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PHOENIX MARS MECA NON-IMAGING RDR V1.0 (PDS)

NSSDCA ID: PSPG-00784

Availability: Archived at NSSDC, accessible from elsewhere

Description

This description was generated automatically using input from the Planetary Data System.

Data Set Overview ================= The Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) experiment on the Mars Phoenix Lander consists of four instrument components plus command electronics. This MECA Non-Imaging Reduced data set contains data from three of the four MECA components, the Thermal and Electrical Conductivity Probe (TECP), the Atomic Force Microscope (AFM), and the Wet Chemistry Laboratory (WCL). Reduced data from the fourth MECA component, the Optical Microscope (OM), is in a separate data set. More information is found in HECHTETAL2008, KOUNAVESETAL2008, and ZENTETAL2008. The following text describes each component of the data set. TECP Overview ============= An end-effector on the Phoenix Robotic Arm, the Thermal and Electrical Conductivity Probe (TECP) is a probe of soil physical properties including temperature, thermal conductivity and diffusivity, electrical conductivity and permittivity, as well as atmospheric temperature, humidity, and wind speed. These measurements are made with four conical needles, three of which contain electrical heaters and thermometers, and a hygrometer sensor mounted separately in the body of the TECP. The scientific objectives of the TECP are to provide ground-truth for orbital surface thermal measurements and input parameters for thermal models by directly measuring the thermal properties of Martian regolith; to measure the concentration and nature of water in Martian regolith in solid, 'non-frozen,' liquid, and vapor states; to determine changes in the reservoirs of water when soil is freshly exposed and; to characterize the movement of water in and out of the soil by measuring atmospheric humidity, temperature, and wind speed above the surface. The MECA TECP portion of the PHOENIX MARS MECA NON-IMAGING RDR V1.0 data set is a collection of electrical conductivity (EC), relative humidity (HUM), relative permittivity (PRM), and thermocouple (needle) temperature (TC) data sorted by time. Data are sorted by time, with each data file containing one one sol's worth of data for each data type. TECP Parameters =============== Spatial parameters are given for each TECP sample in the RDR data set. These parameters allow the end-user to determine the exact position of the TECP during each data collection. The coordinates are given in several reference frames that are discussed in the Coordinate System section of this document. TIP_POS_R_PF - Radial coordinate of TECP needle tips centroid in Payload Frame cylindrical coordinates TIP_POS_THETA_PF - Azimuthal coordinate of TECP needle tips centroid in Payload Frame cylindrical coordinates, measured clockwise (as viewed from above) from the +x-axis TIP_POS_Z_PF - Vertical coordinate of TECP needle tips centroid in Payload Frame cylindrical coordinates, measured positive downward ANGLE_TECP_RA - Angle of TECP long axis (+z axis in TECP frame) relative to a vector that is parallel to the RA forearm and pointing away from the lander. This angle is measured clockwise as viewed from the TECP side of the RA wrist joint. TIP_POS_X_LLF - X coordinate of the TECP needle tips centroid in the Local Level Frame TIP_POS_Y_LLF - Y coordinate of the TECP needle tips centroid in the Local Level Frame TIP_POS_Z_LLF - Z coordinate of the TECP needle tips centroid in the Local Level Frame, measured positive downward ANGLE_TECP_Z_LLF - Angle of TECP long axis (+z axis in TECP frame) relative to the positive z-axis of the Local Level Frame (parallel to gravity vector) TECP Processing =============== There are four types of TECP data, electrical conductivity (designated EC), humidity (designated HUM), relative permittivity or dielectric constant (designated PRM) and temperature (TC). The EC data is formatted as four ASCII tables, a conversions table, two tables with conversion constants, and a data table that contains a time-series of measurements. The HUM, PRM and TC data are all formatted as a conversions table followed by a data table that contains a time-series of measurements. The conversions table contains the DN to physical unit equations for the particular data type. Table 4.5 of the MECA RDR SIS found in the DOCUMENTS directory of this archive lists all the DN to physical unit conversions used to convert TECP EDR data into TECP RDR data. TECP Data ========= There are four types of TECP data, TECP_EC, TECP_HUM, TECP_PRM and TECP_TC. The TECP_EC data is a time-series of electrical conductivity measurements. The TECP_HUM data is a time-series of relative humidity measurements. The TECP_PRM data is a time-series of relative permittivity data, and the TECP_TC data is a time-series of temperature measurements. The TECP data are organized as ASCII CSV data files. The TECP_EC data files are structured as a 2-column conversions table that holds the DN to physical unit conversion equations. The conversions table is followed by a 4-column table that holds the gain specific probe constant conversion coefficients. Next is a 7-column table that contains the gain specific resistance conversion coefficients and last the 13-column data table. The TECP_HUM, TECP_PRM, and TECP_TC data files are all structured in the same way. The file begins with a 2-column conversions table that holds the DN to physical unit conversions used to make the RDRs. The conversions table is followed by the data table. The EC and HUM data are 13-column data tables. The PRM data table is a 12-column data table and the TC data table is a 16-column table. Each of the four TECP data types are organized as ASCII comma separated variable (CSV) data files containing data from a single Martian sol, with a detached ASCII text PDS label file for each data file. Data from each measurement day will be grouped by instrument (TECP) then by sol. TECP Ancillary Data =================== The first table in all the TECP RDR data types is a conversions table. This table gives the DN to physical unit conversion equations used to convert the raw TECP EDR DN value data to physical units. The EC data type also contains a table of calibration coefficients used in the EC conversions. It is possible that these coefficients could change over the course of the mission. If they do change, the change will be noted in this document, as well as in the RDR SIS. TECP Coordinate System ====================== TECP orientation information is given in all four TECP data types. The orientation information is obtained from the Robotic Arm (RA) and was acquired at the time of the most recent RA move. The orientation information is given in both the payload frame and in the local level frame for ease of use. The definitions of the PHOENIX coordinate systems are documented below: Local Level - Same as payload frame, and it moves with the Lander +X - North +Z - down along gravity vector +Y - East Payload Frame - At the shoulder of the Robotic Arm. Attached and moves with the Lander +X - along Lander X (point out into the work space) +Z - down along Lander (vertical axis) +Y - along Lander -Y Site Frame - Same as payload frame when first defined and never moves relative to Mars. Possible to define multiple site frames in case the Lander moves/slips. Same as local level TECP Software ============= No TECP specific software will be provided at this time. As the data products are ASCII, any software that can handle ASCII files can be used to view the products. TECP Media/Format ================= As part of the MECA Non-Imaging RDR data set, TECP RDRs will be delivered using Internet file transfer protocol. Data formats will be based on standards for such products established by the Planetary Data System (PDS) [PDSSR2001]. AFM Overview ============ The Atomic Force Microscope (AFM) is part of the MECA Microscopy Station, which comprises a Sample Wheel and Translation Stage (SWTS), an optical microscope (OM), and the AFM. The MECA AFM is located between the OM and the SWTS inside the darkened MECA enclosure on the spacecraft deck. It scans a small region (from 1-65 micron square) on any of 69 substrates, each 3-mm in diameter, positioned along the rim of the SWTS. The chief scientific objectives of the AFM are to analyze small dust and soil particles in terms of their size, size distribution, shape, and texture. The AFM is particularly well suited to analyze particles carried by the wind, which are believed to be in the size range 1-3 micron. A full description of the MECA AFM can be found in [HECHTETAL2008]. The MECA AFM portion of the PHOENIX MARS MECA NON-IMAGING RDR V1.0 data set is a collection of scan data sorted by time. Data types included in this data set are the AFM_SDR, calibrated scan data with x-y scan ranges, the AFM_SDD, a line by line derivative of the calibrated scan data, and the AFM_REPORT, a daily description of AFM mission activities. Data are sorted by time, with each data folder containing one sol's worth of data for each data type. The two scan data AFM RDR data products are formatted to have a detached ASCII PDS label. The SDR and SDD data products consist of five attached data tables. The first table is the header table that describes the AFM scan parameters and other important information pertaining to that scan, followed by the calibrated scan data in four sequential ASCII TABLE objects. AFM Parameters ============== The AFM scan parameters of interest for each scan are captured in the AFM_HEADER_TABLE, which is found at the beginning of the scan data. The following is a list of the header parameters. cmdTimewhole - Spacecraft command receipt time (whole seconds) cmdTimeremainder - Spacecraft command receipt time (remainder) readTimewhole - Time at which last scanline was received from the instrument readTimeremainder - Time at which last scanline was received from the instrument (remainder) dataLength - Record length (minus headers) Bytes Cols - Image width Points Lines - Image height Lines Direction - Scan direction mask. 1 = forward, 2 = backward Channel - 1 = error, 2 = height. channelGain - Determines the topographic height scale, Ranges from 0 to 8, with 0=full range (13.8 microns), and reducing by factors of 2 each time. i.e. Gain of 2 = 3.45 microns. refOMimage - Filename of the relevant OM image taken at the AFM scan position prior to start of the scan. This provides the context for interpreting the AFM scan data. opsToken - Ops token SwtsTemperature - Temperature of the SWTS just prior to the scan Scanrange - Scan range of slow and fast scan axes Height_scaling_factor - The scaling factor used to calibrate the height data (converts DNs to micrometers) Smoothing_factor - Number of points used in the Savitzky-Golay filter function. (for SDD only) AFM_OM_ref_x - The approximate location of the center of the AFM scan field relative to the OM image. X-coordinate in pixels. AFM_OM_ref_y - The approximate location of the center of the AFM scan field relative to the OM image. Y-coordinate in pixels. X-slope - The x-slope of the sub-strait relative to the x-y scanner. Y_slope - The y-slope of the sub-strait relative to the x-y scanner. AFM Processing ============== The AFM_SDR data type is calibrated scan data with x-y scan ranges. The height and scan range data will be calibrated based on data from calibration scans of the AFM pincushion substrate that will be performed just prior to the AFM scans on Mars. The scaling factor used for the conversion from DNs to micrometers will be included in the header of the RDR. Data are presented in units of micrometers and represented by real numbers to three decimal places. The error channel data in this data type are given in units of Volts with no in-situ calibration applied and represented by real numbers to six decimal places. The AFM_SDD data type is a line by line derivative of the calibrated scan data. By converting slope to grayscale, derivatives are a simple way to simulate what the eye would see if the topographs represented macroscopic surfaces illuminated from overhead. The derivative will be performed using the Savitsky-Golav method, following the raster-scanning direction because the discontinuities that are often present between lines would produce unacceptable noise in a true 2-dimensional derivative. Savitzky-Golay is a simple running filter that smoothes data while optionally performing various orders of derivatives, depending on the selection of filter parameters. It is equivalent to performing a local polynomial regression of degree k on at least k+1 equally-spaced points. For the AFM derivatives, selection of the number of points will be done manually depending on the noisiness of the data. The number of points used is recorded in the derivative header table in the smoothing_factor field. AFM Data ======== There are three AFM data types, the AFM_SDR, the AFM_SDD and the AFM REPORT. The AFM_SDR is the converted scan data record and the AFM_SDD is the scan data derivative. The first two data types are structured as five table units (files) that contain a 20 or 21-column 4-row header table, a 1536-column forward scan error table, a 1536-column forward scan height data table, a 1536-column backward scan error table, and a 1536-column backward scan height table. The AFM REPORT is a text file that describes the activities of a measurement day. See Appendix D for label examples and table structures. The AFM_SDR and AFM_SDD are organized as ASCII comma separated variable (CSV) data files containing data from a single scan of the AFM, with a detached ASCII text PDS label file for each data file. The AFM REPORT is an ASCII text file with an attached ASCII PDS label. Data from each measurement day will be grouped by instrument (AFM) and then by sol. AFM Ancillary Data ================== The AFM REPORT data type is ancillary data that explains the daily operations of the AFM. This is an ASCII text file with an attached PDS label that contains a narrative of events during an operational day. There will be one file per sol that is manually generated by an AFM team member. This file may contain items such as rationalemfor picking a particular target, difficulties in making a particular measurement, or other general information that is not easily captured elsewhere. AFM Coordinate System ===================== The AFM scan plane is a square that is rotated clockwise by 45-degrees and flipped vertically relative to an OM image. The axis that defines a scan line (the one along which scan samples are taken) is called the fast-axis (i.e. it increments/decrements more rapidly). The other axis determines scan line rows and is only incremented/decremented at the end of each scan line. Thus it is referred to as the slow-axis. The default fast-axis for the AFM is the x-axis, the default slow axis is the y-axis. Note that the scan point (0,0) is in the middle of the scan plane, i.e. for a 256 x 256 scan, the scan field goes from -127 to +127 in x and -127 and +127 in y. The starting point of a scan is not the origin of the scan field however, but the most negative x and y positions, i.e. for a 256 x 256 scan, the scan starts at the point (x=-127,y=-127) and proceeds to more positive values in both directions. The scan data is ordered such that the first line of data in the file represents the first line of data acquired by the AFM. The AFM acquires the scan data in an 'upward' (or positive 'y') direction in the AFM scan coordinate system. However, as described above and shown in Figure 4 1, the AFM coordinate system is flipped and rotated relative to the OM coordinate system. Thus, plotting the data in the order that it is shown in the file produces an 'upside down' image relative to the MECA-OM image. AFM Software ============ No AFM specific software will be provided at this time. As the data products are ASCII, any software that can handle ASCII files can be used to view the products. AFM Media/Format ================ As part of the MECA Non-Imaging RDR data set, AFM RDRs will be delivered using Internet file transfer protocol. Data formats will be based on standards for such products established by the Planetary Data System (PDS) [PDSSR2001]. WCL Overview ============ MECA's wet chemistry laboratory (WCL) comprises four single-use modules, each consisting of a beaker assembly and an actuator assembly. The modules mix soil samples with a leaching solution in a pressure vessel for electrochemical analysis. The scientific objective of the WCL is to determine the total pH, redox properties, and concentration of the principal aqueously solvated components of the acquired soil samples. Chemical data is returned by 26 distinct sensors, some redundant, lining the walls of each beaker. These measure: Temperature; pH (3); conductivity; oxidation-reduction potential; the anions chloride (2), bromide, and iodide; cations sodium, potassium, calcium, magnesium; and barium, used in a sulfate titration. Also included are electrodes for cyclic voltammetry, anodic stripping voltammetry, and chronopotentiometry (3). Lithium electrodes (2) are used as a reference relative to the known concentration of lithium salts in the solution. Sensors for nitrate, ammonium, dissolved oxygen and carbon dioxide, which for various reasons do not provide a quantitative measure of soil composition, are used only for context. A heater is imbedded in the base of the beaker to maintain water temperature during operation. A full description of the MECA WCL can be found in [KOUNAVESETAL2008]. The MECA WCL portion of the PHOENIX MARS MECA NON-IMAGING RDR V1.0 data set is a collection of chemical data, conductivity, cyclic voltammetry, chronopotentiometry, and pressure and temperature data that is sorted by time. Data types included in this data set are: ISE - Ion-Selective electrode data, CND - conductivity data, CV - Cyclic voltammetry data, CP - Chronopotentiometry data, PT - Pressure and temperature data. Data are sorted by data type and by time, with each data folder containing one sol's worth of data for each data type. WCL Parameters ============== Important measurement parameters are recorded in the header table found at the beginning of each of the RDRs. The header tables for the ISE, CND, and PT data types are identical, and contain the following parameters: PRODUCT_TYPE - The product type, MECA_WCL_CND PLANET_DAY_NUMBER - Mission Sol number on which the data was acquired PLANET_DAY_TYPE - The measurement day type. A = first day of measurements on a sample, B = second day of measurements on a sample. O = other. WCL_CELL - The number of the WCL cell(0-3) PARENT_EDR - The EDR filename from which the RDR was generated. START TIME - SCLK time of first record in data set. END TIME - SCLK time of last record in data set. X_RECORDS - Number of data points in time-series. In each case these parameters are followed by the equation or equations used to convert the raw DN values from the EDRs to the calibrated RDR physical unit values. In the PT case, the header table is followed by a conversion factor table that contains the conversion factors used in the DN to physical units equations. The conversion values found in the RDRs are the definitive values. The CV and CV data types contain the following header information: WCL_CELL - Number of the WCL cell (0-3) CMD_Time - This is the time that the command was issued from the spacecraft computer to the MECA subsystem across the serial interface. Units are seconds of Spacecraft Clock (SCLK). Read_time - This is the time that the data was returned to the spacecraft computer across the serial interface from the MECA subsystem. Units are seconds of Spacecraft Clock (SCLK) Mode - The instrument mode CV = 1 DO = 2 ASV = 3 CP_S1 = 4 CP_S2 = 5 CP_P = 6 Gain - The instrument gain setting which can equal 1,2,3, 4,5,6,or 7. mVMin or nAMin - The minimum scan value mVMax or nAMax - The maximum scan value CV_Scan_rate or CP_Scan_time - Time of scan or rate of scan in seconds. Number_of_Samples - Number of samples in the scan, maximum value is 2015. The CV and CP header information is preceded by the DN to physical unit conversion factors. The RDRs are the definitive source for the conversion factors. The WCL calibration report, located in the Calibration directory of this archive, is the definitive source for the conversion equations. WCL Processing ============== WCL RDR data products will be generated by the MECA Science Team using software at the SOC, JPL or their home institutions. The RDRs produced will be 'processed' data (NASA Level 1). The input will be one or more MECA non-imaging EDR or RDR data products and the output will be formatted according to the MECA Non-Imaging RDR SIS. In general, the processing involved in creating the MECA Non-Imaging RDRs is a conversion from EDR DN values to physical units using conversion equations and factors derived from ground based instrument calibrations. The details of the conversion equations and factors can be found in the MECA Non-imaging RDR SIS and the WCL Calibration report, both found in this archive. WCL Data ======== ISE --The ISE data type contains the mV value for each ISE sensor reading in the RDR. The readings are a result of a potential across the sensor's membrane/solution interface, the value of which is dependent on the activity of the selected ionic species in the beaker solution. CND --The MECA electrical conductivity (EC) data type holds the EC measurements in a time-series of two ranges of microsiemen per centimeter. The EC of a solution is a measure of its ability to carry a current and is thus directly proportional to the total concentration of dissolved ionic species in the water. CV -The CV data type contains a time-series of electrode potential (mV) and current (nA) data for measurements made by Conventional cyclic voltammetry using either a macro-electrode or an array of micro-electrodes; Anodic Stripping Voltammetry using the micro-electrode; and a Dissolved Oxygen measurement acquired with an ion selective electrode with CV-style detection. CP -The CP data type contains a time series of electrode potential (mV) and current (nA) data for measurements made with one of the three CP electrodes mounted in the WCL beaker walls. The CP electrodes include: two 1 mm diameter Ag electrodes (CP_S1 and CP_S2) and one 1 mm diameter Pt (CP_P) electrode. In a WCL CP measurement, which is sometime referred to a coulombic titration, the electrochemical cell potential is measured as the current is stepped (or ramped) from zero to a set current. PT -The PT data type contains time-series data of pressure measurements of the internal pressure sensor as well as temperature data from each of three sensors mounted on the water tank, the sample drawer, and in the beaker wall. The pressure and temperature readings apply to the active WCL cell (known from the command history), and the units of the RDR data are mbar for pressure and Celsius for temperature. The tank sensor is used to monitor and verify thawing of the stored leaching solution, while the drawer sensor monitors the operation of sample introduction and reagent addition actuators. The beaker sensor is critical for analysis of chemical data. WCL Ancillary Data ================== Ancillary data needed to convert any of the WCL data types from raw EDR DN values to physical units are given in the individual RDRs. Additional information on sensor calibrations can be found either in the WCL calibration report (Calibration Directory of this archive) or in [KOUNAVESETAL2008]. The ISE, CND and PT data types also contain an events table that records various events over the course of the sample analysis. This table records such things as the time of sample delivery to the analysis cell, and the time of additions to the sample. A full description of the events can be found in the MECA Non-Imaging RDR SIS. WCL Coordinate System ===================== Information pertaining to where each of the four samples (one per WCL cell) were taken is recorded in the sample OPS_TOKEN, found in the file name of each RDR. The OPS_TOKEN can be used to relate the RDRs to information from the Robotic Arm (RA). The RA is used to scoop Martian soil into the MECA WCL. Correlation of the RA OPS_TOKENs to the MECA WCL RDRs will give the users information about the conditions under which each sample was collected. WCL Software ============ No WCL specific software will be provided at this time. As the data products are ASCII, any software that can handle ASCII files can be used to view the products. WCL Media/Format ================ As part of the MECA Non-Imaging RDR data set, WCL RDRs will be delivered using Internet file transfer protocol. Data formats will be based on standards for such products established by the Planetary Data System (PDS) [PDSSR2001]. These data are available on-line from the Planetary Data System (PDS) at: http://pds-geosciences.wustl.edu/GEO/phx-m-meca-4-nirdr-v1/phxmec_1xxx/

Alternate Names

  • PHX-M-MECA-4-NIRDR-V1.0

Discipline

  • Planetary Science: Geology and Geophysics

Additional Information

Spacecraft

Experiments

Questions and comments about this data collection can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Michael H. HechtData ProviderNASA Jet Propulsion Laboratorymhecht@haystack.mit.edu
Dr. Michael H. HechtGeneral ContactNASA Jet Propulsion Laboratorymhecht@haystack.mit.edu
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