The Green Bank Telescope

Green Bank Telescope 4mm Receiver

Introduction

NRAO is developing a 4mm dual-beam receiver to cover the low-frequency end of the 3mm atmospheric window from 68--92 GHz. In addition to the wide-range of science enabled, the receiver will allow us to quantify the performance of the GBT at 3mm and refine the pointing-and-control system for the GBT. Spectroscopy is the primary science goal for the instrument, but VLBI observations over at least part of the frequency range will also be supported.

Key Science

Based on the ASTRO-2010 Decadale Survey, four key research areas have been identified for the GBT. The 4mm receiver would greatly enhance the science capabilities in all of these areas.

  • Fundamental Physics -- With the VLBA, the GBT 4mm receiver would allow us to probe the fundamental physics near the base of powerful black hole jets in nearby galaxies.
  • The Context of Star Formation -- Molecular spectroscopy of the deuterium species and the other important transitions associated with dense molecular gas with the GBT 4mm receiver would revolutionize studies of the structure and physical properties of cold cloud cores from which stars form.
  • Origin of Life -- The GBT 4mm receiver will carry out molecular spectroscopy of complex organic molecules and pre-biotic molecules in the ISM and comets which are key for studying the conditions from which life eventually forms.
  • Galaxies Across Cosmic Time -- The GBT 4mm receiver would permit the studies of CO(1-0) at intermediate redshifts where the evolution of galaxies is proceeding rapidly and allow for the studies of the dense gas tracers, such as HCN and HCO+, in local star-forming galaxies.
Science Case for the GBT 4mm Receiver (pdf)

Specification Summary

  • Tunable frequency range: 68-92GHz (Coverage to 93.2GHz is highly desirable.)
  • Polarization: Dual linear with selection of circular using a 1/4 wave plate for VLB observations.
  • Number of beams: Two beams with dual polarization.
  • Beam separation: 4.7 arcmin nominal.
  • Observing modes:
    • Spectroscopy: Connections to the GBT Spectrometer via the common fiber IF system will be supported.
    • Total power: Total power detection in the GBT IF Rack and the DCR will be supported.
    • VLBI: Connections of one beam to the VLB Data Acquistion Rack via the common IF system will be supported. Provision for phase cal injection at IF will be provided.

Technical Information

See the 4mm Receiver Project Book for technical details and science case: GBT 4mm Receiver Project Book.
See Photo Archive for images of the 4mm Receiver.

Proposal Information

First Light with the Initial GBT 4mm System:

First light was obtained in May 2011 (First Light)
NRAONSFAUI

The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Last updated 05 January 2012 by David Frayer