North Fort Myers, United States
North Fort Myers, United States

Time filter

Source Type

Jenniskens P.M.,Carl Sagan Center
Journal of Spacecraft and Rockets | Year: 2010

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.


News Article | September 12, 2016
Site: www.fastcompany.com

The scientific community was abuzz recently when it was widely reported that Russian astronomers, along with an Italian researcher, had recorded a signal that was, as of then, unexplained. After looking into what exactly was detected—something from the solar system HD 164595 some 94 light-years away—the Russian astronomers issued a statement explaining that the signal was most likely not extraterrestrial. But organizations focusing on the search for alien life, such as the Search for Extraterrestrial Intelligence (SETI) Institute and the Messaging Extraterrestrial Intelligence (METI) Institute, are continuing to look into the event. Part of the reason is because the signal was received over a year ago, on May 15, 2015, according to a SETI blog post. At the time, though, the discoverers didn’t immediately alert the SETI community, a breach of long-established practice and protocol. How did that breakdown happen? One reason SETI’s protocol likely sputtered is simple. Even though the drafted document has been written and revised for over two decades, the nine rules researchers are supposed to follow when they receive what they think may be an extraterrestrial signal don't necessarily conform to the dynamic nature of the field. Technologies are constantly changing, making it easier to see places we've never seen before, like surface of a comet, for instance. Scientists are still sorting out how best to act on the new data that's coming in all the time. SETI's rules are a set of defensive actions: if x happens, then y next. That makes them similar to the way measures are created in the cybersecurity sector; SETI’s rules exist to protect those involved but are usually carried out during exceptional circumstances. Security professionals generally have plans in place about what to do during an emergency, yet the reality never plays out the same as it did when conceptualized. Perhaps the most glaring example of this was the 2013 Target data breach, which exposed personal and payment information of some 40 million customers. The company had numerous security protocols in place—which, according to Bloomberg Businessweek, may have even detected the hack while it was happening. But when theoretical security planning was pushed into active procedure, several things went awry. While Target was alerted by federal law enforcement about two weeks after the hack, data breaches take an average of 146 days to be discovered, according to a report from Mandiant. The potential receipt of an alien signal likewise needs to be vetted, which can also chew up a considerable amount of time. Franck Marchis, a principal investigator at the Carl Sagan Center of the SETI Institute, explained that it's a way to ensure findings are real. Astronomers must "use the scientific method," he said. "Before making an announcement, you contact your colleagues," he explained. "You ask them to confirm that they also see the signal." Researchers are working around the globe scanning the skies for any sort of abnormality they can detect. Every so often, they find something that defies explanation. The reason SETI has prescribed rules in place is to give a semblance of order to the process of figuring out these unknowns. The scientists I spoke to described the protocol as a safeguard to make sure every signal is properly vetted. But as Seth Shostak, a senior astronomer at the SETI Institute who was part of the committee that crafted the document, told me, the protocol is just a prescription. "It’s recommended behavior," he said. "There’s no force of law." After years of meetings and reviews, the protocol has become widely accepted in the astronomy community. And according to Shostak, it’s a "valuable document." Both he and Marchis pointed to a signal SETI detected in 1997 that ended up being a false alarm. Though it looked promising, after colleagues weighed in, it became clear that the blip was in fact terrestrial. Still, it's not always a smooth experience. If a promising signal is detected, it creates excitement. A scientist emailing a few friends about the discovery could also notify the press. "It spreads very quickly," Shostak explained. Often a finding that has yet to be completely vetted by the entire astronomy community gets leaked. That is also reassuring, according to Shostak. He said that findings can get overlooked by the entities that matter—namely the government and the military. But the press has a way of garnering widespread interest that can then get the community involved in a healthy, global debate. The downside: "What’s actually going to happen is a very messy media story," Shostak said, "with conflicting reports." Yet methodological fissures still remain in the astronomy world. Earlier this year Fast Company reported on the widening difference of opinions when it comes to studying potentially alien lifeforms. While organizations like SETI focus on passively scanning the open skies for any external sign of life, other organizations like METI—Messaging Extraterrestrial Intelligence—believe it may be more useful to take a more proactive searching approach. Meanwhile, the protocol itself states: "No response to a signal or other evidence of extraterrestrial intelligence should be sent until appropriate international consultations have taken place." Despite this, the scientists I talked with maintained that nearly every expert in the field is at least aware of the protocol and should know how follow it. But in this case, the team that discovered this faraway blip waited for over a year before making any sort of noise. While this may seem odd, there's at least one possible explanation for the announcement’s timing. Claudio Maccone, the Italian researcher (who is also the chair of the International Academy of Astronautics Permanent SETI Committee) who first saw the signal, is scheduled to show his findings at the 67th International Astronautical Congress (IAC) in Guadalajara later this month. Still, this doesn’t quite explain why the Russian astronomers already issued a statement saying it was most likely no extraterrestrial. Shostak told me that he asked Maccone why the team didn’t alert others about the finding last year. "He said they were shy," Shostak explained. "I don’t know what that means." Though the protocol has been updated again somewhat recently, it's clear that even the most high-tech scientists can be hampered by rudimentary organizational breakdowns. Do these perceived hiccups actually help push the science forward? Shostak sees the messiness as inevitable; Marchis points to just how important it is that others follow the protocol to truly corroborate findings. Either way, the truth is out there.


Davila A.F.,Carl Sagan Center | Hawes I.,University of Canterbury | Araya J.G.,University of Antofagasta | Gelsinger D.R.,Johns Hopkins University | And 4 more authors.
Frontiers in Microbiology | Year: 2015

The Atacama Desert of northern Chile is one of the driest regions on Earth, with areas that exclude plants and where soils have extremely low microbial biomass. However, in the driest parts of the desert there are microorganisms that colonize the interior of halite nodules in fossil continental evaporites, where they are sustained by condensation of atmospheric water triggered by the salt substrate. Using a combination of in situ observations of variable chlorophyll fluorescence and controlled laboratory experiments, we show that this endolithic community is capable of carbon fixation both through oxygenic photosynthesis and potentially ammonia oxidation. We also present evidence that photosynthetic activity is finely tuned to moisture availability and solar insolation and can be sustained for days, and perhaps longer, after a wetting event. This is the first demonstration of in situ active metabolism in the hyperarid core of the Atacama Desert, and it provides the basis for proposing a self-contained, endolithic community that relies exclusively on non-rainfall sources of water. Our results contribute to an increasing body of evidence that even in hyperarid environments active metabolism, adaptation, and growth can occur in highly specialized microhabitats. © 2015 Davila, Hawes, Araya, Gelsinger, DiRuggiero, Ascaso, Osano and Wierzchos.


PubMed | Bowie State University, Carl Sagan Center, CSIC - National Museum of Natural Sciences, University of Antofagasta and 2 more.
Type: | Journal: Frontiers in microbiology | Year: 2015

The Atacama Desert of northern Chile is one of the driest regions on Earth, with areas that exclude plants and where soils have extremely low microbial biomass. However, in the driest parts of the desert there are microorganisms that colonize the interior of halite nodules in fossil continental evaporites, where they are sustained by condensation of atmospheric water triggered by the salt substrate. Using a combination of in situ observations of variable chlorophyll fluorescence and controlled laboratory experiments, we show that this endolithic community is capable of carbon fixation both through oxygenic photosynthesis and potentially ammonia oxidation. We also present evidence that photosynthetic activity is finely tuned to moisture availability and solar insolation and can be sustained for days, and perhaps longer, after a wetting event. This is the first demonstration of in situ active metabolism in the hyperarid core of the Atacama Desert, and it provides the basis for proposing a self-contained, endolithic community that relies exclusively on non-rainfall sources of water. Our results contribute to an increasing body of evidence that even in hyperarid environments active metabolism, adaptation, and growth can occur in highly specialized microhabitats.


Boyd I.D.,University of Michigan | Martin A.,University of Michigan | Martin A.,University of Kentucky | Wiebenga J.E.,University of Michigan | And 2 more authors.
Journal of Spacecraft and Rockets | Year: 2013

Hypersonic flowfield and radiation analyses are performed before and after flight to study the physical conditions experienced by the automated transfer vehicle Jules Verne during reentry before breakup. Results are compared to those obtained with a miniature Echelle spectrograph operated from an airborne platform, measuring the flux density of atomic line emissions from oxygen and nitrogen, as well as many metals. Molecular emissions fromCNand AlO are also detected. The vehicle lost its solar panels at 86kmand first broke up at 75 km. The main cargo cabin held together until 68 km. Postflight analyses focus on altitudes of 86, 75, and 68 km. A first analysis includes only air species, correctly predicting the observed oxygen and nitrogen atomic line intensities. N+2 band emission is systematically overestimated by at least a factor of 20, indicating a need for revision of the radiation model for this system. A second analysis includes blowing of metals (aluminum, sodium, potassium, and magnesium) from the vehicle surface. The blowing rates are inferred by requiring the computed and measured emissions to match. Magnesium and aluminum originate from ablation of structural elements, while sodium and potassium may have originated as impurities in paint. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc.


Jenniskens P.,Carl Sagan Center | Koop M.,Lockheed Martin | Albers J.,Lockheed Martin
Journal of Spacecraft and Rockets | Year: 2010

The radiation emitted by the Stardust sample return capsule during reentry intoEarth's atmosphere on 15 January 2006 was measured with a staring airborne intensified camera, equipped with an objective transmission grating. The instrumental setup was designed to provide low-resolution spectra of the capsule's radiation, even if other instrumentswould fail in tracking the object. Spectra were recorded at the video frame rate of 30 Hz. The spectra covered the range of 380-860 nm, with a dispersion of 2:3 nm/pixel and a full-width-at-half-maximum resolution of 7 nm. Fully calibrated results, to an absolute precision of∼17%, are presented for the time period from 09:57:17 to 09:57:43 Coordinated Universal Time, averaged over periods of 1 s. The data provided records of the CN bandintensity detected throughout flight (unsaturated), the continuum emission (partially saturated), and the shock plasma emissions of oxygen and nitrogen during peak heating (partially saturated). A spectrum of wake radiation is also presented. © 2010 by the American Institute of Aeronautics and Astronautics, Inc.


Harms F.,Wolfratshauserstrasse 48 | Wolf J.,Deutsches SOFIA Institute | Raiche G.,Thermophysics Facility Branch | Jenniskens P.,Carl Sagan Center
Journal of Spacecraft and Rockets | Year: 2010

Observations were made during the reentry of the Stardust sample return capsuleon 15 January 2006 in order to calibrate the level of radiation from the capsule surface,from the bow shock, and from its wake. A sensitive cooled charge-coupled device camera was used, equipped with a grating to simultaneously record the first-order spectrum of the capsule and that of the background stars. The radiation of the capsule was dominated by the graybody radiation from the hot surface. This graybody radiation was calibrated against the known radiation of background stars. The purpose of this calibration was to providea cross check for other instruments participating in the airborne Stardust Entry Observing Campaign. In addition, eight short-exposed images were obtained that show the development of billowing and the distortion induced by winds. © 2010 by the American Institute of Aeronautics and Astronautics, Inc.


Wercinski P.F.,Mail Stop | Jenniskens P.,Carl Sagan Center
Journal of Spacecraft and Rockets | Year: 2010

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.


Jenniskens P.,Carl Sagan Center | Wilson M.A.,NASA | Winter M.,Laboratoire EM2C | Laux C.O.,Laboratoire EM2C
Journal of Spacecraft and Rockets | Year: 2010

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.


Taylor M.J.,Center for Atmospheric and Space Science | Jenniskens P.,Carl Sagan Center
Journal of Spacecraft and Rockets | Year: 2010

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.

Loading Carl Sagan Center collaborators
Loading Carl Sagan Center collaborators