Data Set Overview : The Alpha-Particle X-Ray Spectrometer (APXS) is a contact instrument that uses X-ray spectroscopy to determine the elemental composition of soils and rocks. Atmosphere argon can also be measured by the APXS. The APXS is deployed on selected targets along the rover traverse to determine the elemental composition of samples. Materials processed by the Sample Acquisition - Sample Processing and Handling (SA/SPaH) system can also be delivered to the observation tray or to the martian surface for analysis by APXS. Elements heavier than Na can be detected by APXS. If present at sufficient levels, the abundances of these elements can also be determined.  There are two APXS RDR data products. The first product is the summed X-ray spectrum in counts as a function of energy, which is derived from the APXS EDR. The second product is the standard elemental oxide abundance, which is derived from the summed X-ray spectrum. Both products are stored as ASCII text in a Comma Separated Value (CSV) format. Each CSV file has an associated detached PDS label, also stored as ASCII text.  Processing : The APXS X-ray spectrum RDR products are considered CODMAC Level 4 or Resampled Data, equivalent to NASA level 1B. The spectra are generated from the APXS EDR products (CODMAC Level 2, NASA Level 0) archived in the PDS data set MSL-M-APXS-2-EDR-V1.0.  The summed X-ray spectrum, product type RSP, is generated from the APXS EDR product by converting channel number to energy and summing together all buffers acquired at good temperatures. The RSP product consists of two fields, the first of which contains an energy value in eV and the second contains total counts for that energy channel. The count field value for first record is the counting time in seconds. The value for the last record is the overflow, that is, counts observed at that energy and higher. There is a header record at the start of the file that gives field headings for the two fields.  The APXS oxide abundance RDR products are considered CODMAC Level 5 or Derived Data, equivalent to NASA Level 2. The oxide abundance products, product type RWP, are generated from the X-ray spectra.  The oxide abundance product contains abundance data for a set of standard oxides and elements. There are three fields in the product: the oxide or element name, the weight percent, and the standard error of the weight percent value. The first record in the file is a header record that provides a description of the target sample.   Software : APXS RDR products are ASCII comma-delimited files that can be read using a text editor or with spreadsheet software such as Excel. No special software is required.

Confidence Level Overview : See CAMPBELLETAL2012 for a description of the calibration applied to the APXS data.  Review : The APXS RDR products are reviewed internally by the APXS team prior to release to the PDS. PDS also performs an external peer review of the APXS RDR.  Data Coverage and Quality : Nominally one APXS RDR spectrum is generated for each APXS EDR data product, and one APXS RDR oxide abundance product is generated for each RDR spectrum. Both the EDR and the RDR products may be revised during the course of the mission. Revisions are indicated in the product's PDS label by the keywords PRODUCT_VERSION_ID and PRODUCT_CREATION_TIME, and in the ERRATA.TXT file that accompanies the APXS archive.  Limitations : N/A  Data Compression : No data compression is used.