The Magdalena Ridge Observatory Interferometer: a high-sensitivity imaging array

Buscher, David F.; Bakker, Eric J.; Coleman, T. A.; Creech‐Eakman, M. J.; Haniff, Christopher A.; Jurgenson, C. A.; Klinglesmith, Dan; Parameswariah, C.; Young, John S.

doi:10.1117/12.684422

Cited by 8 publications

(2 citation statements)

References 7 publications

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“…The MROI telescope design includes only three mirrors mounted in an altitude-altitude configuration, where the secondary mirror performs the tip-tilt correction. 3 With our 1.4m apertures more closely matched to the atmospheric characteristics and using carefully optimized optical coatings and surfaces, we achieve 85% throughput and 62nm rms wavefront error: see Figure 2(left).…”

Section: Figure 1 Architectural Rendering Of the Now-completed Magdamentioning

confidence: 99%

New approach to very-high-resolution astronomical imaging

Creech‐Eakman¹

2008

SPIE Newsroom

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The Magdalena Ridge Observatory Interferometer will produce extremely sharp images of faint astrophysical targets while minimizing reflections and wavefront aberrations to maintain sensitivity.Astronomical objects are very distant, and so the angular sizes of many astrophysical phenomena are much smaller than can be resolved with conventional telescopes. Optical interferometry allows us to explore very small angular scales. Michelson and Pease first used interferometric observations nearly a century ago to measure the stellar diameter of Betelgeuse. 1 Since then, more than a dozen interferometers have been built worldwide to characterize the sizes and motions of stars and their environments. However, advances in technology have only recently allowed us to reconstruct physically realistic images of these objects rather than merely providing simple size measurements. We are ambitious in building the Magdalena Ridge Observatory Interferometer (MROI), with a mission centered on one primary goal: producing very-high-resolution images of faint astronomical targets. 2 Stellar interferometry works by combining the light from multiple telescopes to form interference fringes. This requires a complex optical system involving multiple light reflections from the light-collecting surfaces to the detectors measuring these fringes. Each reflection adds aberrations to the observed signal and results in photon loss. For other interferometers, often more than 40 reflections are required before the interference fringes are measured. The MROI design minimizes the number of reflections to only 21, allowing scientists to observe much fainter targets than previously accomplished. In addition, the interferometer design (see Figure 1) capitalizes on having small-diameter (1.4m) movable telescopes, so that the array can be reconfigured easily to match the resolution needed for observations of a particular target, much like the operation of our larger radio counterpart, the Very Large Array.

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Section: Figure 1 Architectural Rendering Of the Now-completed Magdamentioning

confidence: 99%

New approach to very-high-resolution astronomical imaging

Creech‐Eakman¹

2008

SPIE Newsroom

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“…The Magdalena Ridge Observatory Interferometer (MROI) [14,15] is our application for closed-loop control; it features a fast optical switchyard [16], which rearranges the beams of light from several telescopes before they are combined and measured. The switchyard works by moving mirrors along tracks, but these tracks are not perfectly straight due to manufacturing defects.…”

Section: Introductionmentioning

confidence: 99%

Low-cost capacitive sensing for precision alignment of mirrors

Bowman¹,

Buscher²

2010

Meas. Sci. Technol.

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Piezoelectric actuators are often used to align mirrors in high-precision optical systems; however they are highly hysteretic and are therefore not repeatable. Closed-loop control is a reliable way to correct for this, but requires an accurate position sensor for feedback. We present a capacitive sensor that is capable of measuring the tilt of a mirror with a noise density of 10 milliarcsec Hz−1/2 and repeatability of better than ±17 milliarcsec (corresponding to a distance of ±4 nm) over a range of more than 6 arcmin. This enables the correction of hysteresis with much better performance at low frequencies than feedforward algorithms or charge controllers. Low cost (a hundredth of the cost of similar systems) and ease of construction and integration with commercially available mirror mounts are its primary advantages. The effect of temperature on the mirror mount was significant, with a change of several arcsec per degree Celsius. However, it was possible to obtain stable performance over periods of several hours in a lab without sophisticated temperature control.

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