The UVIS Solar Stellar Brightness Dataset : The UVIS instrument is part of the remote sensing payload of  the Cassini orbiter spacecraft. UVIS has two spectrographic  channels that provide images and spectra covering the ranges  from 56 to 118 nm and 110 to 190 nm. A third optical path  with a solar blind CsI photocathode is used for a high  signal-to-noise ratio stellar occultation by rings and  atmospheres. A separate hydrogen deuterium absorption cell  measures the relative abundance of deuterium and hydrogen  from their lyman-alpha emission. These channels are  referred to as EUV, FUV, HSP, and HDAC in this document.  The UVIS science objectives include investigation of the  chemistry, aerosols, clouds, and energy balance of the Titan  and Saturn atmospheres; neutrals in the Saturn magnetosphere;  the deuterium-to-hydrogen ratio for Titan and Saturn; icy  satellite surface properties; and the structure and  evolution of Saturns rings. The basic instrument design  adapts proven design concepts using a grating spectrometer  followed by a multi-element detector. We chose to use  imaging, pulse-counting microchannel plate detectors because  of more than a decade of experience using this kind of  detector equipped with a CODACON readout anode. The CODACON (Coded Anode Array Converter) acts as a photon locator. The  photon counts are accumulated in an external memory to build a  picture that is periodically read out for transfer to the spacecraft memory and eventually, transmission to the ground.  The two dimensional format for the CODACON detectors allows  simultaneous spectral and one-dimensional spatial coverage.  The detector format is 1024 x 64 (spectral by spatial). The Cassini HDAC consists of a channel electron  Multiplier photodetector equipped with 3 absorption cell  filters: a hydrogen cell, a deuterium cell and an oxygen  cell. The oxygen cell is not utilized in flight. The  hydrogen and deuterium cells function as adjustable  absorption filters. In each cell a hot tungsten filament  disassociates the hydrogen and deuterium molecules into  atoms, producing an atomic density determined by each of 16  different filament temperatures. These atoms resonantly  absorb the hydrogen and deuterium Lyman-alpha lines passing  through the cells. Cycling the filaments on and off and  comparing the differences in signal gives a direct  measurement of the relative hydrogen and deuterium signals.  Each cell has two filaments controlled by separate filament current regulators. Only one filament at a time per cell is  used during flight. A Pulse Amplifier Discriminator detects  photoelectrons from the CEM and sends pulses to the UVIS  instrument logic. UVIS contains a high speed photometer  with an integration time as short as 2.0 ms to observe stars  occulted by the rings of Saturn. The photon counts collected  from the photocathode are passed as a time ordered sequence to  the instrument, then to spacecraft memory for transfer to the ground. The data in a UVIS observation are a copy of what was in the UVIS  memory buffer. That is, the observation consists of unprocessed  experiment data stored in binary format. An observation  belongs to one of four different types of data product: a  spectrum, a time series of spatial-spectral images, a time  series of detector counts, or an image at one wavelength.  Each observation has a unique identifier that associates it  with a time range and with the configuration of the  instrument during that time. Each data product will contain  one observation and will be completely defined by a PDS  label. The objects will be correct in the sense that they  will conform to PDS formatting requirements and will be  consistent with data archived by the UVIS team. They will  be complete in that they will represent all data taken by  the UVIS instrument. In addition, CODMAC level 3 data products  will be derivable from the archived data and an associated set  of calibration data. The UVIS instrument can generate time series from the HSP and  the HDAC channels. A time series consists of a sequence of  photometer counts each taken during a fixed time interval.  An observation consists of a time series taken during a  particular instrument configuration. The time series  generated by the HDAC channel may have additional  complexity. If the instrument dwell time configuration  parameter is equal to one, the HDAC is in photometer mode and  its output is a time series of detector counts. If the  dwell time is greater than one, the time series can be mapped  into a table of 32 columns, each column corresponding to an  HDACfilament voltage level in the order: d1..d16, h1..h16  where d1..d16 correspond to the 16 voltage levels of the d  cell and h1..h16 the same for the h cell. The time series  can be mapped to the table by mapping contiguous subsequences  into the successive columns of the table. The length of the  subsequence is determined by the dwell time parameter of the instrument configuration. A data product (also referred to  as an observation) consists of a set of data taken during a  single instrument configuration. The UVIS time series data product will be archived as PDS time  series objects. All instrument configuration data for an observation will be contained in the associated PDS label.  For a detailed description of the UVIS instrument see the file ROOT/DOCUMENT/UVIS.TXT on this archive volume. Parameters  :  The observation type for each observation is found in OBSERVATION_TYPE column of INDEX.TAB. The specific purpose of each observation may be found in the object DESCRIPTION field contained in the label. Processing  :  The observation data products are generated by the Laboratory for Atmospheric and Space Physics at the University of Colorado using the Data Archiving and Processing System (DAPS) software. This software receives telemetry packet SFDUs from the Telemetry Data System, extracts science and engineering data, archives the data in a database management system and produces PDS data and label object files located on a CD-ROM or DVD physical storage medium. All time information is generated from the spacecraft clock using  the Cassini SCLKSET files. The DAPS system uses NAIF software and project generated SPICE Kernels to generate pointing information. All of these values are contained in the PDS object label. Data : The UVIS instrument can generate time series from the HSP and the HDAC channels. A time series consists of a sequence of photometer counts each taken during a fixed time interval. An observation consists of a time series taken during a particular instrument configuration. The time series generated by the HDAC channel may have additional complexity. If all the filament levels are 0 then the HDAC is in photometer mode and its output is a time series of detector counts. If there is a non-zero filament level the detector is in modulation mode and the time series can be mapped into a table of 32 columns, each column corresponding to an HDAC filament voltage level in the order:  d1...d16, h1...h16 where d1..d16 correspond to the 16 voltage levels of the d cell and h1..h16 the same for the h cell. The time series can be mapped to the table by mapping contiguous subsequences into  the successive columns of the table. The length of the subsequence is determined by the dwell time parameter of the instrument configuration. A data product consists of a set of data taken during a single instrument configuration.  The UVIS solar and stellar brightness time history data product is archived as a PDS time series object. All instrument configuration data for an observation is contained in the associated PDS label.  Ancillary Data  :  HSP and HDAC calibrations do not have a software implementation, however a description of HSP calibration is located in SOFTWARE/CALIB/HSP_CALIBRATION.TXT. Coordinate System  : In the UVIS data products, all time values that are represented as strings are in UTC time. All time values are derived from the spacecraft clock using the SCLKSCET translation table supplied by the Cassini project. All pointing data are expressed in the J2000 coordinate system. Software : LASP provides software for reading PDS data products. This software is located in the ROOT/SOFTWARE/READERS directory. The software requires Java 1.4 compatible class libraries and RSI/IDL version 6.  Instructions for running the routines are located in the file  READERS_README.TXT, located in the same directory.  These readers are provided as a convenience for users to access the data. Users may choose another approach if desired. The readers enable users to load PDS objects into an RSI/IDL process where they are represented as 3 dimensional arrays of integers corresponding to the PDS Qube object in which they are stored. PDS label data are stored in an IDL structure variable.  DISC FORMAT : (e.g. IBM PC, Macintosh, Sun, VAX) may access the data. Specifically, the disc is formatted according to the UDF-Bridge DVD format standard 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 CD conform to the 27.3 file naming convention i.e., 1. The file name portion may be up to 29 characters long; or 2. The extension may be up to 29 characters long, 3. In no case, however, may the total file name length, including the . exceed 31 characters.

Confidence Level Overview : The UVIS data objects are organized into separate observations. Each observation contains data taken from one configuration of the instrument. There may be more than one observation generated from one instrument configuration. This may occur because science data generated by the UVIS instrument is dropped when corrupted data is detected or transmission failures occur. The UVIS ground system detects this and divides the data into two observations, one terminated prior to the data drop the next beginning immediately afterword. The start time and duration of an observation correspond to the end times of the first and last records in the observation. Incomplete observations are filled with zeroes. Over 95% of data taken by the instrument is contained in the UVIS archive.  Only one hardware feature affects UVIS data. A light leak in the instrument casing causes an increase in the background counts in the lower half of the EUV channel wavelength range. This effect is detectable by visual inspection of a graph of the data. No tools for detection or correction of these background counts exists. One anomaly in the flight software caused data errors to appear when multiple windows which do not cover the entire EUV or FUV detector are defined. In an observation, the data errors appear as randomly located spikes in detector count values, and one  completely incorrect spatial line located at a random spatial  index. These errors are detectable by visual inspection of a  plot of the data. The anomaly was fixed by a revison to the software and effects data between launch and 2001-071 09:00:00 UTC Review : This volume has completed a peer review by the PDS. The peer review panel consisted of Lyle Huber, Mitch Gordon, Steven Adams, Ron Joyner and Mark Vincent representing PDS, David Judd and Wayne Pryor from the, UVIS team Diane Connor from the Cassini Project and Kurt Retherford and John Clarke as outside users.