URAT: astrometric requirements and design history

The U.S. Naval Observatory Robotic Astrometric Telescope (URAT) project aims at a highly accurate (5 mas), ground-based, all-sky survey. Requirements are presented for the optics and telescope for this 0.85 m aperture, 4.5 degree diameter field-of-view, specialized instrument, which are close to the capability of the industry. The history of the design process is presented as well as astrometric performance evaluations of the toleranced, optical design, with expected wavefront errors included.Comment: 12 pages, 7 figures, SPIE 2006 Orlando conf. proc. Vol. 626

Catalytic surface effects on space thermal protection system during Earth entry of flights STS-2 through STS-5

An on going orbiter experiment catalytic surface effects experiment being conducted on the Space Shuttle is discussed. The catalytic surface effects experiment was peformed on four of the five flights of Columbia. Temperature time histories and distributions along the midfuselage and wing of the orbiter were used to determine the surface catalytic efficiency of the baseline high temperature reusable surface insulation. Correlation parameters are shown that allow the comparison of all flight data with predictions from the design and surface emittance decreased as a result of contaminants during the five flights of the Space Shuttle

Optomechanical cooling in a continuous system

Radiation-pressure-induced optomechanical coupling permits exquisite control of micro- and mesoscopic mechanical oscillators. This ability to manipulate and even damp mechanical motion with light---a process known as dynamical backaction cooling---has become the basis for a range of novel phenomena within the burgeoning field of cavity optomechanics, spanning from dissipation engineering to quantum state preparation. As this field moves toward more complex systems and dynamics, there has been growing interest in the prospect of cooling traveling-wave phonons in continuous optomechanical waveguides. Here, we demonstrate optomechanical cooling in a continuous system for the first time. By leveraging the dispersive symmetry breaking produced by inter-modal Brillouin scattering, we achieve continuous mode optomechanical cooling in an extended 2.3-cm silicon waveguide, reducing the temperature of a band of traveling-wave phonons by more than 30 K from room temperature. This work reveals that optomechanical cooling is possible in macroscopic linear waveguide systems without an optical cavity or discrete acoustic modes. Moreover, through an intriguing type of wavevector-resolved phonon spectroscopy, we show that this system permits optomechanical control over continuously accessible groups of phonons and produces a new form of nonreciprocal reservoir engineering. Beyond this study, this work represents a first step towards a range of novel classical and quantum traveling-wave operations in continuous optomechanical systems.Comment: Manuscript with supplementary information. 17 pages, 4 Figures. Minor correction in Fig.

Efficient low-power terahertz generation via on-chip triply-resonant nonlinear frequency mixing

Achieving efficient terahertz (THz) generation using compact turn-key sources operating at room temperature and modest power levels represents one of the critical challeges that must be overcome to realize truly practical applications based on THz. Up to now, the most efficient approaches to THz generation at room temperature -- relying mainly on optical rectification schemes -- require intricate phase-matching set-ups and powerful lasers. Here we show how the unique light-confining properties of triply-resonant photonic resonators can be tailored to enable dramatic enhancements of the conversion efficiency of THz generation via nonlinear frequency down-conversion processes. We predict that this approach can be used to reduce up to three orders of magnitude the pump powers required to reach quantum-limited conversion efficiency of THz generation in nonlinear optical material systems. Furthermore, we propose a realistic design readily accesible experimentally, both for fabrication and demonstration of optimal THz conversion efficiency at sub-W power levels