While SIM is now likely to be more than 9 years away because of 911, Earthbound interferometry is alive and well.
********************
From Sky & Telescope:
Last week, astronomers achieved an esoteric but significant milestone in the quest to see more and more detail on cosmic objects. Scientists with the Center for High Angular Resolution Astronomy (CHARA) combined starlight from two telescopes atop historic Mount Wilson and created a stable "image" with those beams. This has been done many times before on Mount Wilson and elsewhere. This time, however, the two telescopes were separated by 330 meters, the longest baseline used to date at optical wavelengths, says CHARA director and Georgia
State University professor Harold A. McAlister. They are part of the
six-telescope CHARA Array, slated to begin routine operations next year.

A basic tenet of optics is that a telescope's angular resolution -- the size of the smallest details it can show -- is inversely proportional to the diameter of its light-gathering lens or mirror. Optical interferometers like the CHARA Array are designed to yield the angular resolution of a single mirror or lens hundreds of meters across. They do this by pointing two or more telescopes at a single target, then mixing the light beams thus gathered. The beams interfere with one another, creating fringes that can be analyzed to produce an image of the target (or at least to measure some of its properties). Several optical interferometers operate worldwide, but the CHARA Array's large mirrors and separations (and Mount Wilson's famed atmospheric stability) make it "uniquely suited" to measuring the fundamental properties -- masses, diameters, and
surface temperatures -- of numerous stars, says McAlister.

While the CHARA array can't take "pictures" of extrasolar planets, it will be able to detect the wobbles that such planets induce on stars within binary systems. It also will measure the cyclical swelling and shrinking of pulsating variable stars and resolve disks and jets associated with young stellar objects, says McAlister. The array will work at visual and near-infrared wavelengths and will obtain spectra as well as images of individual stars in many previously unresolved binaries.