TPF-C Technology Plan - Exoplanet Exploration Program - NASA

Figure i-4. Deformable mirror delivered by Xinetics to the HCIT.
The very recent development and adoption of an eighth-order mask design to replace the fourthorder
masks previously baselined have had a major impact on the design and the 2005
technology plan detailed here. At the expense of some system throughput, the system sensitivity
to aberrations is greatly reduced, by more than two orders of magnitude in some cases, as
summarized in Table i-1. This translates into relaxation of a number of the more challenging
mechanical and thermal requirements on the system. This development originated with an
outside collaborator funded through a university contract and was eagerly adopted by the project.
Table i-1. Selected Error Budget Terms at Contrast = 1 × 10 -12 at 4λ/D
Aberration New (8 th Order) Old (4 th Order) Relaxation Ratio
Tilt 4.3 × 10 -2 2.7 × 10 -3 16
Focus 3.8 × 10-3 2.9 × 10 -5 132
Astigmatism 5.3 × 10-3 4.0 × 10-5 132
Coma 1.0 × 10 -3 5.6 × 10 -6 185
Trefoil 2.3 × 10 -3 1.7 × 10 -5 132
Spherical 3.5 × 10 -5 4.9 × 10 -6 7.2
*Aberration units are waves rms at 550 nm.
viii