Daniel A. Klinglesmith

Magdalena Ridge Observatory Interferometer: Status Update

The Magdalena Ridge Observatory Interferometer (MROI) is a ten element optical and near-infrared imaging interferometer being built in the Magdalena mountains west of Socorro, NM at an altitude of 3230 m. The interferometer is being designed and built by a collaboration which includes the New Mexico Institute of Mining and Technology (NMT) as the prime contractor and center for the technical team, and the University of Cambridge, Physics Department at the Cavendish Laboratory, which participates in the design and executes work packages under contract with NMT. This manuscript serves as a status update on MROI, and will present progress and milestones toward the observatorys first fringes in 2008.

Characterization of silver and aluminum custom mirror coatings for the MRO interferometric telescopes

We report on the design, application, and testing of custom protected silver and aluminum coatings for use on the Magdalena Ridge Observatory Interferometers (MROI) unit telescopes. The coatings were designed by Optical Surface Technologies (OST), and tested under normal observational conditions on Magdalena Ridge. Mirror coating samples fabricated by OST were given to MRO, and then placed in an insulated automated enclosure at the observatory site. Within the enclosure, environmental conditions such as temperature and humidity were continuously monitored. The automated enclosure was instructed to open during the night dependent upon weather conditions matching those that would occur under normal operations of the interferometer. This paper tracks the affect of the Magdalena Ridge environment on the performance of the coatings, specifically with regards to reflectivity.

DIMMWIT measurements of the spatial and temporal scale of atmospheric turbulence at COAST and MROI

The DIMMWIT (Differential Image Motion Monitor, Which Is Transportable) is a portable DIMM that can measure the Fried parameter r0 and the average wind speed of the turbulent layers. Analysing DIMM images to calculate r0 is a standard procedure, but wind speeds have rarely been calculated from differential image motion before. Here, we describe how wind speeds can be derived from either differential image motion power spectra or differential image velocities. The DIMMWIT wind speeds are then compared with a wind speed derived from the coherence times, t0, of interferometric fringes recorded simultaneously at COAST (Cambridge Optical Aperture Synthesis Telescope). Although t0, and hence the wind speed, is routinely measured by the interferometer at the COAST site, the Fried parameter had not been studied. The results of seeing campaigns at COAST and MROI (Magdalena Ridge Observatory Interferometer) are presented, along with a comparison of DIMMWIT r0 measurements with the FWHM of long exposure images recorded at the same time.

Weather trends at the Magdalena Ridge Observatory

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.

A new path to first light for the Magdalena Ridge Observatory interferometer

The Magdalena Ridge Observatory Interferometer (MROI) was the most ambitious infrared interferometric facility conceived of in 2003 when funding began. Today, despite having suffered some financial short-falls, it is still one of the most ambitious interferometric imaging facilities ever designed. With an innovative approach to attaining the original goal of fringe tracking to H = 14th magnitude via completely redesigned mobile telescopes, and a unique approach to the beam train and delay lines, the MROI will be able to image faint and complex objects with milliarcsecond resolutions for a fraction of the cost of giant telescopes or space-based facilities. The design goals of MROI have been optimized for studying stellar astrophysical processes such as mass loss and mass transfer, the formation and evolution of YSOs and their disks, and the environs of nearby AGN. The global needs for Space Situational Awareness (SSA) have moved to the forefront in many communities as Space becomes a more integral part of a national security portfolio. These needs drive imaging capabilities ultimately to a few tens of centimeter resolution at geosynchronous orbits. Any array capable of producing images on faint and complex geosynchronous objects in just a few hours will be outstanding not only as an astrophysical tool, but also for these types of SSA missions. With the recent infusion of new funding from the Air Force Research Lab (AFRL) in Albuquerque, NM, MROI will be able to attain first light, first fringes, and demonstrate bootstrapping with three telescopes by 2020. MROI’s current status along with a sketch of our activities over the coming 5 years will be presented, as well as clear opportunities to collaborate on various aspects of the facility as it comes online. Further funding is actively being sought to accelerate the capability of the array for interferometric imaging on a short time-scale so as to achieve the original goals of this ambitious facility

The MROI fringe tracker: first fringe experiment

The MROI fringe tracking beam combiner will be the first fringe instrument for the interferometer. It was designed to utilize the array geometry and maximize sensitivity to drive the interferometer for faint source imaging. Two primary concerns have driven the design philosophy: 1) maintaining high throughput and visibilities in broadband polarized light, and 2) mechanical stability. The first concern was addressed through tight fabrication tolerances of the combiner substrates, and custom coatings. In order to optimize mechanical stability, a unique modular design approach was taken that minimizes the number of internal adjustments. This paper reports initial laboratory fringe and stability measurements.

A new instrument for measuring atmospheric turbulence

The Magdalena Ridge Observatory is a congressionally funded project to deliver a state-of-the-art observatory on the Magdalena Ridge in New Mexico to provide astronomical research, educational and outreach programs to the state. In this paper we report results from one of our undergraduate projects being run at New Mexico Tech. This project focuses on the design and characterization of a novel instrument for sensing the atmospheric flow instabilities related to seeing at the observatory site. The instrument attempts to find the power of turbulence on millisecond time scales by measuring a voltage difference between two active microphones. The principles behind the instrument are explored here and a description of the limitations of the current experimental implementation is given. Initial results from the experiment are presented and compared with simultaneous measurements from a co-located Differential Image Motion Monitor. The instrument is shown to be a valuable and robust tool for monitoring the atmospheric conditions during site testing campaigns, but further data will be needed to confirm the precise nature of the correlation between measurements made with this system and more conventional seeing metrics.