Overview: : The Neutral Particle Imager (NPI) measures integral ENA fluxes in the energy range 0.1 to 60 keV to help satisfy the following scientific objectives: 1. Determine the instantaneous global distributions of plasma and neutral gas near Mars 2. Energy deposition from the solar wind to the ionosphere 3. Search for the solar wind-Phobos interactions Parameters: : All NPI data products have the same format and parameters, and each row (data file record) in the NPI 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 - either SENSOR or MODE. The SENSOR rows are the NPI science data for each sector (32 sectors). The MODE rows contains informational data like Accumulation Time and MCP Mode. 4. Data Type Id - Numeric ID indicating either SENSOR or MODE. 5. Data Name - Short description for data on that row. For example 'Sector 0' for NPI sector 0 science data (SENSOR row), or 'Accumulation Time' for informational data (MODE row). 6. Data Unit - Indicates the data unit (c/sec for SENSOR data, unitless for MODE data). 7. Values - These are the actual data values. For NPI, there is one value per row (sector). 8. Data Quality Value - Quality indicator for the data on that row. See CONFIDENCE_LEVEL_NOTE under 'Data Coverage/Quality' for valid values and descriptions. Data Products: : The only Standard Data Product for the combined NPI PSA Level 1b (EDR) / PSA Level 2 (RDR) is: 1. NPINORM_C_SEC - Neutral Particle Imager NORMal mode data in Counts / SECond (count rate). 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, +5V, or -5V monitor value is not within tolerance 3 - Bad Data: +30V monitor value and (+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.