TPF-C Technology Plan - Exoplanet Exploration Program - NASA

Chapter 1
interferometry, continues to be an excellent source of information related to TPF and the search
for life on other planets. Document 1.3 (h) is the group of standard JPL documents that capture,
at a high level of detail, the plans for implementing each Work Breakdown Structure (WBS)
task. The WAs are signed by the doing organizations and, hence, represent commitments to the
Project that the work will get done for the agreed upon budget and schedule. Most of these
documents can be downloaded from the TPF Library at:
http://planetquest.jpl.nasa.gov/TPF/tpf_index.html.
1.4 Science Objectives of TPF-C
The major scientific objectives of TPF-C are to:
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a) Search for and detect any Earth-like planets in the habitable zone around nearby stars
b) Characterize Earth-like planets and their atmospheres, assess habitability and search for
signatures of life
c) Carry out a program of comparative planetology
d) Enable a program of “revolutionary” general astrophysics
The main scientific goal of TPF-C is to detect directly and characterize Earth-like planets around
nearby stars. The requirements that flow down from this goal define the characteristics of the
observatory design and the mission. In particular, the ability to directly detect planets implies
that TPF-C must be capable of separating the planet light from the starlight. Moreover, the
facility must provide a sensitivity that will enable spectroscopic measurements of the light from
the planet to determine the type of planet, its gross physical properties, and its main atmospheric
constituents; the ultimate goal, of course, is to assess whether life or habitable conditions exist
there.
The science requirements for the mission, as derived by the TPF Science Working Group, are
shown in Table 1-1. One would expect Earth-like planets to be found around stars that are
roughly similar to the sun, and so TPF-C target stars should include main sequence F, G, and K
stars. The habitable zones to be studied span at least the orbital distances of Mars to Venus
(scaled by the square-root of the stellar luminosity), and planets with a half-Earth area should be
detectable. For the search to be statistically meaningful, at least 35 and preferably an additional
130 stars should be included in the search.
TPF-C must use the spectrum of a planet to characterize its surface and atmosphere. The
spectrum of Earth, scaled for semi-major axis and star luminosity, would be used as a reference.
The required spectral resolution is 70 in the visible. TPF must be capable of measuring O 2 , H 2 O,
and O 3 in the visible. In this context, a measurement of a species is defined as the determination
of the equivalent width of a spectral feature of that species to 20% accuracy. We desire that TPF
measure Rayleigh scattering, photosynthetic pigments, CO 2 , and CH 4 at visible wavelengths.
The desired spectral resolutions are 2 times the required values.
TPF-C will also directly detect and characterize the spectrum of planets outside the habitable
zone and determine the spatial and mineralogical distribution of material in the exozodiacal dust
clouds of target systems. This will permit an understanding of the nature of terrestrial planets
within a broader framework that includes the properties of other planetary system constituents.