TPF-I SWG Report - Exoplanet Exploration Program - NASA

D ESIGN AND A R C H I T E C T U R E T RADE S TUDIES
4.9 Imaging Properties
The primary motivation for the Terrestrial Planet Finder missions is their ability to directly detect photons
from Earth-sized planets. Orbit determination requires that the emission can be localized and tracked over
time. Spectroscopy is only meaningful if the photons can be attributed to the right object. This may be
straightforward for the case of a single planet orbiting a star, but it will be very difficult to establish this a
priori. The publication of the first spectrum from an exo-solar Earth would be heavily compromised by
the possibility of spectral contamination by unresolved confusing sources, whether background objects,
lumps in the exozodiacal dust emission, or other planets. It is, therefore, very important that TPF-I can
resolve the emission from the multiple sources that might be present. This is why we must understand the
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Earth-Venus
Earth-Mars
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Separation / mas
Figure 4-22. Angular separations of the Earth–Mars–Venus system viewed at 15 pc. (a) The
angular separations are reduced as the orbits are viewed closer to edge-on. (b) Results of Monte
Carlo simulation showing the probability that planets are separated by less than a particular value.
For example, in 50% of cases we expect that two of the planets will be separated by 45 mas or less.
(c) Same as (b), but includes the anti-star negative images of the planets.
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