Data Set Overview : The Cassini Magnetospheric Imaging Instrument(MIMI) Low Energy Magnetospheric Measurement System (LEMMS) uncalibrated data set includes all data collected from the MIMI Data Processing Unit during the entire Cassini mission [MANWEILERETAL2005]. The original data has been decommutated and decoded by software at the Applied Physics Laboratory (APL) and has been then further ordered and filtered by software at Fundamental Technologies, LLC. The data is provided in an uncalibrated form in conjunction with a PDS MIMI calibration volume COMIMI_0000 which provides specific algorithms for the derivation of calibrated data. This data set includes uncalibrated values for each energy channel for the LEMMS sensor for all times during the mission including the Earth flyby, the Jupiter flyby, interplanetary cruise, and the entire Saturn tour. Data are presented in a set of tables which are of variable length and use a comma to separate various fields. This data set is intended to be the most comprehensive and complete data set included in the Cassini MIMI LEMMS archive. A browse data set is included with Key Parameter data that is calibrated using the algorithms provided in the Calibration volume. In addition, a series of images are provided with the KP browse data that displays the KP data which can lead the user to the particular times of interest. This data set should be among the first used by a user of any of the MIMI LEMMS archive as it will lead one to information required to search for more detailed or highly specialized features in the original data. Parameters : This data set comprises low energy charge particle count rate measurements for each energy channel of the LEMMS detector in a regular and high time rate mode. In addition this data set includes LEMMS PULSE HEIGHT ANALYSIS measurement data for a statistically select sample of the particle measurements. The standard product ID's are: LEMMS Accumulation Rate Data - low energy charge particle count rate measurements LEMMS Fine Rate Accumulation Data - low energy charge particle count rate measurements for a select list of channels at a high time resolution. LEMMS Pulse Height Analysis Data - Statistically sampled set of discrete particle measurements. The data is organized in time by the spin of the spacecraft. When the spacecraft is in staring mode then the MIMI DPU automatically creates a virtual spin that divides the time collection periods into 16 sectors, 16 subsectors, and 16 microsectors and maintains a simple organizational structure for characterizing the collection of the time into time segments. When the spacecraft is spinning at a minimally defined spin rate (adopted by the MIMI DPU) then the MIMI data is automatically segregated into 16 sectors, 16 subsectors, and 16 microsectors. When the spacecraft is spinning and the LEMMS instrument is rotating the LEMMS rotation period is synchronized to the spacecraft spin period so that there are 16 sectors in a spin, 16 subsectors in a sector and 16 microsectors in a subsector. The CHEMS and INCA instrument collection times are then also keyed to these values. Processing : Data in this data set were processed by the use of a number of software programs which assemble segmented mini-packets in the raw telemetry packets into complete sets, de-compress the data that were compressed by one of a number of compression algorithms by the MIMI flight software onboard and organize the channel data into appropriate time segments. Data : The MIMI LEMMS uncalibrated data set includes three ASCII CSV tables (each associated with a Standard Product ID) of count rate data as a function of time collected from the MIMI LEMMS Detectors and collated into channel sets. Each table contains variable length records for which the fields are comma delimited. LEMMS Accumulation Rate Data ---------------------------- Fields include: a purpose identifier where science data records are identified with purpose : sci starting and ending ephemeris times Spin, sector, subsector (and for LEMMS Fine Rate (FRT) data microsector) SCLOCK and spin period that are used to derive the starting ephemeris time Notes regarding the SCLOCK value: 1. Only the SCLOCK major segment value is provided - MIMI currently does not have access to the fine SCLOCK value hence SCLOCK resolution is limited to +- 1/2 SCLOCK count 2. The SCLOCK is only available from telemetry at the beginning of each spin. All other published SCLOCKS are derived from the spin starting SCLOCK, the spin numbers (for the current and next available spins), and the spin period. 3. SCLOCK values are assumed to drive the value of the ephemeris times and not vice-versa. All effort is made to validate the published ephemeris times but since updates to the Cassini SCLOCK kernel in SPICE can occur the values of ephemeris time are only as accurate as the currently published Cassini SCLOCK SPICE kernel. Spacecraft staring mode where staring : 0 when spinning and 1 otherwise LEMMS Channel count rate data organized as: Low Energy Telescope channels A0-A8 - These channels are sensitive to protons and heavier ions. The A0-A4 channels are somewhat sensitive to electrons. B0-B3 - These channels are sensitive to protons and He. BE - This channel is sensitive to 1 - 2.6 MeV energetic electrons. C0-c7 - These channels are associated with magnetically sweeped particles and are sensitive to electrons AS, BS, ES, FS are the singles rates measured by the A, B, E and F detectors. E2/F2S is the ratio of the E2 to F2 singles rates High Energy Telescope channels E0-E7 - These channels are sensitive to electrons and somewhat sensitive to X-rays G1 - This channel is sensitive to X-rays only P1-P9 - These channels are mainly sensitive to protons. P1-P2 are sensitive to all species of charged particles and X-rays P7-P9 are also sensitive to He H1-H5 - These channels are sensitive to He and heavier species H5 is also sensitive to 20-25 MeV protons Z1-Z3 - These channels are sensitive to species heavier than He D1-D3, D41 are the singles rates for each of the D detectors in the LEMMS system Priority Channels In various portions of the mission, a subset of main channels are identified to provide high time resolution data (for each two microsectors). The totals of the sums for each of these priority channels are included in the list of channels for diagnostic use. The number and specific selection of priority channels varies over the life of the mission. LEMMS Center look angle in Degrees, which provides the angle between the pointing of the low energy telescope of the LEMMS instrument with respect to the -Z axis. The LEMMS instrument rotates around the -Y axis. LEMMS Fine Rate Accumulation Data --------------------------------- Fields include: a purpose identifier where science data records are identified with purpose : sci starting and ending ephemeris times Spin, sector, subsector (and for LEMMS Fine Rate (FRT) data microsector) SCLOCK and spin period that are used to derive the starting ephemeris time Notes regarding the SCLOCK value: 1. Only the SCLOCK major segment value is provided - MIMI currently does not have access to the fine SCLOCK value hence SCLOCK resolution is limited to +- 1/2 SCLOCK count 2. The SCLOCK is only available from telemetry at the beginning of each spin. All other published SCLOCKS are derived from the spin starting SCLOCK, the spin numbers (for the current and next available spins), and the spin period. 3. SCLOCK values are assumed to drive the value of the ephemeris times and not vice-versa. All effort is made to validate the published ephemeris times but since updates to the Cassini SCLOCK kernel in SPICE can occur the values of ephemeris time are only as accurate as the currently published Cassini SCLOCK SPICE kernel. Spacecraft staring mode where staring : 0 when spinning and 1 otherwise LEMMS Channel count rate data organized based upon the current set of priority channels The set of priority channels changes from time to time during the mission. The specific channels for any particular data file are identified by the headers of that data file. LEMMS Center look angle in Degrees, which provides the angle between the pointing of the low energy telescope of the LEMMS instrument with respect to the -Z axis. The LEMMS instrument rotates around the -Y axis. LEMMS Pulse Height Analysis Data -------------------------------- Fields include: a purpose identifier where science data records are identified with purpose : sci starting and ending ephemeris times Spin, sector, subsector SCLOCK and spin period that are used to derive the starting ephemeris time Notes regarding the SCLOCK value: 1. Only the SCLOCK major segment value is provided - MIMI currently does not have access to the fine SCLOCK value hence SCLOCK resolution is limited to +- 1/2 SCLOCK count 2. The SCLOCK is only available from telemetry at the beginning of each spin. All other published SCLOCKS are derived from the spin starting SCLOCK, the spin numbers (for the current and next available spins), and the spin period. 3. SCLOCK values are assumed to drive the value of the ephemeris times and not vice-versa. All effort is made to validate the published ephemeris times but since updates to the Cassini SCLOCK kernel in SPICE can occur the values of ephemeris time are only as accurate as the currently published Cassini SCLOCK SPICE kernel. Spacecraft staring mode where staring : 0 when spinning and 1 otherwise LEMMS Detector Channel count rate data is an array of counts for each of the three low energy telescope solid state detectors. Each field contains the counts observed within each of the 64 energy bins for each of the detectors (A, E1, and F1) accumulated over the specific time interval. The Detector energy bins are quasi-logarithmically spaced. See the MIMI_CALIBRATION calibration file for spacing deltas and min and max energies. LEMMS Center look angle in Degrees, which provides the angle between the pointing of the low energy telescope of the LEMMS instrument with respect to the -Z axis. The LEMMS instrument rotates around the -Y axis. Ancillary Data : Included with the LEMMS data set volumes are ancillary data files representing the MIMI Key Parameter (KP) data. The MIMI KP data is a calibrated subset of the important channels for each of the MIMI detectors. The subset of channels have been identified to most reasonably show characteristic energetic particle events during the mission. The KP data is calculated at an arbitrarily defined 60 second cadence which is different than the approximate collection times for the instruments as identified below for standard operations: (It must be realized that the collection times vary based upon the telemetry rate but nothing more than a factor of 2, 4, or 8.) Instrument Product Type Approx Collection Time (s) ------------------------------------------------------------ LEMMS Accumulation 5 (each subsector) LEMMS Fine Rate 0.6 (each microsector) LEMMS PHA 5 (each subsector) CHEMS Accumulation 4 CHEMS Science 5 (each subsector) CHEMS PHA 80 (each sector) INCA Accumulation 7.5 INCA IMAGES 180 (2 sectors) INCA PHA 22 Data points for each record of the KP data are first Median Quartile Filtered then averaged (except in the case where the median is zero) for each sector. The sectored data is then interpolated into the 60 second data cadence of the KP data file. The KP data is then converted into a flux in units of 1/(cm^2*sr*sec*KeV) or for the case of CHEMS 1/(cm^2*sr*sec*keV/e) Browse plots for each of the KP data files are produced. There are 7 different browse plots available. Inst Wild Card File Name Plotted KP data --------------------------------------------------------------------- LEMMS LEMMS_KP_ELEC_(yyyydoy)_(ver#).JPG KP LEMMS Electron flux LEMMS LEMMS_KP_ION_(yyyydoy)_(ver#).JPG KP LEMMS Ion flux CHEMS CHEMS_KP_HEP_(yyyydoy)_(ver#).JPG KP CHEMS Helium Plus flux per charge CHEMS CHEMS_KP_HEPP_(yyyydoy)_(ver#).JPG KP CHEMS Helium Plus Plus flux per charge CHEMS CHEMS_KP_HP_(yyyydoy)_(ver#).JPG KP CHEMS Hydrogen Plus flux per charge CHEMS CHEMS_KP_OP_(yyyydoy)_(ver#).JPG KP CHEMS Oxygen Plus per charge INCA INCA_KP_(yyyydoy)_(ver#).JPG Hydrogen TOF flux Usage Note ---------- The KP browse data and associated browse plots are to be used as an initial characterization of the particle environment and are NOT to be used for publications. The data is not at publication quality and is provided as is. Coordinate System : The data in this data set are measurements of count rates based upon the orientation of the LEMMS instrument (LEMMS Center look direction). Particle flux effects are then determined by transforming from a spacecraft centered coordinate system, properly rotated to account for the appropriate LEMMS telescope and look direction, into whatever external coordinate (reference system) is most appropriate. Software : There is no sample software provided as of the writing of this catalog file although the calibration volume does provide algorithms for conversion of count rates into flux. Media/Format : These data are supplied to the Planetary Data System via electronic means and are then broken into segments based upon the media currently prescribed by PDS.

Confidence Level Overview : This data set contains all calibrated data for the LEMMS Detector as part of the Cassini MIMI instrument for the interval described above. Every effort has been made to ensure that all data returned to APL from the spacecraft is included and that the calibrated browse data products are accurate. The LEMMS C0 channel (and less so for the C1 channel) has occasional exceptionally high rates (spectral indexes exceeding 6) that are due either to direct solar exposure and/or to specular reflection from various parts of the spacecraft. This was first identified during the Earth - Jupiter Cruise phase of the mission. Priority channels were reorganized during this time but with the unexpected result that the C1 channel was being corrupted without the ability to identify the source of the corruption at a high time resolution which the priority channels provide. Just prior to SOI the priority channels were again re-established to include the C0 channel for the specific purpose of enabling the data user to develop algorithms to eliminate those data values that include this contamination. The low energy A (A0 - A4) channels are subject to contamination by electrons. As of January 2005, the LEMMS detector no longer has the ability to rotate. Various attempts to correct this anomaly have been tried with the result of moving the fixed position to other nearby pointing directions but these attempts have failed in their ability to restart full motion of the detector. Review : The MIMI LEMMS data will be reviewed internally by the Cassini MIMI team prior to release to the PDS. The data set will also be peer reviewed by the PDS. Data Coverage and Quality : All data in the stated interval are included, to the best of our knowledge and attempts to determine completeness. In general, the instrument was operated only briefly during early tour for the following intervals: 1. Antenna deployment 1997-10-25T00:00 - 1997-10-26T05:30 2. Venus 1 flyby 1998-04-26T12:54 - 1998-05-08T19:21 3. Instrument Checkout 1998-12-30T09:10 - 1999-01-19T05:40 4. Venus 2 flyby 1999-06-24T09:08 - 1999-06-24T21:20 5. Earth flyby 1999-08-13T17:39 - 1999-09-14T22:20 Only data for interval 5 is provided to PDS due to technical issues in processing. Beginning in February of 2000 the instrument was operated more-or-less continuously with small daily runs of approximately 8 hours. Intermittent data collection occurred during 2002 and 2003 with multiple day gaps in the data Large Data Gaps: 1. Cruise 2000-066 - 2000-155 2. Cruise 2000-210 - 2000-246 3. Cruise 2000-311 - 2000-320 4. Cruise 2000-322 - 2000-333 5. Post Jupiter Cruise 2003-018 - 2003-104 6. Post SOI 2004-187 - 2004-193 - Spacecraft safing shut off 7. Saturn 2012-293 - 2012-303 - propellant gauging test Those days for which the instrument did not collect data either due to the instrument being off or due to communication issues, the data set will not contain any files. Limitations : As noted above the A0 and C0 channels (and somewhat less so the C1, A1 and additional C and A channels) have occasional significant corruption of the count rate due to direct solar pointing and/or due to specular reflection of UV from various parts of the spacecraft. There has as yet been no systematic algorithm developed to capture when these events occur either by the spectral power of the data or else by the pointing excepting in the situation when the LEMMS instrument itself is directly pointed into the Sun. This last situation can be easily identified by using the SPICE routines. The KP browse data and associated browse plots are to be used as an initial characterization of the particle environment and are NOT to be used for publications. The data is not at publication quality and is provided as is.