Target Declination Limits

As a phased-array system installed on level ground, LOFAR has greatest sensitivity when observing at high elevations.  Below approximately 30 degrees elevation sensitivity drops significantly such that the Sun becomes the only viable target for interferometric observation below about 10 degrees elevation.

Commissioning observations have managed successful imaging of a target at -7 degrees declination, but imaging is not straightforward and the following points need to be noted:

  • The thermal noise cannot be attained at these declinations;
  • Short baselines have to be flagged;
  • Some additional flagging of data may be required.

Furthermore, the shorter length of time that such targets are above a useable horizon can severely limit the u-v coverage attainable.  Therefore for interferometric observations, -5 degrees declination should be regarded as a lower limit and targets should preferably be above the celestial equator.  Proposers wishing to image targets below the celestial equator are expected to justify that their observing programme can attain the sensitivity and/or u-v coverage required.

Pulsar observations have been successfully carried out in beam-formed mode at declinations down to -29 degrees.  In this mode, the main limitation is the sensitivity required and the duration of observation needed to attain this sensitivity.

 

Design: Kuenst.    Development: Dripl.    © 2020 ASTRON