Mössbauer data sets

Data Set Overview

This data set is used to study the mineralogic composition of iron-bearing phases in Martian rocks and soils. For a Moessbauer experiment on any target, MIMOS II stores in memory for return to the Earth the following information: (1) a PHA spectrum for each of the 5 detectors; (2) five Moessbauer spectra (one reference and four sample spectra) for each of the 13 temperature intervals for a total of 65 spectra; (3) reference and sample temperatures; and (4) engineering data (e.g., the error signal for the velocity transducer). The Moessbauer spectra are in counts per channel for 512 channels. In (2), the four sample Moessbauer spectra in each temperature interval can selected in a number of ways. For example, they can be the 14.4 keV spectrum from each of the four detectors or the sum of the 14.4 and 6.4 keV spectra for each of the four detectors. Alternatively, the four spectra can be 14.4 and 6.4 keV spectra, each summed over two detectors. The spectra can be analyzed individually or combined to produce higher quality spectra. Combining spectra from different temperature intervals will depend on how strongly the spectra depend on temperature.

Processing

This SIS uses the Committee On Data Management And Computation (CODMAC) data level numbering system to describe the processing level of EDR data products. MB EDR data products are considered CODMAC Level 2 or Edited Data (equivalent to NASA level 0) products. The EDR data files are generated from Level 1 or Raw Data, which are the telemetry packets within the project specific Standard Formatted Data Unit (SFDU) record.

The MB EDR data products will be generated by the MIPL (Multimission Image Processing Laboratory) at JPL under the OPGS using the telemetry processing software, mertelemproc. The EDR data products will be raw uncalibrated data reconstructed from telemetry data products generated by the SSW team and formatted according to this EDR SIS. Meta-data acquired from the telemetry data headers will be used to populate the PDS label. There will not be multiple versions of an MB EDR. If telemetry data is missing partial data sets will be created and the missing data will be filled with zeroes. The data will be reprocessed after all data are received and the original version will be overwritten.

Data

A MB EDR data product consists of five contiguous blocks of binary data or a single block and a detached ASCII PDS label. Each data block is 32 Kbytes long for a total size of 160 Kbytes or 32 Kbytes. The five data blocks are a copy of the instrument's memory buffer. The EDR file contains Moessbauer spectra for a given target measured in thirteen temperature windows, along with temperature data, an energy spectrum, a drive error signal spectrum, copies of the instrument parameter block and logbook. In addition, the file contains ten compressed Moessbauer spectra stored in the EEPROM as backup in case the instrument loses power. The backup spectra are updated during data acquisition, approximately every 6 minutes.

Data from the instrument's SRAM occupy the first four blocks in the Moessbauer EDR data product. It contains three copies of the instrument parameter block, a drive error signal, temperature data, an energy spectrum, and Moessbauer spectra from 13 temperature windows.

Each copy of the instrument parameter block in the SRAM is 512 bytes long. The SRAM has three copies of the parameter block for a total of 1536 bytes. The drive error signal, which monitors the operation of the MB drive unit, has 512 channels with two bytes per channel. The drive error signal values are stored in LSB first order. The MB EDR file contains temperature data recorded by three sensors: one on the electronics board, one on the sensor head, and one on the reference sensor. Each temperature value is scaled and stored as a two byte integer in MSB first order. The file contains 256 temperature records. Within each record, the order of values is board sensor, sample sensor, and reference sensor. The following equations contain the conversion of the scaled temperatures into Kelvin:

• Board sensor = 273.2 + 25 + (scaled value * 1.638*2500/4096+608)/2
• Sample sensor = (scaled value)/10
• Reference sensor = (scaled value)/10

The energy spectrum, which monitors the operation of the detectors, contains 256 channels of data for each of 5 detectors. Each value is a three byte integer stored in LSB first order. The data are aggregated so that data for the first detector are followed by data for the second detector and so on.

Moessbauer data collected during a measurement are divided into temperature windows defined by a selectable lookup table. Each Moessbauer temperature window consists of five spectra (one for each detector). One spectrum contains 512 channels with three bytes per channel stored in LSB first order. The first channel of each spectrum gives the measurement lifetime, where lifetime is the number of cycles that the MB drive unit has executed during the measurement. The collection of MB spectra can be described as a three-dimensional array with axes of temperature window, detector, and channel, with the channel axis varying the fastest.

The fifth data block of the MB EDR data file contains a copy of the instrument FRAM and EEPROM memory, along with copies of one Moessbauer temperature window, the drive error signal, instrument parameter block, and temperature data. The FRAM consists of three copies of the instrument parameter block and the instrument logbook. The logbook has 256 records with eight bytes in each record. The structure of the logbook is described in the Moessbauer Spectrometer Information Interface Control Document. The EEPROM contains ten compressed MB spectra. The data are compressed by combining data from several temperature windows or from several detectors. Each compressed MB spectrum has 512 channels with three bytes per channel stored in LSB first order.

Software

A reader program, called mb2asc, will be available for a variety of computer platforms to convert the MB EDR binary format data into ASCII format. This reader will be archived with the EDR data products. The ASCII format data can be imported into spread sheet and plotting programs.

Media/Format

The data set will initially be delivered and kept online. Upon Mission completion, the Moessbauer EDRs will be delivered to PDS on DVD as part of the complete MER EDR data set.

Data Set Overview

The MB RDR data products are ASCII formatted tables. Each ASCII table has an associated detached PDS label, also formatted as ASCII. There are several types of MB RDR data products from intermediate data reduction to more highly derived ones. MB Summed Spectra RDR products are expressed as summed spectra in counts as a function of channel number[MORRISETAL2004], [KLINGELHOEFERETAL2004].

Processing

This dataset uses the Committee On Data Management And Computation (CODMAC) data level numbering system to describe the processing level of the MB RDR data products. These data products are considered CODMAC Level 4 ['Resampled Data' equivalent to NASA Level 1-B].

The MB RDR data products are produced by MB instrument team members from the Johannes Gutenberg University (Mainz, Germany) using software tools developed by the MB team. The RDR data products - summed spectra in counts as a function of channel number - is generated after each sol in which MB data were acquired. This step comprises an extraction of the MB spectra from the EDR products and subsequent conversion into ASCII formatted tables.

MB RDR data products are generated from binary EDR files that are extracted from the OSS to the MB team workstations. Once RDR data products are generated, they are transferred back to the OSS for access by other MER science and operations team members. After a science validation period, the MB RDR data products are transferred to the PDS for final validation and archiving in accordance with the MER archive plan.

Data

Each MB RDR data file is a table. The number of columns and rows in the table is dependent on the type of RDR. Columns are variable length and are delimited with commas. Each row is terminated with a carriage return and line feed character. There are 6 product types in this data set as described below. The first product type (MGC) is a table of 14 keV (gamma-ray) MB spectra as a function of channel number. The second product type (MXC) is a table of 6 keV (X-ray) MB spectra as a function of channel number. The third product type (RSC) is a table of 14 keV reference spectra as a function of channel number. The fourth product type (DSC) is a table of differential signal as a function of channel number. The fifth product type (ESC) is a table of energy spectra as a function of channel number. The sixth product type (ESE) is a table of energy spectra in counts as a function of energy.

Velocity calibration files for surface and CCT measurements are provided in the CALIB directory of the archive. These files consist of thirteen columns: one per each temperature window. The temperature windows correspond to the temperature windows in the MB spectra products (MGC and MXC). The last temperature window in each velocity calibration file contains a room temperature extrapolation of the velocity scale.

Software

MB RDRs are formatted so that they can be directly imported into spreadsheet and plotting software packages.

Media/Format

The data set will initially be delivered and kept online.

Data Set Overview

The Moessbauer spectrometers on the two Mars Exploration rovers identified Fe-bearing phases and quantitatively measured the relative abundance of Fe (as percentage of total Fe) according to oxidation state (e.g., Fe2+ and Fe3+), coordination state (e.g., octahedrally-coordinated), and specific Fe-bearing phases (e.g., percentage of total Fe associated with olivine) at Meridiani Planum (Opportunity) and Gusev Crater(Spirit). For more information on the MER Moessbauer spectrometers please see mer1_mb_inst.cat and mer2_mb_inst.cat.

This archive contains Percent Total Fe products for both MER-1 and MER-2 rovers. The archive consists of one table for each rover. Each table has a detached PDS label that describes the content of the table.

Processing

The processing of this archive is described in detail in [MORRISETAL2006A], [MORRISETAL2006B], and [MORRISETAL2008] listed in ref.cat. The archive consists of one table each for MER-1 and MER-2 rovers. Each table contains the percent Moessbauer areas for component subspectra, where subspectral area is the percentage of total Fe associated with specific Fe-bearing phases. Note that subspectral areas do not provide information about the proportion of the iron-bearing phases themselves unless the concentration of Fe in those phases is independently modeled.

Subspectral areas were determined using a variety of commercial and in-house least-squares fitting computer programs in which peak line shape function, peak center, peak width, and area were adjustable parameters. Five double and four sextet subspectra were required to fit the Moessbauer spectra. Note that not all nine subspectra are present in every spectrum. All spectra were fit independently by at least two of the authors of [MORRISETAL2006A], [MORRISETAL2006B], and [MORRISETAL2008], which are listed in ref.cat. Two approaches were used during fitting procedures. In one approach, spectra were fit using individual peaks, and in the other approach spectra were fit using individual subspectra. Values of subspectral areas (percentage of total Fe associated with specific Fe-bearing phases) reported are average values from independent fits by 2-4 co-authors. The reported error is the larger of 2% (absolute) or the deviation from the average value of the independent fits. Fitting constraints included the following:

1. The two peaks in doublet subspectra were constrained to have equal areas and widths.
2. The six peaks in sextet subspectra were often constrained to the ratio 3:2:1:1:2:3
3. Because of the strong overlap of the innermost two peaks of sextet subspectra with doublet subspectra and other sextet subspectra, their positions were often constrained using the positions of the other four peaks and 0.572 for the g-factor ratio of the 14.4 KeV excited state to the ground state of Fe-57.

The areas include a correction factor (the f-factor) to account for differences in recoil-free fractions according to oxidation state (f(Fe3+)/f(Fe2+)) = 1.21 independent of mineralogical composition.

Phase identification was done using a combination of literature databases of Moessbauer parameters, intercorrelations of subspectral areas, and correlation of subspectral areas with APXS elemental data.

Additional processing to improve counting statistics and additional constraints imposed on certain targets or for certain phases where the combination of reasonable counting statistics and high subspectral area was not sufficient is described in detail in [MORRISETAL2006A], [MORRISETAL2006B], and [MORRISETAL2008].

Data

The archive consists of one table each for MER-1 and MER-2 rovers. The table MERA_MB_PCT_TOTAL_FE.CSV contains the percentage of total Fe in Fe-bearing phases from subspectral areas in Spirit (MER-A) Moessbauer Spectra. The table MERB_MB_PCT_TOTAL_FE.CSV contains the percentage of total Fe in Fe-bearing phases from subspectral areas in the Opportunity (MER-B) Moessbauer Spectra.

Field names and phase assignments are abbreviated as show in the table below.

Field names	D	Doublet Moessbauer spectrum
	S	Sextet Moessbauer spectrum
Phase assignments	OL	Olivine
	PX	Pyroxene
	ILM	Ilmenite
	CHR	Chromite
	MT	Magnetite
	NPOX	Nanophase Ferric Oxide
	FE3SULFATE	Fe3+-bearing sulfate
	JAR	Jarosite
	HM	Hematite
	PYR/MAR	Pyrite/Marcasite
	GT	Goethite
	Tr	Troilite
	A-FE	Fe/Ni Metal Alloy (kamacite)

Absolute errors are included in the tables in fields named *_ERR. An entry of 0 (zero) denotes that the doublet or sextet was not used in the least squares fitting procedure. Subspectral areas are f-factor corrected. These comma-separated-value tables are suitable for reading into a spreadsheet program such as Microsoft Excel.

A detached PDS label accompanies each table that describes the content and format of the table. All detached label and document files are in stream format files with a carriage return (ASCII 13) and line feed character (ASCII 10) at the end of each record. This allows files to be read by the MacOS, DOS, Unix, and VMS operating systems.

Software

No software is included in this archive. The data products can be viewed in a text editor or in a spreadsheet program such as Microsoft Excel.

Confidence Level Note

Please refer to [MORRISETAL2006A], [MORRISETAL2006B], and [MORRISETAL2008] listed in ref.cat.