Data Set Overview  :   This data set contains Calibrated data taken by New Horizons  Student Dust Counter  instrument during the PLUTOCRUISE mission phase.  The mission of the SDC is to analyze the size and distribution of Interplanetary Dust Particles (IDPs) along the New Horizons trajectory to the Kuiper Belt. SDC comprises twelve thin, permanently polarized polyvinylidene fluoride (PVDF) plastic film sensors, with a combined area of about 0.1 m**2, mounted on the top surface of a support panel and normal to the spacecraft ramdirection (flight velocity). In addition, there are two reference sensors, identical to the top surface sensors, mounted on the back side of the detectorsupport panel and protected from any dust impacts, used to monitor background noise levels.  An impacting IDP causes a depolarization charge when it penetrates the PVDF film on one of the sensors. That charge is then measured by that sensor's electronics (channel); if the measurement is above a preset level, the instrument records and stores the event for later downlink. The level preset is adjusted based on in-flight Noise Floor Calibrations, and there are extensive autonomy rules adjusting SDC behavior, even turning channels off forup to thirty days at a time, to avoid overloading the storage system with noise.  SDC was designed to detect events for particles down to about one picogram at Pluto [BAGENALETAL2016]; that detection limit is lower than earlier in the mission where the spacecraft velocity was higher. The SDC instrument has a temperature- and velocity-dependent calibration, first converting the raw measurement to charge, then converting charge to particle mass.  The common data product is a binary table of downlinked event data: time; sensor channel; magnitude; threshold magnitude. Associated data products are housekeeping data such as instrument temperatures for calibration and near-in-time spacecraft thruster events, which may induce false positives i.e.SDC events not caused by IDPs. The channels in the binary table for raw data are numbered from 0 to 13; the channel in the binary table for calibrated dataare numbered from 1 to 14.  Some time between instrument delivery to the spacecraft and launch, the detector on one channel began exhibiting symptoms of degraded electrical contacts to the PVDF; data from that channel (channel number 10 in raw data; channel number 11 in calibrated data) are still processed but should be ignored.    SDC Data Summary  :   In the years following the Jupiter encounter, designated as the  PLUTOCRUISE mission phase, SDC collected science data intermittently  during hibernation. There were also Annual Checkouts (ACOs), STIM  calibrations, Noise calibrations, and an anomaly in November, 2007.   SDC's main science data collection periods are during hibernation.  During ACOs, science data date are taken intermittently but the user  must be careful in analyzing this since there is usually more  activity on the spacecraft than during hibernation. STIM and Noise  refer to scheduled calibrations and are done with a regular cadence  of one per year after the Jupiter encounter; they occurred  sporadically in the early years of the mission. Refer to the  sequence tables, and/or the PDS data label keywords  NEWHORIZONS:SEQUENCE_ID and NEWHORIZONS:OBSERVATION_DESC, to  identify and remove calibration data from any science analysis.   Note that some SDC data files have the same stop and start time and  a zero exposure time. The reason for this is that the start and  stop time for SDC data files are the event times for the first and  last events in the files, so for files that contain a single event,  these two values are identical.   SDC was designed to take advantage of the quiet state of the  spacecraft during non-encounter mission phases, especially  hibernation. Various active spacecraft operations cause mechanical  shocks that are picked up by the polyvinylidene fluoride (PVDF)  sensors and registered by SDC as science events. This is  particularly true during three-axis pointing and active spin mode  when the spacecraft frequently fires short bursts of the attitude  thrusters. However because the thruster-induced events are often  frequent enough to violate the SDC autonomy rule B (section 3.4.2 of  Horanyi et al. (2008) [HORANYIETAL2008]), during some spacecraft  maneuvers many SDC detector channels are switched off, by autonomy  processing, for prolonged periods. Level four data reduction  (referred to in section 4 of Horanyi et al. (2008)  [HORANYIETAL2008]) is used to filter out any events that appear  within a second of any thruster firing, thereby allowing science  recovery between firings. The science team anticipates that the  techniques and results of such Level four processing will be  provided in future, higher-level data sets.   Autonomy rules can also affect SDC threshold settings; threshold  settings are designed to keep the SDC detection limit above a noise  floor. Refer to the SDC instrument catalog, file CATALOG/SDC.CAT,  and Horanyi et al. (2008) [HORANYIETAL2008], for descriptions of  threshold parameters and how they affect instrument behavior and  recorded data.   STIM (Stimulus) and Noise (Noise floor) refer to scheduled  calibrations and are done with a regular cadence of one per year  after the Jupiter encounter; they occurred sporadically in the early  years of the mission. Refer to the sequence tables, and/or the PDS  data label keywords NEWHORIZONS:SEQUENCE_ID and  NEWHORIZONS:OBSERVATION_DESC, to identify and remove calibration  data from any science analysis.   N.B. The duration of the off, as well as the on, periods must be  considered in making any calculation of average dust detection event  rates.   During spacecraft checkout activities in first six months of the  Post-Launch mission phase, spacecraft activity was high and these  autonomous off/on transitions occurred quite frequently, there were  several periods, some weeks or months long, where SDC was either  completely off, or on for only hours or minutes at a time. Later on  during the Launch phase, and much later during the Pluto Cruise  phase, the autonomy levels for turning off channels were relaxed,  and the transition to more frequent hibernation operations meant  that autonomous off/on transitions occurred less frequently.   All per-channel off and on transitions, whether initiated by  autonomy or by spacecraft on/off commands to the entire instrument,  are recorded for the entire mission to-date in a PDS TABLE file that  is provided with all SDC data sets; updated versions will be  provided as the mission progresses. The high frequency of off/on  transitions, as described in the previous paragraph, is apparent in  this PDS TABLE.   As of early 2014, there have been no events caused by large  particles observed in any of these data sets; this has been noted as  exceptional by peer reviewers of SDC data sets. The science team  agrees and this topic is an active discussion within the science  team; the science team anticipates that this will be addressed in  some future delivery of SDC data sets.   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_SDC_PLUTOCRUISE.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.   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.    SDC updates for Pluto Cruise  Data Sets V2.0  :   The previous Pluto Cruise data sets' deliveries (V1.0) went  through peer review in December, 2014. When subsequent versions  of those data sets were being delivered, some with additional data  (from August, 2014 through January, 2015) before all of those  previous liens were resolved, the previous data sets were left as  is, with those liens folded into the newer data sets.   New observations added with this version (V2.0) include ongoing  cruise observations from August, 2014 through January, 2015.   Other changes for this version were re-running of the ancillary  data in the data product, updated geometry from newer SPICE  kernels, minor editing of the documentation, catalogs, etc., and  resolution of liens from the December, 2014 review, plus those  from the May, 2016 review of the Pluto Encounter data sets.i    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.   SDC data calibration is a two-step process: raw data numbers from a  particle impact are converted to a charge, and the charge is  converted to a particle mass via the ground calibrations obtained at  a dust acceleration facility. Refer to the provided documentation  for more information. The latest calibration procedure is described  in James et al., (2010) [JAMESETAL2010].    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.   SDC_0123456789_0X700_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 **  : : :  SDC SDC 0X700   * 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)  : :  0x700 - SDC Science Data/SDC    Instrument description  ----------------------   Refer to the following files for a description of this instrument.   CATALOG   SDC.CAT   DOCUMENTS   SDC_SSR.*  SOC_INST_ICD.*  NH_SDC_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   SDC Field Of View definitions:   /DOCUMENT/NH_FOV.*  /DOCUMENT/NH_SDC_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.    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-PLUTOCRUISE-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_SDC_PLUTOCRUISE.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.    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 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.     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 SDC Principal Investigator:   Mihaly Horanyi, LASP, University of Colorado   Mihaly Horanyi   Laboratory for Atmospheric  and Space Physics  University of Colorado  Boulder, CO 80302-0392  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-SDC-2-PLUTOCRUISE-V2.0,   may not have corresponding data products in the calibrated data set,   NH-X-SDC-3-PLUTOCRUISE-V2.0.    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_SDC_PLUTOCRUISE.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.   For SDC, the stimulus calibration activity is known to generate  false positive events in the science data. This data set includes  a PDS TABLE, DOCUMENT/SDC_STIM_Vnnnn.TAB, that lists time periods  when stimulus calibrations were active (several times during  Launch and Jupiter mission phases, and about half an hour per  year during Annual CheckOuts (ACO) in the Pluto Cruise mission  phase. Eventually, the Science Operations Center (SOC)  operational pipeline may be enhanced to filter individual events  that occur near stimulus events.    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  instrument. Furthermore, for pointing instruments with one or more  spatial components to their detectors, a table has been provided  in the DOCUMENT/ area with XY (two-dimensional) positions of each  inferred target in the primary data products. If those values are  several thousand pixels off of a detector array, it is a strong  indication that the actual target of that observation is something  other than the inferred target, or no target at all e.g. dark sky.    Review  :  This dataset was peer reviewed and certified for scientific use on  2017-01-05.