Data Set Overview  :   This data set contains Raw data taken by  the New Horizons Alice Ultraviolet Imaging Spectrograph  instrument during the CRUISE TO FIRST KBO ENCOUNTER 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: PixelList 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 PixelList 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.   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_*.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  observation.    Version  :   This is VERSION 2.0 of this data set.   This version includes all data from the previous version and  adds data acquired by the spacecraft between 12/07/2017 and  08/13/2018. This is the complete dataset.   TARGET_NAME values were expanded and made more consistent across all  instruments.   This version includes functional testing during the wakeup check  from hibernation, high voltage (HV) dark tests, InterPlanetary Medium  (IPM) Lyman-Alpha upstream and downstream measurements, spacecraft -  instrument interference testing, and calibration testing using Rho Leo.  Descriptions of the Rho Leo calibration and the Wakeup Check are given  here:   *--- 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   General statement about data set versions after V1.0  ----------------------------------------------------  The pipeline (see Processing below) was re-run on these data for each  version since the first (V1.0). A pipeline rerun usually changes the  FITS headers but not the FITS data of raw data sets. In some cases  calibrated FITS data may change because the calculated geometry of an  observation has changed. See data set version-specific sections below  for significant exceptions to this general statement, i.e. changes to  pipeline processing, calibration processing, and data delivered.   Note that even if this is not a calibrated data set, 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.    Processing  :   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.    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.   ALI_0123456789_0X4B0_ENG.FIT  ^^^ ^^^^^^^^^^ ^^^^^ ^^^\__/  | | | | ^^  | | | | |  | | | | +--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 PixelList Lossless (CDH 1)/ALI  0x4b1 - ALICE PixelList Packetized (CDH 1)/ALI  0x4b4 - ALICE PixelList Lossless (CDH 2)/ALI  0x4b5 - ALICE PixelList 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    Notes:  ------  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, PixelList 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.   CATALOG   ALICE.CAT   DOCUMENTS   ALICE_SSR.*  SOC_INST_ICD.*  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:   /DOCUMENT/NH_FOV.*  /DOCUMENT/NH_ALICE_V###_TI.TXT     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  NEWHORIZONS:OBSERVATION_DESC and NEWHORIZONS:SEQUENCE_ID keywords in  the PDS label, plus the provided sequence list (see Ancillary Data  below) to assess the possibility that there was an intended target.  These two keywords are especially useful for STAR targets as often  stars are used as part of instrument calibrations, and are  included as part of the sequencing description which is captured  in these keywords.    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-J/P/SS-SPICE-6-V1.0 .   Every observation provided in this data set was taken as a part of a  particular sequence. The sequence identifier (REQID) 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.    Time  :   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  http://naif.jpl.nasa.gov/).   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   or   JD2453755.256337 TDB.   The leapsecond adjustment (DELTA_ET : ET - UTC) was 65.184s at  NH launch, and the first three additional leapseconds occurred  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 documentation, 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.     Software  :   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,  contact   New Horizons ALICE Principal Investigator:   S. Alan Stern   Southwest Research Institute (SwRI)  Department of Space Studies  1050 Walnut Street, Suite 400  Boulder, CO 80302  USA

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,   NH-X-ALICE-2-KEMCRUISE1-V2.0,   may not have corresponding data products in the calibrated data set,   NH-X-ALICE-3-KEMCRUISE1-V2.0.    Data coverage and quality  :  Every observation provided in this data set was taken as a part of a  particular sequence.   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 H Lya wavelengths than the bare, uncoated  glass, which gives rise to high signal levels from the box area of the  slit i.e. the lollipop fuzz.   The Alice team plans to provide an update to their calibration for the  second KEM Cruise 1 delivery. The current calibration uncertainty is  5 percent for data around and post the Pluto encounter. The calibration  change is due to the gain sag during that encounter, particularly from  the Solar Occultation.   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  :   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 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  instrument.   Finally, note that, within the FITS headers of the data products,  the sequence tables, and other NH Project-internal documents used  in this data set and/or inserted into the data set catalog,  informal names are often used for targets instead of the canonical  names required for the TARGET_NAME keyword. For example, during  the Pluto mission phase, instead of the TARGET_NAME '15810 ARAWN  (1994 JR1)' there might be found any of the following: 1994JR1;  1994 JR1; JR1. For all values where the PDS keyword TARGET_NAME  is used (e.g. in PDS labels and in index tables), the canonical,  PDS-approved names are used (if not, please bring this to the  attention of PDS so it can be rectified). However, within the  context of this data set, these project abbreviations are not  ambiguous (e.g. there is only one NH target with 'JR1' in its  name), so there has been, and will be, no attempt to expand such  abbreviations where they occur outside formal PDS keyword values.    Review  :  This dataset was peer reviewed and certified for scientific use by  the PDS.