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At least 1,441 records · Page 80
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NASA NTRS2017

The Triggering Mechanism of coronal jets and CMEs: Flux Cancelation

Recent investigations show that coronal jets are driven by the eruption of a small-scale filament (10,000 - 20,000 km long, called a minifilament) following magnetic flux cancelation at the neutral line underneath the minifilament. Minifilament eruptions appear to be analogous to larger-scale solar filament eruptions: they both reside, before the eruption, in the highly sheared field between the adjacent opposite-polarity magnetic flux patches (neutral line); jet-producing minifilament and larger-scale solar filament first show a slow-rise, followed by a fast-rise as they erupt; during the jet-producing minifilament eruption a jet bright point (JBP) appears at the location where the minifilament was rooted before the eruption, analogous to the situation with CME-producing larger-scale filament eruptions where a solar flare arcade forms during the filament eruption along the neutral line along which the filament resided prior to its eruption. In the present study we investigate the triggering mechanism of CME-producing large solar filament eruptions, and find that enduring flux cancelation at the neutral line of the filaments often triggers their eruptions. This corresponds to the finding that persistent flux cancelation at the neutral is the cause of jet-producing minifilament eruptions. Thus our observations support coronal jets being miniature version of CMEs.

Coronal Jets↗
NASA NTRS2015

Trajectories for a Near Term Mission to the Interstellar Medium

Trajectories for rapid access to the interstellar medium (ISM) with a Kuiper Belt Object (KBO) flyby, launching between 2022 and 2030, are described. An impulsive-patched-conic broad search algorithm combined with a local optimizer is used for the trajectory computations. Two classes of trajectories, (1) with a powered Jupiter flyby and (2) with a perihelion maneuver, are studied and compared. Planetary flybys combined with leveraging maneuvers reduce launch C3 requirements (by factor of 2 or more) and help satisfy mission-phasing constraints. Low launch C3 combined with leveraging and a perihelion maneuver is found to be enabling for a near-term potential mission to the ISM.

ISM↗
NASA NTRS2017

The XXL Survey: First Results and Future

The XXL survey currently covers two 25 deg2 patches with XMM observations of approximately 10 ks. We summarize the scientific results associated with the first release of the XXL dataset, which occurred in mid-2016.We review several arguments for increasing the survey depth to 40 ks during the next decade of XMM operations. X-ray(zeta less than 2) cluster, (zeta less than 4) active galactic nuclei (AGN), and cosmic background survey science will then benefit from an extraordinary data reservoir. This, combined with deep multi-lambda observations, will lead to solid standalone cosmological constraints and provide a wealth of information on the formation and evolution of AGN, clusters, and the X-ray background. In particular, it will offer a unique opportunity to pinpoint the zeta greater than1 cluster density. It will eventually constitute a reference study and an ideal calibration field for the upcoming eROSITA and Euclid missions.

general↗
NASA NTRS2017

Washboard Terrain on Pluto

Washboard texture or patterning consists of fields of parallel to sub-parallel ridges typically spaced ~1-2 km crest to crest and a few 100 m in amplitude (Fig. 4a in Moore et al., 2016, Science, 351, 1284-1293). For the most part, underlying topography can be easily discerned. We will refer to discrete, well-bounded patches of these landforms as Washboard Terrain (WT). WT is observed to occur along the rim, and just beyond the rim, of Sputnik basin from the West to NNW. Where it is seen in high-resolution data, it has clearly defined limits, beyond which it would be able to be seen if it were there. WT doesn't occur at very low latitudes or very high latitudes (ranging from 22degN to 62degN). WT seems to occur most conspicuously on relatively level, gently sloping terrain. It is restricted to elevations between approximately 2 km to less than +1.5 km (i.e. not at high elevations). The most noticeable regional aspect of the area in which WT occurs is the sinuous valley network, which is suspected to have been formed, or at least substantially modified, by glaciation. WT also appears to occur mainly on an intermediate-albedo reddish material, where seen in enhanced color data. Where it occurs in level terrain, WT tends to trend ENE - there doesn't seem to be a strong local control of its orientation in response to valley drainage directions. WT can display a greater range of orientations where it occurs in higher-relief (not higher elevation) settings such as spurs. WT appears superposed on very ancient landscapes, but is itself cratered locally by clusters of small (approximately 1-3 km) craters, which may be secondaries. This implies that WT may be intermediate in age. Of several working hypotheses, we currently provisionally favor that WT may be akin to terrestrial recessional moraines (or de Geer moraines) associated with the retreat of a higher stand of N2 glaciation that once overfilled Sputnik basin. These putative moraine features may owe their spacing to superseasonal retreat on Milankovitch timescales of approximately 1 Ma. If this hypothesis has validity, then perhaps the intermediate-albedo reddish material may be akin to ground moraine deposits.

Moore, Jeffrey M.↗
NASA NTRS2017

Strategies Toward Automation of Overset Structured Surface Grid Generation

An outline of a strategy for automation of overset structured surface grid generation on complex geometries is described. The starting point of the process consists of an unstructured surface triangulation representation of the geometry derived from a native CAD, STEP, or IGES definition, and a set of discretized surface curves that captures all geometric features of interest. The procedure for surface grid generation is decomposed into an algebraic meshing step, a hyperbolic meshing step, and a gap-filling step. This paper will focus primarily on the high-level plan with details on the algebraic step. The algorithmic procedure for the algebraic step involves analyzing the topology of the network of surface curves, distributing grid points appropriately on these curves, identifying domains bounded by four curves that can be meshed algebraically, concatenating the resulting grids into fewer patches, and extending appropriate boundaries of the concatenated grids to provide proper overlap. Results are presented for grids created on various aerospace vehicle components.

overset↗
NASA NTRS2009

Digital Beamforming Scatterometer

This paper discusses scatterometer measurements collected with multi-mode Digital Beamforming Synthetic Aperture Radar (DBSAR) during the SMAP-VEX 2008 campaign. The 2008 SMAP Validation Experiment was conducted to address a number of specific questions related to the soil moisture retrieval algorithms. SMAP-VEX 2008 consisted on a series of aircraft-based.flights conducted on the Eastern Shore of Maryland and Delaware in the fall of 2008. Several other instruments participated in the campaign including the Passive Active L-Band System (PALS), the Marshall Airborne Polarimetric Imaging Radiometer (MAPIR), and the Global Positioning System Reflectometer (GPSR). This campaign was the first SMAP Validation Experiment. DBSAR is a multimode radar system developed at NASA/Goddard Space Flight Center that combines state-of-the-art radar technologies, on-board processing, and advances in signal processing techniques in order to enable new remote sensing capabilities applicable to Earth science and planetary applications [l]. The instrument can be configured to operate in scatterometer, Synthetic Aperture Radar (SAR), or altimeter mode. The system builds upon the L-band Imaging Scatterometer (LIS) developed as part of the RadSTAR program. The radar is a phased array system designed to fly on the NASA P3 aircraft. The instrument consists of a programmable waveform generator, eight transmit/receive (T/R) channels, a microstrip antenna, and a reconfigurable data acquisition and processor system. Each transmit channel incorporates a digital attenuator, and digital phase shifter that enables amplitude and phase modulation on transmit. The attenuators, phase shifters, and calibration switches are digitally controlled by the radar control card (RCC) on a pulse by pulse basis. The antenna is a corporate fed microstrip patch-array centered at 1.26 GHz with a 20 MHz bandwidth. Although only one feed is used with the present configuration, a provision was made for separate corporate feeds for vertical and horizontal polarization. System upgrades to dual polarization are currently under way. The DBSAR processor is a reconfigurable data acquisition and processor system capable of real-time, high-speed data processing. DBSAR uses an FPGA-based architecture to implement digitally down-conversion, in-phase and quadrature (I/Q) demodulation, and subsequent radar specific algorithms. The core of the processor board consists of an analog-to-digital (AID) section, three Altera Stratix field programmable gate arrays (FPGAs), an ARM microcontroller, several memory devices, and an Ethernet interface. The processor also interfaces with a navigation board consisting of a GPS and a MEMS gyro. The processor has been configured to operate in scatterometer, Synthetic Aperture Radar (SAR), and altimeter modes. All the modes are based on digital beamforming which is a digital process that generates the far-field beam patterns at various scan angles from voltages sampled in the antenna array. This technique allows steering the received beam and controlling its beam-width and side-lobe. Several beamforming techniques can be implemented each characterized by unique strengths and weaknesses, and each applicable to different measurement scenarios. In Scatterometer mode, the radar is capable to.generate a wide beam or scan a narrow beam on transmit, and to steer the received beam on processing while controlling its beamwidth and side-lobe level. Table I lists some important radar characteristics

Rincon, Rafael F.↗
NASA NTRS2018

Flux Cancelation as the Trigger of Coronal Hole Jet Eruptions

Coronal jets are frequent magnetically-channeled narrow eruptions. They occur in various solar environments: quiet regions, coronal holes and active regions. All coronal jets observed in EUV and X-ray images show a bright spire with a base brightening, also known as jet bright point (JBP). Recent studies show that coronal jets are driven by small-scale filament eruptions (e.g. Hong et al. 2011, Shen et al. 2012, Adams et al. 2014, Sterling et al 2015). We (Panesar et al. 2016b) found in on disk quiet regions that coronal jets originate at a neutral line between dominant-polarity flux and a patch of canceling minority-polarity flux.

Panesar, Navdeep K.↗
NASA NTRS2018

IRIS and SDO Observations of Solar Jetlets Resulting from Flux Cancelation

Jets of all sizes are frequent magnetically channeled narrow eruptions. They occur in various solar environments: quiet regions, coronal holes and active regions. All coronal jets observed in UV, EUV and X-ray images show a bright spire with a base brightening, also known as jet bright point (JBP). Recent studies show that coronal jets are driven by small-scale filament eruptions. We found in on disk quiet regions and coronal holes that coronal jets originate at a neutral line between dominant-polarity flux and a patch of canceling minority-polarity flux.

Panesar, Navdeep K.↗
NASA NTRS2018

CubeX: A Compact X-Ray Telescope Enables Both X-Ray Fluorescence Imaging Spectroscopy and Pulsar Timing Based Navigation

This paper describes the benefits of a miniaturized X-ray telescope payload in the context of a lunar mission. The first part describes the payload in detail, the second part summarizes a small satellite mission concept that utilizes its compact form factor and performance. The CubeX instrument can be used for both X-ray fluorescence (XRF) imaging spectroscopy and X-ray pulsar timing based navigation (XNAV). Using our recent technological advances in X-ray optics and sensors, CubeX combines high angular resolution (<1 arcminutes) Miniature Wolter-I X-ray optics (MiXO) with a common focal plane consisting of high spectral resolution (<150 eV at 1 keV) CMOS X-ray sensors and a high timing resolution (< 1 usec) SDD X-ray sensor. This novel combination of the instruments enables both XRF measurements and XNAV operations without moving parts. The high angular resolution of the MiXO opens a wide range of orbital configurations for observation. Given that performance, the instrument has unprecedented small volume (~1×1×6U), mass (<6 kg), and power (<9W) requirements and opens a wide range of applications for a variety of targets and missions including NEOs and Martian moons. In this paper we illustrate one potential application for a lunar mission concept: The elemental composition of the Moon holds keys to understanding the origin and evolution of both the Moon and the Earth. X-ray fluorescence (XRF), induced either by solar X-ray flux or energetic ions, carries decisive signatures of surface elemental composition. X-ray observations, therefore, give a unique, powerful diagnostic tool for remotely determining elemental abundances including major rock forming elements such as Mg, Al, Na, Si, Fe, and Ca. Through high-resolution XRF imaging spectroscopy, CubeX searches for small patches of elusive lower crust and mantle material excavated within and around impact craters. CubeX identifies regional compositional variations and allows straightforward comparison of elemental distributions with the surface topography from LRO and the gravity data from GRAIL. The elemental compositions of the lower crust and the mantle are sensitive to the conditions of the giant impact which led to the Moon's formation and the subsequent lunar magma ocean (LMO), and thus they are key missing pieces in understanding the formation and early evolution of the Moon. In between XRF observations, CubeX also leverages the technology of high resolution X-ray imaging and time series measurements to conduct XNAV operations and evaluate their performance. Deep space navigation is a critical issue for small planetary missions. XNAV can enable low-cost autonomous deep-space navigation, and has the potential to greatly assist, or even outperform, NASA's Deep Space Network (DSN) or ESA's European Space Tracking (ESTRACK). CubeX is designed to perform sequential observations of 3-4 millisecond pulsars (MSPs) to solve the spacecraft trajectory for absolute navigation, and explore the remote sensing capability of XNAV. In the presented mission concept, the Moon's relative proximity enables a straightforward evaluation of the XNAV performance through DSN.

x-ray spectroscopy↗
NASA NTRS2018

Cybersecurity Information Technology

As technology and security measures improve, hackers keep looking for new techniques and vulnerabilities that allow them to gain access to sensitive data. This includes but is not limited to: user accounts, personal information, databases, operating systems, developmental and testing systems, and operational systems. A hacker is an individual that uses technology such as computers, tablets, and phones for unauthorized access to data. As technology becomes more robust at preventing known attacks, new vulnerabilities always exists. These vulnerabilities usually go unnoticed by developers and could potentially be exploited by an attacker. To prevent hackers from stealing sensitive and potentially harmful information, we must protect our systems and data against these criminals by developing new methods to mitigate the damage caused by these vulnerabilities and prevent them from occurring in the first place. An excellent way to discover how hackers compromise systems is by identifying and analyzing existing vulnerabilities and patching them. The National Aeronautics and Space Administration (NASA) is one of the many federal agencies that operates under a constant threat by hackers. NASA puts a tremendous amount of effort to maintain and improve their security measures, protect critical systems, and secure sensitive information from attackers who would attempt to use it against our nation's interests.

Hackers↗
NASA NTRS2018

High Power W-Band/F-Band Schottky Diode Based Frequency Multipliers

A solid state device chip including diodes (generating a higher frequency output through frequency multiplication of the input frequency) and a novel on-chip power combining design. Together with the on-chip power combining, the chip has increased efficiency because the diodes' anodes, being micro-fabricated simultaneously on the same patch of a GaAs wafer under identical conditions, are very well balanced. The diodes' GaAs heterostructure and the overall chip geometry are designed to be optimized for high power operation. As a result of all these features, the device can generate record-setting power having a signal frequency in the F-band and W-band (30% conversion efficiency).

Siles Perez, Jose Vicente↗
NASA NTRS2018

Using Machine-Learning Methods and Expert Prediction Probabilities to Forecast Solar Flares

It has long been known that studying connection between solar flares and properties of magnetic field in active regions is very important for understanding the flare physics and developing space weather forecasts. The Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI) obtains tremendous amounts of magnetic field data products. However the operational NOAA Space Weather Prediction Center (SWPC) forecasts of solar flares still represent prediction probabilities issued by the experts. In this research we investigate the possibilities to enhance the daily operational flare forecasts performed at the SWPC by developing a synergy of the expert predictions and physics-based criteria, and by employing machine-learning methods. Among the physics-based criteria we consider the descriptors of the Polarity Inversion Line (PIL) and Space weather HMI Active Region Patches (SHARP), and derive from them daily characteristics of the entire Sun. We also consider the daily descriptors of the GOES Soft X-Ray (SXR) 1-8 Angstroms flux such as the flare history of the previous days and averaged X-Ray flux. We estimate the effectiveness in separation of flaring and non-flaring cases for each characteristic, as well as for the expert prediction probabilities, and find that some PIL, SHARP and SXR descriptors are as effective as the expert prediction probabilities and should be considered to issue the flare forecast. Finally, we train and test several Machine-Learning classification algorithms (Support Vector Classifiers with various kernel functions, k-Nearest Neighbor Classifier, Random Forest Classifier, and Neural Networks) using the most effective descriptors and expert prediction probabilities, and compare the obtained predictions with the current SWPC forecasts.

Machine-Learning↗
NASA NTRS2018

Using Mineralogy of the Bagnold Dune Field in Gale Crater to Interpret Eolian Sediment Sorting on the Martian Surface

The Mars Science Laboratory Curiosity rover landed in Gale crater in August 2012 to characterize modern and ancient surface environments. Curiosity executed a two-phase campaign to study the morphology, activity, physical properties, and chemical and mineralogical composition of the Bagnold Dune Field, an active eolian dune field on the lower slopes of Aeolis Mons (Mount Sharp). Detectable aspects of dune sand mineralogy have been examined from orbit with the visible/short-wave infrared spectrometer CRISMand the thermal-infrared spectrometers THEMIS and TES. CRISM data demonstrate variations in plagioclase, pyroxene, and olivine abundances across the dune field. Curiosity analyzed sediments from two locations in the dune field to evaluate the causes of the mineralogical differences observed from orbit. The Gobabeb sample was collected from Namib Dune, a barchanoidal dune on the upwind margin of the dune field, and the Ogunquit Beach sample was collected from the Mount Desert Island sand patch located downwind from Namib. These samples were sieved to <150 μm and delivered to the CheMin X-ray diffraction instrument for quantitative mineralogical analysis. CRISM-derived mineralogy of the Namib Dune and Mount Desert Island and CheMin-derived mineralogy of the Gobabeb and Ogunquit Beach samples can be used in a value-added manner to interpret grain segregation at the bedform to dune-field scale and evaluate contributions from local sediment sources. Models of CRISM data demonstrate that Mount Desert Island is more enriched in olivine and less enriched in plagioclase than Namib dune, suggesting that fine-grained mafic sediments are preferentially mobilized downwind. Curiosity data indicate olivine also forms a coarse lag on the lee sides of barchanoidal dunes. Minor abundances of hematite, quartz, and anhydrite and small differences in the crystal chemistry of plagioclase and pyroxene derived from CheMin data suggest that sediments from the underlying lacustrine rocks also contribute to the Bagnold sands.

Rampe, E. B.↗
NASA NTRS2018

Thermal Radiation in the Cryogenic Regime

The effectiveness of using a patchTFAWS 2018 – August 20-24, 2018 21• Surroundings added as a very closely spaced surfacenear the outer layer of the MLI stack• same emissivity of 0.61• Resulting heat leak -5.78 W/m2– Close to ideal, floating shields case with no seams– Suggests that patching over seams ought to be very effective

Elchert, Justin P.↗
NASA NTRS2018

Transient Heater Analysis for Orion Thermal Vacuum Testing

The Space Environments Complex (SEC) at NASA's Plum Brook Station is currently being prepared to perform thermal vacuum testing of the Orion spacecraft. This thermal vacuum, or T-VAC test will be run for a period of 60 days, which will be the longest such test ever conducted at SEC. The Orion Crew Module (CM) and Service Module (SM) will undergo T-VAC testing in SEC's Space Simulation Vacuum Chamber to ensure the functionality of these systems in a high vacuum environment at extremely cold temperatures. The T-VAC test setup in SEC was modeled and simulated in Thermal Desktop. The initial results from thermal analysis showed areas on the chamber floor to reach very low temperatures, which were below the minimum operating range of certain hardware located on or near the chamber floor. These hardware including elastomeric seals on the GN2 piping, bearing pads and O-rings are essential to both test and the operation of the SEC facility, and must be kept well above -20°F throughout the duration of the T-VAC test. Thus, further analysis was conducted to include the placement of patch heaters on the chamber floor in an effort to increase the temperature near colder areas on the floor. The results and findings from this analysis showed that using these heaters will result in a favorable temperature distribution on the chamber floor. This paper will discuss the methods used in the analysis, and the results obtained to determine the optimal configuration of these heaters on the chamber floor.

Wilhite, Jarred↗
NASA NTRS2018

Transient Heater Analysis for Orion Thermal Vacuum Testing

The Space Environments Complex (SEC) at NASA’s Plum Brook Station is currently being prepared to perform thermal vacuum testing of the Orion spacecraft. This thermal vacuum, or T-VAC test will be run for a period of 60 days, which will be the longest such test ever conducted at SEC. The Orion Crew Module (CM) and Service Module (SM) will undergo T-VAC testing in SEC’s Space Simulation Vacuum Chamber to ensure the functionality of these systems in a high vacuum environment at extremely cold temperatures. The T-VAC test setup in SEC was modeled and simulated in Thermal Desktop. The initial results from thermal analysis showed areas on the chamber floor to reach very low temperatures, which were below the minimum operating range of certain hardware located on or near the chamber floor. These hardware including elastomeric seals on the GN2 piping, bearing pads and O-rings are essential to both test and the operation of the SEC facility, and must be kept well above -20°F throughout the duration of the T-VAC test. Thus, further analysis was conducted to include the placement of patch heaters on the chamber floor in an effort to increase the temperature near colder areas on the floor. The results and findings from this analysis showed that using these heaters will result in a favorable temperature distribution on the chamber floor. This paper will discuss the methods used in the analysis, and the results obtained to determine the optimal configuration of these heaters on the chamber floor.

Wilhite, Jarred↗
NASA NTRS2017

From Prototype to Flight: Qualifying a Ka-Band Parabolic Deployable Antenna (KaPDA) for CubeSats

CubeSats have experienced a number of exciting technological advancements in the past several years. However, until recently, there has been very limited development in the area of high gain CubeSat antennas, which are critical for both high data rate communications and radar science. A Ka-band high gain antenna would provide a 10,000 times increase in data communication rates over an X-band patch antenna and a 100 times increase over state-of-the-art S-band parabolic antennas. Because of this, three years ago the Jet Propulsion Laboratory (JPL) initiated a research and technology development effort to advance CubeSat communication capabilities, with one of the key thrusts being the Ka-band parabolic deployable antenna (KaPDA). This antenna started with the ambitious goal of fitting a 42 dB, 0.5 meter, 35 Ghz antenna in a 1.5U (10 cm x 10 cm x 17 cm) canister. This paper discusses the process of taking the antenna from a first prototype to the flight design, which is flying on the RainCube mission, and earth science CubeSat. The prototype antenna was constructed in early 2015, and then upgraded to an engineering model at the end of 2016 to compensate for lessons learned. The flight version is currently under construction, and scheduled to be finished in 2016. KaPDA is the second deployable parabolic antenna to fly on a CubeSat, and the first of its kind to operate at Ka-band enabling a number of opportunities for high rate deep space antenna communications and radar science.

Sauder, Jonathan↗