TPF-I SWG Report - Exoplanet Exploration Program - NASA

C HAPTER 6
Table 6-1. Comparison of 2005 Flight Requirements with Pre-Phase A Nulling Testbed
Requirements
Technology Specifications Performance to Date Performance
target prior to
Phase A
Flight
Performance
(Preliminary)
Starlight Suppression
Formation Flying
Average null depth
0.5 × 10 -5 (25 % BW)
5.0 × 10 -7 (laser)
Less than
1 × 10 -6 *
Amplitude control 0.2 % 0.12% 0.13
Less than
7.5 × 10 -7 *
Phase control 2.0 nm 2.0 nm 1.5 nm
Stability timescale Not tested 5,000 s > 50,000 s
Bandwidth 8.3–10.7 μm (25%) 8.3–10.7 μm (25%) 7–17 μm
Number of s/c 2 robots 3 robots 5 s/c
Relative control
7-cm range, 80-arcmin
bearing
5 cm range, 60
arcmin bearing
* The new stretched X-array design relaxes both these null depth requirements to 1 × 10 -5 .
2-cm range, 20-
arcsec bearing
Planet Extraction: Using the Planet Detection Testbed (PDT), demonstrate extraction of a simulated
(laser) planet signal at a star/planet contrast ratio of ≥ 10 6 for a rotation of the flight formation lasting ≥
5000 s. Accompany these results with a control system model of the Planet Detection Testbed, validated
by test data, to be included in the control system model of the flight-instrument concept. Success shows
flight-like planet sensing at representative stability levels within a factor of 20 of the contrast at 1/10 the
flight observation duration. Gate TRL 5.
Dispersion Control at Temperature: Using the Adaptive Nuller, demonstrate that optical beam
amplitude can be controlled with a precision of ≤ 0.2% and phase with a precision of ≤ 5 nm over a
spectral bandwidth of > 3 μm in the mid IR for two polarizations at ≤ 40 K. Accompany these results
with a model of the Adaptive Nuller, validated by test data, to be included in the model of the flightinstrument
concept. This demonstrates the approach for compensating for optical imperfections that
create instrument noise that can mask planet signals at the temperature required for flight operations.
Gate TRL 5.
6.1.2 Formation Flying Gates
Formation Flying (5-Spacecraft Simulation With Fault Recovery): Using the Formation Algorithms
& Simulation Testbed, simulate the safing and recovery of a five-spacecraft formation subjected to a set
of typical spacecraft faults that could lead to mission failures unique to formation flying such as
collisions, sensor faults, communication drop-outs, or failed thrusters in on or off states. Simulations can
be limited to single-fault scenarios. This demonstrates the robustness of formation control architecture, as
well as fault-tolerance of the on-board formation guidance, estimation, and control algorithms to protect
against faults that have a reasonable probability of occurring sometime during the TPF-I prime mission
and that are unique to TPF-I’s unprecedented use of close formation flying. Gate TRL 5.
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