Long Baseline Array

Long Baseline Array
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Name	Long Baseline Array
Organization	CSIRO, ATNF
Country	Australia
Established	1992
Wavelength	Radio
Type	Very Long Baseline Interferometer

Long Baseline Array The Long Baseline Array is an Australian radio interferometer facility used for very long baseline interferometry and high-resolution astrometry. It provides sub-milliarcsecond angular resolution for observations of active galactic nuclei, pulsars, masers, and transient sources by linking antennas across continental distances. The facility supports multi-wavelength campaigns with observatories and space missions, enabling synergy with instruments and programs in Australia, Europe, Asia, and the Americas.

Overview

The array combines antennas from national and regional facilities including the Australia Telescope Compact Array, Parkes Observatory, Mopra, Hobart, Ceduna, and antennas associated with the Commonwealth Scientific and Industrial Research Organisation and the Australian Telescope National Facility. It operates as a national facility for radio astronomy alongside collaborations with the European VLBI Network, Very Long Baseline Array, and East Asian VLBI Network. The instrument is integral to programs involving pulsar timing, maser astrometry, active galactic nucleus imaging, and transient follow-up with partners such as the Square Kilometre Array Organisation, Max Planck Institute for Radio Astronomy, and National Astronomical Observatory of Japan.

History and Development

Initial proposals for a long-baseline interferometer in Australia built on experience from the Parkes radio telescope and the Molonglo Observatory Synthesis Telescope. During the late 20th century, development paralleled advances at institutions such as NASA, the Jet Propulsion Laboratory, and the European Southern Observatory. Key milestones involved the commissioning of the Australia Telescope Compact Array, upgrades to Parkes, and integration of international stations to match developments at the National Radio Astronomy Observatory and the Dominion Radio Astrophysical Observatory. Funding and management were coordinated through national bodies including CSIRO and grants influenced by major projects like the Square Kilometre Array planning and international Memoranda of Understanding with observatories such as the Max Planck Institute and the National Astronomical Observatory of Japan.

Instruments and Facilities

Core elements include dish antennas at Parkes, ATCA, Mopra, Hobart, and Ceduna, supplemented by international partner dishes. Receivers cover centimetre-band frequencies used by programs with the Australian Research Council, the European VLBI Network, and collaborators at institutions like the University of Sydney and the University of Tasmania. Backends include hydrogen maser frequency standards and digital recording systems compatible with the Mark series recorders used at the Very Long Baseline Array and the International VLBI Service. Antenna control and scheduling are coordinated with operations groups at CSIRO, the ATNF, and partner facilities such as the Max Planck Institute for Radio Astronomy and the National Radio Astronomy Observatory.

Observing Techniques and Data Processing

Observations use phase-referencing, fringe-fitting, and pulsar gating techniques developed in parallel with methods at the European VLBI Network and the Very Long Baseline Array. Correlation is performed at dedicated correlators similar to those at the Joint Institute for VLBI ERIC and the DiFX software correlator used by the Australian community and partners such as the Curtin University node and the Leibniz Institute for Astrophysics Potsdam. Data calibration follows standards employed by the International VLBI Service, involving amplitude calibration, delay models tied to hydrogen maser standards, and geodetic parameter estimation with links to the International Earth Rotation and Reference Systems Service and the Global Navigation Satellite System community.

Scientific Contributions and Key Results

The facility has produced high-resolution imaging of quasars and blazars, contributing to studies linked with the Fermi Gamma-ray Space Telescope, the European Space Agency missions, and surveys coordinated with the Sloan Digital Sky Survey. Astrometric parallax measurements of masers have informed Galactic structure models employed by research groups at the Max Planck Institute and the Harvard–Smithsonian Center for Astrophysics. Pulsar proper motion and timing work underpin investigations connected to the Parkes Pulsar Timing Array, the International Pulsar Timing Array, and gravitational wave background limits explored alongside LIGO and Virgo collaborations. Transient source follow-up has complemented efforts by the Vera C. Rubin Observatory, the Neil Gehrels Swift Observatory, and the Australian Square Kilometre Array Pathfinder.

Collaborations and Networks

The array participates in international networks including the European VLBI Network, the East Asian VLBI Network, and cooperates with the Very Long Baseline Array, the International VLBI Service, and the Square Kilometre Array Organisation. Scientific partnerships involve universities and institutes such as the Australian National University, Curtin University, the University of Tasmania, CSIRO, Max Planck Institute for Radio Astronomy, National Astronomical Observatory of Japan, and the National Radio Astronomy Observatory. Operational links extend to space agencies and missions run by NASA and ESA, and data-sharing agreements align with global initiatives like the International LOFAR Telescope and multi-messenger programs involving LIGO, Virgo, and IceCube.

Category:Radio telescopes