PDS: Data Set Information

Data Set Information
DATA_SET_NAME	NEW HORIZONS ALICE PLUTO ENCOUNTER CALIBRATED V2.0
DATA_SET_ID	NH-P-ALICE-3-PLUTO-V2.0
NSSDC_DATA_SET_ID
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_DESCRIPTION	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 list. --- 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_VISUV_MAP. --- 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 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. 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 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 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 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, 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. 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. 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. 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 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 USA
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_NAME	NEW HORIZONS
MISSION_START_DATE	2006-01-19T12:00:00.000Z
MISSION_STOP_DATE	2021-09-30T12:00:00.000Z
TARGET_NAME	CHARON PLUTO SUN
TARGET_TYPE	SATELLITE PLANET SUN
INSTRUMENT_HOST_ID	NH
INSTRUMENT_NAME	ALICE ULTRAVIOLET IMAGING SPECTROGRAPH
INSTRUMENT_ID	ALICE
INSTRUMENT_TYPE	SPECTROGRAPH
NODE_NAME	Small Bodies
ARCHIVE_STATUS	SUPERSEDED
CONFIDENCE_LEVEL_NOTE	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-P-ALICE-2-PLUTO-V2.0, may not have corresponding data products in the calibrated data set, NH-P-ALICE-3-PLUTO-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_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 instrument. Review ====== This dataset was peer reviewed and certified for scientific use on 12-5-2016.
CITATION_DESCRIPTION	Stern, A., NEW HORIZONS Calibrated ALICE PLUTO ENCOUNTER V2.0, NH-P-ALICE-3-PLUTO-V2.0, NASA Planetary Data System, 2016.
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.
PRODUCER_FULL_NAME	BRIAN CARCICH
SEARCH/ACCESS DATA	SBN Comet Website

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