The National Ecological Observatory Network (NEON) is a planned facility of the National Science Foundation with the
mission to enable understanding and forecasting of the impacts of climate change, land use change and invasive species
on continental-scale ecology. Airborne remote sensing plays a critical role by providing measurements at the scale of
individual shrubs and larger plants over hundreds of square kilometers. The NEON Airborne Observation Platform is
designed to bridge scales from organism and stand scales, as captured by plot and tower observations, to the scale of
satellite based remote sensing. Fused airborne spectroscopy and waveform LiDAR is used to quantify vegetation
composition and structure. Panchromatic photography at better than 30 cm resolution will retrieve fine-scale information
on land use, roads, impervious surfaces, and built structures. NEON will build three airborne systems to allow for
regular coverage of NEON sites and the capacity to respond to investigator requests for specific projects. The system
design achieves a balance between performance and development cost and risk, taking full advantage of existing
commercial airborne LiDAR and camera components. To reduce risk during NEON construction, an imaging
spectrometer design verification unit is being developed at the Jet Propulsion Laboratory to demonstrate that operational
and performance requirements can be met. As part of this effort, NEON is also focusing on science algorithm
development, computing hardware prototyping and early airborne test flights with similar technologies. This paper
presents an overview of the development status of the NEON airborne instrumentation in the context of the NEON
The Terrestrial Planet Finder Interferometer (TPF-I) mission requires a set of formation-flying collector telescopes that direct the incoming light to a beam combiner where the beams are combined and detected to identify habitable planets. A baseline TPF collector design, using a primary mirror of 4.2 meters in diameter, is used here to conduct a dynamic study. The objective is to investigate the effects of dynamic response of the spacecraft on the system optical performance at the presence of disturbances that arise from the reaction wheel assembly and thruster loading, respectively. Frequency responses where the frequency is associated with the flywheel speed are presented in the paper. The results focus on the surface oscillation of the primary mirror and the point at which the secondary mirror is located. Transient response simulations under the baseline four thruster-assembly configuration were conducted using various duty cycles and thrust levels determined by the TPF formation rotation requirements. This paper will also describe an investigation conducted using new IMOS (Integrated Modeling of Optical Systems), which is an open, multi-disciplinary, and Matlab-based dynamic/optical system simulation code. A pre-processor that is able to generate the sub-structure modal models required by ISYSD (Integrated System Dynamics) was developed in new IMOS. ISYSD is used to develop a high-fidelity system dynamic model by integrating the sub-structure modal models. Finally, the paper will summarize current and future work in order to meet the TPF dynamic requirements.
The Terrestrial Planet Finder Interferometer (TPF-I) is a space-based NASA mission for the direct detection of Earth-like planets orbiting nearby stars. At the mid-infrared wavelength range of interest, a sun-like star is ~107 times brighter than an earth-like planet, with an angular offset of ~50 mas. A set of formation-flying collector telescopes direct the incoming light to a common location where the beams are combined and detected. The relative locations of the collecting apertures, the way that the beams are routed to the combiner, and the relative amplitudes and phases with which they are combined constitute the architecture of the system. This paper evaluates six of the most promising solutions: the Linear Dual Chopped Bracewell (DCB), X-Array, Diamond DCB, Z-Array, Linear-3 and Triangle architectures.
Each architecture is constrained to fit inside the shroud of a Delta IV Heavy launch vehicle using a parametric model for mass and volume. Both single and dual launch options are considered. The maximum separation between spacecraft is limited by stray light considerations. Given these constraints, the performance of each architecture is assessed by modeling the number of stars that can be surveyed and characterized spectroscopically during the mission lifetime, and by modeling the imaging properties of the configuration and the robustness to failures. The cost and risk for each architecture depends on a number of factors, including the number of launches, and mass margin. Quantitative metrics are used where possible.
A matrix of the architectures and ~30 weighted discriminators was formed. Each architecture was assigned a score for each discriminator. Then the scores were multiplied by the weights and summed to give a total score for each architecture. The X-Array and Linear DCB were judged to be the strongest candidates. The simplicity of the three-collector architectures was not rated to be sufficient to compensate for their reduced performance and increased risk. The decision process is subjective, but transparent and easily adapted to accommodate new architectures and differing priorities.
This overview paper describes the system design of the structurally-connected interferometer (SCI) concept studied for the Terrestrial Planet Finder (TPF) project. This paper covers progress since August 2003 and serves as an update to a paper presented at that month's SPIE conference, "Techniques and Instrumentation for Detection of Exoplanets". SCI trade studies conducted since mid-2003 have focused on key factors driving overall flight segment mass and performance, including launch vehicle packaging, structural design, and instrument layout. This paper summarizes the results of the recent design trades, with discussion of the primary requirements that drive the baseline design concept.