Commensal beam formed and imaging mode

    Combining Imaging and Beam Formed Modes

    Some Beam Formed modes (BF), and even a combination of them, can be run in parallel with the standard imaging mode (IM). 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:
    • 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. 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).
    • At the start of the cycle, BF processing may not yet be available for this mode and the raw data will be ingested instead.
    We offer three modes:

    1) Imaging with Remote + Core stations and Coherent Stokes beamforming with Core stations only

    • One direction / sub-array pointing
    • Two Tied-array beams Stokes I, Stokes IQUV or Complex Voltage
    • Up to 244 subbands
    • Standalone, calibrator-target-calibrator,  target-calibrator strategy

    2) Imaging with Remote + Core stations and Incoherent Stokes beamforming with Core stations only

    • 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
    • Antenna set: LBA_OUTER
    • Beamformed resolution 12.2 kHz, 0.01 seconds
    • Imaging resolution 12.2 kHz, 0.25 seconds
    • Up to 60 subbands
    • This 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) using any of LBA_OUTER, LBA_SPARSE_EVEN, HBA_DUAL, HBA_DUAL_INNER

    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.


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