Exploration of Neighboring Planetary Systems
NASA recently issued "A Road Map for the Exploration of Neighboring Planetary Systems (ExNPS)," a study which examined using space interferometry to detect extra-solar Earth-like planets. One of the proposed initiatives in the report is the Terrestrial Planet Finder, an infrared interferometer consisting of a rotating 75 m truss with four linked telescopes. However, long trusses of this sort are notably difficult to deploy and difficult to control.
The MIT Space Systems Lab (SSL) is presently investigating various designs of the Terrestrial Planet Finder, most notably a configuration using multiple free-flying independent spacecraft. Such a design avoids the difficult control issues of a structurally-connected interferometer, while adding the advantage of a wide range of variable optical baselines, which would improve detection accuracy. However, independent control of free-flying spacecraft to the required centimeter or lower precision of an interferometer is a daunting issue. Plus, the added mass of propulsion systems and control and power buses make a multiple spacecraft design bigger and more expensive to launch.
In cooperation with the TPF team assembled by NASA, SSL is actively comparing the two high-level configurations to determine the optimal for the eventual design and construction of the Terrestrial Planet Finder. In addition, the study provides relevant information to other future space interferometers by assembling a design framework in which design considerations and trade space restraints may be examined early in the design process, thereby saving both time and money.