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 ~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 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.
KEYWORDS: Mirrors, Education and training, Beam path, Relays, Beam diameter, Telescopes, Optical components, Design, Beam combiners, Signal to noise ratio
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.
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 ∼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 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.
The Magdalena Ridge Observatory Interferometer (MROI) is designed to operate 10 1.4m telescopes simultaneously, with baselines ranging from 7.8-347 m and limiting infrared fringe-tracking magnitudes of 14 – it is arguably the most ambitious optical/infrared imaging interferometer under construction today. In this paper we had intended to present an update of activities since the 2018 SPIE meeting as we approached a demonstration of first fringes with the facility originally anticipated for the fall of 2020. However, due to the global pandemic and a loss of funding for our project via AFRL, we have been unable to make the progress we intended. In this paper, we present results up through March, 2020 and a brief discussion of the path forward for the facility.
We present the design and testing of FOURIER, the first generation science beam combiner for the MROI. FOURIER is a three-way, J, H and K band image plane combiner which is designed primarily for observations at faint limiting magnitudes. We outline the main science requirements and discuss how the design of FOURIER contributes to meeting these requirements. We present the first laboratory characterisation of the instrument including validation of the PSF profile, demonstration of high contrast fringes, and the spectral resolution of the instrument, all of which show promising results. We conclude by discussing the path to deployment of FOURIER at the MROI ahead of the first science observation at the array.
The first unit telescope of Ridge Observatory Interferometer is integrated on the array and starlight has been observed in the Beam Combining Area for the first time. From the telescope, the beam travels in vacuum over a path of >50m, including a beam relay system and delay line. This feat was made possible by a prototype version of the Automated Alignment System that we are developing for minimising fringe visibility loss due to misalignment. We present results of on-site validation of UTLIS, a reference light source at the unit telescope acting as a proxy for starlight, and BEASST, a Shack-Hartmann sensor that simultaneously detects beam angle and position.
The Magdalena Ridge Observatory Interferometer (MROI) has been under development for almost two decades. Initial funding for the facility started before the year 2000 under the Army and then Navy, and continues today through the Air Force Research Laboratory. With a projected total cost of substantially less than $200M, it represents the least expensive way to produce sub-milliarcsecond optical/near-infrared images that the astronomical community could invest in during the modern era, as compared, for instance, to extremely large telescopes or space interferometers. The MROI, when completed, will be comprised of 10 x1.4m diameter telescopes distributed on a Y-shaped array such that it will have access to spatial scales ranging from about 40 milliarcseconds down to less than 0.5 milliarcseconds. While this type of resolution is not unprecedented in the astronomical community, the ability to track fringes on and produce images of complex targets approximately 5 magnitudes fainter than is done today represents a substantial step forward. All this will be accomplished using a variety of approaches detailed in several papers from our team over the years. Together, these two factors, multiple telescopes deployed over very long-baselines coupled with fainter limiting magnitudes, will allow MROI to conduct science on a wide range and statistically meaningful samples of targets. These include pulsating and rapidly rotating stars, mass-loss via accretion and mass-transfer in interacting systems, and the highly-active environments surrounding black holes at the centers of more than 100 external galaxies. This represents a subsample of what is sure to be a tremendous and serendipitous list of science cases as we move ahead into the era of new space telescopes and synoptic surveys. Additional investigations into imaging man-made objects will be undertaken, which are of particular interest to the defense and space-industry communities as more human endeavors are moved into the space environment.
In 2016 the first MROI telescope was delivered and deployed at Magdalena Ridge in the maintenance facility. Having undergone initial check-out and fitting the system with optics and a fast tip-tilt system, we eagerly anticipate installing the telescope enclosure in 2018. The telescope and enclosure will be integrated at the facility and moved to the center of the interferometric array by late summer of 2018 with a demonstration of the performance of an entire beamline from telescope to beam combiner table shortly thereafter. At this point, deploying two more telescopes and demonstrating fringe-tracking, bootstrapping and limiting magnitudes for the facility will prove the full promise of MROI. A complete status update of all subsystems follows in the paper, as well as discussions of potential collaborative initiatives.
Stable beam alignment of an optical interferometer is crucial for maintaining a usable signal-to-noise ratio during science measurements on faint astronomical targets. The Magdalena Ridge Observatory Interferometer will use an Automated Alignment System (AAS) that performs a start-of-night alignment procedure and subsequent alignment corrections in between observations, all without the need for human intervention. Its design has recently been updated in line with a revised error budget for MROI requiring that two axis drifts during science operations should not exceed 15 milliarcseconds in tilt, referred to the sky, nor 1% of the beam diameter in shear. For each beam line, the AAS provides two reference light beams, a pair of quad cells to monitor coarse alignment, and a tilt and shear detector for tracking fine drifts. The tilt and shear detector is a novel application of a Shack-Hartmann array that permits the simultaneous measurement tilt and shear well within requirements for MROI. Results of laboratory testing and simulations are presented here.
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