Integrating position-tracking drifts into VLBI correlation

Determine how position and attitude drifts measured by the Balloon-borne VLBI Experiment’s position-tracking sensors can be applied to real interferometric data and ingested by DiFX, the standard VLBI correlator software, or a modified version of DiFX.

Background

The Balloon-borne VLBI Experiment reconstructs the balloon telescope’s position and attitude using GPS, accelerometers, a gyroscope, and auxiliary sensors. This reconstruction is required to correct the geometric time delay between the balloon and ground-based telescopes at 22 GHz, where the balloon can move by many wavelengths during a one-second coherence interval.

Although the paper reports stationary-test estimates of approximately 0.2 mm position drift and 0.4 arcsec attitude drift over one second, it does not establish how these sensor-derived drifts should be incorporated into actual interferometric data processing. The unresolved task is to determine how the estimates can be supplied to DiFX or a modified correlator, potentially to guide fringe searches across successive time chunks.