Optimization of Interferometers for Space-Based Planet Detection

One way of meeting the formidable challenge of directly detecting faint extra-solar planets near bright stars is space-based infrared nulling interferometry. However, with multiple, large, cryogenic telescopes involved, this approach is inherently complex and expensive, necessitating a careful identification of the critical measurement capabilities and the simplest system capable of providing them. On the other hand, in any novel measurement approach, a degree of versatility may be beneficial, to allow for on-orbit parameter optimization. In previous papers, the capabilities and characteristics of potential interferometric pupil plane configurations were compared, and the regime of three to four telescope apertures was found to provide an acceptable compromise between functionality and simplicity. However, due to the large number of parameters, no single "optimum" case was identified. Here, the capabilities of three and four telescope nullers are explored further, in order to elaborate the tradeoff between simplicity and functionality within this more restricted range. Of these choices, the four-telescope case provides both a better level of functionality, and more potential versatility. In fact, there seems little reason to consider interferometers more complex than four telescopes for first generation nulling interferometry missions. On the other hand, three-telescope nullers have more limited capabilities, but they can nevertheless provide a minimum set of functionalities, and so should receive serious consideration as "minimum" missions