. Each observation includes 6, 600 second histograms with  
     Pluto and Charon in the long and narrow portion of the slit. If          
     you visualize the slit as being the shape of a lollipop, the long        
     and narrow portion of the slit would correspond to the stick of the      
     lollipop. This region is known as the 'slot'.                            
     They meet a goal to determine the time variability of Pluto's surface    
     and atmosphere, and the airglow variability over several rotations. The  
     long-time base of this observation is to look for variability in         
     Pluto's atmosphere or excitation mechanisms. Deep histograms are         
     obtained roughly daily over a few set intervals on approach to document  
     and study the variability of atmospheric airglow emissions from H, O,    
     and N atoms/ions, N2 and CO band emissions, and to search for other      
     emissions such as from S, Ar, and Ne atoms. Pluto will not be resolved,  
     but it is possible that extended emission in the system could be seen,   
     though model brightness estimates indicate this is unlikely. Models      
     predict emission brightnesses of 0.01 to a few Rayleighs.                
     *--- PC_PIXELLIST                                                        
     Functional test of P-Alice, with a few minutes of data using Pixel       
     *--- UNOCC_SUN                                                           
     Unocculted sun observation.                                              
     A series of different exposures, 1 histogram for each, at 1, 10, 100,    
     and 1000 seconds. This is a histogram instead of pixellist, but          
     otherwise, it uses the same orientation, observation setup, and same     
     instrument parameters (voltage, etc) as P_OCC.                           
     *--- PC_VISUV_MAP                                                        
     PEAL_01_PC_VISUV_MAP_B_12 is a 40 minute P-Alice Histogram on Pluto and  
     Charon in the P-Alice box, taken 15 days before closest approach. For    
     these types of observations taken less than 10 days before closest       
     approach, Pluto and Charon are targeted in the slot. The goal is: Color  
     and Composition of Non-Encounter Hemispheres of Pluto & Charon. The      
     scientific motivation is to document the rotational disk-integrated UV   
     lightcurves of Pluto and Charon, primarily for surface composition, and  
     to search for spectral features indicative of surface materials such as  
     H2O-ice. It is expected that only the longer wavelengths will have       
     small enough opacity to see Pluto's surface, based on current            
     (1992-2007) gaseous CH4 observations.                                    
     *--- PC_Multi_Map_A/B                                                    
     Multi_Map_A5 has 4, 600 second P-Alice Airglow histograms with Pluto in  
     the box, similar to PC_VISUV_MAP. These observations are all multiple    
     300 second Airglow histograms, similar to PC_VISUV_MAP. For the          
     Multi_Map_B observations, Pluto is aligned in the center of the slot.    
     All of the PC_Multi_Map observations have the same goals as              
     *--- PC_Airglow_Appr                                                     
     There were 5 total of these observations, with Appr_3 and Appr_4 being   
     the last 2, taken a few hours before closest approach.                   
     PC_Airglow_Appr_3 has 10, 300 second histograms, and PC_Airglow_Appr_4   
     has 18, 150 second histograms. They meet a number of primary mission     
     goals. In addition to the goals for PC_VISUV_MAP and PC_Multi_Map,       
     these measurements also can be used for Pluto/Charon Hemisphere Surface  
     Composition Maps, to determine Pluto's Atmospheric Composition (N2, CO,  
     CH4, Ar), and the secondary goal of searching for emissions from minor   
     species (e.g., H, or perhaps C) in the airglow spectra.                  
     The observations provide the best practical S/N on the airglow and       
     information on its spatial distribution with both dayglow and            
     nightglow. Airglow observations from Pluto are very weak, but are        
     expected to provide the primary means for detecting certain minor        
     atmospheric species, including Ar and CO. Typical expected limb          
     brightnesses are a few Rayleighs or less, with the exception of H Lyman  
     alpha, which is expected to be 50-100 Rayleighs (note that this should   
     be darker than the background interplanetary signal from H Lyman alpha,  
     which should be ~100-200 Rayleighs). Most of these emissions are         
     excited by photoelectron impact (peaking in emission rate at ~1000 km    
     altitude), and modeling the observed emissions will yield density        
     estimates for the parent species. It is important to note that N+        
     emissions result from dissociation/ionization/excitation of N2, and      
     provide no information regarding Pluto's ionosphere.                     
     The observations can also be used to generate Pluto- and                 
     Charon-resolved UV surface maps. P-Alice is used for surface             
     composition studies of the sunlit face of Pluto, mostly looking for      
     H2O, and the instrument is used as a backup for LEISA composition        
     mapping. Water ice and certain other frosts have FUV absorption bands    
     that could be detected by making albedo maps. These observations can     
     also provide the disk-integrated rotationally resolved UV light curves   
     of Pluto and Charon, in support of surface composition studies.          
     Any additional Alice airglow or H Lyman alpha coronal data would be      
     useful for investigating atmospheric composition. Most of the near       
     encounter observations are designed for high-resolution surface          
     studies. Although the Alice instrument has poor spatial resolution, its  
     time-tagging ability makes it very flexible at taking useful data        
     whenever there is an opportunity (i.e., whenever MVIC, LEISA, or REX     
     are making primary observations).                                        
     *--- P_Alice_Airglow_Held                                                
     These observations are Alice airglow observations of Pluto in held       
     histogram mode, taken just before closest approach. Held_1 is 180        
     seconds, and Held_2 is 65 seconds. In addition to the goals from         
     PC_Airglow_Appr, these observations see the Pluto airglow at the limb.   
     As with the near-encounter airglow observations, these limb              
     observations are to ensure we obtain spatially-resolved airglow data.    
     At the bright limb, Pluto's airglow emissions should be ~10x brighter    
     due to the extended path length.                                         
      Every observation provided in this data set was taken as a part of a    
      particular sequence.  A list of these sequences has been provided in    
      file DOCUMENT/SEQ_ALICE_PLUTO.TAB.                                      
      N.B. Some sequences provided may have no corresponding observations.    
      For a list of observations, refer to the data set index table. This     
      is typically INDEX.TAB initially in the INDEX/ area of the data set.    
      There is also a file SLIMINDX.TAB in INDEX/ that summarizes key         
      information relevant to each observation, including which sequence      
      was in effect and what target was likely intended for the               
      This is VERSION 2.0 of this data set.                                   
      The pipeline (see Processing below) was re-run on these data for each   
      version since the first (V1.0).  As a result, ancillary information,    
      such as observational geometry and time (SPICE), may be updated.        
      This will affect, for example, the calibration of the data if parameters
      such as the velocity or orientation of the target relative to the       
      instrument, or the recorded target itself, have changed.                
      See the following sections for details of what has changed over each    
      version since the first (V1.0).  Note that even if this is not a        
      calibrated data set, the calibration changes are listed as the data     
      will have been re-run and there will be updates to the calibration      
      files, to the documentation (Science Operations Center - Instrument     
      Interface Control Document:  SOC_INST_ICD) and to the steps required    
      to calibrate the data.                                                  
This P2 Pluto Encounter dataset release provides updates to the Pluto dataset 
between P1 (data on the ground by 7/31/2015) and P2 (data on the ground by    
1/31/2016). All liens from the initial Pluto delivery have also now been      
resolved. For ALICE it contains only data from the Pluto Encounter period. It 
includes the additional observations below:                                   
Obs. Name (Request ID), Obs Date, Downlink Start, Downlink End, Obs. Target   
PEAL_01_Cocc 2015-07-14 2015/263 2015/346 Charon Occultation                  
PEAL_01_C_LEISA_HiResDump 2015-07-14 2015/292 2015/292 Charon observation     
PEAL_01_O_UnOccSun 2015-07-14 2015/264 2015/264 Unocculted Sun Histograms     
PEAL_01_O_UnOccSun_B 2015-07-15 2015/335 2015/335 Unocculted Sun Histograms   
PEAL_01_PCNH_Multilong_1d1 2015-07-13 2015/292 2015/292 Pluto, Ch, Nix, Hyd   
PEAL_01_PC_Airglow_Appr_1a 2015-07-13 2015/292 2015/292 Pluto and Charon obs  
PEAL_01_PC_Airglow_Appr_1b 2015-07-14 2015/292 2015/292 Pluto and Charon obs  
PEAL_01_PC_Airglow_Appr_2 2015-07-14 2015/292 2015/292 Pluto and Charon obs   
PEAL_01_PC_Airglow_Fill_0 2015-07-13 2015/292 2015/292 Pluto and Charon obs   
PEAL_01_PC_Airglow_Fill_2 2015-07-13 2015/292 2015/292 Pluto and Charon obs   
PEAL_01_PC_Airglow_Fill_DOY174 2015-06-23 2015/247 2015/247 Pluto, Charon obs 
PEAL_01_PC_Multi_Map_A_3 2015-07-02 2015/229 2015/229 Pluto and Charon obs    
PEAL_01_PC_Multi_Map_A_7 2015-07-03 2015/226 2015/226 Pluto and Charon obs    
PEAL_01_PC_VISUV_MAP_B_3 2015-06-26 2015/246 2015/246 Pluto and Charon obs    
PEAL_01_PC_VISUV_MAP_B_6 2015-06-27 2015/244 2015/244 Pluto and Charon obs    
PEAL_01_PC_VISUV_MAP_B_9 2015-06-28 2015/244 2015/244 Pluto and Charon obs    
PEAL_01_Pocc 2015-07-14 2015/269 2015/272 Pluto Occultation                   
PEAL_01_PoccEgress 2015-07-14 2015/267 2015/275 Pluto Occultation             
PEAL_01_P_Airglow_Dep_1 2015-07-14 2015/292 2015/292 Pluto observation        
PEAL_01_P_Airglow_Dep_2 2015-07-15 2015/292 2015/292 Pluto observation        
PEAL_01_P_Airglow_Dep_A_1 2015-07-16 2015/292 2015/292 Pluto observation      
PEAL_01_P_Airglow_Dep_A_2 2015-07-17 2015/292 2015/292 Pluto observation      
PEAL_01_P_Airglow_Dep_A_3 2015-07-18 2015/292 2015/292 Pluto observation      
PEAL_01_P_Airglow_Dep_A_4 2015-07-19 2015/292 2015/292 Pluto observation      
PEAL_01_P_Color_2 2015-07-14 2015/253 2015/253 Pluto observation              
PEAL_01_P_LEISA_HiResDump 2015-07-14 2015/292 2015/292 Pluto observation      
PEAL_01_P_LORRIDump 2015-07-14 2015/292 2015/292 Pluto observation            
PEAL_01_P_LORRI_Alice_Dep_1 2015-07-14 2015/292 2015/292 Pluto observation    
PEAL_01_P_LORRI_Alice_Dep_2 2015-07-14 2015/292 2015/292 Pluto observation    
PEAL_01_P_LORRI_Alice_Dep_3 2015-07-15 2015/292 2015/292 Pluto observation    
PEAL_01_P_LORRI_Alice_Dep_4 2015-07-15 2015/292 2015/292 Pluto observation    
PEAL_01_X_PLASMAROLL_3 2015-07-14 2015/264 2015/264 Airglow Histogram         
PEAL_02_PC_Airglow_Fill_2 2015-07-13 2015/292 2015/292 Pluto and Charon obs   
PEAL_03_PC_Airglow_Fill_2 2015-07-13 2015/292 2015/292 Pluto and Charon obs   
PEAL_04_PC_Airglow_Fill_2 2015-07-13 2015/292 2015/292 Pluto and Charon obs   
PEAL_05_PC_Airglow_Fill_2 2015-07-13 2015/292 2015/292 Pluto and Charon obs   
      The data in this data set were created by a software data               
      processing pipeline on the Science Operations Center (SOC) at           
      the Southwest Research Institute (SwRI), Department of Space Operations.
      This SOC pipeline assembled data as FITS files from raw telemetry       
      packets sent down by the spacecraft and populated the data labels       
      with housekeeping and engineering values, and computed geometry         
      parameters using SPICE kernels.  The pipeline did not resample          
      the data.                                                               
      The observations in this data set are stored in data files using        
      standard Flexible Image Transport System (FITS) format.  Each FITS      
      file has a corresponding detached PDS label file, named according       
      to a common convention.  The FITS files may have image and/or table     
      extensions. See the PDS label plus the DOCUMENT files for a             
      description of these extensions and their contents.                     
      This Data section comprises the following sub-topics:                   
      - Filename/Product IDs                                                  
      - Instrument description                                                
      - Other sources of information useful in interpreting these Data        
      - Visit Description, Visit Number, and Target in the Data Labels        
      Filename/Product IDs                                                    
        The filenames and product IDs of observations adhere to a             
        common convention e.g.                                                
         ^^^ ^^^^^^^^^^ ^^^^^ ^^^\__/                                         
         |        |       |    |  ^^                                          
         |        |       |    |   |                                          
         |        |       |    |   +--File type (includes dot)                
         |        |       |    |      - .FIT for FITS file                    
         |        |       |    |      - .LBL for PDS label                    
         |        |       |    |      - not part of product ID                
         |        |       |    |                                              
         |        |       |    +--ENG for CODMAC Level 2 data                 
         |        |       |       SCI for CODMAC Level 3 data                 
         |        |       |                                                   
         |        |       +--Application ID (ApID) of the telemetry data      
         |        |          packet from which the data come                  
         |        |          N.B. ApIDs are case-insensitive                  
         |        |                                                           
         |        +--MET (Mission Event Time) i.e. Spacecraft Clock           
         +--Instrument designator                                             
      Note that, depending on the observation, the MET in the data filename   
      and in the Product ID may be similar to the Mission Event Time (MET)    
      of the actual observation acquisition, but should not be used as an     
      analog for the acquisition time.  The MET is the time that the data are 
      transferred from the instrument to spacecraft memory and is therefore   
      not a reliable indicator of the actual observation time.  The PDS label 
      and the index tables are better sources to use for the actual timing of 
      any observation.  The specific keywords and index table column names for
      which to look are                                                       
        * START_TIME                                                          
        * STOP_TIME                                                           
        * SPACECRAFT_CLOCK_START_COUNT                                        
        * SPACECRAFT_CLOCK_STOP_COUNT                                         
        Instrument   Instrument designators              ApIDs **             
        ===========  ==================================  =============        
         ALICE        ALI                                0X4B0 - 0X4B7 *      
         * Not all values in this range are in this data set                  
         ** ApIDs are case insensitive                                        
         There are other ApIDs that contain housekeeping values and           
         other values.  See SOC Instrument ICD (/DOCUMENT/SOC_INST_ICD.*)     
         for more details.                                                    
        Here is a summary of the types of files generated by each ApID        
        (N.B. ApIDs are case-insensitive) along with the instrument           
        designator that go with each ApID:                                    
      ApIDs   Data product description/Prefix(es)                             
      =====   ===================================                             
      0x4b0 - ALICE Pixel List Lossless (CDH 1)/ALI                           
      0x4b1 - ALICE Pixel List Packetized (CDH 1)/ALI                         
      0x4b4 - ALICE Pixel List Lossless (CDH 2)/ALI                           
      0x4b5 - ALICE Pixel List Packetized (CDH 2)/ALI                         
      0x4b2 - ALICE Histogram Lossless (CDH 1)/ALI                            
      0x4b3 - ALICE Histogram Packetized (CDH 1)/ALI                          
      0x4b6 - ALICE Histogram Lossless (CDH 2)/ALI                            
      0x4b7 - ALICE Histogram Packetized (CDH 2)/ALI                          
        1) CDH 1 and CDH 2 refer to the spacecraft redundant Command and Data 
           Handling systems in general, and here specifically to their        
           respective Solid State Recorders (SSRs) 1 and 2, where ALICE data  
           be stored and prepared for downlink.  ALICE can send data to SSR   
           1 or to SSR 2, or, for mission-critical data, to both redundantly. 
           ALICE shares its channel to the SSRs with the Long-Range           
           Reconaissance Imager (LORRI), so both instruments cannot store     
           data simultaneously.  ALICE has the capability to store histogram  
           data to instrument-internal storage, and to transfer it to the     
           SSR(s) later; such an operation is called a Held Histogram, and    
           it allows ALICE to take data at the same time that LORRI is taking 
           and writing data to the SSR(s).                                    
        2) Packetized and Lossless refer to the method used on-board to       
           convert raw, high-speed instrument data on the SSR to low-speed    
           data ready for downlink.  The conversion process is generally      
           referred to as compression, even though Packetized conversion does 
           not reduce the data volume  In practice, Pixel List data always    
           use Packetized compression.  Histogram data may use Packetized or  
           Lossless compression.  Depending on the actual data contents,      
           Lossless compression reduces data volume by 60 to 90% or more;     
           for nominal science data a factor of 3 or more is normal.          
           Lossless compression is used whenever possible to reduce downlink  
           data volume.  There is no difference, between Packetized and       
           Lossless compression, in the resultant FITS files after processing 
           by the Science Operations Center (SOC) data pipeline.              
      Instrument description                                                  
        Refer to the following files for a description of this instrument.    
          NH_ALICE_V###_TI.TXT  (### is a version number)                     
      Other sources of information useful in interpreting these Data          
        Refer to the following files for more information about these data    
          NH Trajectory tables:                                               
            /DOCUMENT/NH_MISSION_TRAJECTORY.*   - Heliocentric                
          ALICE Field Of View definitions:                                    
      Visit Description, Visit Number, and Target in the Data Labels          
      The observation sequences were defined in Science Activity Planning     
      (SAP) documents, and grouped by Visit Description and Visit Number.     
      The SAPs are spreadsheets with one Visit Description & Number per row.  
      A nominal target is also included on each row and included in the data  
      labels, but does not always match with the TARGET_NAME field's value in 
      the data labels.  In some cases, the target was designated as RA,DEC    
      pointing values in the form ``RADEC=123.45,-12.34'' indicating Right    
      Ascension and Declination, in degrees, of the target from the           
      spacecraft in the Earth Equatorial J2000 inertial reference frame.      
      This indicates either that the target was either a star, or that the    
      target's ephemeris was not loaded into the spacecraft's attitude and    
      control system which in turn meant the spacecraft could not be pointed  
      at the target by a body identifier and an inertial pointing value had   
      to be specified as Right Ascension and Declination values.  PDS-SBN     
      practices do not allow putting a value like RADEC=... in the PDS        
      TARGET_NAME keyword's value. In those cases the PDS TARGET_NAME value   
      is set to CALIBRATION.  TARGET_NAME may be N/A (Not Available or Not    
      Applicable) for a few observations in this data set; typically that     
      means the observation is a functional test so N/A is an appropriate     
      entry for those targets, but the PDS user should also check the         
      the PDS label, plus the provided sequence list (see Ancillary Data      
      below) to assess the possibility that there was an intended target.     
      Specifically for ALICE observations, any observation that has an        
      observation description or sequence ID that includes the words dump     
      or held will usually have N/A as its target, but that indicates the     
      observation was actually taken as part of an earlier sequence and held  
      held locally in instrument memory (i.e. a Held Histogram; see the       
      Notes in the Data section below), and the Dump sequence represents the  
      commands that transferred the instrument data onto the spacecraft       
      Solid-State Recorders (SSRs).  In the cases of Held Histograms, the     
      user should check the previous sequence in the sequence list.  For      
      other cases note that if the characters _P_, _C_, or _PC_ are in the    
      sequence ID, then the intended target was likely Pluto, Charon, or      
      Pluto and Charon together, respectively.                                
    Ancillary Data                                                            
      The geometry items included in the data labels were computed            
      using the SPICE kernels archived in the New Horizons SPICE              
      data set, NH-X-SPICE-6-PLUTO-V1.0.                                      
      Every observation provided in this data set was taken as a part of a    
      particular sequence.  A list of these sequences has been provided in    
      file DOCUMENT/SEQ_ALICE_PLUTO.TAB.  In addition, the                    
      sequence identifier (ID) and description are included in the PDS label  
      for every observation.  N.B. While every observation has an associated  
      sequence, every sequence may not have associated observations.  Some    
      sequences may have failed to execute due to spacecraft events (e.g.     
      safing).  No attempt has been made during the preparation of this data  
      set to identify such empty sequences, so it is up to the user to        
      compare the times of the sequences to the times of the available        
      observations from INDEX/INDEX.TAB to identify such sequences.           
      There are several time systems, or units, in use in this dataset:       
      New Horizons spacecraft MET (Mission Event Time or Mission Elapsed      
      Time), UTC (Coordinated Universal Time), and TDB Barycentric            
      Dynamical Time.                                                         
      This section will give a summary description of the relationship        
      between these time systems.  For a complete explanation of these        
      time systems the reader is referred to the documentation                
      distributed with the Navigation and Ancillary Information               
      Facility (NAIF) SPICE toolkit from the PDS NAIF node, (see                                                        
      The most common time unit associated with the data is the spacecraft    
      MET.  MET is a 32-bit counter on the New Horizons spacecraft that       
      runs at a rate of about one increment per second starting from a        
      value of zero at                                                        
        19.January, 2006 18:08:02 UTC                                         
        JD2453755.256337 TDB.                                                 
      The leapsecond adjustment (DELTA_ET = ET - UTC) was 65.184s at          
      NH launch, and the first three additional leapseconds occured           
      in at the ends of December, 2009, June, 2012 and June, 2015.            
      Refer to the NH SPICE data set, NH-J/P/SS-SPICE-6-V1.0, and the         
      SPICE toolkit docmentation, for more details about leapseconds.         
      The data labels for any given product in this dataset usually           
      contain at least one pair of common UTC and MET representations         
      of the time at the middle of the observation.  Other portions           
      of the products, for example tables of data taken over periods          
      of up to a day or more, will only have the MET time associated          
      with a given row of the table.                                          
      For the data user's use in interpreting these times, a reasonable       
      approximation (+/- 1s) of the conversion between Julian Day (TDB)       
      and MET is as follows:                                                  
        JD TDB = 2453755.256337 + ( MET / 86399.9998693 )                     
      For more accurate calculations the reader is referred to the            
      NAIF/SPICE documentation as mentioned above.                            
    Reference Frame                                                           
      Geometric Parameter Reference Frame                                     
      Earth Mean Equator and Vernal Equinox of J2000 (EMEJ2000) is the        
      inertial reference frame used to specify observational geometry items   
      provided in the data labels.  Geometric parameters are based on best    
      available SPICE data at time of data creation.                          
      Epoch of Geometric Parameters                                           
      All geometric parameters provided in the data labels were computed at   
      the epoch midway between the START_TIME and STOP_TIME label fields.     
      The observations in this data set are in standard FITS format           
      with PDS labels, and can be viewed by a number of PDS-provided          
      and commercial programs. For this reason no special software is         
      provided with this data set.                                            
    Contact Information                                                       
      For any questions regarding the data format of the archive,             
      New Horizons ALICE Principal Investigator:                              
        Alan Stern, Southwest Research Institute                              
      S. Alan Stern                                                           
      Southwest Research Institute                                            
      Department of Space Studies                                             
      1050 Walnut Street, Suite 400                                           
      Boulder, CO   80302                                                     
DATA_SET_RELEASE_DATE 2016-10-31T00:00:00.000Z
START_TIME 2015-01-25T03:09:59.701Z
STOP_TIME 2015-07-19T07:28:00.881Z
MISSION_START_DATE 2006-01-19T12:00:00.000Z
MISSION_STOP_DATE 2021-09-30T12:00:00.000Z
NODE_NAME Small Bodies
Confidence Level Overview                                                 
      During the processing of the data in preparation for                    
      delivery with this volume, the packet data associated with each         
      observation were used only if they passed a rigorous verification       
      process including standard checksums.                                   
      In addition, raw (Level 2) observation data for which adequate          
      contemporary housekeeping and other ancillary data are not available    
      may not be reduced to calibrated (Level 3) data.  This issue is raised  
      here to explain why some data products in the raw data set,             
      may not have corresponding data products in the calibrated data set,    
    Data coverage and quality                                                 
      Every observation provided in this data set was taken as a part of a    
      particular sequence.  A list of these sequences has been provided in    
      file DOCUMENT/SEQ_ALICE_PLUTO.TAB.  N.B. Some sequences                 
      provided may have zero corresponding observations.                      
      Refer to the Confidence Level Overview section above for a summary      
      of steps taken to assure data quality.                                  
      The lollipop-shaped fuzz in images of some ALICE spectra, seen as high  
      signal levels at the box end of the slit around Hydrogen Lyman-alpha (H 
      Lya) wavelengths, is due to a characteristic of the detector and        
      aperture.  To make the Micro Channel Plate (MCP) more sensitive to UV   
      light, it was coated with potassium bromide (KBr) photocathodes from    
      520 to 1180 Angstrom and with cesium iodide (CsI) photocathodes from    
      1250 to 1870 Angstrom. A vertical strip - a spectral band of 70         
      Angstrom centered at ~1216 Angstrom - of the MCP was masked and left    
      uncoated to reduce the sensitivity of the detector to H Lya             
      radiation. In the slit portion of the aperture (0.1deg wide x 4deg      
      high), the diffraction grating keeps the strong H Lya line within that  
      uncoated band. However, in the 2x2 degree box portion of the aperture   
      designed to capture the Sun during occultations, the H Lya spreads out  
      beyond the uncoated 70-Angstrom band over another ~55 Angstroms of more 
      sensitive photocathode-coated detector on either side. The quantum      
      efficiencies of the photocathode- coated surfaces are about an order of 
      magnitude more sensitive to sensitive to H Lya wavelengths than the     
      bare, uncoated MCP glass, which gives rise to high signal levels from   
      the box area of the slit i.e. the lollipop fuzz.                        
    Observation descriptions in this data set catalog                         
      Some users will expect to find descriptions of the observations         
      in this data set here, in this Confidence Level Note.  This data        
      set follows the more common convention of placing those                 
      descriptions under the Data Set Description (above, if the user is      
      reading this in the DATASET.CAT file) of this data set catalog.         
    Caveat about TARGET_NAME in PDS labels and observational intent           
      A fundamental truth of managing data from some spacecraft missions      
      is that the intent of any observation is not suitable for insertion     
      into the command stream sent to the spacecraft to execute that          
      observation.  As a result, re-attaching that intent to the data         
      that are later downlinked is problematic at best. For New Horizons      
      that task is made even more difficult as the only meta-data that        
      come down with the observation is the unpredictable time of the         
      observation.  The task is made yet even more difficult because          
      uplink personnel, who generate the command sequences and initially      
      know the intent of each observation, are perpetually under              
      deadlines imposed by orbital mechanics and can rarely be spared for     
      the time-intensive task of resolving this issue.                        
      To make a long story short, the downlink team on New Horizons has       
      created an automated system to take various uplink products, decode     
      things like Chebyshev polynomials in command sequences representing     
      celestial body ephemerides for use on the spacecraft to control         
      pointing, and infer from those data what the most likely intended       
      target was at any time during the mission.  This works well during      
      flyby encounters and less so during cruise phases and hibernation.      
      The point to be made is that the user of these PDS data needs to        
      be cautious when using the TARGET_NAME and other target-related         
      parameters stored in this data set.  This is less an issue for the      
      plasma and particle instruments, more so for pointing instruments.      
      To this end, the heliocentric ephemeris of the spacecraft, the          
      spacecraft-relative ephemeris of the inferred target, and the           
      inertial attitude of the instrument reference frame are provided        
      with all data, in the J2000 inertial reference frame, so the user       
      can check where that target is in the Field Of View (FOV) of the        
      This dataset was peer reviewed and certified for scientific use on      
ABSTRACT_TEXT This data set contains Calibrated data taken by the New Horizons Alice Ultraviolet Imaging Spectrograph instrument during the Pluto encounter mission phase. This is VERSION 2.0 of this data set. This data set contains ALICE observations taken during the the Approach (Jan-Jul, 2015) and Encounter mission sub-phases, including flyby observations taken on 14.July, 2015; the data are limited to those downlinked from the spacecraft as of the end of January, 2016. The rest of the downlinked data for this mission phase will be delivered in a future data set. Refer to the data set description above and the sequence table provided in the documentation for more detail about which observations are present in this data set. This is version 2.0 of this data set. Changes since version 1.0 include data downlinked between the end of July, 2015 and the end of January, 2016. These include Pluto and Charon occultations, Airglow observations during the weeks before and after the flyby, Approach VIS-UV and multi-maps, color and hi-resolution observations during the flyby, PEPSSI (plasma roll) and LORRI other ride-alongs, Also, updates were made to the documentation and catalog files, primarily to resolve liens from the V1.0 peer review.
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