Why a dedicated 225 GHz phase correction system ?
Peter Hall

  • ATCA will never have 1 mm band astronomy receivers and IRAM would rather not use their 1 mm receivers for sounding.

(Also, IRAM receiver stability will degrade with the closed-cycle cooling due soon)

  • 225 GHz sounding has been demonstrated as the basis of a sensitive, robust, phase correction system (IRAM). Other suggested frequencies/approaches (e.g. JCMT 183 GHz) may give interesting meteorological information but are almost certainly less robust in the phase correction role.
  • A separate WVR package gives independence from other ATCA receivers meaning:

- phase correction instantly usable at any observing band;
- phase correction WVR is optimised for sensitivity and stability (best sounding frequency, most stable technology);
- phase correction does not compromise astronomy receiver sensitivity;
- phase correction WVR does not occupy valuable turret space.

  • ATNF has already developed a sensitive, stable, WVR compatible with our monitoring and control philosophy.
  • ATNF can be the first to establish the physics of sounding using separate (but coaxial) astronomy and sounding beams.

What we know so far…..

  • 225 GHz clear-sky sounding works. IRAM are currently building the capacity for phase correction into the PdBI data editing and processing package.
  • We have built a 225 GHz WVR with the sensitivity and stability required for phase correction.

What we propose to do….

  • Build a second WVR ($40k + 1.5 p-y).
  • Collaborate with IRAM in adapting Plateau de Bure atmospheric model to Narrabri (M. Bremer visit).
  • Verify phase correction on ATCA 2-element interferometer ( wavelength < 3 cm).
  • Construct 4 more WVRs ($130k-$160k) for routine ATCA phase correction.

Note…

ATUC has already given support for the construction of a second WVR.

Projects
Public