2. Single-dish Observing Methods

Single-dish observing methods implemented or proposed for the NCCS are:

• Continuum radiometry, which employs two methods, scanning and stepping:
  • scanning, which, from the point of view of the observer, includes multiple types for which increasing numbers of parameters need to be specified:
    • passive (drift) scans, where the telescope is parked at an earlier RA than the target and Earth rotation produces the scan
    • scan in one coordinate while tracking in the other:
      • RA scan, track (park) in Dec
      • Dec scan, track RA (or park in HA)
    • active scanning in the coordinate systems:
      • Equatorial
      • Galactic
      • Ecliptic
      • Horizon (Altazimuth)
      • Topocentric (Telescope)
      • other Longitude + Latitude
    • Maps are constructed from sets of scans:
      • maps made from scans observed individually, at any suitable time
      • maps made from uninterrupted sets of scans that must be set up as one entity.
  • stepping, i.e. tracking in RA at positions stepped around a beam pattern at
    • second or first null in RA and Dec,
    • half power points in RA and Dec,
    • beam centre in RA and Dec,
    • zero-crossing point of dual beam receivers.
• Spectrometry, which employs three methods:
  • tracking the target position and switching in frequency between the two halves of the scan;
  • tracking the target position for half the scan and a reference position a specified distance away for the other half;
  • take a single reference off-source spectrum and use it with many on-source spectra of different targets.
  Doppler tracking of the changing Vlsr correction or comet velocity is used, by controlling a local oscillator frequency.
• Pulsar timing, in which the pulsar is tracked and its signal is recorded synchronously with the predicted doppler-shifted pulse period.