NSSDCA ID: PSSB-00737
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 Calibrated data taken by New Horizons Alice Ultraviolet Imaging Spectrograph instrument during the PLUTOCRUISE 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. P-Alice Activities Overview at Annual CheckOuts (ACOs) during the Pluto Cruise mission phase started with the standard WakeUp sequence (memory/code checks, aperture door performance test, pixelhack issue verification, 24 hours of decontamination and three one hour dark observations) and finished with the standard Button-Up sequence (code and parameter refresh). Other activities (with targets as noted) were calibrations for flux (Spica, rho-Leo, gamma-Grus, HD93521, Sun in Solar OCcultation Channel, SOCC), flatfield (rho-Leo), airglow scattered light and SOCC pointing calibrations (Spica, zeta-Pup), SOCC flat (Sun), dark sky stares, spinning dark observations (in some cases the Sun strobes through the slit), pointing and short wavelength calibration (HD93521), InterPlanetary Medium (IPM) histograms and pixellist observations, dual target tests (HD214680 = 8 Lac, HD214168 = 10 Lac), MEV Solar Wind (HEET) baseine observation, Pluto encounter rehearsals, and instrument interference tests. 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_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 1.0 of this data set. Processing ========== The data in this data set were created by a software data processing pipeline on the Science Operation Center (SOC) at the Southwest Research Institute (SwRI), Department of Space Studies. 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_0X0AB_ENG_1.FIT ^^^ ^^^^^^^^^^ ^^^^^ ^^^ ^__/ | | | | | ^^ | | | | | | | | | | | +--File type (includes dot) | | | | | - .FIT for FITS file | | | | | - .LBL for PDS label | | | | | - not part of product ID | | | | | | | | | +-- Version number from the SOC | | | | (Science Operations Center) | | | | | | | +--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 | | | +--MET (Mission Event Time) i.e. Spacecraft Clock | +--Instrument designator * For those datasets where the NH project is delivering CODMAC Level 1 & 2 data (REX & PEPSSI), ENG and SCI apply to CODMAC Level 1 & 2 data, respectively. Instrument Instrument designators ApIDs =========== ================================== ============= ALICE ALI 0X4B0 - 0X4B7 * * Not all values in this range are in this data set There are other ApIDs that contain housekeeping values and other values. See the documentation for more details. Here is a summary of the types of files generated by each ApID 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 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. The PDS standards 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. 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_ALICE_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; that is, some sequences may have failed to execute due to spacecraft events (e.g. safing) and there will be observations associated with those sequences. No attempt has been made during the preparation of this data set to identify if any, or how many, such empty sequences there are, so it is up to the user to compare the times of the sequences to the times of the available observations from the INDEX/INDEX.TAB table 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) over this dataset is 65.184s. 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 NASA Headquarters 300 E Street SW Washington, DC 20546-0001 USA
These data are available on-line from the Planetary Data System (PDS) at:
https://pdssbn.astro.umd.edu/holdings/nh-x-alice-3-plutocruise-v1.0/
Questions and comments about this data collection can be directed to: Dr. David R. Williams
Name | Role | Original Affiliation | |
---|---|---|---|
Dr. Alan Stern | Data Provider | NASA Headquarters | alan.stern@nasa.gov |
Dr. Joseph Peterson | General Contact | Southwest Research Institute | joe@boulder.swri.edu |