Near Earth Environment

McDonnell, Tony; McBride, Neil; Green, Simon; Ratcliff, P.R.; Gardner, David J.; Griffiths, Andrew D.

doi:10.1007/978-3-642-56428-4_4

Cited by 20 publications

(16 citation statements)

References 80 publications

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“…and where u is the differential size index and u = 3s − 2 (McDonnell et al 2001). For a system in collisional equilibrium, where it is assumed all meteoroids have the same strength, s = 11/6 (Dohnanyi 1969), while s = 2 represents a meteoroid distribution where mass is equally distributed per decade of mass.…”

Section: Introductionmentioning

confidence: 99%

A reproducible method to determine the meteoroid mass index

Pokorný

Brown

2016

A&A

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Context. The determination of meteoroid mass indices is central to flux measurements and evolutionary studies of meteoroid populations. However, different authors use different approaches to fit observed data, making results difficult to reproduce and the resulting uncertainties difficult to justify. The real, physical, uncertainties are usually an order of magnitude higher than the reported values. Aims. We aim to develop a fully automated method that will measure meteoroid mass indices and associated uncertainty. We validate our method on large radar and optical datasets and compare results to obtain a best estimate of the true meteoroid mass index. Methods. Using MultiNest, a Bayesian inference tool that calculates the evidence and explores the parameter space, we search for the best fit of cumulative number vs. mass distributions in a four-dimensional space of variables (a, b, X 1 , X 2 ). We explore biases in meteor echo distributions using optical meteor data as a calibration dataset to establish the systematic offset in measured mass index values. Results. Our best estimate for the average de-biased mass index for the sporadic meteoroid complex, as measured by radar appropriate to the mass range 10 −3 > m > 10 −5 g, was s = −2.10 ± 0.08. Optical data in the 10 −1 > m > 10 −3 g range, with the shower meteors removed, produced s = −2.08 ± 0.08. We find the mass index used by Grün et al. (1985) is substantially larger than we measure in the 10 −4 < m < 10 −1 g range.

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Section: Introductionmentioning

confidence: 99%

A reproducible method to determine the meteoroid mass index

Pokorný

Brown

2016

A&A

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“…The interstellar dust enters the Solar System with a speed of 26 km −1 and its direction of 259 • ecliptic longitude and +8 • latitude was found to be compatible with the direction of the interstellar neutral helium gas as detected by Ulysses [32,53]. In-situ measurement methods allowed the determination of dust masses for individual dust impacts and the detected grain sizes differed with distance to the Sun revealing a lack of small grains (<3 μm) inside a heliocentric distance of 3 AU [33,54]. At distances between 0.7 and 3 AU the Cassini and Galileo dust instruments detected only particles bigger than 0.5 μm [1,3].…”

Section: Local Interstellar Dustmentioning

confidence: 92%

“…Dust particles impacting on a thin (10-100 nm) Al film will have a ballistic limit defined as the maximum thickness of aluminium which can be perforated [33]. The limit is a function of both the mass and velocity of a particle and is derived from empirical formulae generated from laboratory impact data [15].…”

Section: Dust Cameras and Instrumentationmentioning

confidence: 99%

SARIM PLUS—sample return of comet 67P/CG and of interstellar matter

et al. 2012

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“…Most of the crater diameters on aluminum were less than 10 m in diameter. Studies that relate crater size to particle diameter find that at impact velocities of around 2 km s 1 , craters tend to be similar to or less than the particle diameter, whereas at 1 km s 1 , the crater diameters drop significantly below the particle diameter [17,18]. In the case of the aluminum sample, the most abundant crater sizes were less than 4 m. Relating the number of such craters, 449 mm 2 , to similarly sized particles leads to the conclusion that the mass deposition associated with the craters is approximately 2 orders of magnitude smaller than that detected by the QCM without taking material ejection into account.…”

Section: Condensate Deposition Ratesmentioning

confidence: 96%

Analysis of Space Shuttle Primary Reaction-Control Engine-Exhaust Transients

Hester¹,

Chiu²,

Winick³

et al. 2009

Journal of Spacecraft and Rockets

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A series of 22 primary reaction-control-system engine attitude-control firings were observed from the Maui Space Surveillance Site during the space shuttle STS-115 mission. The firings occurred during a pass over Maui on 19 September 2006 during which the orbiter was in sunlight and the observatory was in darkness. The observed attitude maneuvers maintained the orbiter in an orientation in which its long axis was aligned with the line of sight from the observatory. This ensured that the thrust vectors of all the observed engine firings were perpendicular to the line of sight, providing an optimal side-on observation of the exhaust. The firings ranged between 80 and 320 ms in duration and involved 2 or 3 engines for pitch, roll, and yaw adjustments. A 0.328 deg field-of-view acquisition scope of the 3.6 m telescope of the Advanced Electro-Optical System provided unfiltered imagery in the near-ultraviolet visible spectral region. The most interesting white-light features were transients, one observed at engine start up and two at shutdown. The analysis of the transient speeds reveals that the startup transient consists of either unburned propellant droplets or higher-pressure gas evaporated from droplets and that the shutdown transients are attributable to a slightly staggered release of unburned oxidizer and fuel, respectively. The first (oxidizer) shutdown transient is the brightest feature, for which an intensity evolution analysis is conducted. The analysis of the groundbased data is fully consistent with spectral features attributable to primary reaction-control-system engine transients observed in previous measurements from the space shuttle bay using an imager spectrograph. Nomenclature A= Brook scaling parameter for density, cm 1 A = Brook scaling parameter for flux, g A 0 = Lorentzian scaling parameter for density, cm 1 deg 2 A 0 = Lorentzian scaling parameter for flux, g deg 2 B= Brook angular distribution parameter, unitless C p = specific heat at constant pressure, J g 1 K 1 D = particle diameter, m D 0 = initial particle diameter, m d = horizontal video-image frame width at range, R, km F = exhaust particle flux, cm 2 s 1 F S = solar spectral flux, W cm 2 g = spectral atmospheric transmission and sensitivity factor, unitless IR e ; x = radiant intensity along image coordinate x perpendicular to the thrust axis at nozzle distance R e , W cm 2 IR e ; y = volume emission rate at nozzle distance R e , where y is the radial distance with respect to the thrust axis, W cm 3 I = angular volume emission-rate distribution, W cm 3 I' = scattered intensity as a function of the solar scattering angle, W sr 1 m = particle mass, g N = number density, particles cm 3 P; T = Planck radiation function, W sr 1 cm 2 Hz 1 P vap = vapor pressure, torr _ Q = heat gain rate, W _ Q Earth = Earthshine heating rate, W _ Q rad = radiative cooling rate, W _ Q sub = heat of sublimation cooling rate, W _ Q sun = solar radiation heating rate, W R = range, km R = range vector, km R e = axial distance to the nozzle exit, m r = particle ...

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Near Earth Environment

Cited by 20 publications

References 80 publications

A reproducible method to determine the meteoroid mass index

A reproducible method to determine the meteoroid mass index

SARIM PLUS—sample return of comet 67P/CG and of interstellar matter

Analysis of Space Shuttle Primary Reaction-Control Engine-Exhaust Transients

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