TPF-C Technology Plan - Exoplanet Exploration Program - NASA

Plan for Technology Development
Top-Level Phase A Technology Development Activities:
For Phase A, the pre-Phase A testbeds (HCIT, Mask Characterization, Dilatometer, micro-slip,
and scatterometer) continue to be utilized. In addition, the TDM is fabricated and tested. A laser
frequency stability testbed and a precision hexapod testbed are developed. A protoflight primary
mirror and mount may be initiated during this period. The protoflight mirror (PFM) will be
specified to enable flight qualification. The microslip characterization facility is extended to
accommodate testing of hinge and latch component microdynamics. Pointing control and
subscale thermal shroud testbeds are initiated. Deployment of the sunshade is demonstrated. An
effort focused on large-amplitude wavefront actuators is initiated if an actuated PM has been
selected. Instrument technology developments are defined and initiated.
Top-Level Phase B Technology Development Activities for the Terrestrial Planet
Finder Coronagraph:
As Phase B begins, the work on the dilatometer, the TDM, transmissive optics, micro-slip, mask
characterization, and instrument technology has been completed. The HCIT continues to
demonstrate masks and deformable mirrors. The laser frequency stability testbed flows into the
closed-loop position control testbed. The work on a hinge and latch testbed and the pointing
control testbed continues. A thermal shroud will be tested for isolation at a sub-scale level in an
overdriven condition and at close-to-flight levels. A sub-scale EM isothermal cavity control
system testbed will be developed and extended later through the installation of a sub-scale
primary for a full-assembly thermal-stability test. If the project has initiated the development of a
protoflight mirror in Phase A, it is expected to be under development though probably not
complete by the end of Phase B. The PFM is expected to be qualified for flight in Phase C, thus
becoming the TPF-C flight mirror. An EM secondary mirror will be fabricated.
7.2 Pre-Phase A Milestones
7.2.1 Milestone 1: Starlight Suppression on the HCIT
Planned Completion Date: Q3 FY05
Milestone #1 will demonstrate technology for Earth-like planet detection by coronagraphic
starlight suppression to a level within an order of magnitude of the required TPF-C contrast at
the required angle necessary to distinguish a planet signal from its star.
The HCIT has achieved 0.9 × 10 -9 average contrast over an area ranging from 4 to 10λ/D, using a
laser source (λ=785 nm). Contrast stability is on the order of 0.5 × 10 -10 per hour. In near-term
experiments, emphasis will be placed on speckles near 4λ/D, to demonstrate that performance is
not near a fundamental limit at those angles. This will complete the milestone.
Monochromatic performance will benefit from the following planned improvements:
• Installation of a 64 × 64 DM, which should improve the contrast by up to a factor of two.
• Improved thermal stability of the testbed components, which will reduce the impact of
thermal drift over the timescale of an experiment. The dominant contributor may be the
DM, whose temperature variation is a factor of 10 larger than what was seen when testing
DMs in a different vacuum chamber. (Actuator gain is a strong function of temperature.)
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