Monday, January 23, 2012

Chilbolton Observatory on Blue Peter Goes Stargazing

Unfortunately they didn't visit the LOFAR-UK station, but you can see the Greenwich Observatory's Public Astronomer, Dr. Marek Kukula visit the Chilbolton Observatory (home of LOFAR-UK) to talk about tracking space debris with the 25m dish on the special episode of Blue Peter made to tie in with the BBC StargazingLIVE series. (watch on iPlayer).

LOFAR "geeks" talk at Intech

By popular demand following the Intech Space Lecture on LOFAR last November, Derek Mckay-Bukoski will give a second talk at Intech on LOFAR focusing  on the technical aspects of the project.

Thursday 1st March 2012, 7.30pm.

Wednesday, January 11, 2012

LOFAR in Science, Nature and Scientific American

This image was picked up as a "Science Shot" from Science. It's an X-ray/Radio image of Cygnus A. The blue shows X-ray emission from Chandra indicating hot gas around the galaxy. The orange is a new radio image from LOFAR which shows how the jets are interacting with this gas. Credit: (c) J. McKean and M. Wise, ASTRON

Following the press release from AAS219, LOFAR has been covered in stories in Nature (Radio Array Starts Work, 10 Jan 2012), Science (Science Shot: New Telescope Captures Supermassive Black Hole, 10 Jan 2012), and Scientific American (a reproduction of the Nature article retitled as Radio Array Starts to Detect Whispers from Universe, 10 Jan 2012)

Tuesday, January 10, 2012

LOFAR related PhD at Southampton Uni

Please see the below advertisement for a PhD position at the University of Southampton, which is open to any EU student.

The deadline for applications is February 29th. Click for more details

Monitoring the Ionosphere with LOFAR Chilbolton – Anna Scaife (Southampton), Ian Heywood (Oxford), Bruce Swinyard (RAL)

The variable ionosphere is a calibration issue for both radio astronomy and the RF communications industry, causing both retardation and absorption of radio signals as they pass through the atmosphere. These effects are dependent on the temporal and spatial distribution of total electron content (TEC) in the ionosphere. Their impact varies as a linear function of wavelength, and so signals at low frequencies are most affected. This consideration is consequently an important factor in the calibration of very low frequency radio telescopes such as the LOw Frequency ARray (LOFAR) where such effects are further complicated by the wide reception patterns of the LOFAR antennas, which are substantially larger than the scale of ionospheric fluctuations. A consequence of this fact is that traditional self-calibration techniques for radio astronomy, which rely on reception patterns smaller than or approaching the size of ionospheric fluctuations, are no longer sufficient and a more detailed modeling of the ionosphere is required to completely correct for contaminating effects. Moreover, the recovery of polarization information from astronomical Faraday rotation is dependent on corrections for the absolute ionospheric density along the line of sight, in addition to the relative values required for imaging. Models based on long-term, statistical records can provide useful indications of time-averaged ionospheric conditions, but are generally not suitable for accurate representations of the ionosphere at any in- stant. This is because the short-term variability of the ionosphere regularly causes its morphology to differ from time-averaged conditions. At present, the most numerous and easily accessible ionospheric data come from the international network of ground-based GPS receivers. However, the spatial and temporal sampling of available GPS data is sufficient for neither complete calibration of radio astronomical measurements nor reliable ionospheric modeling. However, linking real-time GPS data to the data reduction of telescopes such as LOFAR, as well as linking ionospheric monitoring using known radio sources to tomographic inversion of the ionosphere from GPS measurements will provide advantages to both disciplines.

The project will make use of the LOFAR Chilbolton station SEPCAM instrument as a riometer for measuring absolute differences in ionospheric fluctuations from the diffuse all-sky radio background, as well as data from the combined International LOFAR Telescope in order to measure small-scale fluctuations through their effect on the astrometry of known radio sources as a function of time. These data will be combined with GPS-based ionospheric modeling tools to look at comparisons between satellite-based and astronomy-based ionospheric measurements. These techniques will be combined into a real time ionospheric correction and prediction network linking the LOFAR Chilbolton data reduction pipeline and the GPS based MIDAS ionospheric inversion tool. This network will have the dual purpose of improving astronomical calibration through linked GPS measurements; and improving ionospheric modeling through the use of astronomical measurements. The student will use the SEPCAM riometry data to tie down the absolute ionospheric levels over LOFAR Chilbolton and their long and short term behavior. These data will be combined with constraints from polarized astronomical sources with known rotation measures to provide a details of the temporal and spatial variation in absolute ionospheric TEC. This absolute measure can then be used as a prior on the local absolute ionospheric TEC, and combined with the relative astrometric disturbance of a grid of known bright radio sources, the student will develop an inversion to be implemented through the MIDAS framework to recover a 4-dimensional ionospheric tomographic mapping of the local ionosphere, which can be compared and combined with GPS based inversions

International LOFAR Telescope has press conference at the American Astronomical Society Meeting

Yesterday evening (UK time) scientists from the LOFAR headquarters at ASTRON had a press conference at the American Astronomical Society meeting happening this week in Austin, Texas. They presented some of the first science results from the International LOFAR Telescope (ILT) and announced the start of the first All-Sky Survey. You can watch the below webcast of this press conference on the AAS website.

The below is the press release which went out at the same time as the conference. It is also available in Dutch at the NOVA (Nerderlandse Onderzoekschool Voor Astronomie) website.

International LOFAR Radio Telescope presents first science, kicks off All-Sky Survey 

World’s most complex radio telescope begins its first low frequency survey of the sky, as it prepares to open its doors to the international astronomy community this year. 

Scientists from the International LOFAR Telescope (ILT) today announced the kick-off of the project’s first all-sky survey at low radio frequencies and its first open call for observing proposals from the international astronomical community. LOFAR, the Low Frequency Array, is an innovative radio telescope built in the Netherlands and across northern Europe. LOFAR will make the still largely unexplored low-frequency radio sky accessible to astronomers for the first time. It will search for the first stars and black holes in the universe, hunt for cosmic radio bursts, pulsars, and ultra-high energy cosmic particles, study the sun and planets, and explore cosmic magnetic fields.

Cygnus A radio galaxy 
LOFAR is being used to study supermassive black holes and the affect they have on their local environment. A classic example of an active galaxy is Cygnus A, which lies in a nearby cluster of galaxies at a distance of about 700 million lightyears. At the center of this galaxy is a powerful active nucleus that emits jets of plasma at relativistic speeds. An early LOFAR image at 240 MHz shown here that these jets extend far beyond the stellar part of the galaxy, up to 200 thousand light years from the center, before abruptly interacting with the intra-clust (Image Credits:  J. McKean and M. Wise, ASTRON) 

The project will complete its hardware construction phase in 2012 and open its doors for researchers from all over the world. Early science results from the commissioning phase of LOFAR were presented at the American Astronomical Society meeting in Austin, Texas. 

The first major observing project of LOFAR will be the Multi-frequency Snapshot Sky Survey (MSSS). The survey will ultimately yield the most accurate catalogue of radio sources ever produced at these very long radio wavelengths. Designed to observe light at radio wavelengths from 2 to 20 meters, LOFAR can observe multiple, large areas of the sky simultaneously. This means it can survey the radio sky faster. “With LOFAR, we can systematically explore the low-frequency radio sky like never before and see, for example, powerful black holes throughout the entire universe.” says MSSS Project Leader, Dr. George Heald. This initial survey is expected to take several months to complete, although final processing of the data will likely take longer. Much deeper, follow-up surveys are also planned. 

When it opens later this year to the science community, LOFAR will already offer some unique capabilities to radio astronomers. LOFAR is a fully digital radio telescope that uses fiber optic cables to connect more than 20,000 low-cost antennas via the internet into a single large telescope. These antennas are grouped together into 48 separate stations distributed over the northeastern part of the Netherlands as well as in Germany, France, the UK, and Sweden. Funding for additional stations has also recently been approved in Poland. Signals from these stations are combined using an IBM BlueGene/P supercomputer to create a telescope with a collecting area of 12 football fields and a resolution equivalent to a telescope 1,000 km in diameter. The combination of many antennas and large effective size gives LOFAR unprecedented sensitivity and resolving power at long radio wavelengths.

The first science team within the LOFAR project counting on this increased sensitivity to achieve their scientific goals is the Epoch of Reionization (EoR) project, led by Prof. Ger de Bruyn. The EoR team hopes to detect extremely feeble signals from the highly redshifted neutral hydrogen 21cm emission line produced during the earliest phase of the Universe before the first stars and galaxies formed.  LOFAR’s large collecting area makes it uniquely suited to detect these extremely faint signals. According to Prof. de Bruyn, “Detection of signals from highly redshifted neutral hydrogen, emitted during the childhood years of the Universe, would be a watershed moment in cosmology.” If the EoR observation detection proves successful, the results will reveal detailed information on the first stars and galaxies born in the universe.  Several pilot observations by the EoR team have already yielded some of the deepest LOFAR images yet, and the most sensitive ever at these wavelengths. Even deeper observations are planned for the coming year to push closer to the required detection sensitivity of the EoR signal itself. 

EoR deep field 
Deepest image ever produced at 2 m wavelength. The image shows a glimpse of the very distant, very young universe. Every dot in this image is associated with a galaxy hundreds of millions, even billions of light years away. An additional few hundred hours of follow up observations will eventually lead to detection of radio waves from the moment the first Galaxies began to shine. The image, recorded at 140 MHz, is 13x13 degrees across, showing details of only 6 arc seconds with a noise level of 120 micro-Jansky per beam. The effective total exposure time is 10 hours. (Image Credits:  S. Yatawatta, ASTRON) 

Low-frequency radio imaging is particularly challenging due to the Earth’s variable ionosphere and interference from man-made radio transmitters, such as FM radio stations. “The first phase of commissioning has demonstrated that a fully digital telescope can overcome these obstacles, which have plagued low-frequency astronomy for so long.”, says Heino Falcke, chair of the International LOFAR Telescope (ILT).  “After ten years of hard work on this project, it is fantastic to see that it actually works.”  

LOFAR’s unique capabilities are already proving useful for researchers studying pulsars, the highly magnetized and rapidly rotating neutron stars formed during the gravitational collapse of a massive star following a supernova. Many of these objects give off brief but intense bursts of radio emission lasting in some cases only millionths of a second. LOFARs sensitivity and highly accurate clocks make it possible to study pulsars over the lowest 4 octaves of the observable radio spectrum all at once. When combined with data from other radio telescopes operating at shorter wavelengths, LOFAR observations can isolate the origin of pulsar’s radio emission to within 100km above the magnetic poles of the star. LOFAR’s large field of view will also be used to perform efficient surveys to study known pulsars and detect new ones. 

LOFAR will offer its unique scientific capabilities to the astronomical community starting in May with the announcement of its first open call for observing projects. A fraction of the available observing time for the coming year will be allocated to a number of Key Science Projects with the remaining time available for open-sky observing projects. “LOFAR really is the most versatile radio telescope in the world. When we open the doors in May, this amazing new facility will be available to any scientist in the world to use.”, said LOFAR Project Scientist, Dr. Michael Wise. 

International LOFAR Telescope Operations are coordinated by ASTRON, the Netherlands Institute for Radio Astronomy, on behalf of a consortium consisting of the Netherlands, Germany, France, the UK, and Sweden.  Many of the technological solutions developed for LOFAR, in particular the calibration of phased-arrays as well as large-scale data transport and processing, will be highly relevant for future radio telescope projects such as the Square Kilometer Array (SKA). The SKA is a 1.5 billion euro, global science project to build the world's largest and most sensitive radio telescope over the next decade. LOFAR represents the first of several SKA technology pathfinder projects to come online. 

Friday, January 6, 2012

Lunar Eclipse Over LOFAR Station near Exloo

Today's ASTRON image of the day is this lovely shot of last month's lunar eclipse taken over a LOFAR station near Exloo by radio astronomer Megan Argo.

Lunar eclipse over LOFAR. Credit: Megan Argo.

Wednesday, January 4, 2012

LOFAR-UK Station Damaged by Storms

During the night of 2nd-3rd Jan 2012, gale force winds over the UK resulted in some damage to the LOFAR international station UK608, located at the Chilbolton Observatory near Winchester in Hampshire. Wind speeds at the site exceed 60 mph (97 km/h) accompanied by heavy rain, as a major low pressure system began to pass over the UK. 

Image of the UK storm early in the morning of Jan 3rd 2012 from NASA's Aqua Satellite (via @metofficestorms)

Chilbolton staff working in the main building (about 1 mile from the array) noticed a dislodged HBA (high band antenna) cover on the morning of Jan 3rd 2012. A HBA tile is made up of 16 antennas held in place by white polystyrene cells all covered by a thick black weather proof cover, making a dislodged cover dramatically visible from a distance. 

An image of an HBA with part of the cover removed for testing. This reveals some of the lids, plus one antenna "cell" with the lid removed. You can also see more of the structure of HBAs in our video tour of Chilbolton.
Fortunately only one of the HBA tiles lost its cover, but 10 of the antenna "cells" within this tile lost their lids exposing the delicate antenna parts to heavy rain and damaging some of the internal structure. Debris was also blown all over the fields around UK608.

Unfortunately the LBA (low band antenna) array fared much worse. In total thirteen of the 96 antennas have been damaged or destroyed. Two of these antennas were completely blown away (including the metal grids), and eleven have been blow down. A further four antennas have been dislodged and may be partially damaged. 

Dame Jocelyn Bell-Burnell poses by an LBA during the UK608 opening. For more information on LBAs see our Chilbolton video tour.

Chilbolton staff members should be thanked by all of us for extraordinary effort during the ongoing severe weather yesterday (gale force winds and torrential rain) to mitigate further damage and collect debris.  They have been hard at work again today further securing the damaged array, as the UK is not out of the weather yet with moderate to strong winds forecast for the next 24 hours.

Work is also ongoing to assess the full extent of the damage, particularly to the LBA array, and make plans for the repairs. However the design of a LOFAR station is such that it can function at almost full efficiency with a few antennas down. So while the loss of a full HBA looks dramatic, it should only have a minor effect on the data quality in the high band. And the remaining (up to) 83 functioning LBAs (or 86% of the antennas) should also be able to make successful observations.