A5047345012- Geophysics and Gravity Measurements
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- History and Developments in Astronomy
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- Historical Astronomy and Related Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Inertial Sensor and Navigation
- Geomagnetism and Paleomagnetism Studies
- GNSS positioning and interference
- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Satellite Communication Systems
- Geophysics and Sensor Technology
- Advanced Frequency and Time Standards
- Astrophysics and Star Formation Studies
- Relativity and Gravitational Theory
- Historical Geography and Cartography
- Spacecraft Design and Technology
- Geology and Paleoclimatology Research
- Antenna Design and Optimization
- Manufacturing Process and Optimization
- Statistical and numerical algorithms
Rutherford Appleton Laboratory
2005-2016
Science and Technology Facilities Council
2005-2008
The Nautical Institute
2006
Australian Astronomical Observatory
1976-1981
In the 2006–2009 triennium, International Astronomical Union (IAU) Working Group on Numerical Standards for Fundamental Astronomy determined a list of Current Best Estimates (CBEs). The IAU 2009 Resolution B2 adopted these CBEs as (2009) System Constants. Additional work continues to define process updating and creating standard electronic document.
A new precession-nutation model for the Celestial Intermediate Pole (CIP) was adopted by IAU in 2000 (Resolution B1.6). The model, designated 2000A, includes a nutation series non-rigid Earth and corrections precession rates longitude obliquity. also specifies numerical values pole offsets at J2000.0 between mean equatorial frame Geocentric Reference System (GCRS). In this paper, we discuss models consistent with 2000A (i.e. MHB 2000, provided Mathews et al. [CITE]) provide range of...
We have made the first complete map of stellar velocity field within 100 arcsec nucleus bright elliptical galaxy NGC 5128 (Cen A) and obtained complementary long-slit spectra out to 400 arsec along optical major axis. These data show that ellipsoidal component is rotating slowly (maximum line-of-sight 40km s –1) approximately perpendicular dust lane about a projected axis lying in pa |$\sim\,135^{\circ}$| opposite sense expected if warp were due stable orbits round triaxial potential. The...
The ALMA North American and European prototype antennas have been evaluated by a variety of measurement systems to quantify the major performance specifications. Nearfield holography was used set reflector surfaces 17 microns RMS. Pointing fast switching determined with an optical telescope millimeter wavelength radiometry, yielding 2 arcsec absolute 0.6 offset pointing accuracies. Path length stability measured be less than or approximately equal 20 over 10 minute time periods using...
Context.The precession-nutation transformation describes the changing directions on celestial sphere of Earth's pole and an adopted origin right ascension. The coordinate system for is geocentric reference system, two are intermediate (CIP) (CIO), latter having supplanted equinox this purpose following IAU resolutions in 2000. triad based CIP CIO called system; prediction topocentric additionally requires Earth rotation angle (ERA), counterpart Greenwich sidereal time (GST) former system.
The solar submillimeter-wave telescope (SST) is the only one of its kind dedicated to continuous observations. Two radiometers at 0.740 mm (405 GHz), and four 1.415 (212 GHz) are placed in Cassegrain focal plane 1.5-m dish El Leoncito high altitude site, San Juan, Argentina. aperture efficiencies close design predictions: 20% 35% for 2 4 arcminutes beam sizes 405 212 GHz, respectively. positioner absolute pointing accuracy 10 arcseconds. Spectral coverage complemented by ground-based...
Context. The present IAU model of precession, like its predecessors, is given as a set polynomial approximations various precession parameters intended for high-accuracy applications over limited time span. Earlier comparisons with numerical integrations have shown that this valid only few centuries around the basic epoch, J2000.0, while more distant epochs it rapidly diverges from solution. In our preceding studies we also obtained preliminary developments precessional contribution to...
In this tutorial we summarize the physics and mathematics behind refractive electromagnetic wave bending delay. Refractive delay through Earth's atmosphere at both radio/millimetric optical/IR wavelengths are discussed, but with most emphasis on former, Atacama Large Millimeter Array (ALMA) applications in mind. As modern astronomical measurements often require sub-arcsecond position accuracy, care is required when selecting algorithms. For spherically-uniform model atmospheres generally...
With a 100mx110m off-axis paraboloid dish, the Green Bank Telescope (GBT) is largest fully steerable radio telescope on Earth. A major challenge facing large ground-based telescopes achieving sufficient pointing accuracy for observing at high frequencies, up to 116 GHz in case of GBT. Accurate requires ability blindly acquire source locations and perform ad hoc corrections determined by nearby calibrator sources order obtain starting position accurate within small margin error target's...
The IAU 2000 precession consists of the 1976 ecliptic (Lieske et al. [CITE], A&A, 58, 1) and part 2000A equator adopted by Resolution B1.6 (Mathews J. Geophys. Res., 107, B4, 10.1029/2001JB000390). In this paper we provide a range new expressions as possible replacements for precession. are based upon so-called P03 solution Capitaine ([CITE], 412, 567) ecliptic. addition an improved model is discussed. This was obtained in exactly same way but using refined contributions non-rigid Earth...
Expressions for the position of Celestial Intermediate Pole (CIP) and Ephemeris Origin (CEO) in Geocentric Reference System (GCRS) have been computed using IAU 2000A precession-nutation. These expressions are use new transformation between GCRS International Terrestrial (ITRS) which is recommended by Resolution B1.8. Various comparisons numerical checks performed classical transformations based on revealed necessary improvements to be applied form order achieve required level accuracy. Once...
Context.The 2006 IAU General Assembly has adopted the P03 model of Capitaine et al. (2003a) recommended by WG on precession and ecliptic (Hilton 2006) to replace 2000 model, which comprised Lieske (1977) with adjusted rates. Practical implementations this new "IAU 2006" are therefore required, involving choices procedures algorithms.
A search for optical pulsations from radio pulsars has resulted in identification of the Vela pulsar (PSR 0833–45), and upper limits to pulsed emission PSR0736–40, 0740–28, 1055–52 1449–64. Improved measurements position, magnitude colour are consistent with its a faint blue star small excess. If luminosity is proportional P−n where P period, our results n = 10.5.
This paper provides expressions to be used implement the new definition of UT1 corresponding IAU 2000 resolutions either in (CEO-based) or classical (equinox-based) transformations between International Terrestrial Reference System (ITRS) and Geocentric Celestial (GCRS). The expression for Greenwich Sidereal Time (GST) has agreement at microarcsecond level, one century, with Earth Rotation Angle (ERA) quantity s positioning Ephemeris Origin (CEO) on equator CIP. computations using...
A typical modern telescope control system points by first calculating the direction of target in nominal mount coordinates and then applying small corrections to demanded angles. The pointing refers rotation axis instrument mount, rotator demands are calculated <i>via</i> parallactic angle. This simple approach works well enough when accuracy objectives modest. However, a more rigorous can pay off, form improved pointing, accurate guide probe predictions, reduced residual field reliable...
We have resolved the WC9 star Ve 2-45 at a wavelength of 2.2 μm. The shell circumstellar dust is optically thin, and has characteristic radius 0.04 arcsec. This in agreement with simple models shell, will help to constrain more elaborate models, when they become available.
The light curve of the Crab Nebula pulsar has been observed using an aperture 1.3 arcsec with Anglo-Australian Telescope. background was measured in annulus 2 radius, contamination from being estimated pulsed component. resultant a minimum intensity 0.6 per cent peak. Around is ∼ 70 linearly polarized, and at other phases our measures accord earlier work.
Optical observations of the Vela pulsar have resulted in an improved pulse profile. The results suggest that two main components are asymmetric and there is significant pulsed emission at other phases
An analysis of the alignment and pointing accuracy UK 1.2-m Schmidt telescope has resulted in a remarkably accurate determination parameters involved. The resulting improvement greatly increased efficiency guide star acquisition. polar axis elevation angle is adjusted for every photograph order to minimize field rotation due atmospheric refraction. A method determining optimum setting described.