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 2016 are:
- 24 Core Stations
- 14 Remote Stations
- 12 International Stations
- Number of stations available for LBA observations: 50
- Number of stations available for HBA (Dual) observations: 74
Observers 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)
Up to 488 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 95.16 MHz (200 MHz clock) or 76.13 MHz (160 MHz clock).
As the sensitivity of station beams drops significantly for targets below ~30 degrees elevation, targets with declinations below -5 degrees are not recommended for interferometric observation with LOFAR. Proposers wishing to image low-declination targets will need to justify that the required sensitivity and/or u-v coverage can be attained with their proposed observing programme. More details are given here.