Instrument Calibrations and Data Analysis Procedures for the NEAR X-Ray Spectrometer

Starr, R.; Clark, P. E.; Murphy, M. E.; Floyd, S. R.; McClanahan, T. P.; Nittler, L. R.; Trombka, J. I.; Evans, L. G.; Boynton, W. V.; Bailey, S. H.; Bhangoo, J. S.; Mikheeva, I. B.; Brückner, J.; Squyres, S. W.; McCartney, Elaina; Goldsten, J.; McNutt, R. L.

doi:10.1006/icar.2000.6453

Cited by 25 publications

(14 citation statements)

References 13 publications

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“…The NEAR-Shoemaker XRS has been described in great detail elsewhere (Goldsten et al, 1997;Trombka et al, 1997;Starr et al, 2000) so we describe it only briefly. The asteroidpointing detector package consists of three sealed gas-filled proportional counters, each with 25 cm* collecting area and thin (25 pm) Be windows.…”

Section: Near-shoemaker X-ray Spectrometermentioning

confidence: 99%

“…To reduce this unwanted background, rise-time discrimination circuitry was used. The rejection efficiency for charged particles and gamma rays was determined to be -70% at 5.9 keV (Starr et al, 2000). Rise-time discrimination was not used below 3 keV because below this energy the difference in rise time between x-rays and cosmic rays is not sufficient to reject the background without also greatly diminishing the number of valid x-ray events.…”

Section: Near-shoemaker X-ray Spectrometermentioning

confidence: 99%

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X‐ray fluorescence measurements of the surface elemental composition of asteroid 433 Eros

Nittler

Starr

Lim

et al. 2001

Meteorit & Planetary Scien

117

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Abstract-We report major element ratios determined for the S-class asteroid 433 Eros using remotesensing x-ray fluorescence spectroscopy with the near-Earth asteroid rendezvous Shoemaker x-ray spectrometer (XRS). Data analysis techniques and systematic errors are described in detail. Data acquired during five solar flares and during two extended "quiet Sun" periods are presented; these results sample a representative portion of the asteroid's surface. Although systematic uncertainties are potentially large, the most internally consistent and plausible interpretation of the data is that Eros has primitive Mg/Si, AI/Si, Ca/Si and Fe/Si ratios, closely similar to H or R chondrites. Global differentiation of the asteroid is ruled out. The S/Si ratio is much lower than that of chondrites, probably reflecting impact-induced volatilization and/or photo-or ion-induced sputtering of sulfur at the surface of the asteroid. An alternative explanation for the low S/Si ratio is that it reflects a limited degree ofmelting with loss of an FeS-rich partial melt. Size-sorting processes could lead to segregation of Fe-Ni metal from silicates within the regolith of Eros; this could indicate that the Fe/Si ratios determined by the x-ray spectrometer are not representative of the bulk Eros composition.

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Section: Near-shoemaker X-ray Spectrometermentioning

confidence: 99%

Section: Near-shoemaker X-ray Spectrometermentioning

confidence: 99%

X‐ray fluorescence measurements of the surface elemental composition of asteroid 433 Eros

Nittler

Starr

Lim

et al. 2001

Meteorit & Planetary Scien

117

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“…(1 997), Trombka et al (1 997,20OOa), Evans et al (2000), Starr et al (2000) describe the NEAR x-ray and gamma-ray detector systems in detail, and here we give a brief summary. The NEAR XGRS system is a non-dispersive spectroscopic system.…”

Section: Instrumentationmentioning

confidence: 99%

The NEAR‐Shoemaker x‐ray/gamma‐ray spectrometer experiment: Overview and lessons learned

Trombka¹,

Nittler²,

Starr³

et al. 2001

Meteorit & Planetary Scien

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Abstract-The near-Earth asteroid rendezvous (NEAR)-Shoemaker remote-sensing x-ray/gammaray spectrometer (XGRS) completed more than a year of operation in orbit and on the surface of 433 Eros. Elemental compositions for a number of regions on the surface of Eros have been derived from analyses of the characteristic x-ray and gamma-ray emission spectra. The NEAR XGRS detection system was included as part of the interplanetary network (IPN) for the detection and localization of gamma-ray bursts (GRBs). Preliminary results for both the elemental composition of the surface of Eros and the detection of GRBs have been obtained. In addition to the science results, the design and operation of the NEAR XGRS is considered. Significant information important for the design of future remote sensing XGRS systems has been obtained and evaluated. We focus on four factors that became particularly critical during NEAR: (1) overall spacecraft design, (2) selection of materials, (3) increase of the signal-to-noise ratio and (4) knowledge of the incident solar x-ray spectrum.

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“…For this reason, the MESSENGER XRS planetary viewing sensor consists of three identical gas-filled proportional counters. Designed and built by Oxford Instruments Analytical Oy of Finland (formerly Metorex International Oy), the counters are an improved version of those flown on the NEAR mission (Starr et al 2000). Gas-proportional counters measure individual X-ray photons that enter the gas-filled chamber through a thin beryllium window and produce an ion electron pair (by the photoelectric effect).…”

Section: Planetary Sensorsmentioning

confidence: 99%

“…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). Three planet-viewing gas proportional counters (GPCs), including balanced filters and energetic particle detection, are used to maximize the active detector area and resolve the abundances of the lighter elements from Mercury.…”

Section: Introductionmentioning

confidence: 99%

The X-Ray Spectrometer on the MESSENGER Spacecraft

et al. 2007

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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.

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Instrument Calibrations and Data Analysis Procedures for the NEAR X-Ray Spectrometer

Cited by 25 publications

References 13 publications

X‐ray fluorescence measurements of the surface elemental composition of asteroid 433 Eros

X‐ray fluorescence measurements of the surface elemental composition of asteroid 433 Eros

The NEAR‐Shoemaker x‐ray/gamma‐ray spectrometer experiment: Overview and lessons learned

The X-Ray Spectrometer on the MESSENGER Spacecraft

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