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.
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.
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 (MROI) Beam Relay System (BRS) comprises a network of airevacuated 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 × 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 ∼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.
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