The Magdalena Ridge Observatory Interferometer (MROI) is a long-baseline optical interferometer under construction in New Mexico, which will eventually comprise ten relocatable 1.4 meter diameter Unit Telescopes (UTs). When finished, the MROI will have a sub-milliarcsecond angular resolution enabling high sensitivity observations of objects such as active galactic nuclei, young stars and star formation, binary systems, stellar surfaces, and geosynchronous assets. The Infrared Coherencing Nearest Neighbors (ICoNN) fringe tracker is the most critical instrument at the MROI. ICoNN is a nearest neighbor beam combiner whose main function is to "phase up" the array by tracking the atmospheric piston fluctuations in time and instructing a series of delay lines to correct the atmospherically-induced optical path difference. This "freezes" the fringes on the science detector allowing them to make high quality measurements. ICoNN has been designed and partially commissioned, but due to advances in detector technology it will be upgraded to a modern SAPHIRA infrared detector. The SAPHIRA detector has recently been received. This paper explores plans for the upgrade and final commissioning process, which includes the integration of the new detector, alignment of the internal cold optics, and final integration and testing of multiple subsystems.

The European Interferometry Initiative (EII; https://european-interferometry.eu/) is an open association of Institutes from 15 European countries collaborating on the exploitation and development of optical/infrared long baseline interferometry. Since its formation in the early 2000s the EII has fostered the development of interferometry in Europe and worldwide through programmes that develop the technology for making interferometric observations, support existing users of interferometry facilities, and encourage new generations of users to learn about and exploit interferometry for science observations. We discuss the successes and lessons learned in the delivery of the programmes initiated and managed by the EII, including the development of new hardware, software and techniques, the initiation of the VLTI Expertise Centres to support users, and training and networking through the VLTI summer schools and the Fizeau exchange programme. We discuss possible future programmes to further support and develop the interferometry community.

The Magdalena Ridge Observatory Interferometer is an ambitious project to build a 10 telescope long-baseline optical/near-infrared in the mountains about a one-hour drive outside of Socorro, NM. The project is being led by New Mexico Institute of Mining and Technology and being built in cooperation with our primary collaborators at the University of Cambridge. We are currently funded via a cooperative agreement with the Air Force Research Lab in Albuquerque, NM to demonstrate imaging capabilities on geosynchronous objects. We have recently installed the second full beamline for the interferometer system and are working our way towards first fringes on an similar to 8m baseline later this year. In this manuscript, we report on the status of each of the subsystems, the installation progress and challenges to date, and on the ramp-up to measurements of first fringes. We also report on plans for early science and offer public shared-risk access with the facility in the near future.

The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs ([U]BV, RIZ, YJH) providing a spectral resolution of similar to 100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 mu m with the goal of extending it to 0.35-2.4 mu m with the addition of an U arm to the BV spectrograph and a separate K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Modularity and fibre-feeding allows ANDES to be placed partly on the ELT Nasmyth platform and partly in the Coude room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature's fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of almost 300 scientists and engineers which include the majority of the scientific and technical expertise in the field that can be found in ESO member states.

The Beam Relay System at the Magdalena Ridge Observatory Interferometer, exposed to outdoor environmental conditions, includes 6-inch mirrors mounted on aluminum frames and steel platforms, equipped with piezoelectric motors and a laser/camera alignment system. This subsystem faces challenges with misalignments that disrupt observations, addressed by a proposed correction strategy. The system uses temperature sensor data around mirrors to predict and correct misalignments as a feedforward control system through calibrated motors, and incorporates a periodic closed-loop control system using light source and camera. Advanced predictive models refined over time using temperature, shear, and tilt data, aim to maintain beam stability within interferometric tolerances, ensuring optimal performance.

The Magdalena Ridge Observatory Interferometer has been designed to deliver an unprecedented capability for model-independent imaging of faint astronomical targets. As a consequence, its design methodology has focused on optimizing the interferometric sensitivity of all of its opto-mechanical subsystems. We report here on initial testing of one of the MROI beam-trains, outlining the performance metrics utilized to characterize the elements of the optical train from the Unit Telescopes through to the MROI beam combiner tables, the tests performed on each subsystem, and how our results compare to the design error budget for the MROI. The impact of the tests on the initial sensitivity limit of the MROI are discussed.

The Magdalena Ridge Observatory Interferometer (MROI) Beam Relay System (BRS) comprises a network of air-evacuated pipes and relay stations, consisting of a pier and vacuum can containing a relay mirror, shear alignment sensors, and control electronics. Located at precise points along the arms of the interferometer array, the BRS piers contain remotely controllable mirrors which can be precisely adjusted to direct light from the adjacent unit telescope down the beamline and into the Beam Combining Facility (BCF), where interference fringes are made. Changing the array configuration is a planned function of interferometer operation, but is time consuming and complicated, as it will involve moving mirror assemblies between the vacuum cans (VC). The Vacuum Can Hub (VCH) is a network Modbus message processor and instrumentation hub that connects the Vacuum Can (VC) instrumentation to the MROI power and communication infrastructure via a single Power over Ethernet (PoE) access point. This greatly simplifies and speeds up array reconfiguration. In this paper we shall discuss the MROI Automated Alignment System (AAS), which is tasked with ensuring precise alignment of beamlines connecting the UTs with the BCF, and its role as supervisor of the VCH. We also discuss the BRS components interfaced by the VCH: first, the VC 1-wire temperature sensor network, whose data is used by the AAS for driving fine adjustments of the BRS relay mirrors via the AAS's feed-forward open-loop thermal mechanical model. Second, twin shear sensors used for coarse beam alignment, each consisting of custom designed 10 x 10 pixel photodiode arrays, whose electronics and software allow direct access by the AAS by using the VCH's message routing capabilities. The VCH's ability to translate and relay Modbus messages between the network and serial domain allow high flexibility in defining the quantity and types of BRS hardware that can be installed in VCs.

Beam misalignment causes visibility loss in fringe measurements made by long-baseline optical interferometers. An Automated Alignment System (AAS) has been designed for the Magdalena Ridge Observatory Interferometer (MROI) to keep the visibility loss associated with misalignment under similar to 1%. Production versions of collimated reference light sources and precision beam alignment sensors for the AAS have recently been integrated into the first beamline of the MROI. This paper describes the lessons learned during their installation and provides results from their site acceptance tests.

The Magdalena Ridge Observatory Interferometer (MROI) and its first science beam combiner the Free-space Optical multi-apertUre combineR for IntERferometry (FOURIER) are undergoing the first phase of construction near Magdalena, New Mexico. MROI and FOURIER are designed for unprecedented sensitivity to enable imaging of faint astronomical targets. FOURIER provides highly sensitive simultaneous interferometric observations in the J, H, and K bands. In preparation for first fringes with FOURIER, we are developing a data reduction pipeline to produce high quality science ready data products adhering to the OIFITS2 data standard.

ABSTRACT Image plane beam combination in optical interferometers multiplexes the interference fringes from multiple baselines on to a single detector. The beams of starlight are arranged in a non-redundant pattern at the entrance of the combiner so that the signal from each baseline can be separated from one another in the frequency domain. If the signals from different baselines overlap in the frequency domain, this can give rise to a systematic error in the fringe measurements known as baseline crosstalk. In this paper, we quantify crosstalk arising from the combination of atmospheric seeing and beam propagation over distances of the order of hundreds of metres. We find that in idealized conditions atmospheric wavefront errors and beam propagation do not contribute to crosstalk. However, when aperture stops are included in the optical beam train we observe that wavefront errors can result in squared visibility errors arising from crosstalk as high as ΔV2 = 6.6 × 10−3 under realistic observing conditions.

FOURIER is the first-generation science beam combiner for the MROI. It is a three-way, J, H and K band image plane combiner. The FOURIER design emphasises low visibility losses and high optical throughput and is designed around a low-noise SAPHIRA detector. Based on laboratory measurements of its throughput and visibility losses, FOURIER is expected to reach limiting magnitudes of 12.3, 13.2 and 11.7 in the J, H and K bands, respectively, within 5 minutes of incoherent integration assuming 0.7′′ seeing and a detector read noise of 0.3 electrons. As FOURIER observes as red as the K band, the detector and most of its optics are placed within a liquid nitrogen cryostat. We present the design of FOURIER’s cryostat, as well as laboratory tests of the instrument’s cryogenic performance. We also report room temperature characterisation of the optics. Finally, we discuss the path forward from the current status of the instrument to first fringes in 2023.

The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs (UBV, RIZ, YJH) providing a spectral resolution of ∼100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 µm with the goal of extending it to 0.35-2.4 µm with the addition of a K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Its modularity will ensure that ANDES can be placed entirely on the ELT Nasmyth platform, if enough mass and volume is available, or partly in the Coudé room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature's fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of more than 200 scientists and engineers which represent the majority of the scientific and technical expertise in the field among ESO member states.

The Magdalena Ridge Observatory Interferometer has been conceived to be the most ambitious optical/near-infrared long-baseline imaging interferometer in the world today. We anticipate receiving the second telescope mount and enclosure and associated beamline infrastructure to enable us to attempt first fringes measurements early in 2023. Having reached this important milestone, we anticipate receiving the third copy of all beamline components about one year later and attempting closure phase measurements thereafter. We will present a status update and plans under the new Cooperative Agreement with AFRL for the next phases of the project.

The Magdalena Ridge Observatory Interferometer (MROI) will soon incorporate an Automated Alignment System (AAS) to help limit visibility losses due to beam misalignment to ~1%. This paper focuses on two key AAS components: (1) a dual-wavelength beacon at each unit telescope and (2) a detector for measuring the shear and tilt of beams of light arriving from the telescopes in the beam combining laboratory. We share initial results of acceptance tests for these components. Finally, we outline a plan for fully validating their performance against a list of derived requirements.

Xenomai1 is a hard real-time operating system suitable for many low-latency tasks encountered in astronomical instruments. It is open source, has microsecond-level response time and coexists with the Linux kernel, thereby facilitating the execution of hard real time code on Linux systems. This presentation presents experience coding systems with Xenomai for the Magdalena Ridge Observatory Interferometer. Firstly an overview of Xenomai is given, focusing on how it achieves hard real time performance and how it can be used to interact with hardware using Linux-like device drivers. Secondly, a generic outline of the development process is given, including the mindset needed, general pitfalls to be avoided, and strategies that can be employed depending on how open the hardware and any existing source code is. Two specific case studies from the Magdalena Ridge Observatory are then presented: Firstly, the fast tip-tilt system, which must read out a 32x32 subframe from an EMCCD camera, determine a stellar image centroid and send a correction voltage to a tip-tilt mirror at up to 1kHz. Secondly, the MROI delay line metrology system, which must read laser metrology position data for ten delay line trolleys and send correction voltages to their cat’s eyes at 5kHz. Finally, some future challenges to development with Xenomai and other hard real time operating systems are discussed: processors with functionality such as system management interrupts that are beyond operating system control, and the trend towards buffered or closed interfaces between computers and hardware.