# Will the Magdalena Ridge Optical Interferometer be able to image extended objects like the surface of the Moon?

Inspired by several questions:

If one wanted to resolve 1 meter or smaller detail on the surface of the Moon from the surface of the Earth (about 2.6E-09 or 0.5 mas) at say 1 micron wavelength one would need a baseline of order 400 meters.

The longest current optical baselines are only 40 to 80 meters and the longest one currently under construction is the Magdalena Ridge Optical Interferometer which

will have ten 1.4 m (55 in) telescopes located on three 340 m (1,120 ft) arms. Each arm will have nine stations where the telescopes can be positioned, and one telescope can be positioned at the center.

This is sufficient to have of the order of 1 meter resolution at the Moon's distance, but being optimized for star-like sources it's not clear if it will be able to image extended objects like the surface of the Moon.

Question: Will the Magdalena Ridge Optical Interferometer be able to image extended objects like the surface of the Moon, or is it designed only to separate a few star-like objects, e.g. binary stars or star + planetary systems?

note: If information on this specific observatory isn't available, it would be certainly informative to extrapolate from existing imaging work from long baseline optical interferometers. The Moon presents a big challenge since its surface brightness extends over quite a large solid angle, so pinholes at the focus of each telescope in the array would generate a lot of diffracted/scattered light, whereas imaging star-like objects against a dark field would be less susceptible.

• If anybody can provide the formulas to calculate equivalent telescope size of an optical array of telescopes, I could add it to this page for quick calculations: win98.altervista.org/telescopio.html I think such formulas also involve wavelength, it's not just a matter of distance between telescopes. – jumpjack Nov 13 '19 at 9:11
• @KeithMcClary Cool! But rats! It's paywalled, I'll have to scramble to find a way to access it, everything shuts down here for a week during the holidays. (pun intended; it's coming up on the year of the mouse) – uhoh Jan 23 '20 at 3:43
• They want \$15 for this? – Keith McClary Jan 23 '20 at 3:51
• Thanks, I sort of knew that. – Keith McClary Jan 23 '20 at 4:41

According to this site The 10 telescopes will be optically linked together in order to make images of astronomical objects with unprecedented detail. The interferometer will have a resolution 100 times greater than the Hubble Space Telescope and will be able to make accurate images of complex astronomical objects many times faster than other existing interferometric arrays.

And: The Interferometer will take delivery of the second telescope enclosure in February 2020 and the second telescope in August 2020. They expect to fully incorporate the second telescope by the end of 2020, which will allow the instrument to produce “fringes,” using the proprietary fringe-tracker called ICoNN.

How America's Spooks Seek to Spy on Distant Satellites The intelligence community has plans for a telescope network that can see not just a blob in orbit but details such as a satellite’s solar panels.

from here.

That's one reason why the U.S. Air Force, which wants to monitor its own orbital assets and presumably those of others, is funding MROI. "They want to know: Did the boom break or did some part of the photovoltaic panels collapse?" says Michelle Creech-Eakman, an astronomer at the New Mexico Institute of Mining and Technology in Socorro and project scientist on MROI. But if the facility succeeds, its biggest impact could be on the field of astronomy, by drawing new attention to the promise of optical interferometry, a powerful but challenging strategy for extracting exquisitely sharp images from relatively small, cheap telescopes.

Radio astronomers have had it easier. The long radio wavelengths mean data from separated dishes can be recorded, digitized, time-stamped by an atomic clock, and combined later for analysis. But optical interferometry is far trickier: The short wavelengths of visible light, running at terahertz frequencies, cannot yet be digitized by any electrical system. So the light must be merged in real time, with nanometer precision.

From here.

Also Reference 3.

• Thanks, this is great news, but Will the Magdalena Ridge Optical Interferometer be able to image extended objects like the surface of the Moon? Is it possible to expand just a little bit on what is meant by "complex objects"? – uhoh Feb 23 '20 at 17:25
• I'll try as soon as i can! – Natsfan Feb 23 '20 at 20:32