We have developed manufacturable approaches to form single, vertically aligned carbon nanotubes,
where the tubes are centered precisely, and placed within a few hundred nm of 1-1.5 μm deep trenches.
These wafer-scale approaches were enabled by chemically amplified resists and inductively coupled
Cryo-etchers to form the 3D nanoscale architectures. The tube growth was performed using dc plasmaenhanced
chemical vapor deposition (PECVD), and the materials used for the pre-fabricated 3D
architectures were chemically and structurally compatible with the high temperature (700 °C) PECVD
synthesis of our tubes, in an ammonia and acetylene ambient. The TEM analysis of our tubes revealed
graphitic basal planes inclined to the central or fiber axis, with cone angles up to 30° for the particular
growth conditions used. In addition, bending tests performed using a custom nanoindentor, suggest that
the tubes are well adhered to the Si substrate. Tube characteristics were also engineered to some extent,
by adjusting growth parameters, such as Ni catalyst thickness, pressure and plasma power during growth.
The NOAA/NESDIS has been conducting studies to see if user requirements can be met by a single constellation of
satellites that would provide high spatial, temporal and spectral resolution data every 15 minutes every where in post
GOES-R and NPOESS time frame. The current Geostationary Operational Environmental Satellites (GOES) at an
altitude of 35,000 km provide observations up to local zenith angles of 75 degrees for monitoring severe weather in real
time. The Polar-orbiting Operational Environmental Satellites (POES) at an altitude of 833 km complement monitoring
in the polar region at a regular time interval. The POES and DMSP (Defense Meteorological Satellite Program) satellites
will be merged into a new satellite system referred to as the National Polar-orbiting Operational Environmental Satellite
System (NPOESS) which is under development.
The Jet Propulsion Laboratory (JPL) has been supporting this study by analyzing characteristics of Medium Earth Orbits
(MEO) as an observation venue to meet user requirements. An optimal altitude of 10,400 km has been selected based on
the manageable radiation impacts on the electronics. This paper presents the initial encouraging results in several areas such as: orbit selection, constellation, coverage, revisit time analyses, communications options, scan mechanisms, and
instrument concepts.
Lessons learned from the Atmospheric Infrared Sounder (AIRS) and the Moderate Resolution Imaging Spectroradiometer (MODIS) projects highlight areas where further technology development is needed to address future land, ocean and atmospheric measurement needs. Although not established as requirements at this time, it is anticipated that scientists will expect improvements in the areas of spatial, spectral, radiometric, polarimetric, temporal and calibration performance for future instruments. This paper addresses each of these performance areas and provides lessons learned from MODIS and AIRS. We also present expectations in performance of a Medium Earth Orbit (MEO) Infrared Imaging Spectrometer based on information from the NASA Instrument Incubator Program and industry reports. Tradeoffs are presented vs orbit altitude (LEO, MEO and GEO) and provide a "systems" perspective to future measurement concepts.
Diffractive lenses offer two potential advantages for very large aperture space telescopes; very loose surface-figure tolerances and physical implementation as thin, flat optical elements. In order to actually realize these advantages one must be able to build large diffractive lenses with adequate optical precision and also to compactly stow the lens for launch and then fully deploy it in space.
We will discuss the recent fabrication and assembly demonstration of a 5m glass diffractive Fresnel lens at LLNL. Optical performance data from smaller full telescopes with diffractive lens and corrective optics show diffraction limited performance with broad bandwidths. A systems design for a 20m space telescope will be presented. The primary optic can be rolled to fit inside of the standard fairings of the Delta IV vehicle. This configuration has a simple deployment and requires no orbital assembly. A twenty meter visible telescope could have a significant impact in conventional astronomy with eight times the resolution of Hubble and over sixty times the light gathering capacity. If the light scattering is made acceptable, this telescope could also be used in the search for terrestrial planets.
An analytical description of the scattered light from a 10 meter diameter Diffractive Optical Element lens-based telescope operating at 1 micron wavelength has been formulated. The specifics of the grating and blaze as well as physical manufacturing constraints were made a part of the problem to be solved. A major simplifying approximation made is that a 1 dimensional lens was assumed for the calculations. This simplified model still serves to illustrate the important effects and limitations of a high performance lens used as a telescope. Focal plane light scattering has been rigorously determined for simplified cases.
This study was undertaken at the JPL to identify salient features of two competing instrument designs and to select the design that best meets the goals of the Space Interferometry Mission. Features were examined in terms of meeting performance, cost, schedule and risk requirements. The study included the spacecraft, the space environment, metrology considerations, stabilization of optics with temperature, spacecraft structure, complexity, and end-to- end testing among other items. The most significant determinant was the fundamental implementation of the instrument's metrology system. The impact on the testbed program associated with the mission was considered the second most important issue. An error propagation formalism was developed to address various instrument geometries examined as part of this study. The formalism propagates metrology errors from the gauge readings through to the angle on the sky. An introduction to the formalism is presented.
The Space Interferometry Mission (SIM) will perform astrometry to a resolution of a few micro arc seconds. The development of this mission is being led by the California Institute of Technology, JPL for the National Aeronautics and Space Administration. A recent trade study was performed to compare two significantly different architectures. This paper will describe the two configurations and contrast some of their differences and similarities.
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