NSSDCA ID: PSSB-00785
Availability: Archived at NSSDC, accessible from elsewhere
This description was generated automatically using input from the Planetary Data System.
Data Set Overview ================= This data set contains Raw data taken by New Horizons Pluto Energetic Particle Spectrometer Science Investigation instrument during the PLUTO mission phase. PEPSSI (Pluto Energetic Particles Spectrometer Science Investigation) is a particle telescope and a time-of-flight (TOF) spectrometer that measures ions and electrons over a broad range of energies and angles. Particle composition and energy spectra are measured for H to Fe from ~ 30 keV to ~1 MeV (but not all species are uniquely separated) and for electrons from ~30 keV to 700 keV. PEPSSI comprises a time-of-flight (TOF) section and a solid-state detector (SSD) array that measures particle energy. The combination of measured energy and TOF provides unique particle identification by mass and particle energy depending on the range: for protons from ~30 keV to ~1 MeV; for heavy (CNO) ions from ~80 keV to ~1 MeV. Lower-energy (>3 keV) ion fluxes are measured by TOF only, but without the SSD signal, providing velocity spectra at these energies as well. Due to storage and bandwidth limitations, all event data cannot be stored or telemetered to the ground. Instead, a round-robin algorithm is used to save Energy, TOF, and timing data for select events. The common data products contain these event and summary measurements, accumulated over fixed periods of 86,400 seconds, with each period in a single file comprising multiple binary tables. The documentation provided with this data set describes the data format. Encounter PEPSSI data --------------------A subset of the closest approach flyby data is located in directory DATA/20150714_029913/ of this data set. That includes high-time resolution data over two periods with durations of forty minutes and fifteen minutes. Overview of PEPSSI data in this V3.0 data set --------------------------------------------The first-delivered data set included low-time resolution data from Approach, CORE and Departure subphases through the end of July, 2015. It also included two selected periods of high-resolution data from the CORE subphase on the day of Pluto flyby (14 Jul 2015): the first period starts ninety minutes after Pluto closest approach and lasts about forty minutes; the second starts nine hours after closest approach and lasts about fifteen minutes. Early downlink of these two periods of PEPSSI data ensured the instrument satisfied its mission requirements. The second-delivered data set fills in the periods of high-resolution data at flyby, it also provides ongoing departure observations through the end of January, 2016. This third- and final-delivered data set fills in the rest of the sequenced high-time resolution encounter data, plus the departure data taken in the months after encounter. Overview of PEPSSI data taken during the Pluto Encounter mission phase ---------------------------------------------------------------------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); a Transition sub-phase ending in late October, 2016, closing out the Pluto Encounter mission phase. For this final PEPSSI delivery for the Pluto mission phase, this data set includes the Approach data plus the CORE and Departure sequences' data, as well as normal operation and Calibration Campaign data during Transition, and has all data downlinked through the end of October, 2016. During the Approach phase, PEPSSI performed functional tests including a memory refresh, and otherwise operated as normal, turning off and on around spacecraft trajectory correction maneuvers, and taking data during a series of plasma rolls, on DOY 107, 115, 121, 128, 148, 156, and 176. There were two other dedicated SWAP and PEPSSI rolls on DOY 163 and 171. PEPSSI was powered on and collecting data throughout the encounter time frame. PEPSSI was generally turned on and taking data for the Departure and Transition sub-phases, the exceptions being when PEPSSI was turned off during spacecraft events such as 3-axis operations and trajectory correction maneuvers. Due to a spacecraft safing event on 04 July, 2015 (DOY 185), the balance of the science load from then-executing 15184 sequence (nominal start time on DOY 184 in 2015) was sacrificed to ensure the 15188 CORE load with the flyby sequence could be loaded onto the spacecraft and started on time. As a result, there is a gap in the PEPSSI data from approximately DOY 186 to DOY 188. 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_PEPSSI_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 observation. Version ======= This is VERSION 3.0 of this data set. 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). That will typically change only the FITS headers but not the FITS data of raw data sets. In some cases this may change the calibration 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. An all-instrument Calibration Campaign occurred in July 2016. For all instruments, calibrations were updated as of April 2017 which changed the data in the calibrated data sets. Calibration changes are described in the data set version-specific sections. 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. PEPSSI updates for Pluto Encounter Data Sets V3.0 ============== This P3 Pluto Encounter dataset release includes all data from the previous two Pluto deliveries and adds data that was downlinked from 1/31/2016 through 10/31/2016. This dataset completes delivery of all data covering the Pluto Encounter and subsequent Calibration Campaign. For PEPSSI, most of the Pluto Encounter data was downlinked in the 15229 load in August 2015. Since then, PEPSSI has stayed on and taken data continuously, other than a few power cycles around spacecraft events such as 3-Axis operations and trajectory correction maneuvers. Also, updates were made to the calibration files, documentation, and catalog files. Significant changes were made to the PEPSSI packet processing and calibration, too extensive to go into here. Data from all previous data sets should be discarded. Refer to the data set documentation for details about processing of PEPSSI data. PEPSSI updates for Pluto Encounter Data Sets V2.0 ============== 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 PEPSSI, most of the Pluto Encounter data was downlinked in the 15229 load in August 2015. Since then, PEPSSI has stayed on and taken data continuously, other than a few power cycles around spacecraft events such as 3-Axis operations and trajectory correction maneuvers. 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. PEP_0123456789_0X691_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 ** =========== ================================== ============= PEPSSI PEP 0X691 - 0X698 * * 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) ===== =================================== 0x691 - PEPSSI High Priority Science (long integration) 0x692 - PEPSSI Medium Priority Science (short integration) 0x693 - PEPSSI Low Priority Science (Up to 500 PHA events) 0x694 - PEPSSI Low Priority Science (Up to 500 PHA events) 0x695 - PEPSSI High Priority Science Diagnostic Mode data 0x696 - PEPSSI Medium Priority Science Diagnostic Mode data 0x697 - PEPSSI Diagnostic Mode Event data 0x698 - PEPSSI Diagnostic Mode Event data For historical reasons, PEPSSI products always use an ApID of '0x691' in the filename. Each product actually contains all the data types (ApIDs) available for that day. ApIDs '0x693' and '0x694' are combined during ground processing. So are ApIDs '0x697' and '0x698'. Instrument description ---------------------Refer to the following files for a description of this instrument. CATALOG PEPSSI.CAT DOCUMENTS PEPSSI_SSR.* SOC_INST_ICD.* NH_PEPSSI_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 PEPSSI Field Of View definitions: /DOCUMENT/NH_FOV.* /DOCUMENT/NH_PEPSSI_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. 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_PEPSSI_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. 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 PEPSSI Principal Investigator: Ralph McNutt, Jr., Johns Hopkins Univ., Applied Physics Lab Ralph McNutt, Jr. Johns Hopkins University Applied Physics Laboratory Space Department 11100 Johns Hopkins Road Room MP3-E116 Laurel, MD 20723 USA
These data are available on-line from the Planetary Data System (PDS) at:
https://pdssbn.astro.umd.edu/holdings/nh-p-pepssi-2-pluto-v3.0/
Questions and comments about this data collection can be directed to: Dr. David R. Williams
Name | Role | Original Affiliation | |
---|---|---|---|
Dr. Ralph L. McNutt, Jr. | Data Provider | Applied Physics Laboratory | ralph_mcnutt@jhuapl.edu |