TPF-I SWG Report - Exoplanet Exploration Program - NASA

T E C H N O L O G Y R OADMAP FOR TPF-I
6 Technology Roadmap for TPF-I
The Technology Plan for the Terrestrial Planet Finder Interferometer (Lawson and Dooley 2005)
contains a detailed description of the areas of technical work that need to be developed for TPF-I prior to
entering Phase A of its mission life cycle. The document describes the requirements and error budgets for
the mission relevant to starlight suppression, formation flying, and cryogenic technology. Also included
are testbed descriptions, and for each testbed, a schedule of milestones and technical gates.
The technology plan emphasizes the relationship between error budgets, theoretical predictions, and
experimental results. The approach to technology development for TPF-I includes the notion that as our
understanding of the instrument matures and our ability to model the experiments improves, the
corresponding error budgets need be revised and updated, and the performance targets for each testbed
need to be reassessed. Our understanding of instability noise and methods of its mitigation (described in
Section 4.8) has evolved greatly since 2005. The technology plan is therefore overdue for revision, as it
no longer reflects our current understanding of the mission requirements.
Also worth noting is that the scope of work on TPF-I has been greatly reduced since 2005 because of
changes in the NASA budget. The ongoing work is focused on starlight suppression and formation flying
and is described in the following sections.
6.1 Technology Gates
The technology goals for TPF-I in Pre Phase A are listed here. Within the plan the milestones are listed
that lead towards major gates in technology development. These gates are shown below. It is worth
emphasizing that our current understanding of mitigating instability noise should enable us to relax the
null depth requirement by a factor of ~10 (Lay 2006) over the targets listed here. As such, the technology
gates for starlight suppression now seem overly strict, but they are included here from the 2005 plan for
completeness. A high-level overview of the flight requirements and testbed requirements, as they were
described in 2005, is given in Table 6-1.
6.1.1 Optics and Starlight Suppression Gates
Starlight Suppression (Depth and Bandwidth at Temperature): Using the Achromatic Nulling
Testbed, demonstrate that infrared light over a spectral bandwidth of ≥ 25% can be suppressed by ≥ 10 6 at
≤ 40 K. Accompany these results with an optical model of the Achromatic Nulling Testbed, validated by
test data, to be included in the model of the flight-instrument concept. This demonstrates the approach to
the broad-band starlight suppression needed to characterize terrestrial planets for habitability at a flightlike
temperature. Gate TRL 5.
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