The history of free-flying occulters to search for extrasolar planets goes back to at least the early 1960s. Robert Danielson of Princeton suggested the notion to Lyman Spitzer who published a short analysis of the idea in "The Beginnings and Future of Space Astronomy" in American Scientist in 1962. Lyman Spitzer is known in some circles as the father of space telescopes and was instrumental in the development of the Hubble Space Telescope.
Less than a dozen years later, the next significant step in analysis of the idea came with Gordon R. Woodcock, then a study manager at Boeing. Woodcock validated Spitzer's analysis, extended it, and then suggested a plausible design for implementing the idea. This work was largely unknown until recently as it was included as an appendix to a NASA contractor report on Future Space Transportation Systems.
In the early 1980s, Christian Marchal, of ONERA investigated shapes of occulting screens which are neither disks nor rectangles. He found that the ability of a screen to suppress light from a star can be enhanced by choosing complex shapes.
Many have studied how to use extra-focal-plane occultation techniques since Spitzer and Danielson, however, the idea has not seemed practical until recently. In the mid/late-1990s, a group at Case Western Reserve and JPL, led by Glenn Starkman and Craig Copi independently analyzed the external occulter idea. The initial study, called IRIS, examined space-based occulters used with ground-based and space-based occulters. Later, theysuggested a very large, light-weight apodizing screen to perform occultation work either in conjunction with ground based observatories or with space telescopes. Copi & Starkman called this version of the occulter idea BOSS, and analysis of a version of it was presented at the December 2000 TPF Preliminary Architecture Reviews".
In addition to the BOSS concept, another external occulter concept was suggested at the 1999-2000 TPF Architecture reviews by the Ball Aerospace consortium --the Spergel Inverse Pinhole.
Jean Schneider, webmaster at the Observatoire de Paris and keeper of the Extrasolar Planets Encyclopaedia has also done some analysis on free-flying occulters.
TRW, Boeing SVS, and other companies have even considered occulters as precursor missions to the Terrestrial Planet Finder.
In 2004, Webster Cash, University of Colorado, Boulder, was granted seed money to study a giant pinhole camera in space. In 2005, he and his team came to the conclusion that an external occulter was a more practical solution, and NIAC funded further study of the idea. Their expanded set of concepts carries the title New Worlds Discoverer/Observer/Imager. A NASA Discovery proposal was submitted by the New Worlds team in the spring of 2005. Although it was not accepted for funding, the New Worlds initiative was successful in drawing renewed attention to binary-apodized external occulters.