LOFAR consists of an interferometric array of dipole antenna stations distributed throughout the Netherlands and in several countries in Europe. These stations have no moving parts and, due to the effective all-sky coverage of the component dipoles, give LOFAR a large field-of-view.
At station level the signals from individual dipoles are combined digitally into a phased array. Electronic beam-forming techniques make the system agile and allow for rapid re-pointing of the telescope as well as simultaneous observations of multiple, independent areas of the sky.
The following gives a summary overview of the characteristics of the system.
Number of operational stations:
The number of operational stations in July 2012 are:
- 24 Core Stations
- 9 Remote Stations
- 8 International Stations
- Number of stations available for LBA observations: 41
- Number of stations available for HBA (Dual) observations: 65
Due to the limit in the number of input data streams to the correlator, only 64 station fields can be correlated from the total of the planned 72 HBA (sub)fields (in the HBA_DUAL mode when the core stations are split in two HBA sub-fields).
An observer can choose between the following frequency ranges:
- LBA: 10-90 MHz (200 MHz clock)
- LBA: 30-90 MHz (200 MHz clock)
- HBA: 110-190 MHz (200 MHz clock)
- HBA: 170-230 MHz (160 MHz clock)
- HBA: 210-250 MHz (200 MHz clock)
Note that frequency ranges that use the 160MHz clock are not supported for full automated operations in LOFAR Version 1.0.
Up to 244 subbands of 0.195 MHz (195.312 kHz at 200 MHz clock) and 0.156 MHz (156.250 kHz at 160MHz clock).
This gives a total bandwidth of 47.67 MHz (200 MHz clock) or 38.12 MHz (160 MHz clock).
Operational baselines (July 2012):
a) Within the NL:
North-south= ~83 km, ie, resolution 10 arc sec at 60 MHz
East-West = ~21 km, ie, resolution 40 arcsec at 60 MHz
b) Including international baselines
North-South: ~1292 km, ie, resolution 0.65 arcsec at 60 MHz, 0.2 arcsec at 240 MHz
East West : ~ 1004 km, ie, resolution 0.79 arcsec at 60 MHz, 0.26 arcsec at 240 MHz