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At least 397 records · Page 22

Three new BL Lacertae objects in the Palomar-Green survey

We have identified three BL Lacertae objects in the Palomar-Green Survey which were previously misclassified as DC white dwarfs, namely PG 1246+586, PG 1424+240, and PG 1437+398. Our reclassification is based on the detection of these objects as x-ray sources in the ROSAT all-sky survey and upon our subsequent detection of intrinsic linearly polarized and variable optical emission from these sources. As a result of the ROSAT survey, the number of identified BL Lac objects in the Palomar-Green catalog of UV excess objects has been doubled. Corrected optical positions are presented for PG 1246+586 and PG 1437+398.

Fleming, Thomas A.↗

A Cognitive System Model for Human/Automation Dynamics in Airspace Management

NASA has initiated a significant thrust of research and development focused on providing the flight crew and air traffic managers automation aids to increase capacity in en route and terminal area operations through the use of flexible, more fuel-efficient routing, while improving the level of safety in commercial carrier operations. In that system development, definition of cognitive requirements for integrated multi-operator dynamic aiding systems is fundamental. In order to support that cognitive function definition, we have extended the Man Machine Integrated Design and Analysis System (MIDAS) to include representation of multiple cognitive agents (both human operators and intelligent aiding systems) operating aircraft, airline operations centers and air traffic control centers in the evolving airspace. The demands of this application require representation of many intelligent agents sharing world-models, and coordinating action/intention with cooperative scheduling of goals and actions in a potentially unpredictable world of operations. The MIDAS operator models have undergone significant development in order to understand the requirements for operator aiding and the impact of that aiding in the complex nondeterminate system of national airspace operations. The operator model's structure has been modified to include attention functions, action priority, and situation assessment. The cognitive function model has been expanded to include working memory operations including retrieval from long-term store, interference, visual-motor and verbal articulatory loop functions, and time-based losses. The operator's activity structures have been developed to include prioritization and interruption of multiple parallel activities among multiple operators, to provide for anticipation (knowledge of the intention and action of remote operators), and to respond to failures of the system and other operators in the system in situation-specific paradigms. The model's internal representation has been be modified so that multiple, autonomous sets of equipment will function in a scenario as the single equipment sets do now. In order to support the analysis requirements with multiple items of equipment, it is necessary for equipment to access the state of other equipment objects at initialization time (a radar object may need to access the position and speed of aircraft in its area, for example), and as a function of perception and sensor system interaction. The model has been improved to include multiple world-states as a function of equipment am operator interaction. The model has been used -1o predict the impact of warning and alert zones in aircraft operation, and, more critic-ally, the interaction of flight-deck based warning mechanisms and air traffic controller action in response to ground-based conflict prediction and alerting systems. In this operation, two operating systems provide alerting to two autonomous, but linked sets of operators, whose view of the system and whose dynamics in response are radically different. System stability and operator action was predicted using the MIDAS model.

Corker, Kevin M.↗

Nanosatellite Launch Adapter System (NLAS) Overview

An overview of the Nanosatellite Launch Adapter System (NLAS) is provided that contains information on NLAS' objectives and relevance, structural components and position in the launch vehicle stack, and details on its three main components.

Launch adapter↗

Kibo Robot Programming Challenge 5/21/2020 Checkout Activity Report

This a report on JAXA’s Kibo Robot Programing Challenge (RPC) Checkout activity which took place on 2020-05-21. This activity is an on-orbit test for the upcoming competition organized by JAXA and to be ran by September 2020. It aimed to check the multiple aspects of the operation of Bumble in support of this competition. The activity had three primary objectives: a) verification of four different positions to be visited during the competition, namely Start Position, P1, P2, and P3, b) demonstration of Bumble autonomously moving from the Start Position to P3 without keep-in/keep-out zones and c) demonstration of Bumble autonomously moving from the Start Position to P3 with JAXA’s defined keep-in/keep-out zones. The report emphasizes the confirmation of JAXA’s previously calculated and commanded coordinates for each position and the Astrobee Facilities Team (AFT) estimation of new coordinates in case those coordinates did not match JAXA’s desired target positions per ground and crew procedures. Four estimated coordinates are proposed and various suggestions on operation procedures are given to improve the maneuverability of Bumble during the actual day of the competition.

Astrobee↗

A Discovery of a Candidate Companion to a Transiting System KOI-94: A Direct Imaging Study for a Possibility of a False Positive

We report a discovery of a companion candidate around one of Kepler Objects of Interest (KOIs), KOI-94, and results of our quantitative investigation of the possibility that planetary candidates around KOI-94 are false positives. KOI-94 has a planetary system in which four planetary detections have been reported by Kepler, suggesting that this system is intriguing to study the dynamical evolutions of planets. However, while two of those detections (KOI-94.01 and 03) have been made robust by previous observations, the others (KOI-94.02 and 04) are marginal detections, for which future confirmations with various techniques are required. We have conducted high-contrast direct imaging observations with Subaru/HiCIAO in H band and detected a faint object located at a separation of approximately 0.6 sec from KOI-94. The object has a contrast of approximately 1 × 10(exp −3) in H band, and corresponds to an M type star on the assumption that the object is at the same distance of KOI-94. Based on our analysis, KOI-94.02 is likely to be a real planet because of its transit depth, while KOI-94.04 can be a false positive due to the companion candidate. The success in detecting the companion candidate suggests that high-contrast direct imaging observations are important keys to examine false positives of KOIs. On the other hand, our transit light curve reanalyses lead to a better period estimate of KOI-94.04 than that on the KOI catalogue and show that the planetary candidate has the same limb darkening parameter value as the other planetary candidates in the KOI-94 system, suggesting that KOI-94.04 is also a real planet in the system.

Subaru/HiCIAO↗

Detection of earth-approaching asteroids in near real time

Computer software, called the Moving Object Detection Program (MODP), is described which detects earth-approaching asteroids in near real time. The software runs on a workstation linked to the output of the drift-scanning CCD camera of the Spacewatch Telescope. MOPD recognizes trailed images, detects motion, and accurately determines angular positions and rates of motion for moving objects in the scan images. The results are obtained a few seconds after the image signals are shifted out of the CCD. During 2 months of trial observations with this system, 304 asteroids were detected down to a limiting apparent magnitude for untrailed images of V = 20.5.

Rabinowitz, D. L.↗

Proprioceptive Inference for Dual-Arm Grasping of Bulky Objects Using RoboSimian

This work demonstrates dual-arm lifting of bulky objects based on inferred object properties (center of mass (COM) location, weight, and shape) using proprioception (i.e. force torque measurements). Data-driven Bayesian models describe these quantities, which enables subsequent behaviors to depend on confidence of the learned models. Experiments were conducted using the NASA Jet Propulsion Laboratory’s (JPL) RoboSimian to lift a variety of cumbersome objects ranging in mass from 7kg to 25kg. The position of a supporting second manipulator was determined using a particle set and heuristics that were derived from inferred object properties. The supporting manipulator decreased the initial manipulator’s load and distributed the wrench load more equitably across each manipulator, for each bulky object. Knowledge of the objects came from pure proprioception (i.e. without reliance on vision or other exteroceptive sensors) throughout the experiments.

Backes, Paul↗

A search in the COS-B data base for correlated time variability in regions containing objects of interest

As is well known, association of the gamma-ray sources with celestial objects is, in general, difficult on a pure positional basis, while correlated time variability could obviously provide such proof. This technique can be employed on regions of the gamma-ray sky containing interesting objects of known variability at some wavelength even in the absence of a recognized gamma-ray excess with the aim to extract a weak but predictable signal from the surrounding noise. This technique is applied here on a longer variability time scale, generally of the order of days. Photons coming from the sky regions centered on the various celestial objects considered were selected with energies 100 MeV and with arrival directions within an energy-dependent area of radius of approx 6 deg at 100 MeV. In order to construct a time profile of such photons, their arrival times were grouped in bins of dimensions defined by the available photons number and by the value of the period searched for.

Caraveo, P. A.↗

Reliable automatic plan selection for visual robotic positioning

Reliability analysis techniques developed for robotics are applied to a six-DOF (degree-of-freedom) visual positioning system. The task is to measure an object's pose and then grip the object reliably subject to time and accuracy constraints. Errors due to pixel truncation in the stadimetric vision system, forward kinematic and inverse kinematic uncertainties, and joint position and velocity noise are stochastically modeled. Simulation results for PUMA 500 kinematic and dynamic characteristics are presented.

Mcinroy, John E.↗

Theoretical Modeling in Very Long Baseline Interferometry

Interferometry at radio frequencies between Earth-based receivers separated by intercontinental distances had made significant contributins to astrometry and geophysics during the past three decades, Analyses of such very long baseline interferometric (VLBI) experiments now permit measurements of relative positions of points on the Earth's surface, and angles between celestial objects, at the levels of 1cm and 1 nanoradian, respectively. The relative angular positions of extragalactic radio sources inferred from this technique presently form the best ralization of an inertial reference frame. This review summarizes the current theoretical models that are needed to extract results from the VLBI observables at such levels of accuracy.

interferometric VLBI extragalactic radio sources↗

Telescoping tube assembly

An extensible and retractable telescoping tube positions test devices that inspect large stationary objects. The tube has three dimensional adjustment capabilities and is vertically suspended from a frame. The tube sections are independently supported with each section comprising U-shaped housing secured to a thicker support plate. Guide mechanisms preferably mounted only to the thicker plates guide each tube section parallel to a reference axis with improved accuracy so that the position of the remote end of the telescoping tube is precisely known.

Sturm, Albert J.↗

Development of techniques for gantryless associated-particle imaging

To move fast-neutron radiography using the associated-particle imaging technique from the laboratory to the field, the development of new analysis techniques is required. In particular, the relative positions of the source and detectors need to be determined when they have been placed by hand, the normalization for a particular source–detector geometry needs to be determined without a measurement in the same geometry with no object present, and accurate image stitching is required when multiple detector positions are necessary to image an object. The present work describes methods that employ transmission neutron data to localize a fast-neutron imaging panel with respect to the neutron source, calculate a normalization for a given source–detector geometry, stitch images together, and describes the required system calibrations. The reported techniques enable in-field neutron radiography for cases in which the source–detector geometry is not well known a priori and where operational constraints preclude a normalization measurement.

Heath, Matthew↗

Ammonia downstream from HH 80 North

HH 80-81 are two optically visible Herbig-Haro (HH) objects located about 5 minutes south of their exciting source IRAS 18162-2048. Displaced symmetrically to the north of this luminous IRAS source, a possible HH counterpart was recently detected as a radio continuum source with the very large array (VLA). This radio source, HH 80 North, has been proposed to be a member of the Herbig-Haro class since its centimeter flux density, angular size, spectral index, and morphology are all similar to those of HH 80. However, no object has been detected at optical wavelengths at the position of HH 80 North, possibly because of high extinction, and the confirmation of the radio continuum source as an HH object has not been possible. In the prototypical Herbig-Haro objects HH 1 and 2, ammonia emission has been detected downstream of the flow in both objects. This detection has been intepreted as a result of an enhancement in the ammonia emission produced by the radiation field of the shock associated with the HH object. In this Letter we report the detection of the (1,1) and (2,2) inversion transitions of ammonia downstream HH 80 North. This detection gives strong suppport to the interpretation of HH 80 North as a heavily obscured HH object. In addition, we suggest that ammonia emission may be a tracer of embedded Herbig-Haro objects in other regions of star formation. A 60 micrometer IRAS source could be associated with HH 80 North and with the ammonia condensation. A tentative explanation for the far-infrared emission as arising in dust heated by their optical and UV radiation of the HH object is presented.

Girart, Jose M.↗

Detection of radio continuum emission from Herbig-Haro objects 1 and 2 and from their central exciting source

The region in Orion containing HH 1 and HH 2 was observed with the VLA at 20, 6, and 2 cm on several occasions from 1981 to 1984. At lower resolution, four continuum sources were detected. Two of these sources coincide positionally with HH 1 and HH 2. At 6 cm and higher resolution, HH 1 is resolved into at least two components. The emission is probably bremsstrahlung originating in the same region where the visible line emission is produced. This is the first detection of radio continuum from classic Herbig-Haro objects. At a position closely centered between HH 1 and HH 2, an object that can be interpreted as the energy source of the system was detected. The central source spectrum is S(nu) of about nu to the alpha power, where alpha = 0.4 + or - 0.2, suggesting a stellar wind. Finally, the fourth radio continuum source coincides positionally with an H2O maser and is probably excited by an independent star. There is evidence of time variability in its radio flux. No emission was detected from the Cohen-Schwartz (1979) star at the 0.1 mJy level.

Pravdo, S. H.↗

Experimental modelling of lightning interaction phenomena with a free potential conducting objects

Laboratory experiments were conducted to investigate the physical processes of the development of air discharge and its interaction with free potential conducting objects. The space-time development of lightning in gaps was recorded by a motion picture camera and an optoelectronic transducer. The electric field at different points in the gap was measured using a Pockels device both in the leader stage and in the stage of the return stroke. Experimental results of the streamer zone length measurements in the gaps with lengths up to 65 meters are presented. The physical processes occurring during the interaction of positive and negative long sparks with isolated objects were investigated. The striking probability of isolated conducting spheres with different diameters and the dependence of the strike on the location of the gap are investigated.

Chernov, E. N.↗

Analytical expressions for position error in triangulation solution of point in space for several station configurations

Analytical expressions are derived to first order for the rms position error in the triangulation solution of a point object in space for several ideal observation-station configurations. These expressions provide insights into the nature of the dependence of the rms position error on certain of the experimental parameters involved. The station geometries examined are: (1) the configuration of two arbitrarily located stations; (2) the symmetrical circular configuration of two or more stations with equal elevation angles; and (3) the circular configuration of more than two stations with equal elevation angles, when one of the stations is permitted to drift around the circle from its position of symmetry. The expressions for the rms position error are expressed as functions of the rms line-of-sight errors, the total number of stations of interest, and the elevation angles.

Long, S. A. T.↗

The astrometry programme at Mt. John Observatory

The comet (and minor planet) astrometry program uses one of two 0.6 meter (24 in.) Cassegrain telescopes at Mt. John University Observatory. For astrometric photographs of comets and minor planets a simple guide probe camera is attached to the Cassegrain. Frequently the Cassegrain field does not include sufficient cataloged stars for a satisfactory reduction. In these cases the comet position is transferred to an astrograph plate. Ephemeris data are calculated to the tenth of a day nearest the meridian transit of the object or for dusk or dawn twilight for low objects. Star measurement and identification are checked by reducing positions of cataloged stars.

Gilmore, A. C.↗

Apparatus and method for high-speed characterization of surfaces

This invention permits rapid determination of a three-dimensional contour of an object. The apparatus directs a laser beam onto a point on an object, and the scattered light is received by a position sensitive detector (PSD). The location at which scattered light is received can be related to the displacement of the point on the object, using basic trigonometry. The laser beam is deflected non-mechanically, by passing it through a crystal whose index of refraction is varied in a controlled manner. By proper control of the index of refraction, one can scan the beam across a desired area of the object, without using any moving parts, and can therefore obtain complete information about the contour of the object. The device operates without making any conventional images, and is therefore much faster than comparable devices of the prior art. Also, the laser and beam deflector can be housed in a small optical head which enables the device to reach normally inaccessible areas. The device can compare the test object with a reference object, or it can compare two objects for differences.

Hooker, Jeffery A.↗