scholarly journals A Low frequency Southern Sky Survey Using the Mauritius Radio Telescope

2002 ◽  
Vol 199 ◽  
pp. 25-31
Author(s):  
N. Udaya Shankar
Keyword(s):  
Radio Telescope ◽  
Low Frequency ◽  
Fourier Synthesis ◽  
North East ◽  
The North ◽  
Sky Survey ◽  
Correlation Receiver ◽  
Complex Correlation ◽  
Right Ascension ◽  
East West

The Mauritius Radio Telescope (MRT) is a Fourier synthesis instrument which has been built to fill the gap in the availability of deep sky surveys at low radio frequencies in the southern hemisphere. It is situated in the north-east of Mauritius at a southern latitude of 20°.14 and an eastern longitude of 57°.73. The aim of the survey with the MRT is to contribute to the database of southern sky sources in the declination range −70° ≤ δ ≤ −10°, covering the entire 24 hours of right ascension, with a resolution of 4' × 4'.6sec(δ + 20.14°) and a point source sensitivity of 200 mJy (3σ level) at 151.5 MHz.MRT is a T-shaped non-coplanar array consisting of a 2048 m long East-West arm and a 880 m long South arm. In the East-West arm 1024 fixed helices are arranged in 32 groups and in the South arm 16 trolleys, with four helices on each, which move on a rail are used. A 512 channel, 2-bit 3-level complex correlation receiver is used to measure the visibility function. At least 60 days of observing are required for obtaining the visibilities up to the 880 m spacing. The calibrated visibilities are transformed taking care of the non-coplanarity of the array to produce an image of the area of the sky under observation.This paper will describe the telescope, the observations carried out so far, a few interesting aspects of imaging with this non-coplanar array and present results of a low resolution survey (13' × 18') covering roughly 12 hours of right ascension, and also present an image with a resolution of 4' × 4'.6sec(δ + 20.14°) made using the telescope.

scholarly journals 38. The cambridge survey of radio sources

1957 ◽  
Vol 4 ◽  
pp. 218-220 ◽  
Author(s):  
J. R. Shakeshaft
Keyword(s):  
Radio Telescope ◽  
Wave Length ◽  
Radio Sources ◽  
Polar Diagram ◽  
The North ◽  
Interference Fringes ◽  
Half Power ◽  
The Right ◽  
Right Ascension ◽  
East West

A survey of radio sources at a wave-length of 3·7 metres has been carried out with a large interferometric radio telescope (Ryle and Hewish, 1955) [1] which has a receiving area of about 5000 square metres. Four parabolic troughs are arranged at the corners of a rectangle 600 metres east–west by 50 metres north–south. The reception polar diagram of each, ± 1° by ± 7° to half-power points, is thus filled with interference fringes in the north–south plane as well as the east–west plane. Sources are observed at transit, the time of which gives the right ascension, while the declination is obtained by comparing the observed intensity on successive days as the phase of the north–south pattern is altered.

The mineralogical composition of some Scottish soils

1925 ◽  
Vol 15 (3) ◽  
pp. 257-271 ◽  
Author(s):  
James Hendrick ◽  
George Newlands
Keyword(s):  
Mineralogical Composition ◽  
Fine Sand ◽  
Plant Food ◽  
Sand Fraction ◽  
Extensive Survey ◽  
North East ◽  
The North ◽  
Local Origin ◽  
East West ◽  
Made In

1. Previous investigations showed that certain Scottish soils were of glacial drift origin, that they were comparatively rich in unweathered silicates and therefore in reserves of plant-food, that they showed considerable variation in such silicates and were capable of classification accordingly. Some indication was also shown that the glacial drift, and hence the resulting soil, was sometimes of local origin, its character being determined by the underlying rock. In the present investigation a more extensive survey of Scottish soils has been made in order to discover to what extent these preliminary findings might be applicable generally.2. For this purpose soils have been collected from various localities in the north, north-east, west and south of Scotland, and have been analysed mechanically and the “fine sand” fraction examined mineralogically.

Un diatrème phréatomagmatique montérégien dans les Appalaches du Québec

1996 ◽  
Vol 33 (5) ◽  
pp. 649-655
Author(s):  
David Morin ◽  
Michel Jébrak ◽  
Robert Marquis
Keyword(s):  
Surface Water ◽  
Country Rock ◽  
Near Surface ◽  
Metasedimentary Rocks ◽  
North East ◽  
The North ◽  
Devonian Age ◽  
Fault Network ◽  
Alkaline Lamprophyres ◽  
East West

A subcircular positive magnetic anomaly and breccias affecting a basanite and its country-rock metasedimentary rocks reveal the presence of a diatreme with a diameter of approximately 420 m, at Eastman, in the Quebec Appalachians. The post-Middle Devonian age, the position in the line of the Monteregian plutons, and the basanite composition, which is comparable to that of the Cretaceous Monteregian alkaline lamprophyres, suggest that the diatreme is related to the Monteregian magmatism. It is located at the junction of two orthogonal tectonic corridors: the north-north-east Baie Verte – Brompton line and an east−west fault network along the prolongation of the Ottawa−Bonnechère Graben. These structures are zones of weakness that probably served as a conduit for the ascending magma and near-surface water to trigger phreatomagmatic eruptions.

scholarly journals POTENSI PEMANFAATAN ATAP GEDUNG PUSAT PEMERINTAHAN KABUPATEN BADUNG UNTUK PLTS ROOFTOP

2018 ◽  
Vol 5 (2) ◽  
pp. 119
Author(s):  
I Dewa Gde Yaya Putra Pratama ◽  
I Nyoman Satya Kumara ◽  
I Nyoman Setiawan
Keyword(s):  
Total Energy ◽  
Electrical Power ◽  
Electrical Energy ◽  
South Side ◽  
North East ◽  
The North ◽  
North Side ◽  
Simulation Results ◽  
East West

In the RUPTL PT PLN Years 2017 untill 2026, the goverment aim to reach 5000 MW of PV plant potential in 2025. But, until November 2016, the number of PV plant in Indonesia is around 11 MW. To reach the 5000 MW target, many approach must be use. One of the approach is install PV plant on goverment buildings. Pusat Pemerintahan Kabupaten Badung (Puspem Badung) is a goverment buildings complex which located in Badung Regency, Bali is one of the goverment building that can be use for this approach. This paper aim to know the potency of electrical power dan electrical energy produced by Puspem Badung if the PV plant installed on the north, east, west, and south side of the roof. Electrical energy produced by PV plant is simulated by using System Advisor Model (SAM). From the simulation results, north side of the roof can produce energy of 1.847.361 kWh/year. From the analysis, the total energy that can be produced by PV plant is 6.169.092 kWh/year. This amount can supply Puspem Badung energy need by 124,72 %.

scholarly journals How Accurate are SuperCOSMOS Positions?

2014 ◽  
Vol 31 ◽  
Author(s):  
Adam Schaefer ◽  
Richard Hunstead ◽  
Helen Johnston
Keyword(s):  
Reference Frame ◽  
Stellar Objects ◽  
The North ◽  
Sky Survey ◽  
The Uk ◽  
Celestial Reference Frame ◽  
Right Ascension

AbstractOptical positions from the SuperCOSMOS Sky Survey have been compared in detail with accurate radio positions that define the second realisation of the International Celestial Reference Frame (ICRF2). The comparison was limited to the IIIaJ plates from the UK/AAO and Oschin (Palomar) Schmidt telescopes. A total of 1 373 ICRF2 sources was used, with the sample restricted to stellar objects brighter than BJ = 20 and Galactic latitudes |b| > 10°. Position differences showed an rms scatter of $0.16\text{ arcsec}$ in right ascension and declination. While overall systematic offsets were < $0.1\text{ arcsec}$ in each hemisphere, both the systematics and scatter were greater in the north.

scholarly journals The Central Component Of Centaurus A

1966 ◽  
Vol 19 (3) ◽  
pp. 421 ◽  
Keyword(s):  
Central Component ◽  
The South ◽  
Central Source ◽  
The North ◽  
North Eastern ◽  
The Right ◽  
Right Ascension ◽  
East West ◽  
Centaurus A

Transit observations of Centaurus A with a fan beam 1'�5 wide at 73 cm show that the north-eastern component of the central source has an east-west width of 1'�7 and that the south-western source has a width of 2'�3. Since the situation at 9�1 cm is roughly the reverse of this, the two components must have sharply different spectra. The right ascensions observed are 13h 22m 48s . 0 and 13h 22m 20s�2�os�2 (1950). The right ascension of the centre of NGC5128 has been separately determined as 13h 22m 31s�6�os�3, showing that the two components are at significantly unequal distances from the optical object.

scholarly journals Large-scale changes of the semidiurnal tide along North Atlantic coasts from 1846 to 2018

Ocean Science ◽  
2021 ◽  
Vol 17 (1) ◽  
pp. 17-34
Author(s):  
Lucia Pineau-Guillou ◽  
Pascal Lazure ◽  
Guy Wöppelmann
Keyword(s):  
Sea Level ◽  
North Atlantic ◽  
Large Scale ◽  
Low Frequency ◽  
Underlying Mechanism ◽  
East Atlantic ◽  
North West ◽  
North East ◽  
The North ◽  
The North Atlantic

Abstract. We investigated the long-term changes of the principal tidal component M2 along North Atlantic coasts, from 1846 to 2018. We analysed 18 tide gauges with time series starting no later than 1940. The longest is Brest with 165 years of observations. We carefully processed the data, particularly to remove the 18.6-year nodal modulation. We found that M2 variations are consistent at all the stations in the North-East Atlantic (Cuxhaven, Delfzijl, Hoek van Holland, Newlyn, Brest), whereas some discrepancies appear in the North-West Atlantic. The changes started long before the 20th century and are not linear. The secular trends in M2 amplitude vary from one station to another; most of them are positive, up to 2.5 mm/yr at Wilmington since 1910. Since 1990, the trends switch from positive to negative values in the North-East Atlantic. Concerning the possible causes of the observed changes, the similarity between the North Atlantic Oscillation and M2 variations in the North-East Atlantic suggests a possible influence of the large-scale atmospheric circulation on the tide. Our statistical analysis confirms large correlations at all the stations in the North-East Atlantic. We discuss a possible underlying mechanism. A different spatial distribution of mean sea level (corresponding to water depth) from one year to another, depending on the low-frequency sea-level pressure patterns, could impact the propagation of the tide in the North Atlantic basin. However, the hypothesis is at present unproven.

Nemesis: A Mycenaean settlement near the Menidi Tholos Tomb

1959 ◽  
Vol 53 ◽  
pp. 292-294
Author(s):  
R. Hope Simpson
Keyword(s):  
Ground Level ◽  
The West ◽  
North West ◽  
North East ◽  
The North ◽  
South West ◽  
Original Size ◽  
The Hill ◽  
East West ◽  
Ancient Remains

The site to be described lies on a low hill a little to the north of the small village or suburb of Nemesis, about 150 metres to the west of the main road from Patisia to Koukouvaounes, and 1 kilometre to east-south-east of the Mycenaean tholos tomb at Λυκὸτρυπα, which was excavated by the German Institute in 1879, and is usually called the Menidi Tomb. The site at Nemesis is visible from the tholos tomb, and is separated from it by a gentle valley through which run, in a southerly direction, two streams with steep banks. The eastern stream is the river Kephissos, whose name goes back at least as far as the classical period.The hill of Nemesis stands about 15 to 20 metres above the level of the surrounding land, and measures about 160 m. north-west to south-east × 120 m. north-east to south-west. The hill is an isolated outcrop of conglomerate rock, thinly covered with stony brown earth. It has been eroded over an area about 250 m. north-south × 50 m. east-west, so that its original size was considerably larger than at present, in all about 30,000 square metres. Mycenaean sherds were found over the whole of this area, though mainly in the eroded part, among the lumps of fallen earth and rock. Remains of rubble walling together with several Mycenaean sherds were found here, and also in the steep cliffs formed by the erosion on the west and south sides (this part of the hill has been undermined by recent excavation of the beds of grey clay, which here lie at between 2 and 3 metres below the original ground level). The ancient remains are particularly noticeable in the south-west angle of the cliffs (roughly in the centre of the part of the hill shown on Plate 71a), where there is a greater depth of earth above the rock than is visible elsewhere on the hill.

scholarly journals A steradian of the southern sky at 151.5 MHz using the Mauritius Radio Telescope

2006 ◽  
Vol 2 (14) ◽  
pp. 385-385 ◽  
Author(s):  
V. N. Pandey ◽  
N. Udaya Shankar
Keyword(s):  
Radio Telescope ◽  
Low Frequency ◽  
Sky Survey

AbstractWe present a few results of a low-frequency southern sky survey carried out using the Mauritius Radio Telescope (MRT).

scholarly journals Polarized point sources in the LOFAR Two-meter Sky Survey: A preliminary catalog

2018 ◽  
Vol 613 ◽  
pp. A58 ◽  
Author(s):  
C. L. Van Eck ◽  
M. Haverkorn ◽  
M. I. R. Alves ◽  
R. Beck ◽  
P. Best ◽  
...  
Keyword(s):  
Low Frequency ◽  
Small Population ◽  
Point Sources ◽  
Source Surface ◽  
Radio Sources ◽  
Low Frequencies ◽  
Sky Survey ◽  
Region 10 ◽  
New Generation ◽  
Right Ascension

The polarization properties of radio sources at very low frequencies (<200 MHz) have not been widely measured, but the new generation of low-frequency radio telescopes, including the Low Frequency Array (LOFAR: a Square Kilometre Array Low pathfinder), now gives us the opportunity to investigate these properties. In this paper, we report on the preliminary development of a data reduction pipeline to carry out polarization processing and Faraday tomography for data from the LOFAR Two-meter Sky Survey (LOTSS) and present the results of this pipeline from the LOTSS preliminary data release region (10h45m–15h30m right ascension, 45°–57° declination, 570 square degrees). We have produced a catalog of 92 polarized radio sources at 150 MHz at 4.′3 resolution and 1 mJy rms sensitivity, which is the largest catalog of polarized sources at such low frequencies. We estimate a lower limit to the polarized source surface density at 150 MHz, with our resolution and sensitivity, of 1 source per 6.2 square degrees. We find that our Faraday depth measurements are in agreement with previous measurements and have significantly smaller errors. Most of our sources show significant depolarization compared to 1.4 GHz, but there is a small population of sources with low depolarization indicating that their polarized emission is highly localized in Faraday depth. We predict that an extension of this work to the full LOTSS data would detect at least 3400 polarized sources using the same methods, and probably considerably more with improved data processing.

Sign in / Sign up

Export Citation Format

Share Document