Results from test stations
(click on images to enlarge)

ITS All Sky Survey Map with detected 3C Sources

As shown above the ITS is capable of making snapshot images of the sky above the site. If such snapshots are taken at different times of the day, a different part of the complete sky is imaged. These images can then be combined to produce an all sky map as shown here. This map is composed of 86 snapshots using all available RFI free channels between 29.5 and 30.5 MHz. To make the weak sources on the map visible, the two strongest sources, Cassiopeia A and Cygnus A have been subtracted from the individual snapshots after calibrating the array. All these steps have been done automatically by a computer without human interference, showing that we're able to make an automated data reduction pipeline. The detected sources from the 3C catalog have been indicated. There are more sources which are probably detected, but not very clearly. These are not included here.

credit: Stefan Wijnholds (ASTRON)

Solar and Jupiter bursts

On June 22nd, 2004 we carried out an ITS observation of Solar and Jovian bursts, jointly with the Decametric Array of Nançay (NANÇAY Observatory, France).

The observation was performed in sync-stop mode, such the data recording could be controlled by an external trigger; this trigger was derived from the real-time display at Nançay, such a data snapshot was taken when a Jupiter burst took place. For each snapshot 6.7 seconds of digitized time-series data (at 80 MHz sampling frequency) were recorded, transfered to ASTRON and analyzed offline.

The image to the right shows a 28.05882 MHz map centered on the position of Jupiter during a burst.

credit: Lars Baehren (ASTRON)

Lightning over ITS

The weekend of of July 17.-18., 2004 experienced the passing of a large storm system over the Netherlands. A significant amount of thunderstorm discharges were recorded over the area of the Drenthe province, 'local' lightning activity peaking between 18:30 and 19:00 hours. Analysis of chance observations (consisting of 0.419 seconds digitized time-series data) revealed prominent short-time broad-band radio emission features.
Follow-up observation were carried out on several occasions; the image to the right shows the typical radio emission signature by which electric discharges in thunderstorms can be identified in dynamic spectra. Beamforming of the raw data yields temporal-spatial resolved maps, some cases also allow distance determination.

credit: Lars Baehren (ASTRON)

All Sky Map (1) 30 MHz map of the sky taken with the Initial Test Station (60 antenna’s operating at 10-40 MHz, resolution of ~3 degrees at 30 MHz). Integration time is 6.7 seconds, total bandwidth 1.05 MHz selected from the clean channels in the 24-31 MHz frequency range. The brightest discrete source Cas A (3C461) has been subtracted. Other well known discrete sources are also indicated. The diffuse emission is due to the Milky Way. The resolution of the final array will improve by a factor of ~250,000 (with 100 km baselines) compared with this ITS image and the sensitivity will go up by at least 7 orders of magnitude (more collecting area and longer integration time plus broader bandwidth).

credit: Michiel Brentjens (ASTRON/RUG)

ITS observes a solar burst The observation (click on the picture to the right/left to start the movie) have been done during a demonstration in Amsterdam. When the movie starts, it shows the "normal" sky with Cas A as brightest source on a region of diffuse emission from the galactic plane. At about 10:30 a bright source appears at the southeastern horizon becoming gradually stronger thereby overpowering the other sources in the sky. At about 12:00 its power decreases and Cas A becomes visible again. A check on the location of the source indicated that it could be identified as the sun. Our observation is consistent with measurements from the SOHO satellite which observed a solar burst at that time.

credit: Stefan Wijnholds (ASTRON)

More about ITS: Working with ITS

More information: see NL science case for LOFAR (pdf)

< GO BACK

In case of questions or comments regarding LOFAR, or about these web pages, please contact lofar@astron.nl
Read this disclaimer before proceeding.

Jobs | Pictures | Publications | Archives | Sponsors