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Galileo Orbiter UVS/EUV Jupiter operations EDR data (PDS)

NSSDCA ID: PSPA-00558

Availability: Archived at NSSDC, accessible from elsewhere

Description

This description was generated automatically using input from the Planetary Data System.

Data Set Overview

Observations by the group of Galileo science instruments are coordinated by the Project Science Group (PSG). Spacecraft resources are divided between the needs of the three main disciplines: Atmospheres, Satellites and Magnetospheres. These disciplines coordinate science operations with their three Galileo Science Working Groups (WGs). These are the Satellite Working Group (SWG), the Magnetospheres WG (MWG) and the Atmospheres WG (AWG).

The UVS team constitutes the science group from the University of Colorado. The PI is Dr. Charles W. Hord. The instrument consists of two pieces of hardware, the UltraViolet Spectrometer (UVS) and the Extreme UltraViolet (EUV) Spectrometer. The data resource negotiations with the WGs were considered as one team within the WGs. Data for the separate hardware are kept in separate data files. In the descriptions below, UVS may indicate the team, and thus both instruments, or may refer to only the UVS hardware. Separate EUV observation classes do exist and they are described below. Other data, like calibrations, are included where appropriate.

Each Science WG has its own set of observations. The observations described in this EDR data set label include all observations from the Nominal Mission period, from Jupiter-Orbit-Insertion until End-Of-Millennium Mission, I33. All Jupiter, Torus, satellite, etc target objects are described. Data from different orbits may contain observations from all or none of the described WG Observation classes. EUV data from just before Jupiter-Orbit-Insertion (J0CD) are included in this set. Pre-orbital data are a separate data set.

Experiment Data Record (EDR) data for EUV may be in either of two file formats: one for Playback (PB) data and one for the Phase 2 Real-Time-Science (RTS) data. Some of the observations are done only with the on-board summing RTS mode. Playback (PB) observations are recorded on the tape and played back at full, 1000 bps data rate. EUV obtained only RTS data during the nominal mission. EUV playback was used only in the pre-Jupiter planet encounters.

During the Nominal mission five EUV/UVS cross-calibration observations were made (in G02C, E06A, G08A, C10B and E19.) These were periods when both instruments observed the Hydrogen Lyman-alpha 'sky-background' simultaneously over the same piece of sky. A cross-calibration in C03C observed Spica with the EUV and UVS simultaneously. An observation of the same Earth 1 and Earth 2 EUV star (Sirius) was made during Galileo Europa Mission (GEM) orbit E19C, when the z-axis pointed to the earth in RA and Dec 180 degrees from where it was pre-Jupiter. Besides these two 'absolute stellar cross-calibrations' the EUV occasionally observes an EUV bright star within its field while making torus measurements. These data sets are also archived in the PDS. These EUV stallar observations allowed the team to verify EUV instrument detector stability.

All EUV EDRs are raw, uncalibrated spectra. EDRs have been re-formatted by the team from spacecraft packets. The data set includes all EDR data from orbital operations for the Nominal/Prime Mission. File labels describe the file format of each data file. Each data file record has header information containing time tags, followed by the spectral/sector data (see description below, in MWG observations discussion section). There may be more than one record per file. Generally, each file contains all the data for that individual science Observation_ID, as classed below. EUV RDRs are generally heavily processed data sets and do not normally contain full spectra. EDR calibration is described in the calibration documents and files archived with PDS and discussed in the published papers. A list of recent publications appears at the end of this Description; a long publication list is available on the PDS archive CD.

The PDS label file, for each data file, contains a PRODUCT_NAME which contains the Galileo Observation ID. These 12-character Observation IDs actually appear in the sequence (SEF) file. These are related to the WG Observation classes described below. An example of a PRODUCT_NAME is G07A_UPB_G7MANS01 ____ is the 4-character Orbit load number _EUV_ is EUV for EUV RTS data format __ is the Orbit number OR ------ is the observation name __ is the observation series number. As with all well made plans, these Observation_ID rules were not always followed. The observation names might also be proper names of features or other new names. The data files are named by the observation name given in the SEF. The .DAT file extension indicates the file is a binary Vax formatted data file; an .XDR file extension indicates the file is an IEEE standard (transfer format) file. UVS and EUV data files are distinguished by their file names. Real-time commands to both instruments, especially after spacecraft safing, can generate non-sequenced data files; generally these are POWER files where the configuration returned in the engineering verifies the correct power-on state. The file extensions .LBL and .XLBL are used for the EDR labels. A list of all commands (file: CMD_ARCHIVE.LIS) is in the CD's Document directory.

The UVS Mission science objectives are given, in great detail, in several Galileo JPL mission documents. The Science Requirements Document (625-50) and the Orbit Planning Guides, OPG, (JPL 625-100, Vol. 2) are two. There is an OPG for the Nominal Mission and one for the Galileo Europa Mission. The OPG describes both the instrument objectives and the observation classes as well as specific observation ID names. On-line (web access) copies of the OAPEL (Orbit Activity Planning ELement) planning sheets and graphic designs provide additional information. JPL may have this information available in the public archive. They may also still be online at http://lasp.colorado.edu/galileo/ .

Ancillary Data

These are raw UVS data sets. For analysis, geometry parameters are obtained from the SPICE kernels for the time period of analysis. Two UVS files can be used to verify instrument configuration(s) within any data set. The orbit Status files (form: orbit-number_UVS_PB/RT_ORBIT_STATUS.LIS) and the instrument history command file (CMD_ARCHIVE.LIS) indicate instrument configuration. See also the Experimenter's Handbook file (UVS_HISTORY.DOC) for a compilation of spacecraft and instrument events that effect the data presence or quality. The Galileo SEF (Sequence of Events) file may also be used to verify the UVS configuration during the observation. Calibration files are available from the PDS UVS Instrument sets. Analysis techniques for various data classes are described in the published papers. A publication list is available on the archive CD in GUVSPUBS.CAT.

See also the Galileo Project archives of the SEF and ASRUN sequence products As well as some observation design materials. These may be used to help under- stand each observation. The UVS/EUV team retains some design materials as well. The team visualization tool, called GGGS, can be used to review the observation geometry, based on SEF and SPICE products.

The following is a list of the available orbit Status files. Use these to verify the commanded and obtained instrument configuration. The label describes the contents.

Status and Orbit Status files: The archive has renamed these and incorporated the label in the file header as well as shortened the file name to a format as follows: (Orbit)(instrument, U or E))(PB or RT)(STAT or ST).TXT For example, the file uvs_pb_c03_status.lis;1 is called C9UPBST.TXT . uvs_pb_c03_status.lis;1 uvs_pb_g07_status.lis;8 uvs_rts_e15_status.lis;5 uvs_pb_c09_status.lis;1 uvs_pb_g08_status.lis;2 uvs_rts_e16_status.lis;1 uvs_pb_c10_status.lis;2 uvs_pb_i24_status.lis;1 uvs_rts_e17_status.lis;1 uvs_pb_c21_status.lis;1 uvs_rts_c03_status.lis;32 uvs_rts_e18_status.lis;2 uvs_pb_c22_status.lis;1 uvs_rts_c09_status.lis;1 uvs_rts_e19_status.lis;2 uvs_pb_e04_status.lis;1 uvs_rts_c10_status.lis;8 uvs_rts_g01_status.lis;14 uvs_pb_e06_status.lis;1 uvs_rts_c21_status.lis;1 uvs_rts_g02_status.lis;33 uvs_pb_e11_status.lis;3 uvs_rts_c22_status.lis;1 uvs_rts_g07_status.lis;18 uvs_pb_e12_status.lis;1 uvs_rts_c23_status.lis;1 uvs_rts_g08_status.lis;3 uvs_pb_e14_status.lis;2 uvs_rts_e04_status.lis;19 uvs_rts_g28_status.lis;1 uvs_pb_e15_status.lis;2 uvs_rts_e06_status.lis;1 uvs_rts_i24_status.lis;1 uvs_pb_e17_status.lis;1 uvs_rts_e11_status.lis;5 uvs_rts_i25_status.lis;1 uvs_pb_g01_status.lis;4 uvs_rts_e12_status.lis;2 uvs_rts_i27_status.lis;1 uvs_pb_g02_status.lis;3 uvs_rts_e14_status.lis;3 uvs_rts_j0cd_status.lis;7

Coordinate System

Time tags are given in spacecraft clock (SCET), UTC as well as ground receipt time (ERT), UTC. Specific timing details are given in the file labels. The file TIME_CLOCKS.DOC in the archive Document folder describes the spcecraft timing. All calculations requiring the Jupiter atmospheric radius use a value of 71492. Km.

Any value not recovered by the ground system is assigned a value of -1. Zero is a legitimate UVS EDR value.

Look vector geometry for the UVS instrument is provided in Planetodetic Latitude unless otherwise specified.

Software

UVS EDR data files are written with IDL (Interactive Data Language, a product of Research Systems, Inc. of Boulder, Colorado.) The files are created on a Digital Equipment Vax computer. No special software is necessary to read the simple array structures. On a unix machine, use the IDL OPEN function option referred to a '/VAX_FLOAT'. IEEE transfer files are provided as well; these are the files whose file extensions are .XDR and .LXDR for the data and labels.

Media/Format

The standard distribution format for the data is electronic transfer.

Confidence Level Overview

All EDR data are exactly as recovered from the ground system. Ground system data recovery flags are included in the EDR headers. Resultant reliability and accuracy of the raw data is 100% described. Completeness can be derived from the data file header information.

The UVS instrument experienced a radiation exposure induced degradation in the optics of the grating drive assembly such that the grating did not always travel to the commanded location. A few missed positions begin to occur in orbit E14. The problem got progressively worse during the later orbits of the GEM period. G and N-channel commanding suffers initially due to the greater distance the drive must travel to achieve the commanded grating position. Eventually F-channel positions are compromised as well. Orbit C22 exposed the instrument to much greater radiation than expected and the drive rarely functioned after that. Most of the data in C20 is thought to be reliable, based on the reported achieved grating position, but data in the remaining orbits generally is not reliable. The orbit Status files indicate when incorrect grating registration occurred. See Limitations below.

Pointing accuracy in the supplemental (SPICE) data kernels may be the largest uncertainty in analyzing the data. Reduced downlink capacity caused less raw pointing information to be downlinked. Particularly when the spacecraft was not on gyros, and Target Motion Compensation (TMC), the scan platform may not have been pointing where it was commanded to point. Subsequently, there can be difficulty in coordinating the UVS data with pointing knowledge. Gyros are only used during Encounter sequence load periods; raw pointing knowledge is on 5 RIM centers in Cruise loads and 10 minor frame centers during Encounter loads.

Data Coverage and Quality

Any value not recovered by the ground system is assigned a value of -1. Zero is a legitimate UVS EDR value. The UVS instrument puts out 8-bit values of range 0-277 (octal). The PB data are in this range. The RTS data are accumulated in an on-board 16-bit, roll-over buffer. Zero is a legitimate value; values greater that 2^15 roll-over to zero and continue accumulating. The total summation period is indicated in the data file label.

Limitations

Sequenced science observations may not necessarily have been recovered to the ground. All available EDR UVS data sets are archived in PDS.

Beginning in orbit 14, the UVS instrument data status began to indicate the actual versus commanded grating position was different. The EDR file data information accurately describes where the grating was at the time of the data acquisition. A UVS 'status' file is archived for each orbit which compares the commanded versus actual grating position. These files should always be used to verify commanded configuration and actual grating position.

The Experimenter's Handbook file (UVS_HISTORY.DOC) describes all known anomalies, spacecraft safing of the instrument and power On commanding as well as instrument testing analysis. See also the UVS/EUV command archive file (CMD_ARCHIVE.LIS) for a full compilation of all instrument commanding. That file also lists all instrument heater commands.

These data are available on-line from the Planetary Data System (PDS) at: http://pds-atmospheres.nmsu.edu/PDS/data/gouv_0002/

Alternate Names

  • GO-J-EUV-2-EDR-JUPITER-V1.0
  • GO-J-UVS-2-EDR-JUPITER-V1.0

Discipline

  • Planetary Science: Atmospheres

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. Edwin V. Bell, II

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Charles W. HordData ProviderUniversity of Colorado
Dr. Karen E. SimmonsGeneral ContactUniversity of Coloradoksimmons@lasp.colorado.edu
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