Proceedings Article | 31 August 2005
Proc. SPIE. 5905, Techniques and Instrumentation for Detection of Exoplanets II
KEYWORDS: Signal to noise ratio, Heterodyning, Telescopes, Planets, Space telescopes, Receivers, Interferometry, Imaging systems, Space operations, Image processing
In contrast to standard Michelson interferometry, the idea of entry pupil processing is to somehow convert light gathered at each telescope (of a multi-spacecraft array) into data, then process the data from several telescopes to compute the mutual coherence values needed for image reconstruction. Some advantages are that weak beams of collected light do not have to be propagated to combiners, extreme precision relative path length control among widely separated spacecraft is unnecessary, losses from beam splitting are eliminated, etc. This paper reports our study of several entry pupil processing approaches, including direct electric field reconstruction, optical heterodyne systems and intensity correlation interferometry using the Hanbury Brown-Twiss effect. For all these cases and for amplitude
interferometry, we present image plane signal-to-noise (SNR) results for exo-planet imaging, both in the case of planet emissions and for imaging the limb of planets executing a transit across their stars. We particularly consider terrestrial-class planets at a range of 15 pc or less. Using the SNR and related models, we assess the relative advantages and drawbacks of all methods with respect to necessary aperture sizes, imager sensitivity, performance trends with increasing
number of measurement baselines, relative performance in visible and in IR, relative positioning and path length control requirements and metrology requirements. The resulting comparisons present a picture of the performance and complexity tradeoffs among several imaging system architectures. The positive conclusion of this work is that, thanks to advances in optoelectronics and signal processing, there exist a number of promising system design alternatives for exo-
planet imaging.
