Data Set Information
DATA_SET_NAME CASSINI ORBITER JUPITER UVIS EDITED SPECTRA 1.0
DATA_SET_ID CO-J-UVIS-2-SPEC-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION The UVIS Spectrum 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. 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. S 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 EUV and FUV channels can be read out to produce spectra. Each spectrum is generated by accumulating detector counts over a fixed time interval. The time interval is defined in the instrument configuration associated with the observation. A spectrum consists of a sequence of counts, each count being associated with a detector column (or columns). In the simplest case, a spectrum is a sequence of 1024 integers where each integer is the number of counts taken during a fixed time interval by the detector at a particular wavelength and summed over the spatial dimension of the detector. In more complex cases, each integer in the spectrum corresponds to a set of columns and is derived by summing over both the spatial and spectral dimensions. For example, if the binning defined on the spectral dimension is two, a spectrum will consist of 512 integers, where each integer is derived by first summing 1024 columns in the spatial dimension, then summing contiguous pairs of detector lines in the spectral dimension. A still more complex case involves spectra derived from a set of sub regions of the detector. In this case, the detector is divided into a set of active rectangular sub regions (windows). Each window can be binned in the manner described above. A data product (also referred to as an observation) is a sequence of spectra taken from a window during the same instrument configuration. All instrument configuration information including window, bin, and integration time specifications will be contained in the PDS object label. For a more extensive description of the UVIS instrument see the file ROOT/DOCUMENT/UVIS.TXT on this archive volume.
DATA_SET_RELEASE_DATE 3000-01-01T00:00:00.000Z
START_TIME 1999-01-07T12:00:00.000Z
STOP_TIME N/A (ongoing)
MISSION_NAME CASSINI-HUYGENS
MISSION_START_DATE 1997-10-15T12:00:00.000Z
MISSION_STOP_DATE 2017-09-15T12:00:00.000Z
TARGET_NAME JUPITER
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID CO
INSTRUMENT_NAME ULTRAVIOLET IMAGING SPECTROGRAPH
INSTRUMENT_ID UVIS
INSTRUMENT_TYPE SPECTROGRAPH
NODE_NAME Planetary Atmospheres
ARCHIVE_STATUS SUPERSEDED
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 review panelconsisted of Lyle Huber, Mitch Gordon, Steven Adams, Ron Joyner and MarkVincent representing PDS, David Judd and Wayne Pryor from the UVIS team,Diane Connor from the Cassini Project and Kurt Retherford and John Clarkeas outside users.
CITATION_DESCRIPTION Esposito, L. (et al.), Cassini Ultraviolet Imaging Spectrograph JupiterFlyby Data, NASA Planetary Data System, 'CO-J-UVIS-2-SPEC-V1.0', 2005.
ABSTRACT_TEXT A set of spectra.
PRODUCER_FULL_NAME LARRY ESPOSITO
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