PROCEEDINGS ARTICLE | September 19, 2007
Proc. SPIE. 6693, Techniques and Instrumentation for Detection of Exoplanets III
KEYWORDS: Signal to noise ratio, Telescopes, Stars, Imaging systems, Satellites, Interferometry, Space telescopes, Modulation transfer functions, Planets, Space operations
This paper reports the results of a design study for an exoplanet imaging system. The design team consisted of
the students in the "Electromagnetic Sensing for Space-Bourne Imaging" class taught by the principal author in the
Spring, 2005 semester. The design challenge was to devise a space system capable of forming 10X10 pixel images of
terrestrial-class planets out to 10 parsecs, observing in the 9.0 to 17.0 microns range. It was presumed that this system
would operate after the Terrestrial Planet Finder had been deployed and had identified a number of planetary systems for
more detailed imaging.
The design team evaluated a large number of tradeoffs, starting with the use of a single monolithic telescope,
versus a truss-mounted sparse aperture, versus a formation of free-flying telescopes. Having selected the free-flyer
option, the team studied a variety of sensing technologies, including amplitude interferometry, intensity correlation
imaging (ICI, based on the Brown-Twiss effect and phase retrieval), heterodyne interferometry and direct electric field
reconstruction. Intensity correlation imaging was found to have several advantages. It does not require combiner
spacecraft, nor nanometer-level control of the relative positions, nor diffraction-limited optics. Orbit design, telescope
design, spacecraft structural design, thermal management and communications architecture trades were also addressed.
A six spacecraft design involving non-repeating baselines was selected. By varying the overall scale of the baselines it
was found possible to unambiguously characterize an entire multi-planet system, to image the parent star and, for the
largest base scales, to determine 10X10 pixel images of individual planets.
