Heimdallr and Solarstein: alignment, calibration, and correction in the Asgard suite at the VLTI

• Main Authors: Taras, Adam K, Robertson, J. Gordon, Carter, Josh, Crous, Fred, Courtney-Barrer, Benjamin, McGinness, Grace, Ireland, Michael, Tuthill, Peter
• Format: Journal Article
• Language: English
• Published: 04-07-2024
• Subjects: Physics - Instrumentation and Methods for Astrophysics
• DOI: 10.48550/arxiv.2407.04187

The Asgard instrument suite proposed for the ESO's Very Large Telescope
Interferometer (VLTI) brings with it a new generation of instruments for
spectroscopy and nulling. Asgard will enable investigations such as measurement
of direct stellar masses for Galactic archaeology and direct detection of giant
exoplanets to probe formation models using the first nulling interferometer in
the southern hemisphere. We present the design and implementation of the
Astralis-built Heimdallr, the beam combiner for fringe tracking and stellar
interferometry in K band, as well as Solarstein, a novel implementation of a
4-beam telescope simulator for alignment and calibration. In this update, we
verify that the Heimdallr design is sufficient to perform diffraction-limited
beam combination. Furthermore, we demonstrate that Solarstein presents an
interface comparable to the VLTI with co-phased, equal intensity beams,
enabling alignment and calibration for all Asgard instruments. In doing so, we
share techniques for aligning and implementing large instruments in bulk
optics.