System Capabilities

 

LOFAR

LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR covers the largely unexplored low-frequency range from 10–240MHz and provides a number of unique observing capabilities. Spreading out from a core located near the village of Exloo in the northeast of the Netherlands, a total of 52 LOFAR stations are available for observations. 14 of these have been deployed throughout Germany, France, Sweden, UK, Poland, Ireland and Latvia.

Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR achieves unparalleled sensitivity and angular resolution in the low-frequency radio regime. The LOFAR facilities are jointly operated by the International LOFAR Telescope (ILT) foundation, as an observatory open to the global astronomical community. LOFAR is one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community. LOFAR’s new capabilities, techniques and modus operandi make it an important pathfinder for the Square Kilometre Array (SKA).

LOFAR entered its first operational Cycle in December 2012, following a period of commissioning.

 

SUMMARY OF CURRENT SYSTEM CAPABILITIES

The following gives a summary overview of the characteristics of the LOFAR system. For an overview of functionality available in the next proposal call, please check here.

 

Number of operational stations:

The number of operational stations in January 2020 are:

  • 24 Core Stations (which can be split into 48 substations when using HBA Dual mode) 
  • 14 Remote Stations
  • 14 International Stations
  • Number of stations available for LBA observations: 52
  • Number of stations available for HBA Dual observations: 76
Frequency Ranges:

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)
The following frequency ranges are not offered for cycle 14-17, until further notice:
  • HBA: 170-230 MHz (160 MHz clock)
  • HBA: 210-250 MHz (200 MHz clock)

Available Bandwidth

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).  


Declination Limitations

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. However beam-formed observations have been successfully carried out in beam-formed mode at declinations down to -29 degrees. 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.

The following table reports reccommended minimum elevations [deg] for different observing modes in LBA and HBA bands.

 

 

TECHNICAL CAPABILITIES

In depth information about the system capabilities are given in the incapsulated menu items. The pages describe the general signal path, major observing modes, and their post processing options from the perspective of a potential user.  In some instances, some modes are noted as being "Expert Mode": These are generally modes which require more manual intervention than the regular modes and are offered only to users who are familiar with them from their own commissioning work.  

A more detailed description of the LOFAR array can be found in van Haarlem et al. 2013 (http://arxiv.org/abs/1305.3550)

Also, please note that an extensive description of the capabilities of LOFAR has been given at the LOFAR Data Schools. In particular, you can consult the slides of the last LOFAR Data School here.

 

Contact

For further information, you can contact the ASTRON SDC Operations Group. 

 

 

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