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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.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Astrometry with the Wide-Field Infrared Space Telescope

The Wide-Field Infrared Space Telescope (WFIRST) will be capable of delivering precise astrometry for faint sources over the enormous field of view of its main camera, the Wide-Field Imager (WFI). This unprecedented combination will be transformative for the many scientific questions that require precise positions, distances, and velocities of stars. We describe the expectations for the astrometric precision of the WFIRST WFI in different scenarios, illustrate how a broad range of science cases will see significant advances with such data, and identify aspects of WFIRST’s design where small adjustments could greatly improve its power as an astrometric instrument.

Robyn E. Sanderson↗
NASA NTRS2008

STEPS: JPL's Astrometric Exoplanet Survey

Presentation topics include: STEPS ground-based astrometry at Hale Telescope; the instrument; why astronomy and why M-dwarfs; motion of center of light about center of mass in photocentric orbit; photocentric motion vs. fractional mass; high-resolution imaging of STEPS targets; GU 802 p one possible orbit plotted with data, Keplerian frame; GJ 802 results; STEPS future; and a bibliography of STEPS papers.

astrometry↗
NASA NTRS1995

Measuring Pixel-Position Errors On CCD Imagers

Deviations of positions of pixels on charge-coupled-device (CCD) image detector from nominal rectangular grid pattern measured by method in which coherent-light interference fringes used as reference pattern. Conceived for use in determining pixel-position errors in astrometric cameras flown aboard spacecraft. Also applied to determination of similar errors in (and calibration of) terrestrial CCD cameras used as position sensors; for example, position-measuring cameras that are parts of robotic systems.

Shaklan, Stuart B.↗
DOE OSTI2021

The Dark Energy Survey Data Release 2

In this work, we present the second public data release of the Dark Energy Survey, DES DR2, based on optical/near-infrared imaging by the Dark Energy Camera mounted on the 4 m Blanco telescope at Cerro Tololo Inter-American Observatory in Chile. DES DR2 consists of reduced single-epoch and coadded images, a source catalog derived from coadded images, and associated data products assembled from 6 yr of DES science operations. This release includes data from the DES wide-area survey covering ~5000 deg 2 of the southern Galactic cap in five broad photometric bands, grizY. DES DR2 has a median delivered point-spread function FWHM of g = 1.11'', r = 0.95'', i = 0.88'', z = 0.83'', and Y = 0farcs90, photometric uniformity with a standard deviation of < 3 mmag with respect to Gaia DR2 G band, a photometric accuracy of ~11 mmag, and a median internal astrometric precision of ~27 mas. The median coadded catalog depth for a 1farcs95 diameter aperture at signal-to-noise ratio = 10 is g = 24.7, r = 24.4, i = 23.8, z = 23.1, and Y = 21.7 mag. DES DR2 includes ~691 million distinct astronomical objects detected in 10,169 coadded image tiles of size 0.534 deg2 produced from 76,217 single-epoch images. After a basic quality selection, benchmark galaxy and stellar samples contain 543 million and 145 million objects, respectively. These data are accessible through several interfaces, including interactive image visualization tools, web-based query clients, image cutout servers, and Jupyter notebooks. DES DR2 constitutes the largest photometric data set to date at the achieved depth and photometric precision.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Orbital Motion, Variability, and Masses in the T Tauri Triple System

We present results from adaptive optics imaging of the T Tauri triple system obtained at the Keck and Gemini Observatories in 2015−2019. We fit the orbital motion of T Tau Sb relative to Sa and model the astrometric motion of their center of mass relative to T Tau N. Using the distance measured by Gaia, we derived dynamical masses of M{sub Sa}=2.05±0.14 M {sub ⊙} and M {sub Sb} = 0.43 ± 0.06 M{sub ⊙}. The precision in the masses is expected to improve with continued observations that map the motion through a complete orbital period; this is particularly important as the system approaches periastron passage in 2023. Based on published properties and recent evolutionary tracks, we estimate a mass of ∼2 M {sub ⊙} for T Tau N, suggesting that T Tau N is similar in mass to T Tau Sa. Narrowband infrared photometry shows that T Tau N remained relatively constant between late 2017 and early 2019 with an average value of K = 5.54 ± 0.07 mag. Using T Tau N to calibrate relative flux measurements since 2015, we found that T Tau Sa varied dramatically between 7.0 and 8.8 mag in the K band over timescales of a few months, while T Tau Sb faded steadily from 8.5 to 11.1 mag in the K band. Over the 27 yr orbital period of the T Tau S binary, both components have shown 3–4 mag of variability in the K band, relative to T Tau N.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1992

The BL Lacertae object PKS 1413 + 135 - Is it within or behind a spiral galaxy?

New observations of the very red quasar or BL Lac object PKS 1413 + 135 are presented. Optical imaging and spectroscopy confirm the claim that the host galaxy to this BL Lac is a spiral, and H-band imaging shows the point source centered in the galaxy to within 0.1 arcsec. A reanalysis of Einstein X-ray data finds evidence for an extremely large column density in this source. While the astrometric evidence supports the hypothesis that PKS 1413 + 135 is the very unusual case of a BL Lac object in a spiral galaxy, a highly extincted nuclear source would produce other observable features in this galaxy that are not observed: narrow emission-line region and large thermal IR flux. Their absence argues for this source being background to the spiral.

Stocke, John T.↗
NASA NTRS2008

SIM-Lite Update

Discussion focus on: SIM-Lite Instrument Update - 6m baseline, 50cm, approximately 900M cost; Technology Update - Systematic errors and floor; SIM-Lite terrestrial planet discovery capability; Double blind multiple planet study summary; and the changing landscape of exoplanet science and the role of SIM-Lite. Slides include technology to flight component engineering; instrumental systematic errors; ultra deep search for Earth clones; double blind test, astrometric detection of Earths in multiplanet systems; the current era of exoplanet science and where SIM-Lite fits in; the next frontier and where SIM-Lite fits in, why SIM is unique in discovering Earths; imaging planet status is uncertain without masses and ages; SIM role in establishing how planetary systems form and evolve; and SIM probes of broad planet mass range around young stars.

exoplanets↗
NASA NTRS1992

A gravitational lens candidate with an unusually red optical counterpart

The properties of the strong radio source MG0414 + 0534 are described. It is found to display many of the properties expected in a gravitational lens system. At radio wavelengths and 0.5-arcsec resolution, MG0414 + 0534 is made up of four compact components whose unusual configuration and relative flux densities are similar to those found in confirmed four-image gravitational lens systems. At optical wavelengths three objects are detected, consistent with there being optical objects at the positions of the radio components, given the lower optical resolution. The radio and optical centroid positions agree within the astrometric errors, and the relative ordering of the fluxes is the same. The colors and radiooptical spectral indices are similar, but there are differences larger than the photometric errors and the measured variability (about 30 percent). Extinction by dust might simultaneously explain the unusually red color and the absence of light from a lens.

Hewitt, J. N.↗
DOE OSTI2022

Quasars with Proper Motions and the Link to Double and Multiple AGNs

Gaia used a large sample of photometrically selected active galactic nuclei (AGNs) and quasars to remove the residual spin of its global proper motion system in order to achieve a maximally inertial reference frame. A small fraction of these reference objects have statistically significant astrometric proper motions in Gaia EDR3. We compile a source sample of 105,593 high-fidelity AGNs with accurate spectroscopically determined redshifts above 0.5 from the SDSS and normalized proper motions below 4. The rate of genuinely perturbed proper motions is at least 0.17%. A smaller high completeness sample of 152 quasars with excess proper motions at a confidence level of 0.9995 is examined in detail. Pan-STARRS images and Gaia-resolved pairs reveal that 29% of the sample are either double sources or gravitationally lensed quasars. An Anderson–Darling test on parameters of a smaller high-reliability sample and their statistical controls reveals 17 significant factors that favor multiplicity and multi-source structure as the main cause of perturbed astrometry. Using a nearest-neighbor distance statistical analysis and counts of close companions in Gaia on a much larger initial sample of AGNs, an excess of closely separated sources in Gaia is detected. At least 0.33% of all optical quasars are genuinely double or multiply imaged. We provide a list of 44 candidate double or multiple AGNs and four previously known gravitational lenses. Many proper motion quasars may be more closely separated, unresolved doubles exhibiting the variability imposed motion effect, and a smaller fraction may be chance alignments with foreground stars causing weak gravitational lensing.

Astrometric microlensing effect↗
DOE OSTI2021

Hyper Suprime-Cam Legacy Archive

Abstract We present the launch of the Hyper Suprime-Cam Legacy Archive (HSCLA), a public archive of processed, science-ready data from the Hyper Suprime-Cam (HSC). HSC is an optical wide-field imager installed at the prime focus of the Subaru Telescope and has been in operation since 2014. While ∼1/3 of the total observing time of HSC has been used for the Subaru Strategic Program (SSP), the remainder of the time is used for Principal Investigator (PI)-based programs. We have processed the data from these PI-based programs and make the processed, high-quality data available to the community through HSCLA. The current version of HSCLA includes data taken in the first year of science operation, 2014. We provide both individual and coadd images as well as photometric catalogs. The photometric catalog from the coadd is loaded to the database, which offers a fast access to the large catalog. There are other online tools such as an image browser and an image cutout tool and they will be useful for science analyses. The coadd images reach 24–27th magnitudes at 5σ for point sources and cover approximately 580 square degrees in at least one filter with 150 million objects in total. We perform extensive quality assurance tests and verify that the photometric and astrometric quality of the data is good enough for most scientific explorations. However, the data are not without problems and users are referred to the list of known issues before exploiting the data for science. All the data and documentations can be found at the data release site, 〈https://hscla.mtk.nao.ac.jp/〉.

Tanaka, Masayuki↗
NASA NTRS2008

Extrasolar Planetary Imaging Coronagraph: Visible Nulling Coronagraph Testbed Results

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC will provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 3-year mission lifetime ( 5 year goal) and will revisit planets at least three times at intervals of 9 months. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables high order starlight suppression in broadband light. To demonstrate the VNC approach and advance it's technology readiness the NASA Goddard Space Flight Center and Lockheed-Martin have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed,

Lyon, Richard G.↗
NASA NTRS2009

Visible Nulling Coronagraph Testbed Results

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a NASA Astrophysics Strategic Mission Concept study and a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC would provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 5-year mission lifetime. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables starlight suppression in broadband light from 480-960 nm. To demonstrate the VNC approach and advance it's technology readiness we have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed.

Lyon, Richard G.↗
NASA NTRS1987

Orbit determination accuracy assessment for an asteroid flyby - A Galileo case study

The Galileo spacecraft may be targeted for a close flyby of an asteroid on its way to an encounter with Jupiter. An orbit determination accuracy analysis was carried out for the case of the asteroid 29 Amphitrite based on the use of radio metric and optical data types. Prior to encounter, the uncertainty in the asteroid's position, based on astrometric observations from earth, amounts to several hundred kilometers. This ephemeris uncertainty constitutes the dominant error in the determination of the spacecraft orbit with respect to Amphitrite. It is shown that the spacecraft-asteroid relative position can be improved by imaging asteroid-star pairs with the Galileo charge-coupled device (CCD) camera, enabling an accurate flyby of the asteroid. The main benefit of optical navigation is to enable the instrument pointing updates necessary for closeup viewing of the asteroid. A discussion of the evolution of the target error ellipse parameters as a function of data coverage and various combinations of radiometric and optical data types is also presented.

Kechichian, Jean A.↗
NASA NTRS1995

Potential applications of GSC-2 for GAIA operations

The second guide star catalog (GSC-2) is a project that aims to create a complete catalog of stars and galaxies to about the 18th magnitude, and would contain colors, magnitudes, positions and proper motions. The catalog would provide an object list for the construction of an input catalog for possible future astrometric satellites, such as the global astrometric interferometer for astrophysics (GAIA) satellite. With a schedule that is compatible with the projected timeframe of GAIA, the GSC-2 could be available in time to support the preparatory astrophysical observations for an input catalog. The availability of the digitalized images for the preparation of finding charts would improve the efficiency of this task.

Lasker, Barry M.↗
NASA NTRS2008

[The Extrasolar Planetary Imaging Coronagraph]

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a proposed NASA Exoplanet Probe mission to image and characterize extr asolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC will provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, deter mine orbital inclinations and masses, characterize the atmospheres around A and F type stars which cannot be found with RV techniques, and observe the inner spatial structure and colors of debris disks. EPIC has a heliocentric Earth trailing drift-away orbit, with a 5 year mission lifetime (5 year goal). The robust mission design is simple and flexible ensuring mission success while minimizing cost and risk. The science payload consists of a heritage optical telescope assembly (OTA), and visible nulling coronagraph (VNC) instrument. The instrument achieves a contrast ratio of 10(exp 9) over a 4.84 arcsecond field-of-view with an unprecedented inner working angle of 0.14 arcseconds over the spectral range of 440-880 nm. The telescope is a 1.65 meter off-axis Cassegrain with an OTA wavefront error of /9, which when coupled to the VNC greatly reduces the requirements on the large scale optics, compressing them to stability requirements within the relatively compact VNC optical chain. The VNC features two integrated modular nullers, a spatial filter array (SFA) and an E2V-L3 photon counting CCD. Direct null control is accomplished from the science focal plane mitigating against complex wavefront and amplitude sensing and control strategies.

Clampin, Mark↗
NASA NTRS2010

Global VLBI Observations of Weak Extragalactic Radio Sources: Imaging Candidates to Align the VLBI and Gaia Frames

The space astrometry mission Gaia will construct a dense optical QSO-based celestial reference frame. For consistency between optical and radio positions, it will be important to align the Gaia and VLBI frames (International Celestial Reference Frame) with the highest accuracy. In this respect, it is found that only 10% of the ICRF sources are suitable to establish this link (70 sources), either because most of the ICRF sources are not bright enough at optical wavelengths or because they show extended radio emission which precludes reaching the highest astrometric accuracy. In order to improve the situation, we initiated a multi-step VLBI observational project, dedicated to finding additional suitable radio sources for aligning the two frames. The sample consists of about 450 optically-bright radio sources, typically 20 times weaker than the ICRF sources, which have been selected by cross-correlating optical and radio catalogs. The initial observations, aimed at checking whether these sources are detectable with VLBI, and conducted with the European VLBI Network (EVN) in 2007, showed an excellent 90% detection rate. This paper reports on global VLBI observations carried out in March 2008 to image 105 from the 398 previously detected sources. All sources were successfully imaged, revealing compact VLBI structure for about half of them, which is very promising for the future.

Bourda, Geraldine↗
NASA NTRS1991

First results from the faint object camera - High-resolution imaging of the Pluto-Charon system

The first observations of a solar system target with the Faint Object Camera of the HST are reported. Observations of the Pluto-Charon system were obtained in f/96 and f/288 mode. Pluto and Charon were clearly resolved, and the observed separation and diameters are in accordance with expectations. The f/96 data were astrometrically and photometrically analyzed; preliminary results are presented.

Albrecht, R.↗
NASA NTRS1993

Astrometric Models of the Phobos Orbiter TV Cameras

Astrometric models of the 3 Phobos Orbiter TV cameras, their pointing in inertial space, the position of the Phobos Orbiter with respect to Mars, Phobos and Deimos, and transformations from inertial to body-fixed coordinates are needed to transform between the image coordinates of a picture element (.

Mars Phobos Deimos TV images↗