Instrument Calibrations and Data Analysis Procedures for the NEAR X-Ray Spectrometer
TL;DR: The X-ray spectrometer onboard the Near Earth Asteroid Rendezvous spacecraft will measure X-rays from the surface of 433 Eros in the energy region 0.7-10 keV as discussed by the authors.
About: This article is published in Icarus.The article was published on 2000-10-01. It has received 28 citations till now. The article focuses on the topics: Spectrometer.
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TL;DR: In this paper, the analysis of 205 spatially resolved measurements of the surface composition of Mercury from MESSENGER's X-Ray Spectrometer is presented, and the surface footprints of these measurements are categorized according to geological terrain.
Abstract: [1] We present the analysis of 205 spatially resolved measurements of the surface composition of Mercury from MESSENGER’s X-Ray Spectrometer. The surface footprints of these measurements are categorized according to geological terrain. Northern smooth plains deposits and the plains interior to the Caloris basin differ compositionally from older terrain on Mercury. The older terrain generally has higher Mg/Si, S/Si, and Ca/Si ratios, and a lower Al/Si ratio than the smooth plains. Mercury’s surface mineralogy is likely dominated by high-Mg mafic minerals (e.g., enstatite), plagioclase feldspar, and lesser amounts of Ca, Mg, and/or Fe sulfides (e.g., oldhamite). The compositional difference between the volcanic smooth plains and the older terrain reflects different abundances of these minerals and points to the crystallization of the smooth plains from a more chemically evolved magma source. High-degree partial melts of enstatite chondrite material provide a generally good compositional and mineralogical match for much of the surface of Mercury. An exception is Fe, for which the low surface abundance on Mercury is still higher than that of melts from enstatite chondrites and may indicate an exogenous contribution from meteoroid impacts.
175 citations
TL;DR: In this article, the major-element composition of the surface of Mercury was mapped from orbital MESSENGER X-Ray Spectrometer measurements, and the results revealed highly variable compositions (e.g., Mg/Si and Al/Si range over 0.1 − 0.8 and 0.4, respectively).
165 citations
Cites methods from "Instrument Calibrations and Data An..."
...A “balanced filter” approach (Starr et al., 2000) was therefore employed, in which thin foils of Mg and Al placed in front of two GPCs provide selective absorption at different energies and allow the fluorescent signals from these elements to be deconvolved (Adler et al., 1972; Trombka et al.,…...
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01 Sep 2012
TL;DR: In this article, the analysis of 205 spatially resolved measurements of the surface composition of Mercury from MESSENGER's X-Ray Spectrometer is presented, and the surface footprints of these measurements are categorized according to geological terrain.
Abstract: [1] We present the analysis of 205 spatially resolved measurements of the surface composition of Mercury from MESSENGER’s X-Ray Spectrometer. The surface footprints of these measurements are categorized according to geological terrain. Northern smooth plains deposits and the plains interior to the Caloris basin differ compositionally from older terrain on Mercury. The older terrain generally has higher Mg/Si, S/Si, and Ca/Si ratios, and a lower Al/Si ratio than the smooth plains. Mercury’s surface mineralogy is likely dominated by high-Mg mafic minerals (e.g., enstatite), plagioclase feldspar, and lesser amounts of Ca, Mg, and/or Fe sulfides (e.g., oldhamite). The compositional difference between the volcanic smooth plains and the older terrain reflects different abundances of these minerals and points to the crystallization of the smooth plains from a more chemically evolved magma source. High-degree partial melts of enstatite chondrite material provide a generally good compositional and mineralogical match for much of the surface of Mercury. An exception is Fe, for which the low surface abundance on Mercury is still higher than that of melts from enstatite chondrites and may indicate an exogenous contribution from meteoroid impacts.
156 citations
Vikram Sarabhai Space Centre1, Marshall Space Flight Center2, Southwest Research Institute3, University of Kansas4, Johns Hopkins University Applied Physics Laboratory5, University College London6, Harvard University7, University of Bergen8, Lawrence Livermore National Laboratory9, Goddard Space Flight Center10
TL;DR: In this paper, the authors present a review of the X-ray emission from the solar system bodies, excluding the Sun, and an overview of the main source mechanisms of Xray production at each object.
150 citations
TL;DR: The X-Ray Spectrometer (XRS) onboard the MESSENGER spacecraft has been used to measure the surface elemental composition of the terrestrial planets by observing the Kα lines for the elements Mg, Al, Si, S, Ca, Ti and Fe as discussed by the authors.
Abstract: NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission will further the understanding of the formation of the planets by examining the least studied of the terrestrial planets, Mercury. During the one-year orbital phase (beginning in 2011) and three earlier flybys (2008 and 2009), the X-Ray Spectrometer (XRS) onboard the MESSENGER spacecraft will measure the surface elemental composition. XRS will measure the characteristic X-ray emissions induced on the surface of Mercury by the incident solar flux. The Kα lines for the elements Mg, Al, Si, S, Ca, Ti, and Fe will be detected. The 12° field-of-view of the instrument will allow a spatial resolution that ranges from 42 km at periapsis to 3200 km at apoapsis due to the spacecraft’s highly elliptical orbit. XRS will provide elemental composition measurements covering the majority of Mercury’s surface, as well as potential high-spatial-resolution measurements of features of interest. This paper summarizes XRS’s science objectives, technical design, calibration, and mission observation strategy.
133 citations
Cites background from "Instrument Calibrations and Data An..."
...The XRS instrument owes much of its heritage to the X-ray/gamma-ray spectrometer (XGRS) instrument on the Near Earth Asteroid Rendezvous (NEAR) Shoemaker mission (Starr et al. 2000)....
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References
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Book•
01 Jan 1979
TL;DR: In this paper, the authors present a detailed analysis of the effect of different types of detectors on the performance of the detection of neutrons and their effect on the detection efficiency and error prediction.
Abstract: Chapter 1 Radiation Sources. I. Units And Definitions. II. Fast Electron Sources. III. Heavy Charged Particle Sources. IV. Sources Of Electromagnetic Radiation. V. Neutron Sources. Chapter 2 Radiation Interactions. I. Interaction Of Heavy Charged Particles. II. Interaction Of Fast Electrons. III. Interaction Of Gamma Rays. IV. Interaction Of Neutrons. V. Radiation Exposure And Dose. Chapter 3 Counting Statistics And Error Prediction. I. Characterization Of Data. II. Statistical Models. III. Applications Of Statistical Models. IV. Error Propagation. V. Optimization Of Counting Experiments. VI. Limits Of Detectability. VII. Distribution Of Time Intervals. Chapter 4 General Properties Of Radiation Detectors. I. Simplified Detector Model. II. Modes Of Detector Operation. III. Pulse Height Spectra. IV. Counting Curves And Plateaus. V. Energy Resolution. VI. Detection Efficiency. VII. Dead Time. Chapter 5 Ionization Chambers. I. The Ionization Process In Gases. II. Charge Migration And Collection. III. Design And Operation Of Dc Ion Chambers. IV. Radiation Dose Measurement With Ion Chambers. V. Applications Of Dc Ion Chambers. VI. Pulse Mode Operation. Chapter 6 Proportional Counters. I. Gas Multiplication. II. Design Features Of Proportional Counters. III. Proportional Counter Performance. IV. Detection Efficiency And Counting Curves. V. Variants Of The Proportional Counter Design. VI. Micropattern Gas Detectors. Chapter 7 Geiger-Mueller Counters. I. The Geiger Discharge. II. Fill Gases. III. Quenching. IV. Time Behavior. V. The Geiger Counting Plateau. VI. Design Features. VII. Counting Efficiency. VIII. Time-To-First-Count Method. IX. G-M Survey Meters. Chapter 8 Scintillation Detector Principles. I. Organic Scintillators. II. Inorganic Scintillators. III. Light Collection And Scintillator Mounting. Chapter 9 Photomultiplier Tubes And Photodiodes. I. Introduction. II. The Photocathode. III. Electron Multiplication. IV. Photomultiplier Tube Characteristics. V. Ancillary Equipment Required With Photomultiplier Tubes. VI. Photodiodes As Substitutes For Photomultiplier Tubes. VII. Scintillation Pulse Shape Analysis. VIII. Hybrid Photomultiplier Tubes. IX. Position-Sensing Photomultiplier Tubes. X. Photoionization Detectors. Chapter 10 Radiation Spectroscopy With Scintillators. I. General Considerations In Gamma-Ray Spectroscopy. II. Gamma-Ray Interactions. III. Predicted Response Functions. IV. Properties Of Scintillation Gamma-Ray Spectrometers. V. Response Of Scintillation Detectors To Neutrons. VI. Electron Spectroscopy With Scintillators. VII. Specialized Detector Configurations Based On Scintillation. Chapter 11 Semiconductor Diode Detectors. I. Semiconductor Properties. II. The Action Of Ionizing Radiation In Semiconductors. III. Semiconductors As Radiation Detectors. IV. Semiconductor Detector Configurations. V. Operational Characteristics. VI. Applications Of Silicon Diode Detectors. Chapter 12 Germanium Gamma-Ray Detectors. I. General Considerations. II. Configurations Of Germanium Detectors. III. Germanium Detector Operational Characteristics. IV. Gamma-Ray Spectroscopy With Germanium Detectors. Chapter 13 Other Solid-State Detectors. I. Lithium-Drifted Silicon Detectors. II. Semiconductor Materials Other Than Silicon Or Germanium. III. Avalanche Detectors. IV. Photoconductive Detectors. V. Position-Sensitive Semiconductor Detectors. Chapter 14 Slow Neutron Detection Methods. I. Nuclear Reactions Of Interest In Neutron Detection. II. Detectors Based On The Boron Reaction. III. Detectors Based On Other Conversion Reactions. IV. Reactor Instrumentation. Chapter 15 Fast Neutron Detection And Spectroscopy. I. Counters Based On Neutron Moderation. II. Detectors Based On Fast Neutron-Induced Reactions. III. Detectors That Utilize Fast Neutron Scattering. Chapter 16 Pulse Processing. I. Overview Of Pulse Processing. II. Device Impedances. III. Coaxial Cables. IV. Linear And Logic Pulses. V. Instrument Standards. VI. Summary Of Pulse-Processing Units. VII. Application Specific Integrated Circuits (ASICS). VIII. Components Common To Many Applications. Chapter 17 Pulse Shaping, Counting, And Timing. I. Pulse Shaping. II. Pulse Counting Systems. III. Pulse Height Analysis Systems. IV. Digital Pulse Processing. V. Systems Involving Pulse Timing. VI. Pulse Shape Discrimination. Chapter 18 Multichannel Pulse Analysis. I. Single-Channel Methods. II. General Multichannel Characteristics. III. The Multichannel Analyzer. IV. Spectrum Stabilization And Relocation. V. Spectrum Analysis. Chapter 19 Miscellaneous Detector Types. I. Cherenkov Detectors. II. Gas-Filled Detectors In Self-Quenched Streamer Mode. III. High-Pressure Xenon Spectrometers. IV. Liquid Ionization And Proportional Counters. V. Cryogenic Detectors. VI. Photographic Emulsions. VII. Thermoluminescent Dosimeters And Image Plates. VIII. Track-Etch Detectors. IX. Superheated Drop Or "Bubble Detectors". X. Neutron Detection By Activation. XI. Detection Methods Based On Integrated Circuit Components. Chapter 20 Background And Detector Shielding. I. Sources Of Background. II. Background In Gamma-Ray Spectra. III. Background In Other Detectors. IV. Shielding Materials. V. Active Methods Of Background Reduction. Appendix A The NIM, CAMAC, And VME Instrumentation Standards. Appendix B Derivation Of The Expression For Sample Variance In Chapter 3. Appendix C Statistical Behavior Of Counting Data For Variable Mean Value. Appendix D The Shockley-Ramo Theorem For Induced Charge.
8,458 citations
"Instrument Calibrations and Data An..." refers background in this paper
...A detailed description of the response of proportional counters can be found in Knoll (1989). The gas proportional counters on NEAR have a chamber diameter of 42 mm and are filled with P-10 gas, a mixture of 90% argon and 10% methane, to an absolute pressure of 1200 mbar....
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...A detailed description of the response of proportional counters can be found in Knoll (1989)....
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...(See, for example, Knoll, 1989)....
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TL;DR: The results indicate the existence of a differential lunar highland crust, probably feldspathic, related to the plagioclase-rich materials previously found in the samples from Apollo 11, Apollo 12, Apollo 14, Apollo 15, and Luna 16.
Abstract: Although only part of the information from the x-ray fluorescence geochemical experiment has been analyzed, it is clear that the experiment was highly successful. Significant compositional differences among and possibly within the maria and highlands have been detected. When viewed in the light of analyzed lunar rocks and soil samples, and the data from other lunar orbital experiments (in particular, the Apollo 15 gamma-ray spectroscopy experiment), the results indicate the existence of a differential lunar highland crust, probably feldspathic. This crust appears to be related to the plagioclase-rich materials previously found in the samples from Apollo 11, Apollo 12, Apollo 14, Apollo 15, and Luna 16.
95 citations
TL;DR: The lunar surface was mapped with respect to magnesium, aluminum, and silicon as aluminum/ silicon and magnesium/ silicon intensity ratios along the projected ground tracks swept out by the orbiting Apollo 16 spacecraft to confirm the idea that the moon has a widespread differentiated crust (the highlands).
Abstract: The lunar surface was mapped with respect to magnesium, aluminum, and silicon as aluminum/ silicon and magnesium/ silicon intensity ratios along the projected ground tracks swept out by the orbiting Apollo 16 spacecraft. The results confirm the observations made during the Apollo 15 flight and provide new data for a number of features not covered before. The data are consistent with the idea that the moon has a widespread differentiated crust (the highlands). The aluminum/ silicon and magnesium/ silicon concentration ratios correspond to those for anorthositic gabbros through gabbroic anorthosites or feldspathic basalts. The x-ray results suggest the occurrence of this premare crust or material similar to it at the Descartes landing site.
57 citations
TL;DR: In this article, the authors discuss the nature of such variations expected for missions to an asteroid, the Moon, and Mercury, and discuss an effective means of removing the effects of solar variability from surface measurements, as indicated by the agreement between theoretical models presented here and Apollo X-ray observations.
Abstract: Remote X-ray spectrometry will play a key role in the geochemical exploration of solar system bodies, provided the methodology for data analysis efficiently detects and removes solar source and flight trajectory-induced geometric variations. In this paper, we discuss the nature of such variations expected for missions to an asteroid, the Moon, and Mercury. An effective means of removing the effects of solar variability from surface measurements, as indicated by the agreement between theoretical models presented here and Apollo X-ray observations, is also discussed. We calculate X-ray spectra anticipated for these targets using probable surface compositions, solar outputs, and flight trajectories. Generally, the spectra show three distinctive regions where line intensities are clearly correlated with surface abundances: a high-energy Fe region, a moderate-energy Ca region, and a low-energy region which contains Mg, Al, and Si lines. In addition, we calculate anticipated integration times required for acceptable levels of certainty and estimate spatial resolutions achievable for those integration times for elements Mg, Al, Si, S, Ca, Ti, and Fe. Required integration times are lower (on the order of minutes or even seconds) and achievable spatial resolutions improved (on the order of kilometers) for the lower energy lines and for periods of higher solar activity. Using the Near Earth Asteroid Rendezvous (NEAR) mission to asteroid 433 Eros as an example, we describe a recommended approach for analysis of X-ray measurements based on our findings. Most importantly, we clearly demonstrate that major scientific goals for future exploration of asteroids, Mercury, and the Moon can be met by obtaining remote orbital X-ray measurements of these bodies.
56 citations
"Instrument Calibrations and Data An..." refers background or methods in this paper
...LIBRATION 509 Detailed discussions of these processes can be found in Clark (1979), Trombka et al. (1979), Yin et al. (1993), and Clark and Trombka (1997)....
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...Laboratory and field calibrations, in conjunction with theoretical calculations, are required in order to obtain photon-to-elemental composition conversion factors. eter data is described in Clark (1979) and Clark and Trombka (1997)....
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TL;DR: The X ray/gamma ray spectrometer (XGRS) instrument on board the NEAR spacecraft will map asteroid 433 Eros in the 07 keV to 10 MeV energy region as discussed by the authors.
Abstract: The X ray/gamma ray spectrometer (XGRS) instrument on board the Near Earth Asteroid Rendezvous (NEAR) spacecraft will map asteroid 433 Eros in the 07 keV to 10 MeV energy region Measurements of the discrete line X ray and gamma ray emissions in this energy domain can be used to obtain both qualitative and quantitative elemental compositions with sufficient accuracy to enable comparison to the major meteorite typies It is believed that Eros is an S-type asteroid, the most common of the near-Earth asteroids The determination of whether Eros consists of either differentiated or undifferentiated materials is an important objective of this mission Observations of Eros during the NEAR mission will contribute significantly to our understanding of the structure and composition of this asteroid The NEAR spacecraft was successfully launched on February 17, 1996 The NEAR XGRS was turned on during the week of April 7, 1996, and all detector systems operated nominally Background spectra have been obtained
54 citations