The AUSTRAL VLBI observing program     

L. Plank  J. E. J. Lovell  J. N. McCallum  D. Mayer  C. Reynolds  J. Quick  S. Weston  O. Titov  S. S. Shabala  J. Böhm  T. Natusch  M. Nickola  S. Gulyaev 《Journal of Geodesy》2017,91(7):803-817

The AUSTRAL observing program was started in 2011, performing geodetic and astrometric very long baseline interferometry (VLBI) sessions using the new Australian AuScope VLBI antennas at Hobart, Katherine, and Yarragadee, with contribution from the Warkworth (New Zealand) 12 m and Hartebeesthoek (South Africa) 15 m antennas to make a southern hemisphere array of telescopes with similar design and capability. Designed in the style of the next-generation VLBI system, these small and fast antennas allow for a new way of observing, comprising higher data rates and more observations than the standard observing sessions coordinated by the International VLBI Service for Geodesy and Astrometry (IVS). In this contribution, the continuous development of the AUSTRAL sessions is described, leading to an improvement of the results in terms of baseline length repeatabilities by a factor of two since the start of this program. The focus is on the scheduling strategy and increased number of observations, aspects of automated operation, and data logistics, as well as results of the 151 AUSTRAL sessions performed so far. The high number of the AUSTRAL sessions makes them an important contributor to VLBI end-products, such as the terrestrial and celestial reference frames and Earth orientation parameters. We compare AUSTRAL results with other IVS sessions and discuss their suitability for the determination of baselines, station coordinates, source coordinates, and Earth orientation parameters.  相似文献   

VLBI observations of GNSS-satellites: from scheduling to analysis   总被引：1，自引：1，他引：0  

Lucia Plank  Andreas Hellerschmied  Jamie McCallum  Johannes Böhm  Jim Lovell 《Journal of Geodesy》2017,91(7):867-880

The possibility of observing satellites with the very long baseline interferometry (VLBI) technique has been discussed for several years in the geodetic community, with observations of either existing satellites of the global navigation satellite systems or of satellites dedicated to realise a space tie. Such observations were carried out using the Australian telescopes in Hobart and Ceduna which, for the first time, integrated all the necessary steps: planning the observations (automated scheduling), correlation of the data and the generation of a series of time delay observables suitable for a subsequent geodetic analysis. We report on the development of new and the adaptation of existing routines for observing and data processing, focusing on technology development. The aim was to use methods that are routinely used in geodetic VLBI. A series of test experiments of up to six hours duration was performed, allowing to improve the observations from session to session and revealing new problems still to be solved. The newly developed procedures and programs now enable more observations. Further development assumed, this bears the prospect of being directly applied to the observation of dedicated space-tie satellites.  相似文献   

ATLAS, and Wide-Angle Tail Galaxies in ATLAS     

Minnie Y. Mao  Rob Sharp  D. J. Saikia  Ray P. Norris  Melanie Johnston-Hollitt  Enno Middelberg  Jim E. J. Lovell 《Journal of Astrophysics and Astronomy》2011,32(4):585-588

Using the Australia Telescope Compact Array (ATCA), ATLAS (Australia Telescope Large Area Survey) is imaging two fields totalling 7 square degrees down to 10 μJy beam^− 1 at 1.4 GHz. We have found 6 wide-angle tail galaxies (WATs), 4 of which have sufficient data to identify associated galaxy overdensities. The largest WAT, at a red-shift of 0.22, appears to be associated with an overdensity of galaxies that is spread over an unusually large extent of 12 Mpc, with a velocity range of 4500 km s^− 1. Here we present the WATs in ATLAS and discuss the implications of these observations for future large-scale radio surveys such as ASKAP-EMU.  相似文献   

Agencement in housing markets: The case of the UK construction industry     

Heather Lovell  Susan J. Smith 《Geoforum》2010,41(3):457-468

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Interstellar Scintillation and Annual Cycles in the BL Lac Source PKS 1519-273     

David L. Jauncey  Helen M. Johnston  Hayley E. Bignall  J.E.J. Lovell  Lucyna Kedziora-Chudczer  A.K. Tzioumis  Jean-Pierre Macquart 《Astrophysics and Space Science》2003,288(1-2):63-68

We have measured annual cycles in the time scales of the rapid, intra-day variability of the total and circularly polarized flux density, of the unusual BL Lac source PKS 1519–273 at 4.8 and 8.6 GHz. This data was collected at the ATCA over the last seven years, and establishes unequivocally interstellar scintillation as the principal mechanism responsible for this cm-wavelength intra-day variability.  相似文献   

Preface     

Stuart Crampin  John H. Lovell 《Geophysical Journal International》1991,107(3):385-385

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The Cretaceous–Paleogene unconformity in England: Uplift and erosion related to the Iceland mantle plume     

Andrew S. Gale  Bryan Lovell 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(3):421-435

During the late Cretaceous to early Paleogene, the present-day area of Britain and Ireland emerged from nearly total submergence by the chalk sea. What mechanism was responsible for this major marine regression? Combined studies of Paleogene depositional sequences offshore and coeval igneous rocks onshore, show that significant episodic uplift of northern Britain was at that time largely controlled by the early development of the Iceland mantle plume. How far south did this influence of the Iceland plume extend across England, and even beyond? We present new maps of the structure and denudation of the chalk surface in southern England. Some 500 m thickness of chalk was removed from the crest of a Chilterns–East Anglia dome before deposition of the earliest Paleogene sediments. Allowing for isostatic amplification by erosion, minimum uplift of the chalk surface above sea level was c.125 m. Early Paleogene crustal shortening of that chalk surface was by a factor of at most 1.01, contributing a maximum uplift of 25 m of the floor of the chalk sea. Compressional forces were not the main cause of the Cretaceous–Paleogene unconformity in southern England, as in the interpretation of this event as a distant reflection of the development of the Alps to the south. Postulated contemporary changes in global sea-level are also inadequate to account for the development of the unconformity in southern England. Here we suggest with some confidence that the main vertical surface movements involved in creating the unconformity were controlled by the Iceland mantle plume, as in northern Britain. We speculate that another hotspot, in Central France, may have influenced Paleogene sedimentation in the Paris Basin in a comparable fashion. We consider how to distinguish between our proposed mantle control of regional relative sea-level and global controls of Paleogene sea level.  相似文献   

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Sarah Lovell 《New Zealand geographer》2015,71(2):116-117

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Complex kame belt morphology,stratigraphy and architecture     

Harold Lovell  Stephen J. Livingstone  Clare M. Boston  Adam D. Booth  Robert D. Storrar  Iestyn D. Barr 《地球表面变化过程与地形》2019,44(13):2685-2702

The development of glacier karst at the margins of melting ice sheets produces complex glaciofluvial sediment-landform assemblages that provide information on ice sheet downwasting processes. We present the first combined geomorphological, sedimentological and geophysical investigation of the Brampton Kame Belt, an important glaciofluvial depositional zone at the centre of the last British-Irish Ice Sheet. Ground-penetrating radar (GPR) data allow the broad scale internal architecture of ridges (eskers) and flat-topped hills (ice-walled lake plains) to be determined at four sites. In combination with sediment exposures, these provide information on lateral and vertical variations in accretion styles, depositional boundaries, and grain size changes. Building on existing work on the subject, we propose a refined model for the formation of ice-walled lake plains resulting from the evolution and collapse of major drainage axes into lakes as stable glacier karst develops during deglaciation. The internal structure of esker ridges demonstrates variations in sedimentation that can be linked to differences in ridge morphologies across the kame belt. This includes low energy flow conditions and multiple accretion phases identified within large S-N oriented esker ridges; and fluctuating water pressures, hyperconcentrated flows, and significant deformation within a fragmented SW–NE oriented esker ridge. In combination with updated geomorphological mapping, this work allows us to identify two main styles of drainage within the kame belt: (1) major drainage axes aligned broadly S-N that extend through the entire kame belt and collapsed into a chain of ice-walled lakes; and (2) a series of smaller, fragmented SW–NE aligned esker ridges that represent ice-marginal drainage as the ice sheet receded south-eastwards up the Vale of Eden. Our study demonstrates the importance of integrated geomorphological, sedimentological and geophysical investigations in order to understand complex and polyphase glaciofluvial sediment-landform assemblages. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.  相似文献   

Detection of nitrogen sulfide in Comet Hale-Bopp.     

W M Irvine  M Senay  A J Lovell  H E Matthews  D McGonagle  R Meier 《Icarus》2000,143(2):412-414

We report the first detection of the nitrogen sulfide (NS) radical in a comet. The abundance relative to water is at least a few hundredths of a percent for Comet Hale-Bopp.  相似文献