The New Millennium separated spacecraft interferometer

Spaceborne optical interferometry has been identified as a critical technology for many of NASA’s 21st century science visions. Included in the visions are interferometers that can probe the origins of stars and galaxies, and can ultimately study Earth-like planets around nearby stars. To accomplish this feat, separation of an interferometer’s small collecting apertures by large baselines are required-hundreds of meters up to thousands of kilometers. Thus the large separations require multiple spacecraft formation flying. Furthermore, optical pathlengths over these distances must be controlled to the nanometer level. This level of control demands tightly coupled spacecraft controls, active optics, metrology, and starlight detection technologies. To date, these technologies have been demonstrated only in ground applications with baselines of order of a hundred meters; space operation will require a significant capability enhancement. This paper describes the New Millennium separated spacecraft optical interferometer mission concept and technologies. The mission is designed to provide a technology demonstration for tightly coupled multiple spacecraft formations and very long baseline optical interferometry. The interferometer would be distributed over three small spacecraft: two spacecraft would serve as collectors, directing starlight toward a third spacecraft which would combine the light and perform the interferometric detection. The interferometer baselines would variable, allowing baselines of 100 m to 1 km in an equilateral formation, to provide angular resolutions from 5 to 0.5 nanoradian (1 to 0.1 milliarcsec).