Data Set Information
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| DATA_SET_NAME |
CASSINI ORBITER STAR UVIS CALIBRATION DATA 1.0
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| DATA_SET_ID |
CO-X-UVIS-2-CALIB-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
UVIS Calibration Dataset Overview: The UVIS instrument is part of the remote sensing payloadof the Cassini orbiter spacecraft. UVIS has twospectrographic channels that provide images and spectracovering the ranges from 56 to 118 nm and 112 to 191 nm. Athird optical path with a solar blind CsI photocathode isused for a high signal-to-noise ratio stellar occultation byrings and atmospheres. A separate hydrogen deuteriumabsorption cell measures the relative abundance of deuteriumand hydrogen from their lyman-alpha emission. Thesechannels are referred to as EUV, FUV, HSP, and HDAC in thisdocument. The UVIS science objectives include investigationof the chemistry, aerosols, clouds, and energy balance ofthe Titan and Saturn atmospheres; neutrals in the Saturnmagnetosphere; the deuterium-to-hydrogen ratio for Titan andSaturn; icy satellite surface properties; and the structureand evolution of Saturns rings. The basic instrumentdesign adapts proven design concepts using a gratingspectrometer followed by a multi-element detector. We choseto use imaging, pulse-counting microchannel plate detectorsbecause of more than a decade of experience using this kindof detector equipped with a CODACON readout anode. TheCODACON (Coded Anode Array Converter) acts as a photonlocator. The photon counts are accumulated in an externalmemory to build a picture that is periodically read out fortransfer to the spacecraft memory and eventually, transmissionto the ground. The two dimensional format for the CODACONdetectors allows simultaneous spectral and one-dimensionalspatial coverage. The detector format is 1024 x 64 (spectralby spatial). The Cassini HDAC consists of a channel electron Multiplierphotodetector equipped with 3 absorption cell filters: ahydrogen cell, a deuterium cell and an oxygen cell. Theoxygen cell is not utilized in flight. The hydrogen anddeuterium cells function as adjustable absorption filters.In each cell a hot tungsten filament disassociates thehydrogen and deuterium molecules into atoms, producing anatomic density determined by each of 16 different filamenttemperatures. These atoms resonantly absorb the hydrogenand deuterium Lyman-alpha lines passing through the cells.Cycling the filaments on and off and comparing thedifferences in signal gives a direct measurement of therelative hydrogen and deuterium signals. Each cell has twofilaments controlled by separate filament currentregulators. Only one filament at a time per cell is usedduring flight. A Pulse Amplifier Discriminator detectsphotoelectrons from the CEM and sends pulses to the UVISinstrument logic. UVIS contains a high speed photometerwith an integration time as short as 2.0 ms to observestars occulted by the rings of Saturn. The photon countscollected from the photocathode are passed as a time orderedsequence to the instrument, then to spacecraft memory fortransfer to the ground. The data in a UVIS observation are a copy of what was inthe UVIS memory buffer. That is, the observation consists ofunprocessed experiment data stored in binary format. Anobservation belongs to one of four different types of dataproduct: a spectrum, a time series of spatial-spectralimages, a time series of detector counts, or an image at onewavelength. Each observation has a unique identifier thatassociates it with a time range and with the configurationof the instrument during that time. Each data productcontains one observation and is completely defined by a PDSlabel. The objects are correct in the sense that they conformto PDS formatting requirements and are consistent with dataarchived by the UVIS team. They are complete in that theyrepresent all data taken by the UVIS instrument. In addition,CODMAC level 3 data products are derivable from the archiveddata and an associated set of calibration data. A UVIS spatial spectral cube (which corresponds to aPDS Qube data structure) is a time ordered sequenceof two-dimensional matrices of EUV or FUV detector counts.In the simplest case, a cube is a time ordered sequence of1024 x 64 matrices in which each element of the matrix isthe number of counts taken at an individual detector cellduring a fixed time interval. The time interval is definedin the instrument configuration associated with theobservation. In more complex cases, each integer in thecube corresponds to a sub region of the detector and isderived by summing over both the spatial and spectraldimensions. For example, if the binning defined on thespectral and spectral dimensions is two, a cube consistsof 32x512 integers, where each integer is derived by summingcontiguous pairs of cells in the spatial and spectraldimensions. The cube object is a sequence of 1024x64 inwhich all data is located in a 32x512 subregion theupper left hand corner of which will be located at 0,0. Allother locations in the cube contain null values. A stillmore complex case involves cubes derived from a set of subregions of the detector. In this case, the detector isdivided into a set of active rectangular sub regions (windows). Each window can be binned in the mannerdescribed above. When binning and windowing is applieddata is in the upper left hand corner of the window.For example, if a detector window is defined with its upperleft corner at 10, 10) and its lower right corner at (20, 20)and its binning is defined to be (2, 2) then the data for theNth spectrum is found in the rectangle with a upper leftcorner equal to (10, 10, N) and a lower right hand corner equalto (15, 15, N) in the Qube. A data product (also referred to as an observation) is acube generated during a particular instrumentconfiguration. All instrument configuration informationincluding window, bin, and integration time specifications arecontained in the PDS object label. For a more extensive description of the UVIS instrument andthe structure and organization of data on this volume see thefile ROOT/DOCUMENTATION/UVIS.TXT on this archive volume.Parameters:The following observation types are found on this volume.CALIB: Measurement of EUV and/or FUV emissions from a solar/stellartarget for the purpose of calibrating wavelength scale, photometricsensitivity, and detector flat fields.The observation type for each observation is found in OBSERVATION_TYPEcolumn of INDEX.TAB. The specific purpose of each observationmay be found in the object DESCRIPTION field contained in the label.Processing:The observation data products are generated by the Laboratory forAtmospheric and Space Physics at the University of Colorado usingthe Data Archiving and Processing System (DAPS) software. Thissoftware receives telemetry packet SFDUs from the Telemetry DataSystem, extracts science and engineering data, archives the datain a database management system and produces PDS data and labelobject files located on a CD-ROM or DVD physical storage medium.All time information is generated from the spacecraft clock usingthe Cassini SCLKSET files. The DAPS system uses NAIF software andproject generated SPICE Kernels to generate pointing information. Allof these values are contained in the PDS object label.Data:A UVIS spatial spectral cube is a time ordered sequence of1024 x 64 matrices in which each element of the matrix is the numberof counts taken at an individual detector pixel during a fixed timeinterval. The time interval is set in the instrument configurationassociated with the observation.UVIS is capable of windowing and binning the EUV and FUV detectors.In these more complex cases, each integer in the cube correspondsto a rectangular subregion of detector cells and is derived by summingover the spatial and spectral dimensions. For example, if the binningdefined on the spectral and spatial dimensions is two, the cube consistsof 32x512 integers, where each integer is derived by summing thecounts from disjoint 2x2 subregions of the detector. The PDS Qubeobject is a sequence of 1024x64 samples, in which all data are locatedin a 32x512 sub-region in the upper left hand corner, located at (0,0).All other locations in the PDS Qube contain null values. A still morecomplex case involves cubes derived from a set of sub regions of thedetector called windows. In this case, the detector is divided into aset of active rectangular sub regions (windows). Each window can alsobe binned in the manner just described. The data stored in the PDSQube are located in the upper left hand corner of the window. Forexample, if a detector window is defined with its upper left cornerat (10,10) and its lower right corner at (20, 20) and its binning isdefined to be (2,2) then the data for the Nth sample is found in therectangle with a upper left corner equal to (10, 10, N) and a lowerright hand corner equal to (15, 15, N) in the 1024x64 sample of thePDS Qube.A data product (also referred to as an observation) is a cubegenerated during a particular instrument configuration, includingpointing and instrument set up. All instrument configurationinformation including window, bin and integration time specificationsare contained in the PDS object label.The following diagrams illustrate these configurations as contained ina sample of a PDS Qube.0 *************************** *ddddddddddddddddddddddddd* *ddddddddddddddddddddddddd* *ddddddddddddddddddddddddd* *ddddddddddddddddddddddddd* *ddddddddddddddddddddddddd*64 ***************************0 1024Fig. 2.2.2.1 An unbinned, single windowed sample where d is data.0 *************************** *ddddddddddddnnnnnnnnnnnnn* *ddddddddddddnnnnnnnnnnnnn*32 *ddddddddddddnnnnnnnnnnnnn* *nnnnnnnnnnnnnnnnnnnnnnnnn* *nnnnnnnnnnnnnnnnnnnnnnnnn*64 ***************************0 512 1024Fig. 2.2.2.2 An unbinned window with an upper left hand corner at 0, 0,and a lower right hand corner at 512, 32. Where d is data, n is null.0 *************************** *dddddnnnnnnnnnnnnnnnnnnnn* *nnnnnnnnnnnnnnnnnnnnnnnnn*32 *nnnnnnnnnnnnnnnnnnnnnnnnn* *nnnnnnnnnnnnnnnnnnnnnnnnn* *nnnnnnnnnnnnnnnnnnnnnnnnn*64 ***************************0 0 256 1024Fig. 2.2.2.3: A window binned by 32 in the spatial dimension and 2 in thespectral dimension with an upper left hand corner at 0, 0, and a lowerright hand corner at 512, 32. Where d is data and n is null.0 *************************** *dddddnnnnnnnnnnnnnnnnnnnn* *nnnnnnnnnnnnnnnnnnnnnnnnn*32 *nnnnnnnnnnndddddddddddddd* *nnnnnnnnnnndddddddddddddd* *nnnnnnnnnnndddddddddddddd*63 ***************************0 0 256 512 1023Fig. 2.2.2.4: Two windows where the first is binned by 32 in thespatial dimension and 2 in the spectral dimension and where the firsthas an upper left hand corner at 0, 0, and a lower right hand cornerat 512, 32. The second is unbinned with an upper left hand corner at512, 32 and a lower right corner at 1023, 63. Where d is data and nis null.Calibration data are used to transform detector counts intogeophysical units. The EUV, FUV channels have an associatedcalibration process. FUV and EUV data are converted to Rayleighs.The UVIS team supplies calibration data files. The calibrationprocess is described below and in the PDS label file associated withthe calibration. data file.Calibration data consist of an MxN matrix and a scalar value. Eachmatrix and scalar should be used to scale the individual integrationsof a raw data product. The result is a calibrated data product whichis isomorphic to the original containing data in units ofkilorayleighs. In addition, each calibration data product contains amapping of detector lines to wavelengths which is stored in the BANDBIN_CENTER keyword value.Calibration data are archived as a PDS Qubes with the dimensions1024x64x1 or 1024x1x1. All instrument configuration data for theobservation is contained in the associated PDS label; in addition thelabel contains instructions for using the calibration data and adetector column to wavelength mapping and the scalar multiplierwhich is stored in the CORE_MULTIPLIER value).In addition to this mechanism, non-standard calibration routinesdeveloped by UVIS team members may be provided. These routines mayrequire user input and control. These procedures are not supportednor are their validity guaranteed, however to the extent that theyare intended for general use by the UVIS team, we will submitalgorithms and associated data and documentation.Ancillary Data:The UVIS team supplies calibration data files and the algorithms usedto generate the FUV and EUV calibration data. The calibrationalgorithms are archived as text files in the SOFTWARE/CALIB directoryof the PDS data volume. The file names contain channel and versioninformation. These algorithms generate calibration data which islocated in the CALIB/VERSION_n/... directories. The algorithms areprovided as a description of the process by which calibration data isgenerated. They are not used to calibrate raw data.Coordinate System:In the UVIS data products, all time values that are represented asstrings are in UTC time. All time values are derived from thespacecraft clock using the SCLKSCET translation table supplied bythe Cassini project. All pointing data are expressed in the J2000coordinate system.Software:LASP provides software for reading PDS data products. This softwareis located in the ROOT/SOFTWARE/READERS directory. The softwarerequires Java 1.4 compatible class libraries and RSI/IDL version 6.Instructions for running the routines are located in the fileREADERS_README.TXT, located in the same directory.These readers are provided as a convenience for users to access thedata. Users may choose another approach if desired. The readersenable users to load PDS objects into an RSI/IDL process where theyare represented as 3 dimensional arrays of integers corresponding tothe PDS Qube object in which they are stored. PDS label data arestored in an IDL structure variable.DISC FORMAT:This disc has been formatted so that a variety of computer systems(e.g. IBM PC, Macintosh, Sun, VAX) may access the data. Specifically,the disc is formatted according to the UDF-Bridge DVD formatstandard which provides ISO 9660 level 2 standard compatibility.For further information, refer to the ISO 9660 Standard Document:RF# ISO 9660-1988, 15 April 1988.Specific to the ISO 9660 level 2 standard, filenames on this CDconform to the 27.3 file naming convention i.e.,1. The file name portion may be up to 29 characters long; or2. The extension may be up to 29 characters long,3. In no case, however, may the total file name length, includingthe . exceed 31 characters.
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| DATA_SET_RELEASE_DATE |
3000-01-01T00:00:00.000Z
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| START_TIME |
1999-01-07T12:00:00.000Z
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| STOP_TIME |
N/A (ongoing)
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| MISSION_NAME |
CASSINI-HUYGENS
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| MISSION_START_DATE |
1997-10-15T12:00:00.000Z
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| MISSION_STOP_DATE |
2017-09-15T12:00:00.000Z
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| TARGET_NAME |
STAR
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| TARGET_TYPE |
STAR
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| INSTRUMENT_HOST_ID |
CO
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| INSTRUMENT_NAME |
ULTRAVIOLET IMAGING SPECTROGRAPH
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| INSTRUMENT_ID |
UVIS
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| INSTRUMENT_TYPE |
SPECTROGRAPH
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| NODE_NAME |
Planetary Atmospheres
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| ARCHIVE_STATUS |
SUPERSEDED
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| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview:The UVIS data objects are organized into separate observations.Each observation contains data taken from one configuration ofthe instrument. There may be more than one observation generatedfrom one instrument configuration. This may occur because sciencedata generated by the UVIS instrument is dropped when corrupteddata is detected or transmission failures occur. The UVIS groundsystem detects this and divides the data into two observations, oneterminated prior to the data drop the next beginning immediatelyafterword. The start time and duration of an observation correspondto the actual times of the first and last records in the observation.Incomplete observations are filled with zeroes. Over 95% of datataken by the instrument is contained in the UVIS archive.Only one hardware feature affects UVIS data. A light leak in theinstrument casing causes an increase in the background counts inthe lower half of the EUV channel wavelength range. This effect isdetectable by visual inspection of a graph of the data. No toolsfor detection or correction of these background counts exists.One anomaly in the flight software caused data errors to appearwhen multiple windows which do not cover the entire EUV or FUVdetector are defined. In an observation, the data errors appearas randomly located spikes in detector count values, and onecompletely incorrect spatial line located at a random spatialindex. These errors are detectable by visual inspection of aplot of the data. The anomaly was fixed by a revison to thesoftware and effects data between launch and 2001-071 09:00:00 UTCReview:This volume has completed a peer review by the PDS. The peer reviewpanel consisted of Lyle Huber, Mitch Gordon, Steven Adams, Ron Joynerand Mark Vincent representing PDS, David Judd and Wayne Pryor from theUVIS team, Diane Connor from the Cassini Project and Kurt Retherfordand John Clarke as outside users.
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| CITATION_DESCRIPTION |
Esposito, L. (et al.), Cassini Ultraviolet Imaging Spectrograph JupiterFlyby Data, NASA Planetary Data System, 'CO-X-UVIS-2-CALIB-V1.0', 2005.
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| ABSTRACT_TEXT |
NULL
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| PRODUCER_FULL_NAME |
LARRY ESPOSITO
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| SEARCH/ACCESS DATA |
Atmospheres Website
Instrument Help
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