Overview: : The Electron Spectrometer (ELS) provides in situ electron measurements in the energy range 0.05 eV to 20 keV to help satisfy the following scientific objectives: 1. Determine the instantaneous global distributions of plasma and neutral gas near Mars by providing undisturbed solar wind parameters 2. Define the local characteristics of the main plasma regions 3. Complement the ENA images Parameters: : All ELS data products have the same format and parameters, and each row (data file record) in the ELS SPREADSHEET data products has eight (8) COLUMN objects (parameters): 1. Start Time - Begin Date/Time in UTC of data samples 2. Stop Time - Ending Date/Time in UTC of data samples 3. Data Type Name - SENSOR, SCAN, or MODE. The SENSOR rows are the ELS science data for each sector (16 sectors). The SCAN rows are the deflection voltages (volts) that correspond to the SENSOR rows. There is one SCAN row per 16 SENSOR rows. The 16 SENSOR rows are followed by one corresponding SCAN row. The SCAN row indicates the deflection voltage per step that corresponds to the previous 16 SENSOR rows for each step. To convert the deflection voltages to center energies (eV), use the K_FACTOR per anode in the calibration tables: eV : volt * K_FACTOR. There are 16 SENSOR rows + 1 SCAN row (17 in all) followed by 23 rows of MODE data for the same time period. The MODE rows contain informational data such as Time/Step Summations and Sector Enable Flags. 4. Data Type Id - Numeric ID indicating SENSOR, SCAN, or MODE. 5. Data Name - Short description for data on that row. For example 'ELS Sector 0 LR' for ELS sector 0 Low Range science data (SENSOR rows for ELSSCIL data products), 'ELS Sector 0 HR' for ELS sector 0 High Range science data (SENSOR rows for ELSSCIH data products), 'Deflection Potential' for SCAN rows, or 'Time Summation' for informational data (MODE row). 6. Data Unit - Indicates the data unit: 'c/acc' (counts per accumulation) for SENSOR data 'volt' for SCAN data 'Unitless' for MODE data 7. Values - These are the actual data values. For this column there are multiple values as indicated by the ITEMS keyword in the label files. This value will vary from file to file, but remains consistent within a data (.CSV) file. For the SENSOR rows, these are the science data sampled at the corresponding deflection volts indicated in the corresponding SCAN row that follows the 16 ELS sector (SENSOR rows) data. The MODE data rows contain only one value each and remaining ITEMS are indicated 'missing' with commas (value,,...,,). Please note that the data values are formatted for a high level of accuracy, and that this does not indicate the accuracy of the ELS instrumentation. 8. Data Quality Value - Quality indicator for the data on that row. The data quality value is only applicable for the SENSOR data. See CONFIDENCE_LEVEL_NOTE under 'Data Coverage/Quality' for valid values and descriptions. Data Products: : The Standard Data Products for ELS PSA Level 1b (EDR) products are: 1. ELSSCIL_C_ACC - ELectron Spectrometer SCIence Low range data in Counts / ACCumulation units. 2. ELSSCIH_C_ACC - ELectron Spectrometer SCIence High range data in Counts / ACCumulation units. NOTE: There is not a one-to-one correspondence between the ELSSCIL and ELSSCIH data products. Most of the time, both products are produced for the same time period. However, there are times when only ELSSCIL products are produced or only ELSSCIH products are produced, not both. Ancillary Data: : It is important for ASPERA-3 science studies to know where in space and time the Mars Express spacecraft and ASPERA-3 instruments are located and what objects (Sun, Mars, Earth, Phobos, Deimos) are in the fields of views. The ASPERA-3 view directions for each sensor can be derived using the SPICE kernels and software. The ASPERA-3 Sensor Frames and Geometry Information document (in DOCUMENT directory) provides a code example (in C and FORTRAN) for determining the view directions for the ASPERA-3 sensors. Coordinate System: : The ASPERA-3 data are always in the instrument reference frame since data are sampled in situ. The GEOMETRY table contains spacecraft related parameters expressed in the J2000 reference frame, and the ASPERA-3 Sensor Frames and Geometry Information document (in DOCUMENT directory) provides information for determining the ASPERA-3 sensors view directions and transforming to the J2000 reference frame. References: : Refer to the ASPERA-3 Experiment to Archive Interface Control Document (EAICD) found in the DOCUMENT directory (MEX_ASPERA3_PSA_ICD_V01_03) for more information and detail concerning data set formulation and contents.

Review: : These data have been reviewed by the instrument team and are of the highest quality that can be generated at this time. Science results based on these data have been published in several journals (Science, Nature, EGU, etc.). After submission to the PDS, these data successfully completed the peer review process. Data Coverage/Quality: : The data quality indicators in the data files for each sensor are associated with the data returned in telemetry. Valid values are: 0 - Good Data: Default because assumption is that data are good unless determined otherwise. 1 - Questionable Data: +30V monitor value is not within tolerance 2 - Invalid Data: +12V, -12V, +5V, or -5V monitor value is not within tolerance or high voltage is not enabled 3 - Bad Data: +30V monitor value and (+12V, -12V, +5V, or -5V monitor value) are not within tolerance 4 - Unknown State: Time related Main Unit housekeeping packet is not available. -1 - Data Unavailable: No data returned for the sensor, so a fill value is used for data quality. Limitations: : There are no known limitations at this time.