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TPF-C Technology Plan - Exoplanet Exploration Program - NASA

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Chapter 1<br />

Back end coronagraph<br />

optics<br />

Y<br />

Z<br />

Secondary<br />

mirror surface<br />

Primary mirror<br />

surface<br />

Tertiary<br />

mirror<br />

surface<br />

X<br />

Z<br />

Figure 1-2. Raytrace diagram showing the overall optical layout of <strong>TPF</strong>-C, with side view<br />

(top) and front view (bottom).<br />

sensitivities to misalignments and polarization effects that would result from higher angles of<br />

incidence. The primary-secondary separation is 12 m, and the secondary mirror is also an offaxis<br />

mirror, elliptical in profile, but with major and minor axes of 83.0 cm and 36.5 cm,<br />

respectively. The effective focal length of the system is 146 m, providing a field-of-view of 3.6<br />

arcsec. As shown in Figure 1-3, the light from the secondary is directed by a flat tertiary mirror<br />

to an optical bench that lies underneath the primary. The optical bench houses a wavefrontcorrection<br />

system, followed by a coronagraph. Further details of the coronagraph optics are<br />

described in the subsequent sections of this document.<br />

6

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