TPF-I SWG Report - Exoplanet Exploration Program - NASA

F UTURE D EVELOPMENTS
7 Preparatory Science for TPF-I
The development of precursor science for TPF-I is shown schematically in Fig. 7-1, which highlights the
major project phases and gate reviews. In green, we indicate the most significant programmatic decisions
the mission must face. In the sections below, we describe in more detail how scientific questions feed
directly into the decisions that TPF-I faces during its development.
7.1 Pre-Phase A
In Pre-Phase A, the focus of TPF-I science will be to contribute to the Mission Concept Review that will
allow TPF-I to enter Phase A of its project life cycle. Key questions will include the level of exozodiacal
emission and its influence on the designs of interferometer architectures, an assessment (mostly complete)
of the spectral markers for TPF-I, and an initial selection of appropriate target stars.
7.1.1 Priority 1: Exozodiacal Dust
For the interferometer, a driving requirement is the need to suppress or reject starlight so that planet light
can be detected. Moreover, atmospheric spectroscopy must be possible within the bands of biomarkers
that have been identified. A starlight rejection of ~ 10 5 –10 6 :1 is needed for a mid-IR interferometer.
Previous architecture studies have shown that the brightness of dust in the habitable zone of the target star
adversely affects the integration time necessary to detect planets. Thus, in addition to a critical assessment
of the technology needed for each architecture, it is important to characterize and understand the
brightness of the average exozodiacal emission surrounding potential target stars prior to the Mission
Concept Review.
• A survey of a representative sample of target stars for dust on all orbital scales, from < 1 AU out to
100 AU, is important for both the mission concept review and selection of preliminary targets.
Although selected stars may be studied through individual peer-reviewed proposals, a program
coordinated between NASA and ESA is needed that will make the best use of missions such as
Spitzer and Herschel.
• The TPF-I and Darwin Projects should also work to coordinate and make best use of upcoming
ground-based facilities, such as the nulling instruments at KI and LBTI.
• Our understanding of levels of exozodiacal dust and the relation of those levels to the search for
planets would be further bolstered by strong support for a wide-ranging program of theory and
modeling.
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