SKA-Low will be a transformational low-frequency radio telescope, providing unprecedented capability to detect and study the EoR, catalog radio emission from galaxies at all cosmic epochs, and answer questions that we do not yet know to pose. Although SKA-Low by itself will not provide the sub-arcsecond angular resolution required for maximising synergy with frontline optical/IR telescopes such as JWST, the planned tied-array mode does indirectly allow this capability by enabling participation in VLBI observations. Effectively linking SKA-Low to the global radio astronomy network requires additional collecting area distributed in patches separated by hundreds to thousands of km.

We are motivated to take the first steps to establish low-frequency VLBI capability in the southern hemisphere. A modest project is sufficient to demonstrate capability, provide the basis of a long-term technology development pathway, and provide motivation for future expansion of SKA-Low to match the original vision of a continent-scale telescope. Our development project is called LAMBDA: the Low-frequency Australian Megametre-Baseline Demonstrator Array.

Technical considerations

A full array would consist of several (4-6) low-frequency aperture arrays using the same antennas and layout as SKA-Low stations. These will be located at sites of existing LBA telescopes in order to reduce establishment costs. Although the project design is not motivated by an attempt to optimise imaging fidelity to achieve specific science goals, we will nevertheless seek to achieve a balanced mixture of intermediate- and long-baseline spacings. In line with our goal of enabling a future-facing technology development pathway, our signal processing will be based on RFSoC technology that is being utilised for other CSIRO projects. Station processing will be designed with flexibility and single-station applications in mind. The system will have sufficient sensitivity to enable in-field ionospheric calibration on the relevant timescales.

Future steps

The initial phase of the LAMBDA project is geared toward a demonstration of technical capability, building on expertise gained by the LOFAR collaboration but benefiting from the wider bandwidth of the SKA-Low antennas; the flexibility afforded by our signal processing solution; and building on existing southern hemisphere capability. First steps will be a demostrator station with the new backend hardware. We will also coordinate with SKAO to ensure alignment of our developments with SKA-Low technical capability and deployment plans. In parallel, we will work with the science community to articulate and assess the science case for an expanded version of LAMBDA that could be supported by a consortium funding model and pave the way for a future upgrade to SKA-Low.

For questions or comments contact: Tessa Vernstrom, Project Scientist tessa.vernstrom [at] csiro.au