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Jenniskens P.M.,Carl Sagan Center
Journal of Spacecraft and Rockets

During entry of the Stardust sample return capsule, measurements of the radiation emitted from the shock-heated flow were obtained with a number of instruments. These instruments viewed the sample return capsule from an airplane located several hundred kilometers from the vehicle. The present study analyzes the radiation generated at two different high-altitude conditions. The flowfields are simulated using both continuum (computational fluid dynamics) and particle (direct simulation Monte Carlo) methods. The flow solutions provide input to a nonequilibrium radiation model to compute line-of-sight spectra that are compared with high-resolution data taken with the Echelle spectrograph during the Stardust entry. Comparisons between simulation and measurements are presented for air spectral features and for metal atomic lines believed to originate from evaporation of thevehicle surface. The comparisons make it possible to identify specific aspects of the airchemistry modeling that require further work. In addition, analysis of the metal spectra provides insight into the likely sources of these impurities. © 2009 by the AmericanInstitute of Aeronautics and Astronautics, Inc. Source

Wercinski P.F.,Mail Stop | Jenniskens P.,Carl Sagan Center
Journal of Spacecraft and Rockets

The 15 January 2006 reentry of the Stardust Sample Return capsule was photographed from 11.2-km altitude onboard NASA's DC-8 Airborne Laboratory in a series of brief 1/320 s exposures with a Nikon D70 digital still camera. The entry was detected from 09:57:13.5 to 09:57:53.5 UTC. Other instruments have demonstrated that most of the observed broadband flux is due to gray body radiation from the hot surface of the thermal protection system, except in the very beginning when strong emission lines of zinc from an ablating paint layer contributed significantly to the blue band. The measured flux in the green band was used to measure the surface-averaged temperature variation during flight, and the corresponding flux in the blue and red bands were used to verify the expected wavelength dependence of the gray body emission. © 2010 by the American Institute of Aeronautics and Astronautics, Inc. Source

Taylor M.J.,Center for Atmospheric and Space Science | Jenniskens P.,Carl Sagan Center
Journal of Spacecraft and Rockets

The 1069 nm line of atomic carbon was detected in radiation emitted during the 15 January 2006 reentry of the Stardust sample return capsule. In time-averaged data, thecorresponding weaker lines in the range of 960-966 nm were also present. The spectra covered the wavelength range from 930 to 1075 nm at a spectral full-width-at-halfmaximum resolution of 1.6 nm. The integrated 1069 nm line intensity decreased from 737 ± 44 W/m2/nm/sr at 80.7 km altitude (09:57:16.5 Universal Time) to 432 ± 44 W/m 2/nm/sr at 70.9 km altitude (09:57:24.5 Universal Time). At the same time, the 1011 nm blend of nitrogen lines increased from 2110 ± 29 to 5378 ± 42 W/m2/nm/sr. Absolute calibration errors add to these values a systematic uncertainty of about 20%. The capsule's heat shield consisted of a phenol-impregnated carbon ablator. Hence, the intensity of the carbon-atom line emission is a measure of the ablation rate during descent, but it also depends on the details of carbon-atom ablation and the excitation in the shock layer. © 2010 by the American Institute of Aeronautics and Astronautics, Inc. Source

Jenniskens P.,Carl Sagan Center | Wilson M.A.,NASA | Winter M.,Laboratoire EM2C | Laux C.O.,Laboratoire EM2C
Journal of Spacecraft and Rockets

During the 2006 Stardust Sample Return Capsule entry observing campaign, the highest spectral resolution data gathered onboard NASA's DC-8 Airborne Laboratory was measured with a fixed-mounted slitless cooled chargecoupled-device spectrograph, called ASTRO.Spectra were recorded around the time of peak heating ∼09 : 57 : 33 Coordinated Universal Time (UTC) on 15 January. The data covered three 0.8-second time intervals centered on09:57:32.5, 34.4 and 36.3 s (±0:5 s) UTC, when the capsule was at an altitude of60 and 210 km from the spectrometer. The observed spectrum was a composite of first-, second-, and third-order emissions. The first-order spectrum contained only continuum emission. Second-order emissions included the 615 nm atomic line of oxygen; third-order emissions included the CN violet 0-0 band, the isoelectric N2 + band, and two Ca+ atomic lines. The Ca+ lines had an instrumental full-width at half-maximum of 0:15 ± 0:01 nm. The CN violet band contour measured vibrational and rotational excitation temperatures of Tv= Tr =8; 000 ± 1; 000 K, if self-absorption is neglected. © 2010 by the American Institute of Aeronautics and Astronautics, Inc. Source

Demergasso C.,Catolica del Norte University | Demergasso C.,Centro de Investigacion Cientifico tecnologico para la Mineria | Dorador C.,Catolica del Norte University | Meneses D.,Catolica del Norte University | And 6 more authors.
Journal of Geophysical Research: Biogeosciences

The Chilean Altiplano is the westernmost part of a large volcanic-sedimentary plateau in the central Andes. High solar irradiance and rapid increase of temperature have contributed to make it a hot spot of global climatic change. In this study, we describe microbial diversity in the summit lake of the Simba volcano (5,870 m) and the evaporitic basins of Salar de Aguas Calientes (4,200 m) and Laguna Lejía (4,325 m) using both culture and culture-independent methods. The results obtained were analyzed together with available information from related environments to describe the traits of the microbial community driven by main environmental factors. Isolated cultures exhibit high resistance to all three types of UV radiation, further supporting the adaptation of microorganisms to the high altitude environment. The microbial community structures at Salar de Aguas Calientes and Laguna Lejía are similar to those from other saline systems and cold environments where Bacteroidetes is the major bacterial group. The abundance of sequences related to alphaproteobacteria and methanogenic populations likely reflects the importance of aerobic anoxigenic phothosynthesis and the cycling of one-carbon compounds in the high altitude lake ecosystems. Geochemistry and microbial communities at Simba as well as those reported in the Licancabur summit lake provide evidence for sulfur-rich environments but under different conditions. Those differences between neighboring mountain lake ecosystems highlight the effect of volcanic activity on microbial communities. The hypothetical ecosystem model described in this work provides a clue to follow the microbial community responses to geophysical environment coupled with rapid climate change. Copyright 2010 by the American Geophysical Union. Source

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