instrument : Alpha Particle X-Ray Spectrometer for RL
Instrument Overview =================== The Alpha Particle X-Ray Spectrometer (APXS) is an instrument that will provide information on the elemental composition of the comet surface. The instrument is based on the interaction of alpha particles and x-rays with matter. It operates in two modes: the alpha mode (Rutherford backscattering) and the x-ray mode for alpha-particle and x-ray induced x-ray spectroscopy. The APXS combines these methods in one single instrument while being low in mass and power consumption. Historically, there was also a proton mode that has been omitted in the new design in favor of an advanced x-ray mode. The acronym APXS stands for the old and new design. Using the x-ray mode, the Rosetta APXS is able to determine in-situ concentrations of elements from sodium to strontium at levels down to several hundred ppm. Light elements such as carbon, nitrogen and oxygen can be detected using the alpha mode, usually with sensitivity of 1 atom %. In addition, most of the elements are determined by both modes, albeit with different efficiency and accuracy. Hydrogen(and helium) cannot be measured at all by nature of the methods, although, water can still be inferred from any excess of oxygen (which APXS determines accurately) over what is required from the overall stoichiometry (assuming no other light elements in the sample). The Rosetta APXS consists of a sensor head, a deployment device and electronics. The sensor head contains Curium-244 alpha sources (with an activity of about 40 mCi at integration time and with a half-life of 18.11 years) that bombard the sample with alpha particles of an energy of about 5.5MeV and x-rays of about 14 to 21 keV (emitted by the Plutonium-240 daughter). The back-scattered alpha particles are measured by six alpha detectors and the x-ray radiation by one high-resolution x-ray detector (energy resolution, measured as full width at half maximum (FWHM), is 180 eV at 6.4 keV at temperatures below -40degC). Scientific Objectives ===================== The goal of the Rosetta APXS experiment is to determine the chemical composition of the cometary surface at the landing site and its potential alteration with time due to increase activity when the comet approaches the Sun. The data obtained will be used to characterize the surface of the comet, to obtain the gas/dust ratio, determine the chemical composition of the dust component, and to compare the dust with the composition of known meteorite types. These results will be brought into context with other measurements made on the lander and the orbiter to fully obtain a more complete picture of the present state of the comet, and to get insight into its evolution and origin. Calibration =========== In the laboratory, the instrument was calibrated in vacuum measuring a geological sample, called SSK-1 (already used for the MPF (Mars Pathfinder Rover Sojourner) and MER (Mars Exploration Rover) APXS) with known composition in a standard geometry (distance between sample surface and detector). The data from this sample are used to compare the performance and sensitivity of the Rosetta APXS with MPF APXS and MER APXS. This cross calibration mainly determines the energy scale, the detector efficiency and the quality of the alpha and the x-ray spectra ( endpoint sharpness in the alpha mode and FWHM of the x-ray lines in the x-ray mode). Using these instrument specific properties, the calibration of the Rosetta APXS can be achieved using the extensive MER calibration and future new calibration measurements tailored to cometary samples. Operational Considerations ========================== The APXS can store the current XRAM content if it is continuously powered with 5V on the KAL line. When it is powered OFF, the content gets lost and is restored with the PROM default values after the next power ON. Please note that after power ON, those values have to be uploaded if values different from the default ones need to be used. That is necessary for example in the case of changing the threshold in order to obtain response for low energies and in the case of the safe LG parameter to operate the deployment of the deployment device. Due to problems observed in previous payload checkouts and for security, the command for downloading the relevant spectra will be sent twice. In that way we assure that even in the case we may have some error with the download of the spectra, the probability of losing important science will be substantially reduced Detectors ========= Silicon drift detector for x-ray detection. 6 alpha solid state silicon detectors. Electronics =========== Details on the electronics of the instrument are described in the APXS ADP. Location ======== The sensor head is located on the outside of the lander, mounted in an opening of the balcony's floor. To bring the APXS in contact with the comet surface, it is moved by the deployment device that can lower and raise the sensor head by a command. Operational Modes ================= Normal mode - used to obtain energy spectra and during data transmission. Deployment mode - used to operate the deployment device. Subsystems ========== Not applicable Measured Parameters =================== Counts vs. energy spectra. 512 channels (1 to 14.5 KeV) for the X-ray mode and 256 channels (0.6 to 6 MeV) for the Alpha mode.

instrument : ALPHA PARTICLE X-RAY SPECTROMETER for MER2
Instrument Overview =================== The Alpha Particle X-Ray Spectrometer (APXS) is part of the Athena payload of the two Mars Exploration Rovers (MER). The APXS sensor head is attached to the turret of the Instrument Deployment Device (IDD) of the rover. The APXS is a very light-weight instrument for determining the major and minor elemental composition of Martian soils, rocks, and other geological materials at the MER landing sites. The sensor head has simply to be docked by the IDD on the surface of the selected sample. X-ray radiation, excited by alpha particles and x-rays of the radioactive sources, is recorded by a high-resolution x-ray detector. The x-ray spectra show elements starting from sodium up to yttrium depending on their concentrations. The backscattered alpha spectra, measured by a ring of detectors, provide additional data on carbon and oxygen. By means of a proper calibration, the elemental concentrations are derived. Together with data from the two other Athena instruments mounted on the IDD, the samples under investigation can be fully characterized. Key APXS objectives are the determination of the chemistry of crustal rocks and soils and the examination of water-related deposits, sediments, or evaporates. Using the rock abrasion tool (RAT) attached to the IDD, issues of weathering can be addressed by measuring natural and abraded surfaces of rocks. Information in this instrument description is taken from The New Athena Alpha Particle X-Ray Spectrometer (APXS) for the Mars Exploration Rovers mission paper [RIEDERETAL2003]. See this paper for more details. Scientific Objectives ===================== The chief scientific objective of the APXS is: 1) to determine the major and minor elemental composition of Martian soils, rocks, and other geological materials at the MER landing sites Calibration =========== During the calibration campaign in the Max Plank Institute Mainz laboratory many geostandards were measured. These standards are powdered geological samples, whose elemental concentrations are certified by qualified institutions. The two flight instruments containing their flight sources were calibrated using 11 validated samples (8 geostandards and 3 meteorites) and a set of oxide and metal standards. A check of the performance of the instrument after the landing on Mars will be done making use of the internal calibration target on the doors and the Compositional Calibration Target (CCT) that is mounted on the rover chassis in reach of the IDD. The x-ray spectrum of the internal calibration target shows gold, nickel, and copper lines. The target consists of a set of thin layers of gold, Kapton (carbon), and nickel on top of the copper-beryllium body of the doors. Energy calibration, FWHM, and linearity can be checked by evaluation of the copper and gold lines and comparison with pre-launch data. Contamination of the beryllium entrance window of the x-ray detector will be noticeable by an intensity reduction of the low-energy M lines of gold compared to the L lines. Energy calibration can be checked with the position of the gold peak (a peak and not a step because of the small thickness of the Au layer). The carbon step provides an additional check of consistency. The CCT consists of a magnetite plate. This target was designed for the needs of the MB, but, it can also be used by the APXS to check its FWHM usually determined for the 6.4-keV line of iron. As the target is mounted on the outside of the rover, it will eventually be covered with dust, but the line shape of the Fe line will not be affected. Operational Considerations ========================== There are a few considerations that must be taken into account to acquire the best data possible: 1) To search for trace elements, two to four hours are sufficient for the x-ray mode. The search for carbon requires at least eight hours for the alpha mode as the alpha sensitivity is low. X-ray and alpha mode always operate together. 2) To properly make an APXS measurement, the sensor head has to be correctly 'docked' at the selected sample by the IDD. The nominal APXS docking procedure is the following: Use images taken by the rover's front cameras: Navcams (navigation cameras) and/or Hazcams (hazard avoidance cameras) to calculate the IDD positioning Open the doors by pressing the APXS contact ring against the CCT or any other solid surface of the rover Position the APXS contact ring up against a selected sample area with a positional accuracy of 10 mm and 10 degrees on a target not previously contacted, or 4 mm and 3 degrees for a target previously contacted by any one of the IDD instruments After data acquisition, the APXS doors are closed by rotating the turret past a roller until the release lever is actuated 3) For touch-and-go operations, optimum resolution for the x-ray detector is obtained at temperatures of 248 K, and the shortest measurement time should be at least 15 minutes Detectors ========= The sensor head is packaged in a cylindrical enclosure 53 mm in diameter and 84 mm in length and terminates in an insulating flange of 68 mm x 68 mm. The front part facing the sample contains the xray detector, mounted on the axis of the instrument, a cylindrical source holder with six alpha sources, and six rectangular alpha detectors. The coaxial arrangement of sources and detectors for alpha particles and x-rays assures that both detectors 'see' the same intensity distribution across the sample. Use of a high resolution x-ray detector (silicon drift detector with 10 mm^2 active area, a 5 micron thick Be-window and an energy resolution of about 160 eV @ 5.9 keV) permits high quality measurements. The advanced detector versions were provided by KETEK, Munich, Germany. There is a second group of detectors, identical to the alpha detectors, but not exposed to alpha particles from the sample.These detectors measure the background contribution to alpha spectra due to cosmic radiation at the surface of Mars and high energy gamma background of the Cm sources as well as the Moessbauer source. The field of view for the x rays is delineated by means of a collimator in front of the detector: the collimator is formed by two apertures made from Zr, one immediately in front of the detector and one in the central orifice of the source holder. The alpha sources (6 pellets) are contained in a source holder that attaches to the sensor head with a spring loaded bayonet-style mechanism. This permits quick and easy exchange of the sources without the need to disassemble the sensor head. The sources are covered with 2.5 micron thick titanium foils, turning them into 'quasi-closed' sources (hermetically sealed sources are under development, but were not available for this mission). The foils prevent contamination of samples with source material, emitted from the sources as a result of 'recoil sputtering', and the same time reduce the energy of the alpha particles from 5.80 MeV to 5.17 MeV, thereby avoiding a resonance in the 12C(alpha, alpha')12C reaction at ca. 5.7 MeV (Figure 6). This measure, together with an optimized design of the source-collimator-detector geometry, significantly reduces the background signals from carbon and oxygen in the Martian CO2-atmosphere. Nevertheless, this background signal remains the limiting factor for the determination of carbon in the samples. Electronics =========== The main electronics consists of the analog signal conditioning segments (6-pole Gaussian filter amplifiers, threshold discriminators and peak detectors), an analog multiplexer, a 16-bit analog-to-digital converter and an 8-bit microcontroller. Control logic determines the presence of a relevant signal and generates an interrupt in the microcontroller. To avoid additional noise in the analog signal chain, the microcontroller is kept in idle mode until the analog signal is processed and buffered in the peak detectors. Selection of the appropriate multiplexer input, conversion of the signal amplitude to a digital number and registration of the signal by incrementing the number of counts in the corresponding amplitude channel of the respective detector is then handled by the microcontroller. Conversion time is typically 200 microseconds. A digital temperature compensation routine that minimizes the influence of temperature changes during long measurements adds another 100 microseconds. For a mean count rate of 100 Hz, a total dead time of below 5 % is achieved. The microcontroller is equipped with a watchdog circuit that performs a soft reset in case of an abnormal program flow. The data are stored in 32 Kbyte SRAM that are buffered by a battery located on the main electronics board. The interface for commanding the instrument and transfer of data consists of an RS 422 serial link. Power is provided to the instrument directly from the board battery (nominally 28 V); voltages required by the electronics (5 V digital, +/-5 V analog and +/-12 V analog) are generated by its own power converter and filters. The x-ray spectrum is divided into 512 channels. The lower threshold is fixed at ~850 eV. This is sufficient to detect Na at 1040 eV. The upper energy limit is about 16 keV. The spectral range includes the K lines up to Zr and the L and M lines of higher Z elements. It also contains elastic scattered Pu lines at 14.3 keV and 12.6 keV, as well as inelastic scattered peaks. The alpha and background spectra use 256 channels and range up to about 6 MeV. Location ======== The APXS sensor head is attached to the turret of the Instrument Deployment Device (IDD) of the rover. Measured Parameters =================== The APXS measures x-ray radiation and backscattered alpha spectra. These measurements can determine the elemental composition of the target on which it is docked.

instrument : ALPHA PARTICLE X-RAY SPECTROMETER for MSL
Instrument Overview =================== The APXS (Alpha-Particle X-ray Spectrometer) for MSL is an improved version of the APXS that flew successfully on Pathfinder and the Mars Exploration Rovers Spirit and Opportunity [RIEDERETAL1997A, RIEDERETAL1997B, RIEDERETAL2003, GELLERETAL2006]. The MSL APXS takes advantage of a combination of the terrestrial standard methods Particle-Induced X-ray Emission (PIXE) and X-ray Fluorescence (XRF) to determine elemental chemistry. It uses curium-244 sources for X-ray spectroscopy to determine the abundance of major elements down to trace elements from sodium to bromine and beyond. The instrument consists of a main electronics unit in the rover's body and a sensor head mounted on the robotic arm. Measurements are taken by deploying the sensor head towards a desired sample, placing the sensor head in contact or hovering typically less than 2 cm away, and measuring the emitted X-ray spectrum for 15 minutes to 3 hours without the need of further interaction by the rover. At the end of the measurement, the rover retrieves the science data of 32 kilobytes, containing up to 13 consecutively taken spectra and engineering data. The internal APXS software splits the total measurement into equal time slots with an adjustable cycle time parameter. This allows us to check for repeatability and to select spectra with sufficient spectral quality. The MSL APXS can activate an internal Peltier cooler for the X-ray detector chip. This results in a sufficient spectral resolution (FWHM) of below 200 eV at 6.4 keV below ~ -5 deg C and best FWHM of < 150 eV below ~ -15 deg C environmental temperature. Compared to the APXS on MER, where the best FWHM was reached at temperatures below ~ -45 deg C, this allows a significantly larger operational time window for APXS analysis. The MSL APXS has approximately 3 times the sensitivity for low Z (atomic number) elements and approximately 6 times for higher Z elements than the MER APXS. A full analysis with detection limits of 100 ppm for Ni and ~ 20 ppm for Br now requires 3 hours, while quick look analysis for major and minor elements at ~ 0.5% abundance, such as Na, Mg, Al, Si, Ca, Fe, or S, can be done in 10 minutes or less. On MER, the elements detected by the APXS in rock and soil samples are typically Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Zn, and Br [RIEDERETAL2004] [GELLERTETAL2006]. Elevated levels of Ge, Ga, Pb, and Rb were found in some of the MER samples [CLARKETAL2007]. The sampled area is about 1.7 cm in diameter when the instrument is in contact with the sample. A standoff results in gradually lower intensity and an increased diameter of the measured spot. Low Z element X-rays stem from the topmost 5 microns of the sample, higher Z elements like Fe are detected from the upper ~50 microns. Sample preparation is not needed; the APXS results average the composition over the sampled area and the oxide abundances measured are renormalized to 100%. However, on MSL, a dust removal tool (brush) is available to remove loose material from a rock surface before making an APXS measurement. The major improvements and changes compared to the MER APXS are: * Improved sensitivity by a factor 3 giving full analysis within ~3 hours * Additional improved sensitivity for high Z elements by increased X-ray source strength * Operable during Martian day by using Peltier cooler for the X-ray detector * Basaltic calibration target mounted on the rover (on the robotic arm azimuth actuator housing), dedicated for the APXS * No alpha channel (no Rutherford Backscattering spectroscopy) * Compressed short duration X-ray spectra ( ~10 seconds ) can be used to steer the arm movement in a 'proximity mode' Principal Investigator ---------------------- The APXS Principal Investigator is Ralf Gellert, University of Guelph, Canada. The MSL APXS is funded by the Canadian Space Agency, with MDA Corporation as prime subcontractor. Funding for the science team comes from CSA, NASA, and the University of Guelph. Scientific Objectives ===================== The main objective of the APXS is to characterize the geological context of the rover surroundings and to investigate the processes that formed the rocks and soils. The high precision and low detection limits, especially for salt forming elements like S, Cl, and Br, allow identification of local anomalies and guided in-situ sample selection for the analytical instruments of MSL. The rover observation tray for processed samples allows the APXS to provide additional characterization of the samples collected and prepared for the analytical instruments, connecting the analytical instrument results with the in-situ samples. MSL sample preparation with the brush allows in-situ APXS investigations of thin alteration rinds or near-surface layers or veins which cannot be collected by the drill for the analytical instruments. Another important aspect of the APXS investigation is to relate the chemical composition of the MSL landing site and the results from the MSL payload to what has been found by the previous landed missions, which used similar X-ray spectroscopy methods. The elemental data can be used to extract normative mineralogy either from scratch or using constraints from the mineralogy provided by CheMin. A newly developed method [CAMPBELLETAL2008] using the backscattered peaks of the primary X-ray radiation allows detection of X-ray invisible compounds like bound water or carbonates, if present in significant amounts ( greater than ~5% by weight). Calibration =========== The APXS was fully calibrated using standard geological samples in the laboratory. An onboard basaltic rock slab, surrounded by a nickel plate, is used periodically to check the performance and calibration of the instrument. The data analysis is theoretically well understood and delivers unambiguous element identification and accuracy on the order of ~10%, mainly limited by microscopic sample heterogeneity (i.e., grain size effects). The APXS data analysis is fast and allows a quick turnaround of results used for tactical rover operations. Operational Considerations ========================== The APXS instrument showed an abnormal behavior on Mars, unseen in the lab during calibration and not seen in any other APXS instrument so far. In some integrations the instrument stopped counting any real x-ray counts in the midst of the data acquisition. If this happens the last sub-spectra don't contain real events, only artificial counts around the lowest detectable energy channel. This behavior, dubbed 'lockup', is currently under investigation. After any powercycle, the effect is gone. To mitigate the loss of scientific data, for longer data acquisitions the integration is therefore split into two integrations with a power cycle in the middle. This is to mitigate the risk that all data is lost if the lockup happens early in a single integration.

instrument : ALPHA PARTICLE X-RAY SPECTROMETER for MER1
Instrument Overview =================== The Alpha Particle X-Ray Spectrometer (APXS) is part of the Athena payload of the two Mars Exploration Rovers (MER). The APXS sensor head is attached to the turret of the Instrument Deployment Device (IDD) of the rover. The APXS is a very light-weight instrument for determining the major and minor elemental composition of Martian soils, rocks, and other geological materials at the MER landing sites. The sensor head has simply to be docked by the IDD on the surface of the selected sample. X-ray radiation, excited by alpha particles and x-rays of the radioactive sources, is recorded by a high-resolution x-ray detector. The x-ray spectra show elements starting from sodium up to yttrium depending on their concentrations. The backscattered alpha spectra, measured by a ring of detectors, provide additional data on carbon and oxygen. By means of a proper calibration, the elemental concentrations are derived. Together with data from the two other Athena instruments mounted on the IDD, the samples under investigation can be fully characterized. Key APXS objectives are the determination of the chemistry of crustal rocks and soils and the examination of water-related deposits, sediments, or evaporates. Using the rock abrasion tool (RAT) attached to the IDD, issues of weathering can be addressed by measuring natural and abraded surfaces of rocks. Information in this instrument description is taken from The New Athena Alpha Particle X-Ray Spectrometer (APXS) for the Mars Exploration Rovers mission paper [RIEDERETAL2003]. See this paper for more details. Scientific Objectives ===================== The chief scientific objective of the APXS is: 1) to determine the major and minor elemental composition of Martian soils, rocks, and other geological materials at the MER landing sites Calibration =========== During the calibration campaign in the Max Plank Institute Mainz laboratory many geostandards were measured. These standards are powdered geological samples, whose elemental concentrations are certified by qualified institutions. The two flight instruments containing their flight sources were calibrated using 11 validated samples (8 geostandards and 3 meteorites) and a set of oxide and metal standards. A check of the performance of the instrument after the landing on Mars will be done making use of the internal calibration target on the doors and the Compositional Calibration Target (CCT) that is mounted on the rover chassis in reach of the IDD. The x-ray spectrum of the internal calibration target shows gold, nickel, and copper lines. The target consists of a set of thin layers of gold, Kapton (carbon), and nickel on top of the copper-beryllium body of the doors. Energy calibration, FWHM, and linearity can be checked by evaluation of the copper and gold lines and comparison with pre-launch data. Contamination of the beryllium entrance window of the x-ray detector will be noticeable by an intensity reduction of the low-energy M lines of gold compared to the L lines. Energy calibration can be checked with the position of the gold peak (a peak and not a step because of the small thickness of the Au layer). The carbon step provides an additional check of consistency. The CCT consists of a magnetite plate. This target was designed for the needs of the MB, but, it can also be used by the APXS to check its FWHM usually determined for the 6.4-keV line of iron. As the target is mounted on the outside of the rover, it will eventually be covered with dust, but the line shape of the Fe line will not be affected. Operational Considerations ========================== There are a few considerations that must be taken into account to acquire the best data possible: 1) To search for trace elements, two to four hours are sufficient for the x-ray mode. The search for carbon requires at least eight hours for the alpha mode as the alpha sensitivity is low. X-ray and alpha mode always operate together. 2) To properly make an APXS measurement, the sensor head has to be correctly 'docked' at the selected sample by the IDD. The nominal APXS docking procedure is the following: Use images taken by the rover's front cameras: Navcams (navigation cameras) and/or Hazcams (hazard avoidance cameras) to calculate the IDD positioning Open the doors by pressing the APXS contact ring against the CCT or any other solid surface of the rover Position the APXS contact ring up against a selected sample area with a positional accuracy of 10 mm and 10 degrees on a target not previously contacted, or 4 mm and 3 degrees for a target previously contacted by any one of the IDD instruments After data acquisition, the APXS doors are closed by rotating the turret past a roller until the release lever is actuated 3) For touch-and-go operations, optimum resolution for the x-ray detector is obtained at temperatures of 248 K, and the shortest measurement time should be at least 15 minutes Detectors ========= The sensor head is packaged in a cylindrical enclosure 53 mm in diameter and 84 mm in length and terminates in an insulating flange of 68 mm x 68 mm. The front part facing the sample contains the xray detector, mounted on the axis of the instrument, a cylindrical source holder with six alpha sources, and six rectangular alpha detectors. The coaxial arrangement of sources and detectors for alpha particles and x-rays assures that both detectors 'see' the same intensity distribution across the sample. Use of a high resolution x-ray detector (silicon drift detector with 10 mm^2 active area, a 5 micron thick Be-window and an energy resolution of about 160 eV @ 5.9 keV) permits high quality measurements. The advanced detector versions were provided by KETEK, Munich, Germany. There is a second group of detectors, identical to the alpha detectors, but not exposed to alpha particles from the sample.These detectors measure the background contribution to alpha spectra due to cosmic radiation at the surface of Mars and high energy gamma background of the Cm sources as well as the Moessbauer source. The field of view for the x rays is delineated by means of a collimator in front of the detector: the collimator is formed by two apertures made from Zr, one immediately in front of the detector and one in the central orifice of the source holder. The alpha sources (6 pellets) are contained in a source holder that attaches to the sensor head with a spring loaded bayonet-style mechanism. This permits quick and easy exchange of the sources without the need to disassemble the sensor head. The sources are covered with 2.5 micron thick titanium foils, turning them into 'quasi-closed' sources (hermetically sealed sources are under development, but were not available for this mission). The foils prevent contamination of samples with source material, emitted from the sources as a result of 'recoil sputtering', and the same time reduce the energy of the alpha particles from 5.80 MeV to 5.17 MeV, thereby avoiding a resonance in the 12C(alpha, alpha')12C reaction at ca. 5.7 MeV (Figure 6). This measure, together with an optimized design of the source-collimator-detector geometry, significantly reduces the background signals from carbon and oxygen in the Martian CO2-atmosphere. Nevertheless, this background signal remains the limiting factor for the determination of carbon in the samples. Electronics =========== The main electronics consists of the analog signal conditioning segments (6-pole Gaussian filter amplifiers, threshold discriminators and peak detectors), an analog multiplexer, a 16-bit analog-to-digital converter and an 8-bit microcontroller. Control logic determines the presence of a relevant signal and generates an interrupt in the microcontroller. To avoid additional noise in the analog signal chain, the microcontroller is kept in idle mode until the analog signal is processed and buffered in the peak detectors. Selection of the appropriate multiplexer input, conversion of the signal amplitude to a digital number and registration of the signal by incrementing the number of counts in the corresponding amplitude channel of the respective detector is then handled by the microcontroller. Conversion time is typically 200 microseconds. A digital temperature compensation routine that minimizes the influence of temperature changes during long measurements adds another 100 microseconds. For a mean count rate of 100 Hz, a total dead time of below 5 % is achieved. The microcontroller is equipped with a watchdog circuit that performs a soft reset in case of an abnormal program flow. The data are stored in 32 Kbyte SRAM that are buffered by a battery located on the main electronics board. The interface for commanding the instrument and transfer of data consists of an RS 422 serial link. Power is provided to the instrument directly from the board battery (nominally 28 V); voltages required by the electronics (5 V digital, +/-5 V analog and +/-12 V analog) are generated by its own power converter and filters. The x-ray spectrum is divided into 512 channels. The lower threshold is fixed at ~850 eV. This is sufficient to detect Na at 1040 eV. The upper energy limit is about 16 keV. The spectral range includes the K lines up to Zr and the L and M lines of higher Z elements. It also contains elastic scattered Pu lines at 14.3 keV and 12.6 keV, as well as inelastic scattered peaks. The alpha and background spectra use 256 channels and range up to about 6 MeV. Location ======== The APXS sensor head is attached to the turret of the Instrument Deployment Device (IDD) of the rover. Measured Parameters =================== The APXS measures x-ray radiation and backscattered alpha spectra. These measurements can determine the elemental composition of the target on which it is docked.

data set : MSL MARS ALPHA PARTICLE X-RAY SPECTROMETER 4/5 RDR V1.0
Calibrated spectra and oxide weight percent data derived from observations of the APXS instrument aboard the Mars Science Laboratory rover.

data set : MSL MARS ALPHA PARTICLE X-RAY SPECTROMETER 2 EDR V1.0
Unprocessed experiment data copied from the memory buffer of the APXS instrument aboard the Mars Science Laboratory rover.

data set : MER 1 MARS ALPHA PARTICLE X-RAY SPECTROMETER 2 XRAYSPEC V1.0
This data set contains Alpha Particle X-ray Spectrometer (APXS) X-ray Spectra Science Reduced Data Records (RDRs) acquired by Opportunity (MER 1) during the Mars Exploration Rover Mission.

data set : ROSETTA-LANDER CALIBRATION APXS 2 PHC V1.0
This data set contains the data referred to PHC Mission Phase (Cruise)

data set : MER ALPHA PARTICLE X-RAY SPECTROMETER 5 OXIDE ABUNDANCE V1.0
Mars Exploration Rover Alpha Particle X-ray Spectrometer Oxide Abundance Data

data set : MER 2 MARS ALPHA PARTICLE X-RAY SPECTROMETER 2 XRAYSPEC V1.0
This data set contains Alpha Particle X-ray Spectrometer (APXS) X-ray Spectra Science Reduced Data Records (RDRs) acquired by Spirit (MER 2) during the Mars Exploration Rover Mission.

data set : MER 2 MARS ALPHA PARTICLE X-RAY SPECTROMETER 2 EDR OPS V1.0
This data set contains Alpha Particle X-ray Spectrometer (APXS) Operations Experiment Data Records (EDRs) acquired by Spirit (MER 2) during the Mars Exploration Rover Mission.

data set : MER 1 MARS ALPHA PARTICLE X-RAY SPECTROMETER 2 EDR OPS V1.0
Mars Exploration Rover 1 Alpha Particle X-ray Spectrometer Experiment Data Record

collection : MER1 APXS Xray Spectra (Partially Processed) Data Collection
This collections contains Xray Spectra (Partially Processed) data from the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 1 (Opportunity). Raw APXS data have been converted to ASCII tables and spectra from previous integrations have been removed.

collection : MER1 APXS Partially Processed Miscellaneous Collection
This collection contains miscellaneous files pertaining to the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 1 (Opportunity), in particular the PDS3 index table.

collection : MER1 APXS Raw Document Collection
This collection contains documents pertaining to the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 1 (Opportunity).

collection : MER1 APXS Calibration Collection
This collection contains calibration data and documents pertaining to the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 1 (Opportunity). The files are duplicates of files in the APXS raw data bundle.

bundle : MER1 APXS Xray Spectra (Partially Processed) Data Bundle
This bundle contains Xray Spectra (Partially Processed) data from the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 1 (Opportunity). Raw APXS data have been converted to ASCII tables and spectra from previous integrations have been removed.

collection : Overview of MSL APXS Targets from Sol 0 to 2301
Supporting Information for: Elemental composition and chemical evolution of geologic materials in Gale crater, Mars: APXS results from Bradbury Landing to the Vera Rubin Ridge

collection : MER2 APXS Raw Data Collection
This collection contains raw data from the Alpha Particle X-ray Spectrometer on Mars Exploration Rover-2 (Spirit).

bundle : MER2 APXS Raw Data Bundle
This bundle contains raw data from the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 2 (Spirit).

collection : MER2 APXS Raw Miscellaneous Collection
This collection contains miscellaneous files pertaining to the Alpha Particle X-ray Spectrometer on Mars Exploration Rover-2 (Spirit), in particular the PDS3 index table.

collection : MER2 APXS Raw Document Collection
This collection contains documents pertaining to the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 2 (Spirit).

collection : MER2 APXS Calibration Collection
This collection contains calibration data and documents pertaining to the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 2 (Spirit).

collection : MSL APXS Raw Data Collection
This collections contains X-ray Spectra and Oxide data from the Alpha Particle X-ray Spectrometer on Mars Science Laboratory (Curiosity).

collection : MSL APXS Raw Miscellaneous Collection
This collection contains miscellaneous files pertaining to the Alpha Particle X-ray Spectrometer on Mars Science Laboratory (Curiosity), in particular the PDS3 index table.

collection : MSL APXS Raw Extras Collection
This collections contains a list of activities conducted by the Alpha Particle X-ray Spectrometer on Mars Science Laboratory (Curiosity).

collection : MSL APXS Raw Document Collection
This collection contains documents pertaining to the Alpha Particle X-ray Spectrometer on Mars Science Laboratory (Curiosity).

collection : MSL APXS Raw Catalog Collection
This collection contains miscellaneous files pertaining to the Alpha Particle X-ray Spectrometer on Mars Science Laboratory (Curiosity), in particular the PDS3 catalog files.

bundle : MSL APXS Raw Bundle
This bundle contains raw data from the Alpha Particle X-ray Spectrometer on Mars Science Laboratory (Curiosity).

bundle : MER APXS Composite Spectra Bundle
This bundle contains a library of target characteristics, metadata, composite spectra, and concentrations created from individual spectra acquired by the Alpha Particle X-ray Spectrometers on Mars Exploration Rovers 1 and 2 (Opportunity and Spirit).

collection : MER APXS Composite Spectra Library
This collection contains a library of target characteristics, metadata, composite spectra, and concentrations created from individual spectra acquired by the Alpha Particle X-ray Spectrometers on Mars Exploration Rovers 1 and 2 (Opportunity and Spirit).

collection : MER1 APXS Raw Data Collection
This collection contains raw data from the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 1 (Opportunity).

collection : MER1 APXS Raw Miscellaneous Collection
This collection contains miscellaneous files pertaining to the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 1 (Opportunity), in particular the PDS3 index table.

bundle : MER1 APXS Raw Data Bundle
This bundle contains raw data from the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 1 (Opportunity).

collection : MER1 APXS Raw Document Collection
This collection contains documents pertaining to the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 1 (Opportunity).

collection : MER1 APXS Calibration Collection
This collection contains calibration data and documents pertaining to the Alpha Particle X-ray Spectrometer on Mars Exploration Rover 1 (Opportunity).

bundle : Mars Target Encyclopedia Database Bundle
Information for how to cite the MTE bundle.

collection : Mars Target Encyclopedia MER-1 Collection
MER-1 collection for the Mars Target Encyclopedia bundle

collection : Mars Target Encyclopedia MER-2 Collection
MER-2 collection for the Mars Target Encyclopedia bundle

bundle : Overview of MSL APXS Targets from Sol 0 to 2301
Supporting Information for: Elemental composition and chemical evolution of geologic materials in Gale crater, Mars: APXS results from Bradbury Landing to the Vera Rubin Ridge

collection : MER Contact Science Target List Data Collection
Data product collection for the MER contact science target bundle

collection : MER APXS Oxide Data Collection
This collection contains oxide data from the Alpha Particle X-ray Spectrometer on the Mars Exploration Rovers.

collection : MER APXS Oxide Miscellaneous Collection
This collection contains miscellaneous files pertaining to the Alpha Particle X-ray Spectrometer Mars Exploration Rovers Oxide data set, in particular the PDS3 index table.

bundle : MER APXS Derived Oxide Data Bundle
This bundle contains oxide abundances derived from the Alpha Particle X-ray Spectrometer data on both Mars Exploration Rovers (Spirit and Opportunity).

collection : MER APXS Oxide Document Collection
This collection contains documents pertaining to the Alpha Particle X-ray Spectrometer on Mars Exploration Rover Oxide data set.

collection : Supporting Information Document for Manganese Mobility in Gale Crater, Mars: Leached Bedrock and Localized Enrichments
Supporting Information Document for Manganese Mobility in Gale Crater, Mars: Leached Bedrock and Localized Enrichments

collection : Summary and Geological Context of MSL APXS Targets from Sol 0 to 3076
Supporting Information for: Manganese Mobility in Gale Crater, Mars: Leached Bedrock and Localized Enrichments

bundle : Summary and Geological Context of MSL APXS Targets from Sol 0 to 3076
Supporting Information for: Manganese Mobility in Gale Crater, Mars: Leached Bedrock and Localized Enrichments

collection : MER Contact Science Target List Context Collection
Context inventory for MER contact science targets

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