# Revisited "Cluster-Cluster" VLBI with future multi-beam low frequency radio interferometers

## TL;DR

This paper explores the synergy of multi-beam VLBI techniques with ASKAP to enhance astrometric precision, wide-field mapping, and future high-resolution observations with the SKA by revisiting and proposing improvements to the 'Cluster-Cluster' VLBI method.

## Contribution

It demonstrates how multi-view VLBI with ASKAP can improve calibration, positional accuracy, and enable wide-field mapping, contributing to future SKA observations.

## Key findings

- Multi-view VLBI improves ionospheric calibration.
- Joint ASKAP and multi-site observations increase astrometric precision.
- Potential for very wide-field VLBI mapping.

## Abstract

We revisit the "Cluster-Cluster" or multi-view Very-Long-Baseline-Interferometry (VLBI) technique from the perspective of its synergy with the multi-beam features inherent in the Australian Square Kilometer Array Pathfinder (ASKAP)and its potential to improve the outcomes of VLBI observations with ASKAP. We include a list of candidate VLBI sites that already support or can be upgraded to support multi-view VLBI located in Australia and overseas, and which have common visibility with ASKAP. The results of our previous "cluster-cluster" observations at 1.6 GHz demonstrated the advantages of this configuration to calibrate the ionospheric distortions responsible for the loss of positional accuracy at low frequencies, using multiple calibrators in a range between 1 to 6 degrees away from the target. Therefore, we conclude that joint observations of ASKAP with other multi-view sites using "cluster-cluster" techniques would improve the outcomes of the high spatial resolution component of ASKAP applied to astrometric projects, achieving higher precision for many more targets, and with lower detection thresholds. Also very wide-field VLBI mapping becomes a possibility. Looking to the future, this would contribute to the development of new techniques that are relevant for future high resolution observations with the SKA.