ESO’s Very Large Telescope Interferometer has a history of record-breaking discoveries in astrophysics and significant advances in instrumentation. The next leap forward is its new visitor instrument, called Asgard. It comprises four natively collaborating instruments: HEIMDALLR, an instrument performing both fringe tracking and stellar interferometry simultaneously with the same optics, operating in the K band; Baldr, a Strehl optimizer in the H band; BIFROST, a spectroscopic combiner to study the formation processes and properties of stellar and planetary systems in the Y-J-H bands; and NOTT, a nulling interferometer dedicated to imaging nearby young planetary systems in the L band. The suite is in its integration phase in Europe and should be shipped to Paranal in 2025. In this article, we present details of the alignment and calibration unit, the observing modes, the integration plan, the software architecture, and the roadmap to completion of the project.
The simultaneous push to unprecedented contrast, spectral and spatial resolution at the Very Large Telescope Interferometer (VLTI), as promised by the Asgard instrument suite, requires unprecedented high Strehl ratios and phase-front stability. This will be the job of Baldr: a new J or H band Zernike wavefront sensor (ZWFS) used as a second stage adaptive optics (AO) system for the VLTI/Asgard instrument suite. ZWFS was selected for Baldr due to its optimal photon sensitivity and the need for Baldr to be extremely low latency to reduce the residuals from the first stage AO systems. Here we briefly present the design of Baldr which uses a novel architecture where all four Baldr beams for adaptive optics from each telescope are sensed with a low-latency C-RED One detector, permitting AO frame rates up to 3.5kHz. With this architecture simulations show that the Baldr design can deliver J-band Strehl ratios for the 1.8m Auxiliary Telescopes (AT’s) of over 80%, which is a significant improvement on the Strehl ratios otherwise delivered to Asgard, which would limit the scientific objectives of the instrument. Finally we present preliminary test-bed results and give an overview of progress and future work.
The TOLIMAN space mission confronts the challenge of detecting Earth analogues in the immediate solar neighbourhood by using novel astrometric techniques. This bespoke, low-cost mission will employ a novel optical and signal encoding system, enabling high-precision measurements that typically require larger instruments. Targeting the Alpha Centauri system, TOLIMAN will utilise an innovative diffractive pupil to mitigate the limitations of a relatively modest satellite and payload infrastructure to make measurements at the extreme precisions required. In this work, we describe the design and manufacturing of the pupil, which employs liquid crystal technologies and substrates with low coefficients of thermal expansion, with the goal of making measurements resistant to inevitable optical distortions and aberrations.
The TOLIMAN space telescope is purpose-built to probe our stellar neighbourhood for potentially habitable Earth-like exoplanets. Our novel diffractive pupil design will allow TOLIMAN to detect extremely subtle changes in the positions of stars in a binary system, down to the microarcsecond scale. One of the many challenging factors in the detection of this diminutive astrometric signal is instability in the telescope pointing, known as jitter.
This work demonstrates the capability of mitigating the blurring effects of telescope jitter through a forward modelling approach and a new precise optical positioning system. We utilise ∂Lux – a cutting-edge differentiable optical simulation framework built in Jax by our team at the University of Sydney – to model the effects of telescope jitter on the final image. The demanding stability requirements have also inspired innovative engineering approaches, including the design of a piezo-driven tip/tilt system. This methodology enables us to recover the crucial astrometric parameters despite telescope pointing instability, offering TOLIMAN the unique opportunity to observe exoplanetary signatures with unprecedented precision.
The TOLIMAN mission will fly a low-cost space telescope designed and led from the University of Sydney. Its primary science targets an audacious outcome in planetary astrophysics: an exhaustive search for temperateorbit rocky planets around either star in the Alpha Centauri AB binary, our nearest neighbour star system. By performing narrow-angle astrometric monitoring of the binary at extreme precision, any exoplanets betray their presence by gravitationally, engraving a tell-tale perturbation on the orbit. Recovery of this challenging signal, only of order micro-arcseconds of deflection, is normally thought to require a large (meter-class) instrument. By implementing significant innovations optical and signal encoding architecture, the TOLIMAN space telescope aims to recover such signals with a telescope aperture of only a 12.5cm. Here we describe the key features of the mission: its optics, signal encoding and the 16U CubeSat spacecraft bus in which the science payload is housed - all of which are now under construction. With science operations forecast on a timescale of a year, TOLIMAN aims to determine if the Sun’s nearest neighbour hosts a potential planetary stepping stone into the galaxy. Success would lay down a visionary challenge for futuristic high speed probe technologies capable of traversing the interstellar voids.
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.
Exo-NINJA will realize nearIR R≈4000 diffraction-limited narrow-field spectro-imaging for characterization of exoplanets and circumstellar disk structures. It uniquely combines mid-R spectroscopy, high throughput, and spatial resolution, in contrast to CHARIS, which does spectro-imaging, and REACH, which is single-point (no spatial resolution). Exo-NINJA’s spectro-imaging at the telescope diffraction limit will characterize exoplanet atmospheres, detect and map (spatially and spectrally) gas accretion on protoplanets, and also detect exoplanets at small angular separation (λ/D) from their host star by spectro-astrometry. Exo-NINJA will link two instruments at the Subaru Telescope using a high-throughput hexagonal multi-mode fiber bundle (hexabundle). The fiber coupling resides between the high contrast imaging system SCExAO, which combines ExAO and coronagraph, and the medium-resolution spectrograph NINJA (R=4000 at JHK bands). Exo-NINJA will provide an end-to-end throughput of 20% compared to the 1.5% obtained with REACH. Exo-NINJA is scheduled for implementation on the Subaru Telescope’s NasIR platform in 2025; we will present a concise overview of its future installation, laboratory tests such as the throughput and focal ratio degradation (FRD) performance of optical fiber imaging hexabundles, in the NIR and the trade-offs for fiber choices for the NINJA-SCExAO hexabundle fiber cable, and the expected on sky performance.
Hector is a new optical integral field spectrograph (IFS) instrument built by Astralis - Australia’s Astronomical Instrumentation Consortium. Hector was commissioned on the Anglo-Australian Telescope (AAT) in 2022. In 2023 it began a 15,000-galaxy IFS survey of nearby z< 0.1 galaxies. The high fill-factor imaging fibre bundles ‘hexabundles’ of the type used on the SAMI instrument, have been improved and enlarged to cover up to 27-arcsec diameter. The aim is to reach 2 effective radii on most galaxies. Hector has a unique and novel robotic positioner that compensates for varying telecentricity over the 2-degree-field of the AAT to recoup the light loss and correct the focus across the field. Hector has 21 hexabundles over that 2-degree field feeding both the new Hector spectrograph (Spector) and existing AAOmega spectrograph. The new dual-arm Spector spectrograph has the highest spectral resolution of any large IFS nearby galaxy survey of 1.3 Angstrom. This is key to enable higher order stellar kinematics to be measured on a larger fraction of galaxies and to link those galaxies to the large-scale environments in which they form. A data reduction pipeline has been developed and is producing science-quality galaxy cubes and the first internal data release is now being used for science.
European Southern Observatory (ESO)’s Very Large Telescope Interferometer (VLTI), Paranal, Chile, is one of the most proficient observatories in the world for high angular resolution astronomy. It has hosted several interferometric instruments operating in various bandwidths in the infrared. As a result, the VLTI has yielded countless discoveries and technological breakthroughs. We propose to ESO a new concept for a visitor instrument for the VLTI: Asgard. It is an instrumental suite comprised of four natively collaborating instruments: High-Efficiency Multiaxial Do-it ALL Recombiner (HEIMDALLR), an all-in-one instrument performing both fringe tracking and stellar interferometry with the same optics; Baldr, a Strehl optimizer; Beam-combination Instrument for studying the Formation and fundamental paRameters of Stars and planeTary systems (BIFROST), a combiner whose main science case is studying the formation processes and properties of stellar and planetary systems; and Nulling Observations of dusT and planeTs (NOTT), a nulling interferometer dedicated to imaging young nearby planetary systems in the L band. The overlap between the science cases across different spectral bands yields the idea of making the instruments complementary to deliver sensitivity and accuracy from the J to L bands. Asgard is to be set on the former AMBER optical table. Its control architecture is a hybrid between custom and ESO-compliant developments to benefit from the flexibility offered to a visitor instrument and foresee a deeper long-term integration into VLTI for an opening to the community.
The Very Large Telescope Interferometer is one of the most proficient observatories in the world for high angular resolution. Since its first observations, it has hosted several interferometric instruments operating in various bandwidths in the infrared. As a result, the VLTI yields countless discoveries and technological breakthroughs. We introduce to the VLTI the new concept of Asgard: an instrumental suite including four natively collaborating instruments: BIFROST, a stellar interferometer dedicated to the study of the formation of multiple systems; Hi- 5, a nulling interferometer dedicated to imaging young nearby planetary systems in the M band; HEIMDALLR, an all-in-one instrument performing both fringe tracking and stellar interferometry with the same optics; Baldr, a fibre-injection optimiser. These instruments share common goals and technologies. Thus, the idea of this suite is to make the instruments interoperable and complementary to deliver unprecedented sensitivity and accuracy from J to M bands. The interoperability of the Asgard instruments and their integration in the VLTI are the main challenges of this project. In this paper, we introduce the overall optical design of the Asgard suite, the different modules, and the main challenges ahead.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.