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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01 Jun 1999-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: A Si-PIN photodiode is being used as a solar X-ray monitor on the Xray/gamma-ray spectrometer experiment which is flying on the Near Earth Asteroid Rendezvous spacecraft.
Abstract: A Si-PIN photodiode is being used as a solar X-ray monitor on the X-ray/gamma-ray spectrometer experiment which is flying on the Near Earth Asteroid Rendezvous spacecraft. Since its launch in February 1996 this photodiode has experienced several brief failures. These anomalies and other performance characteristics will be described. Efforts to reproduce these failures in ground tests with flight spare equipment will also be discussed.
10 citations
"Instrument Calibrations and Data An..." refers background in this paper
...to saturate and effectively turn off the detector ( Starr et al. 1999 )....
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11 Feb 1999-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The NEAR Earth Asteroid Rendezvous (NEAR) spacecraft will encounter the 433Eros asteroid for a one year orbital mission in December 1998 as discussed by the authors, which includes X-ray and gamma-ray (XGRS) spectrometers.
Abstract: The NEAR Earth Asteroid Rendezvous (NEAR) spacecraft will encounter the 433Eros asteroid for a one year orbital mission in December 1998. Its on-board remote sensing instrumentation includes X-ray and gamma-ray (XGRS) spectrometers. NEAR is an orbital mission and long integrations over spatially specific asteroid regions are generally not possible. A methodology for simulating longer integrations has been developed for XGRS and uses unique management, correlative and analytical ground systems to render mapping data products. Evaluation of the spatial environment is accomplished through virtual renderings of the asteroid surface giving incidence, emission and surface roughness factors. Extended computer plate modeling information is employed to optimize ground computer systems processing time. Interactive visualization systems have been developed to manage close to a million spectra that will be collected during the encounter. Feedback systems are employed to inspect, tag and calibrate spectral data products. Mission planning, systems development and managerial responsibilities have been distributed to cooperating science organizations at The Goddard Space Flight Center, The University of Arizona, Cornell University, The Applied Physics Laboratory and The Max Plank Institute.
9 citations
Journal Article•
5 citations
"Instrument Calibrations and Data An..." refers background or methods in this paper
...During the Apollo missions, it was found that this component was constant, so that the dark-side background could be subtracted directly from the pulse height spectra measured on the sunlit side (Trombka et al. 1979)....
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...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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...This basic procedure was developed for the analysis of the spectra obtained during the Apollo program and was used successfully (Trombka et al. 1979)....
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...Methods for performing transformations from pulse height to photon energy space have been developed for data from instruments similar to the NEAR XRS such as the Apollo X-ray spectrometer (Trombka et al. 1979)....
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19 Oct 1999
TL;DR: An X-ray and gamma-ray spectrometer (XGRS) is onboard the NEAR spacecraft to determine the elemental composition of the surface of the asteroid 433Eros.
Abstract: An X-ray and Gamma-ray spectrometer (XGRS) is onboard the Near Earth Asteroid Rendezvous (NEAR) spacecraft to determine the elemental composition of the surface of the asteroid 433Eros. The Eros asteroid is highly non-spherical in physical shape and the development of data management and analysis methodologies are in several areas a divergence from traditional remotely sensed geographical information systems techniques. Field of view and asteroid surface geometry must be derived virtually and then combined with real measurements of solar, spectral and instrument calibration information to derive meaningful scientific results. Spatial resolution of planned geochemical maps will be improved from the initial conditions of low statistical significance per integration by repeated surface flyovers and regional spectral accumulation. This paper describes the results of a collaborative effort of design and development of the NEAR XGRS instrument ground system undertaken by participants at the Goddard Space Flight Center, University of Arizona, Cornell University, Applied Physics Laboratory, and Max Plank institute.
5 citations
11 Feb 1999-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The X-ray proportional counters on board the Near Earth Asteroid Rendezvous (NEAR) spacecraft have exhibited a resolution degradation and recovery phenomenon several times during the long cruise phase of the mission.
Abstract: The X-ray proportional counters on board the Near Earth Asteroid Rendezvous (NEAR) spacecraft have exhibited a resolution degradation and recovery phenomenon several times during the long cruise phase of the mission. The resolution is checked periodically by commanding an 55 Fe source into the window area. The degradation is seen as a low energy tailing of the 5.9 keV photopeak. Two events have occurred which provided good spectral data for better understanding the degradation phenomenon. In November 1997 a large solar particle event occurred that degraded the resolution and excited copper in the collimator. Eventually the detectors returned to normal. In January 1998 the spacecraft performed an Earth swingby gravity assist maneuver. The near Earth environment excited the magnesium and aluminum in the filter elements. The copper line was also produced. The NEAR spacecraft was launched in February 1996 and will rendezvous and orbit the asteroid 433 Eros in early 1999.
5 citations