Asgard Instrument Suite

Overview

The Asgard instrument suite represents the next leap forward for ESO's Very Large Telescope Interferometer (VLTI), building on a legacy of record-breaking discoveries and instrumental innovation. Asgard is a collaborative suite of four advanced instruments, designed to push the boundaries of stellar and planetary system studies.

Instruments

• HEIMDALLR

  Simultaneous fringe tracking and stellar interferometry with shared optics, operating in the K band. Named after Heimdallr, the Norse god who guards the Bifröst bridge, symbolizing the instrument's role in safeguarding and enhancing interferometric observations.

• Baldr

  Strehl optimizer in the J and H bands, enhancing image sharpness and interferometric performance. Named after Baldr, the Norse god of light and purity, symbolizing the instrument's role in optimizing the clarity and quality of astronomical observations.

• BIFROST

  Spectroscopic combiner for studying the formation and properties of stellar and planetary systems in the Y-J-H bands. Named after Bifröst, the bridge connecting Midgard (Earth) and Asgard (the realm of the gods), symbolizing the instrument's role in bridging gaps in our understanding of stellar systems by maximising the angular resolution of VLTI.

• NOTT

  The first VLTI nulling interferometer (formerly Hi-5), using a photonic double-Bracewell combiner in the L′ band (3.5–4.0 µm) to image nearby young planetary systems near the snow line and exozodiacal dust disks. Named after Nótt, the Norse goddess of night, who rides across the sky in her chariot, representing the instrument's focus on nulling starlight to reveal faint planetary companions.

• Solarstein

  The combined internal calibration and alignment unit for the Asgard suite, ensuring precise instrument setup and operation. Named after the Norse goddess of the sun, Sól, who drives the sun's chariot across the sky, and the sunstone that guides Asgard's instruments.

Project Status

The Solarstein, Heimdallr and Baldr copmonent of Asgard have been integrated in July 2025 with commissioning in September 2025. Asgard's NOTT and BIFROST components are part of phase 2: BIFROST has been integrated at VLTI in March 2026. NOTT is in the integration phase in Europe and is scheduled for shipment to Paranal in early 2027.

Funding and Collaboration

The Asgard project has been primarily funded by several different grant and institutional constributions. These are:

• The Australian Research Council (ARC) Linkage Infrastructure Equipment and Facilities (LIEF) scheme (LE220200126). The lead institute for this was the Australian National University, with partner contributing institutes being the University of Sydney, the University of Melbourne, Macquarie University, the University of Exeter, KU Leuven, and the Observatoire de la Côte d'Azur.
• The Astralis consortium through the University of Sydney node, providing support well beyond their commitment listed in the LIEF application.
• The Observatoire de la Côte d'Azur, which provided support well beyond their commitment listed in the LIEF application.
• The European Research Council consolidator grant GAIA-BIFROST (Grant No.101003096) with principle investigator Stefan Kraus
• The European Research Council consolidator grant SCIFY (Grant No. 866070) with principal investigator Denis Defrère
• The European Southern Observatory (ESO) who will host Asgard at Paranal. As a Visitor Instrument, Asgard receives no guaranteed time, but welcomes and supports community access allocated via ESO's standard calls for proposals.

• The Australian Research Council's Discovery project "Equipping VIKiNG: Mid-infrared technology for exoplanet characterisation" (DP190101477) that included technology development for the NOTT instrument, as well as simulation of science outputs.
• The NASA precursor science grant for exozodiacal disk science with principal investigator Steve Ertel
• The Opticon-Radionet Pilot (ORP) programme (H2020). Preparation and integration of Asgard/NOTT into the VLTI, resulting in a full interface control document (see Martinod et al. 2022, 2023, 2024).

Technical Highlights

• Sensitivity optimised instrument - no spectrograph or spatial filtering for Heimdallr
• Fast, low-latency adaptve optics and fringe tracking - standard operation planned with less than 1.5 ms latency including exposure time.
• Multiple observing modes at 1-4 micron wavelengths for diverse science cases