TPF-I SWG Report - Exoplanet Exploration Program - NASA

T E C H N O L O G Y R OADMAP FOR TPF-I
6.2.5 Mid-Infrared Single-Mode Spatial Filters
The TPF-I project has had several contracts for the development and production single-mode mid-infrared
fibers (Ksendzov et al. 2006). As a result of this work the project has approximately 16 high-quality
single-mode fibers that include chalcogenide fibers from the Naval Research Laboratory (Aggarwal et al.
2005) and silver halide fibers from the University of Tel Aviv (Shalem et al. 2005). This is a significant
change from the state of the art in 2002, when only one or two short samples of chalcogenide fibers had
been produced by Le Verre Fluoré (Bordé et al. 2003). The technology for silver halide fibers is now
advanced but still maturing. Computer control of the extrusion process for silver halide fibers has now
greatly reduced inhomogeneities in the fibers. We have been pleased with test results of several bare
samples, but only in 2006 were the first silver halide fibers received complete with casings and
connectors. Nulling tests with these fibers are greatly anticipated because they hold the potential of
extending the long-wavelength range of the testbeds.
6.3 Formation Flying
Formation flying and distributed collaborative systems have been an area of research at JPL dating back
to the 1980s. Formation flying was originally sponsored by NASA as basic research within Code-R under
the Distributed Spacecraft Technology (DST) element. When the two-spacecraft StarLight mission was in
development, the DST efforts were focused towards key formation-flying controls technology, which at
that time was at a relatively low technology-readiness level. A close collaboration between the DST and
the StarLight Formation Guidance and Control (G&C) teams resulted in a rapid maturation of the scalable
formation flying Control Architecture and key algorithms, including, Formation Guidance, Formation
Acquisition, and Collision Avoidance.
The StarLight mission development effort was ended in 2003, and the continuing work became the TPF-I
technology effort aimed at providing a robust demonstration of formation flying through ground-based
laboratory work. This was divided into two complementary efforts: 1) the Formation Algorithms and
Simulation Testbed (FAST), and 2) the Formation Control Testbed (FCT). The FAST, is a high-fidelity
distributed realtime close-loop formation control simulation, while, the Formation Control Testbed (FCT)
is a multi-robot system level hardware testbed to validate the FAST formation control architecture and
algorithms. An overview of these efforts and the results to date are given in the following sections.
Further details are provided in Appendix C.
6.3.1 Formation-Flying Requirements
The top-level “flight requirements” for TPF-I mission are summarized in Table 6-3. Requirements are
listed separately for knowledge and control of range, bearing, attitude, and the first-derivative with respect
to time (rates) of these quantities. The requirements depend on the operating mode of the array. In
addition, a number of functional requirements were also imposed, such as maintaining collision-free
operation at all times, using minimum resources (fuel, time/cryogen, etc.) to accomplish the mission and
be robust to transient faults.
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