Mission Requirements: How to Search for Extrasolar Planets

Abstract

In this chapter we will discuss the motivation, scientific requirements and technical implementation of space-based search for extrasolar planets. We discuss current and planned future missions, with a focus on designs that will be able to collect photons and therefore spectral information of the atmospheres of planets. The interferometric nulling technique, as well as simulations of the observations, are discussed in detail. IntroductionToday, our generation is the first that possesses the technological ability to search for, and observe, planets orbiting other stars -so-called exoplanets. During the middle of the last century, a small number of scientists noted that this capability was emerging and suggested ways to implement it. Most notably, Struve [1] hypothesized that very large planets (Jupiter-sized or larger) could, if orbiting very close to a solar type star, be easily detected by the periodic change they would cause in the radial velocity (the stellar velocity along the line of sight) signature in their star's spectrum. Struve went on to point out that under these circumstances (a large planet close to its star), a percentage of the objects (of order 1%) would undergo eclipses which would also, in principle, be detectable using methods that were just becoming available around that time (e.g., modern photomultipliers as detectors). After these very astute predictions by Struve, almost 40 years were to pass before the hypothesis turned into observable fact when first Latham et al. [2] and then Mayor and Queloz [3] immediately followed by Butler and Marcy [4], discovered such bodies by detecting the radial velocity signature. By this time, the predictions by Struve had been more or less forgotten, and it came as somewhat of a surprise to find these very large planets close to their primary star. This "new" class of planets were then designated "hot Jupiters". Today they