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
60
50
36 m 30 m 20 m
50 days
100 days
200 days
# candidates
40
30
20
10
0
100 150 200 250 300 350
MHZ / mas
Figure 4-28. Dependence of the number of candidate target stars on the array length. For the 100-day limit on
spectroscopic integration time (orange curve), the nominal 36-m design has access to 29 stars. Shrinking this to 30
m extends the maroon and blue areas to the right by a factor of 36/30 in Fig. 4-27 and reduces the number of stars
available to 12. For a 20-m structure this is reduced to 3. Increasing the allowed integration time to 200 days does
not dramatically improve the performance (red curve).
4.10.3 Summary
The major advantage of the SCI architecture is that it does not require the new technology of formation
flying. The maximum size of 36 m is constrained by the volume of the launch shroud, and limits the IWA
and angular resolution. The demands of orbit determination and spectroscopy limit the number of
candidate stars to less than 30. This number falls off rapidly as the array size is reduced.
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