TPF-I SWG Report - Exoplanet Exploration Program - NASA

T E C H N O L O G Y R OADMAP FOR TPF-I
Formation Flying (Multiple Robot Demonstration With Fault Recovery): Using the Formation
Control Testbed, demonstrate that a formation of multiple robots can be safed following the injections of
a set of typical spacecraft faults that have a reasonable probability of occurring during flight.
Demonstrations can be limited to single-fault scenarios. This validates the software simulation of fault
recovery for formation flight. Gate TRL 5.
6.1.3 Cryogenic Technology Gate
Cryocooler Development: With the Advanced Cryocooler Technology Development Program,
demonstrate that the development model coolers meet or exceed their performance requirements to
provide ~30 mW of cooling at 6 K and ~150 mW at 18 K. This demonstrates the approach to cooling the
science detector to a temperature low enough to reveal the weak planet signals. Gate TRL 5. Completed
Q2 2005.
6.1.4 Integrated Modeling Gate
Observatory Simulation: Demonstrate a simulation of the flight observatory concept that models the
observatory subjected to dynamic disturbances (e.g., from reaction wheels). Validate this model with
experimental results from at least the Planet Detection Testbed at discrete wavelengths. Use this
simulation to show that the depth and stability of the starlight null can be controlled over the entire
waveband to within an order of magnitude of the limits required in flight to detect Earth-like planets,
characterize their properties, and assess their habitability. Gate TRL 5.
6.2 Nulling Interferometry
TPF-I is in Pre Phase A of its project life cycle, and its technology development is therefore directed at
demonstrating the feasibility of the techniques that will be used. For starlight suppression it was thought
impractical to demonstrate all that needed to be demonstrated on a single testbed. The effort has therefore
been divided into tasks that can be addressed independently:
1. Deep broad-band two-beam nulling;
2. Planet detection with a four-beam nulling interferometer;
3. Adaptive correction of amplitude and phase; and
4. Suppression of higher-order wavefront modes using single-mode mid-infrared fiber optics.
The requirements for the nulling testbeds from the 2005 technology plan are summarized in Table 6-2.
6.2.1 State of the Art in Nulling Interferometry
Progress in nulling interferometry is summarized in Figure 6-1. The plot shows rejection ratio as a
function of bandwidth, for laboratory experiments that have been undertaken since 1998. On the far lefthand
side of the plot are shown the results obtained using lasers at visible, near-infrared, and mid-infrared
wavelengths. Experiments with bandwidths as large as 28% are shown. Results from ground-based
observations of astronomical targets are not included; the rejection ratio obtained from experiments at
telescopes have been less than 1000:1, dominated by atmospheric fluctuations. Of principal concern to
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