TPF-I SWG Report - Exoplanet Exploration Program - NASA

C HAPTER 5
The optimization works by solving the following question: Given a set of completeness curves vs. time
for the available stars in the current 1-week period, what is the optimum set of integration times that
maximizes the number of planets found
Solve by applying two rules: 1) For stars that are observed, we must be operating at a point on each
completeness curve that has the same slope. Otherwise we can increase efficiency by transferring
integration time from a target with shallow slope to one with steeper slope (i.e., ΔC Δ t = const .
2) The observed stars are those with the highest net efficiencies. Otherwise we could increase overall
δ Ct is maximized).
completeness by swapping in a star with higher net efficiency (i.e., ( )
We then repeat for different values of ΔC Δ t to find the most productive set of integration times.
The baseline mission concept includes a 2-year mission duration with an X-array (aspect ratio of 6:1)
architecture. In this scenario, we assume a 70% integration time efficiency and a 4.3 hr slew time per
target observation. With this baseline, we are able to obtain a total accumulated completeness of 192.0
habitable zones searched with 385 observations over 384 different targets. This is equivalent to stating
that we would find 192 planets if each target had one Earth-like planet and 19 planets if one tenth of the
targets had such a planet. Unlike previous simulations, all but one target (Hipp# 80337) are visited only
Habitable Zone completeness for Earth-sized planet after 2 year survey
30
25
All (1014)
0.8 - 1.0 (48)
0.6 - 0.8 (54)
0.4 - 0.6 (113)
0.2 - 0.4 (169)
Distance / pc
20
15
10
5
0
0 50 100 150 200 250 300
Angular radius of Mid-Habitable Zone / mas
Figure 5-29. Completeness for visited stars.
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