The ICoNN (Infrared Coherencing Nearest Neighbors) fringe tracker system is the heart of the Magdalena Ridge Observatory Interferometer (MROI). It operates in the near-infrared at H or K<sub>s</sub> in such a way that the light being used by the fringe tracker can phase up the interferometric array, but not steal photons from the scientific instruments of the interferometer system. It is capable of performing either in group delay tracking or fringe phase tracking modes, depending on the needs of the scientific observations. The spectrograph for the MROI beam combiner was originally designed for the Teledyne PICNIC array. Developments in detector technology have allowed for an alternative to the original choice of infrared array to finally become available – in particular, the SAPHIRA detector made by Selex. Very low read noise and very fast readout rates are significant reasons for adopting these new detectors, traits which also allow relaxation of some of the opto-mechanical requirements that were needed for the PICNIC chip to achieve marginal sensitivity. This paper will discuss the opto-mechanical advantages and challenges of using the SAPHIRA detector with the pre-existing hardware. In addition to a design for supporting the new detector, alignment of optical components and initial testing as a system are reported herein.
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.<p> </p> 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.
The EXtreme PREcision Spectrograph (EXPRES) is an optical fiber fed echelle instrument being designed and built at the Yale Exoplanet Laboratory to be installed on the 4.3-meter Discovery Channel Telescope operated by Lowell Observatory. The primary science driver for EXPRES is to detect Earth-like worlds around Sun-like stars. With this in mind, we are designing the spectrograph to have an instrumental precision of 15 cm/s so that the on-sky measurement precision (that includes modeling for RV noise from the star) can reach to better than 30 cm/s. This goal places challenging requirements on every aspect of the instrument development, including optomechanical design, environmental control, image stabilization, wavelength calibration, and data analysis. In this paper we describe our error budget, and instrument optomechanical design.
The loop is closed on ICONN, the Magdalena Ridge Observatory Interferometer fringe tracker. Results from laboratory experiments demonstrating ICONN's ability to track realistic, atmospheric-like path difference perturbations in real-time are shown. Characterizing and understanding the behavior and limits of ICONN in a controlled environment are key for reaching the goals of the MROI. The limiting factors in the experiments were found to be the light delivery system and temporary path length correction mechanism; not the on-sky components of ICONN. ICONN was capable of tracking fringes with a coherence loss below 5%; this will only improve in its final deployment.
The Magdalena Ridge Observatory Interferometer has been designed to be a 10 × 1.4 m aperture long-baseline optical/near-infrared interferometer in an equilateral "Y" configuration, and is being deployed west of Socorro, NM on the Magdalena Ridge. Unfortunately, first light for the facility has been delayed due to the current difficult funding regime, but during the past two years we have made substantial progress on many of the key subsystems for the array. The design of all these subsystems is largely complete, and laboratory assembly and testing, and the installation and site acceptance testing of key components on the Ridge are now underway. This paper serves as an overview and update on the facility's present status and changes since 2012, and the plans for future activities and eventual operations of the facilities.
The Yale Exoplanet Laboratory is under contract to design, build, and deliver a high-resolution (R = 60,000) echelle
spectrograph for the Moletai Astronomical Observatory 1.65-meter telescope at the Vilnius University. We present a
fiber-fed, white-pupil architecture that will operate from 400 to 880nm. The optomechanical design implements a
modular approach for stability and ease of alignment that can be reproduced for other telescopes. It will utilize highperformance
off-the-shelf optical components with a custom designed refractive camera for high throughput and good
Pushing the RV technique to the precision required to detect Earth-like planets around Solar-type stars requires extreme stability in the wavelength calibrator. We are developing a wavelength calibration technique based on a Fabry-Perot interferometer locked to a stabilized laser. This approach offers advantages over other methods: it produces a broadband, emission comb output from 380-790 nm that is difficult to achieve with a laser frequency comb; by injecting into the science fibers before and after observations, weak signals from velocities in the stellar photosphere that would be masked by iodine reference lines can be now be identified; and by locking the laser to an atomic transition, the spectrum will be stabilized to better than 1 part in 10 e-11, corresponding to a wavelength solution that is known to better than 1 cms<sup>-1</sup>.
Most subsystems of the Magdalena Ridge Observatory Interferometer (MROI) have progressed towards
final mechanical design, construction and testing since the last SPIE meeting in San Diego - CA. The first
1.4-meter telescope has successfully passed factory acceptance test, and construction of telescopes #2 and
#3 has started. The beam relay system has been prototyped on site, and full construction is awaiting
funding. A complete 100-meter length delay line system, which includes its laser metrology unit, has been
installed and tested on site, and the first delay line trolley has successfully passed factory acceptance
testing. A fully operational fringe tracker is integrated with a prototyped version of the automated
alignment system for a closed looping fringe tracking experiment. In this paper, we present details of the
final mechanical and opto-mechanical design for these MROI subsystems and report their status on
fabrication, assembly, integration and testing.
The Magdalena Ridge Observatory Interferometer has been designed to be a 10 x 1.4 m aperture long-baseline
optical/near-infrared interferometer in an equilateral "Y" configuration, and is being deployed west of Socorro, NM on
the Magdalena Ridge. Unfortunately, first light for the facility has been delayed due to the current difficult funding
regime, but during the past two years we have made substantial progress on many of the key subsystems for the array.
The design of all these subsystems is largely complete, and laboratory assembly and testing, and the installation of many of its components on the Ridge are now underway. This paper serves as an overview and update on the facility's present status, and the plans for future funding and eventual operations of the facilities.
The characterization of ICoNN, the Magdalena Ridge Observatory Interferometer's fringe tracker, through labor tory simulations is presented. The performance limits of an interferometer are set by its ability to keep the optical path difference between combination partners minimized. This is the job of the fringe tracker. Understanding the behavior and limits of the fringe tracker in a controlled environment is key to maximize the science output. This is being done with laboratory simulations of on-sky fringe tracking, termed the closed-loop fringe experi ment. The closed-loop fringe experiment includes synthesizing a white light source and atmospheric piston with estimation of the tracking error being fed back to mock delay lines in real-time. We report here on the progress of the closed-loop fringe experiment detailing its design, layout, controls and software.
We report on the testing of the modulators within the MROI fringe tracking beam combiner. Modulation in
the beam combiner will be performed via modulators introducing an optical path difference in increments of λ/4
into the beams. Knowledge of the path difference introduced needs to be accurate to within 1!. To achieve this accuracy, the modulators are characterized and the desired step waveform optimized through a Fourier analysis technique. Control is implemented in an FPGA embedded system and performance will be monitored by means of a slow loop Fourier algorithm. Details of the progress on characterization, optimization and future implementation are presented here.
The Magdalena Ridge Observatory Interferometer is a 10 x 1.4 meter aperture long baseline optical and near-infrared
interferometer being built at 3,200 meters altitude on Magdalena Ridge, west of Socorro, NM. The interferometer layout
is an equilateral "Y" configuration to complement our key science mission, which is centered on imaging faint and
complex astrophysical targets. This paper serves as an overview and update on the status of the observatory and our
progress towards first light and first fringes in 2012.
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.