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.
There have been astronomical observatories on Magdalena Ridge in south-central New Mexico since the late 1960s. Magdalena Ridge is relatively flat, at an average elevation of 10,560 feet (3220 meters) with a north-south length of 3/4 of a mile. In 2000 the Magdalena Ridge Observatory began site testing for two new facilities: a 2.4-meter optical telescope and a 10-element optical interferometer. As part of that testing, meteorological instrumentation was deployed at several locations across the mountain. As a result, we have an 18 year history of regular experience with the environment, including weather and cloud cover data for much of this time period. We present trends in the basic meteorological parameters: temperature, humidity, barometric pressure, wind speeds and directions, and cloud cover. Diurnal temperatures ranges vary from 15 C° in the spring when it is largest to 10 C° in the summer months when it is smallest. Barometric pressure varies more in the spring and fall than in the summer. Annual rain fall levels vary greatly with an average of about 10 inches of rain per year. The snow amounts have traditionally been very hard to measure as the area is partly above the tree line and wind-blown snow can leave parts of the region barren while other parts have a foot or more of snow. Winds speeds are typically 10 to 20 miles per hour. Wind speeds have been measured above 100 mph (45 m/s), with wind gusts as high as 125 mph (56 m/s), though this is primarily a spring phenomenon. The wind direction is predominately out of the Southwest. Wind speeds at the 2.4-meter telescope location are frequently 2 times as high wind speeds at the optical interferometer site due to the differences in terrain to the West of the two sites. An optical allsky camera has been in operation on the Ridge from 2003 to 2012 with nightly sequences of images obtained on most nights when the winds were less than 15 m/s and the humidity below 90%. Analysis of this imagery shows that a majority of the nights would be useable for astronomical observations. We present an overview of statistics of the site and discuss how these statistics will be used for defining appropriate operational windows for the Magdalena Ridge Observatory Interferometer.
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.
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