Commensal beam formed and imaging mode

    Combining Imaging and Beam Formed Modes

    Some Beam Formed modes, and even a combination of them, can be run in parallel with the standard imaging mode. This allows one to simultaneously image a field while recording high time resolution dynamic spectra to probe sub-second variations of any source in the field.

    The BF+IM commensal observation configuration boundaries are (as of Cycle 16):

    • BF and IM share the exact same station settings (field set, clock, bitmode, antenna set, SAP pointings, etc); The beamforming can use a sub-set of stations used for the imaging observations (as of Cycle 16). In particular for the Coherent Stokes, it is therefore important to use only core stations for combined observation.
    • BF and IM have independent processing settings (frequency & temporal resolution, etc).

    For cycle 16 and long term proposals, we offer three modes that can be used to supported:

    • 1) Imaging with Remote + Core stations and Coherent Stokes beamforming with Core stations only
      • Any available antennaset
      • One direction / sub-array pointing
      • Two Tied-array beams Stokes I, Stokes IQUV or Complex Voltage
      • Up to 244 subbands
      • Standalone, parallel calibrator, or calibrator-target-calibrator strategy
    • 2) Imaging with Remote + Core stations and Incoherent Stokes beamforming with Core stations only
      • Any available antennaset
      • One direction / sub-array pointing
      • One incoherent array beams, Stokes I or Stokes IQUV
      • Up to 244 subbands
      • Standalone, parallel calibrator, or calibrator-target-calibrator strategy
    • 3) Fast Imaging + multi-beam observation with
      • Imaging with Remote (up to 10) + Core stations,
      • Beamformed multi-beam with 6 rings with the Core only
      • LBA_OUTER, LBA_SPARSE_EVEN, HBA_ONE or HBA_ZERO
      • Beamformed resolution 12.2 kHz, 0.01 seconds
      • Imaging resolution 12.2 kHz, 0.25 seconds
      • Up to 60 subbands
    • In cycle 17-19, mode 3 can be accompanied by:
      • Three parallel observations with a single station (2x Stokes IQUV, 0.01s, 12.2 kHz 400 SB and 1x CV, 400 SB) and a parallel fly’s eye observation with up to 14 international stations (12.2 kHz, 0.01s, 400 SB)
    • A full characterization of BF + IM observations needs to be performed in light of the COBALT2 upgrade and the LOFAR MEGA MODE implementation. This will make a wider set of observations available in future cycles.
    SDC Helpdesk