Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Eclipse”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Soil Moisture Active/Passive (SMAP) L-Band Microwave Radiometer Post-Launch Calibration Revisit: Approach and Performance

The soil moisture active passive (SMAP) microwave radiometer is a fully-polarimetric L -band radiometer flown on the SMAP satellite in a 6 AM /6 PM sun-synchronous orbit at 685-km altitude. After the SMAP L1B_TB data product version 4 was released in 2018, the radiometer has undergone further calibration and validation. The goal is to reduce the difference between antenna temperature of ascending and descending orbits during the eclipse, and to reduce the dips in the calibration drift over the cold sky (CS) during the eclipse seasons in 2017 and 2018. The postlaunch calibration algorithm has been revisited by retrieving all of the calibration parameters simultaneously with two different options for the hot calibration source (the global ocean, or the radiometer internal reference load). The performance of the two options are compared here. The option with the radiometer internal reference load has been chosen by the SMAP science team for data release version 5. In addition, a correction offset is applied to the input signal to account for offsets during the early-mission stages with the SMAP synthetic aperture radar transmitter operating alongside the radiometer.

calibration↗
NASA NTRSDate not supplied

Supervisory On-line Optimal Control of an Electric Power Microgrid Design for Lunar Habitation

The following article describes an optimal control algorithm for the operation and study of an electric microgrid designed to power a lunar habitat. A photovoltaic (PV) generator powers the habitat and the presence of predictable lunar eclipses necessitates a system to prioritize and control loads within the microgrid. The algorithm consists of a reduced order model (ROM) that describes the microgrid, a discretization of the equations that result from the ROM, and an optimization formulation that controls the microgrid’s behavior. In order to validate this approach, the paper presents results from simulation based on lunar eclipse information and a schedule of intended loads.

Joseph Young↗
NASA NTRSDate not supplied

BioSentinel Deep Space CubeSat Mission

The BioSentinel mission was recently launched aboard the SLS launch vehicle (LV) as part of the Artemis-1 campaign. This 6U CubeSat carries yeast cells to analyze the effects of radiation at large distances from Earth, becoming the first biological payload in Deep Space. Prelaunch activities included mission design updates, orbit determination rehearsals and the development of a tracking schedule in coordination with the Artemis-1 payload office and the Deep Space Network (DSN). An important influence on the trajectories of Artemis I secondaries was the uncertainty associated with deployment from the Interim Cryogenic Propulsion System (ICPS), the upper stage of the SLS LV. The ICPS was rotating at a rate of 1 rpm; there was also uncertainty in the spin axis attitude, which translated into an unknown clock angle of deployment. The variability in this angle and magnitude of deployment implied the existence of a non-negligible risk of a lunar impact, which was evaluated for various potential launch dates. On November 16 th 2022 BioSentinel successfully deployed from ICPS and the navigation team started to receive tracking data from the DSN and ESA antennas. Soon after deployment, the spacecraft was tumbling and entered safe mode. The mission team recovered the spacecraft and after four tracking passes, we solved for a first ephemeris that was sent to the DSN for better tracking of the spacecraft. After propagating this first ephemeris solution, we determined that we avoided impact with a margin of a few hundred km from the lunar surface. More tracking data over the next few days allowed for a more refined orbit solution predicting a periselene altitude of 406 km and a lunar eclipse lasting 36.5 minutes. Therefore, BioSentinel operators avoided any correction maneuvers on the trajectory and successfully tracked and guide the spacecraft. The spacecraft performed a nominal lunar flyby which provided the pertinent energy to achieve a final Earth-trailing heliocentric orbit. Over the course of two weeks, the mission operators corroborated that the subsystems were functioning as expected after the lunar eclipse and the large ΔV incurred. Science operations started once the mission achieved the nominal orbit in Deep Space. This paper discusses in detail the BioSentinel flight performance, as well as the challenges and lessons learned prior to and during this CubeSat mission.

Andres Dono Perez↗
NASA NTRS2023

Thermal Emission from the Earth-sized Exoplanet TRAPPIST-1 b using JWST

The TRAPPIST-1 system is remarkable for its seven planets that are similar in size, mass, density, and stellar heating to the rocky planets Venus, Earth, and Mars in our own Solar System [1]. All TRAPPIST-1 planets have been observed with the transmission spectroscopy technique using the Hubble or Spitzer Space Telescopes, but no atmospheric features have been detected or strongly constrained [2–5]. TRAPPIST-1 b is the closest planet to the system’s M dwarf star, and it receives 4 times as much irradiation as Earth receives from the Sun. This relatively large amount of stellar heating suggests that its thermal emission may be measurable. Here we present photometric secondary eclipse observations of the Earth-sized TRAPPIST1 b exoplanet using the F1500W filter of the MIRI instrument on JWST. We detect the secondary eclipse in each of five separate observations with 8.7-sigma confidence when all data are combined. These measurements are most consistent with re-radiation of the TRAPPIST-1 star’s incident flux from only the dayside hemisphere of the planet. The most straightforward interpretation is that there is little or no planetary atmosphere redistributing radiation from the host star and also no detectable atmospheric absorption from carbon dioxide (CO 2 ) or other species.

Thermal Emission↗
DOE OSTI2016

Introducing Triquetrum, A Possible Future for Kepler and Ptolemy II

Triquetrum is an open platform for managing and executing scientific workflows that is under development as an Eclipse project. Both Triquetrum and Kepler use Ptolemy II as their execution engine. Triquetrum presents opportunities and risks for the Kepler community. The opportunities include a possibly larger community for interaction and a path for Kepler to move from Kepler's one-off ant-based build environment towards a more common OSGi-based environment and a way to maintain a stable Ptolemy II core. The risks include the fact that Triquetrum is a fork of Ptolemy II that would result in package name changes and other possible changes. In addition, Triquetrum is licensed under the Eclipse Public License v1.0, which includes a patent clause that could conflict with the University of California patent clause. This paper describes these opportunities and risks.

Brooks, Christopher↗
DOE OSTI2013

A retrospective planning analysis comparing intensity modulated radiation therapy (IMRT) to volumetric modulated arc therapy (VMAT) using two optimization algorithms for the treatment of early-stage prostate cancer

The primary aim of this study is to compare intensity modulated radiation therapy (IMRT) to volumetric modulated arc therapy (VMAT) for the radical treatment of prostate cancer using version 10.0 (v10.0) of Varian Medical Systems, RapidArc radiation oncology system. Particular focus was placed on plan quality and the implications on departmental resources. The secondary objective was to compare the results in v10.0 to the preceding version 8.6 (v8.6). Twenty prostate cancer cases were retrospectively planned using v10.0 of Varian's Eclipse and RapidArc software. Three planning techniques were performed: a 5-field IMRT, VMAT using one arc (VMAT-1A), and VMAT with two arcs (VMAT-2A). Plan quality was assessed by examining homogeneity, conformity, the number of monitor units (MUs) utilized, and dose to the organs at risk (OAR). Resource implications were assessed by examining planning and treatment times. The results obtained using v10.0 were also compared to those previously reported by our group for v8.6. In v10.0, each technique was able to produce a dose distribution that achieved the departmental planning guidelines. The IMRT plans were produced faster than VMAT plans and displayed improved homogeneity. The VMAT plans provided better conformity to the target volume, improved dose to the OAR, and required fewer MUs. Treatments using VMAT-1A were significantly faster than both IMRT and VMAT-2A. Comparison between versions 8.6 and 10.0 revealed that in the newer version, VMAT planning was significantly faster and the quality of the VMAT dose distributions produced were of a better quality. VMAT (v10.0) using one or two arcs provides an acceptable alternative to IMRT for the treatment of prostate cancer. VMAT-1A has the greatest impact on reducing treatment time.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

Understanding collective human movement dynamics during large-scale events using big geosocial data analytics

Conventional approaches for modeling human mobility pattern often focus on human activity and movement dynamics in their regular daily lives and cannot capture changes in human movement dynamics in response to large-scale events. With the rapid advancement of information and communication technologies, many researchers have adopted alternative data sources (e.g., cell phone records, GPS trajectory data) from private data vendors to study human movement dynamics in response to large-scale natural or societal events. Big geosocial data such as georeferenced tweets are publicly available and dynamically evolving as real-world events are happening, making it more likely to capture the real-time sentiments and responses of populations. However, precisely-geolocated geosocial data is scarce and biased toward urban population centers. In this research, we developed a big geosocial data analytical framework for extracting human movement dynamics in response to large-scale events from publicly available georeferenced tweets. The framework includes a two-stage data collection module that collects data in a more targeted fashion in order to mitigate the data scarcity issue of georeferenced tweets; in addition, a variable bandwidth kernel density estimation(VB-KDE) approach was adopted to fuse georeference information at different spatial scales, further augmenting the signals of human movement dynamics contained in georeferenced tweets. To correct for the sampling bias of georeferenced tweets, we adjusted the number of tweets for different spatial units (e.g., county, state) by population. To demonstrate the performance of the proposed analytic framework, we chose an astronomical event that occurred nationwide across the United States, i.e., the 2017 Great American Eclipse, as an example event and studied the human movement dynamics in response to this event. Finally, this analytic framework can easily be applied to other types of large-scale events such as hurricanes or earthquakes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

ADAPTIVE OPTICS IMAGES. II. 12 KEPLER OBJECTS OF INTEREST AND 15 CONFIRMED TRANSITING PLANETS

All transiting planet observations are at risk of contamination from nearby, unresolved stars. Blends dilute the transit signal, causing the planet to appear smaller than it really is, or producing a false positive detection when the target star is blended with an eclipsing binary. High spatial resolution adaptive optics images are an effective way of resolving most blends. Here we present visual companions and detection limits for 12 Kepler planet candidate host stars, of which 4 have companions within 4''. One system (KOI 1537) consists of two similar-magnitude stars separated by 0.''1, while KOI 174 has a companion at 0.''5. In addition, observations were made of 15 transiting planets that were previously discovered by other surveys. The only companion found within 1'' of a known planet is the previously identified companion to WASP-2b. An additional four systems have companions between 1'' and 4'': HAT-P-30b (3.''7, {Delta}Ks = 2.9), HAT-P-32b (2.''9, {Delta}Ks = 3.4), TrES-1b (2.''3, {Delta}Ks = 7.7), and WASP-P-33b (1.''9, {Delta}Ks = 5.5), some of which have not been reported previously. Depending on the spatial resolution of the transit photometry for these systems, these companion stars may require a reassessment of the planetary parameters derived from transit light curves. For all systems observed, we report the limiting magnitudes beyond which additional fainter objects located 0.''1-4'' from the target may still exist.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

DEEP, LOW MASS RATIO OVERCONTACT BINARY SYSTEMS. XIII. DZ PISCIUM WITH INTRINSIC LIGHT VARIABILITY

New multi-color photometry for the eclipsing binary DZ Psc was performed in 2011 and 2012 using the 85 cm telescope at the Xinglong Station of the National Astronomical Observatories of China. Using the updated Wilson-Devinney (W-D) code, we deduced two sets of photometric solutions. The overcontact degree is f = 89.7({+-} 1.0)%, identifying DZ Psc as a deep, low mass ratio overcontact binary. The asymmetric light curves (i.e., LC{sub 2} in 2012) were modeled by a hot spot on the primary star. Based on all of the available light minimum times, we discovered that the orbital period of DZ Psc may be undergoing a secular period increase with a cyclic variation. The modulated period and semi-amplitude of this oscillation are P{sub mod} = 11.89({+-} 0.19) yr and A = 0.0064({+-} 0.0006) days, which may be possibly attributed to either cyclic magnetic activity or light-time effect due to the third body. The long-term period increases at a rate of dP/dt=+7.43({+-}0.17) Multiplication-Sign 10{sup -7} days yr{sup -1}, which may be interpreted as conserved mass transfer from the less massive component to the more massive one. With mass transferring, DZ Psc will finally merge into a rapid-rotation single star when J{sub spin}/J{sub orb} > 1/3.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

WIYN OPEN CLUSTER STUDY. LV. ASTROMETRY AND MEMBERSHIP IN NGC 6819

We present proper motions and astrometric membership analysis for 15,750 stars around the intermediate-age open cluster NGC 6819. The accuracy of relative proper motions for well-measured stars ranges from {approx}0.2 mas yr{sup -1} within 10' of the cluster center to 1.1 mas yr{sup -1} outside this radius. In the proper motion vector-point diagram, the separation between the cluster members and field stars is convincing down to V {approx} 18 and within 10' from the cluster center. The formal sum of membership probabilities indicates a total of {approx}2500 cluster members down to V {approx} 22. We confirm the cluster membership of several variable stars, including some eclipsing binaries. The estimated absolute proper motion of NGC 6819 is {mu}{sub x}{sup abs}=-2.6{+-}0.5 and {mu}{sub y}{sup abs}=-4.2{+-}0.5 mas yr{sup -1}. A cross-identification between the proper motion catalog and a list of X-ray sources in the field of NGC 6819 resulted in a number of new likely optical counterparts, including a candidate CV. For the first time we show that there is significant differential reddening toward NGC 6819.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

THE MULTI-COLOR LIGHT CURVES OF THE W UMa TYPE CONTACT BINARY EP ANDROMEDAE

New multi-color CCD photometric light curves of the eclipsing binary EP And were obtained over six nights in 2006, 2011, and 2012. Using the Wilson-Devinney code, we computed the photometric elements of this system. It was discovered that EP And is a W-type W UMa contact binary system with a mass ratio of q = 2.685 and a degree of contact factor f = 24.9%, rather than an A-type system. Combining 28 newly determined times of minimum light derived from 1999 to 2012 with others collected from the literature, a long-term increase (dP/dt = +5.22 Multiplication-Sign 10{sup -8} days yr{sup -1}) with a sinusoidal variation (A = 0.0109 days; T = 40.89 yr) in the orbital period was found. The orbital period secular increases may be interpreted as conservative mass transfer from the less massive component to the more massive one, and cyclic variations of the orbital period may be caused by the light-travel time effect through the presence of a third body. The evolutionary status and the age of the system are also discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

A SEARCH FOR RR LYRAE STARS IN SEGUE 2 AND SEGUE 3

We present an extensive search for RR Lyrae (RRL) stars in and around the ultra-faint Milky Way companions Segue 2 and Segue 3. The former (M{sub V} = –2.5) appears to be an extremely faint dwarf galaxy companion of the Milky Way. The latter (M{sub V} = 0.0) is among the faintest star clusters known. We use B and V band time-series imaging obtained at the WIYN 0.9 m telescope at Kitt Peak National Observatory to search for RRL in these objects. In our Segue 2 observations, we present a previously unknown fundamental mode (RRab) RRL star with a period of P {sub ab} = 0.748 days. With this measurement, we revisit the inverse correlation between (P {sub ab}) and ([Fe/H]) established in the literature for Milky Way dwarf galaxies and their RRL. In this context, the long period of Segue 2's RRab star as well as the known significant spread in metallicity in this dwarf galaxy are consistent with the observed trend in (P {sub ab}) and ([Fe/H]). We derive the first robust distance to Segue 2, using both its RRab star and spectroscopically confirmed blue horizontal branch stars. Using [Fe/H] = –2.16 and –2.44 dex, we find d{sub RRL}= 36.6{sup +2.5}{sub -2.4} and 37.7{sup +2.7}{sub -2.7} kpc; assuming [Fe/H] = –2.257 dex, we find d {sub BHB} = 34.4 ± 2.6 kpc. Although no RRL were present in the Segue 3 field, we found a candidate eclipsing binary star system.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

HATS-3b: AN INFLATED HOT JUPITER TRANSITING AN F-TYPE STAR

We report the discovery by the HATSouth survey of HATS-3b, a transiting extrasolar planet orbiting a V = 12.4 F dwarf star. HATS-3b has a period of P = 3.5479 days, mass of M{sub p} = 1.07 M {sub J}, and radius of R{sub p} = 1.38 R {sub J}. Given the radius of the planet, the brightness of the host star, and the stellar rotational velocity (vsin i = 9.0 km s{sup –1}), this system will make an interesting target for future observations to measure the Rossiter-McLaughlin effect and determine its spin-orbit alignment. We detail the low-/medium-resolution reconnaissance spectroscopy that we are now using to deal with large numbers of transiting planet candidates produced by the HATSouth survey. We show that this important step in discovering planets produces log g and T {sub eff} parameters at a precision suitable for efficient candidate vetting, as well as efficiently identifying stellar mass eclipsing binaries with radial velocity semi-amplitudes as low as 1 km s{sup –1}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

MULTIBAND PHOTOMETRIC AND SPECTROSCOPIC ANALYSIS OF HV Cnc

In this paper, radial velocity and VI- and JHK{sub S} - (Two Micron All Sky Survey) band photometric data of the detached system HV Cnc have been analyzed. The primary component of HV Cnc, which is a member of the M67 cluster, is suspected to be either a blue straggler or turn-off star. The system is a single-lined spectroscopic binary and its light curve shows a total eclipse. Spectroscopic observations of the system revealed the third component, which shows contribution to the total light of the system. Light curve and radial velocity data have been analyzed using the Wilson-Devinney (W-D) code and JHK{sub S} filter definitions computed for the W-D code in this work. Our analysis shows that the mass and radius of the primary and secondary components are 1.31 M {sub ☉}, 0.52 M {sub ☉}, 1.87 R {sub ☉}, and 0.48 R {sub ☉}, respectively. All results are compared with previously published literature values and discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

BVR{sub c}I{sub c} observations and analyses on V2421 Cygni, a precontact W UMa binary

We present the first precision BVRI light curves, synthetic light curve solutions, and a period study for the high amplitude solar type binary, V2421 Cygni. The light curves have the appearance of an Algol (EA) type; however, it is made up of dwarf solar type components in a detached mode with a period of only 0.6331 days with an amplitude of about a full magnitude, i.e., it is a precontact W UMa binary. Flare-like disruptions occur in the light curves following the primary and secondary eclipses possibly due to the line-of-sight track of a gas stream. An associated stream spot and splash spot cause bright equatorial spots on the stellar surface of the primary star. The more massive star is the gainer, making this system a classic, albeit dwarf, Algol.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Multi-wavelength photometry of the T Tauri binary V582 Mon (KH 15D): A new epoch of occultations

We present multi-wavelength (VRIJHK) observations of KH 15D obtained in 2012/2013, as well as a master table of standard photometry spanning the years 1967 to 2013. The system is a close, eccentric T Tauri binary embedded in an inclined precessing circumbinary (CB) ring. The most recent data show the continued rise of star B with respect to the trailing edge of the occulting horizon as the system's maximum brightness steadily increases. The wealth of data in time and wavelength domains allows us to track the long-term CCD color evolution of KH 15D. We find that the V – I behavior is consistent with direct and scattered light from the composite color of two stars with slightly different temperatures. There is no evidence for any reddening or bluing associated with extinction or scattering by interstellar-medium-size dust grains. Furthermore, we probe the system's faint phase behavior at near-infrared wavelengths in order to investigate extinction properties of the ring and signatures of a possible shepherding planet sometimes invoked to confine the CB ring at ∼5 AU. The wavelength independence of eclipse depth at second contact is consistent with the ring material being fully opaque to 2.2 μm. The color-magnitude diagrams demonstrate excess flux in J and H at low light levels, which may be due to the presence of a hot, young Jupiter-mass planet.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Photometric properties for selected Algol-type binaries. VII. V404 and with magnetic activity

We present new CCD light curves of the short-period Algol-type eclipsing binary V404 And obtained in 2009-2011. The time-resolving multiple BVRI color light curves of the year 2011 with full phase coverage were analyzed simultaneously using the latest Wilson-Devinney program. We concluded that the configuration of two starspots on the primary is the most reliable explanation for the light curve distortions observed in 2011. Based on the new photometric solution, we further applied the spot model to explain the other light curves, including the previously published R-band light curves. We revealed that the starspots changed on a long timescale in terms of the spot parameters and the differences between Max. I and Max. II. Moreover, the O – C diagram spanning about 15 yr shows an upward parabola, which indicates a secular increase in the orbital period of V404 And. The orbital period increases at a rate of dP/dt = 5.3(0.3) × 10{sup –7} days yr{sup –1}, which might be interpreted by the angular momentum exchange via magnetic activity.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

The Taiwanese-American occultation survey project stellar variability. III. Detection of 58 new variable stars

The Taiwanese-American Occultation Survey project is designed for the detection of stellar occultations by small-size Kuiper Belt Objects, and it has monitored selected fields along the ecliptic plane by using four telescopes with a 3 deg{sup 2} field of view on the sky since 2005. We have analyzed data accumulated during 2005-2012 to detect variable stars. Sixteen fields with observations of more than 100 epochs were examined. We recovered 85 variables among a total of 158 known variable stars in these 16 fields. Most of the unrecovered variables are located in the fields observed less frequently. We also detected 58 variable stars which are not listed in the International Variable Star Index of the American Association of Variable Star Observers. These variable stars are classified as 3 RR Lyrae, 4 Cepheid, 1 δ Scuti, 5 Mira, 15 semi-regular, and 27 eclipsing binaries based on the periodicity and the profile of the light curves.

79 ASTRONOMY AND ASTROPHYSICS↗