Physical Sciences

Actuated Hybrid Mirror Telescope

A new type of lightweight, wide-aperture, precise telescope is under development. The figure depicts the planned Actuated Hybrid Mirror Telescope (AHMT), which is intended to demonstrate a new approach to the design and construction of wide-aperture spaceborne telescopes for astronomy and Earth science. This technology is also appropriate for Earth-based telescopes.

Posted in: Physical Sciences, Briefs

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Stellar Gyroscope for Determining Attitude of a Spacecraft

A paper introduces the concept of a stellar gyroscope, currently at an early stage of development, for determining the attitude or spin axis, and spin rate of a spacecraft. Like star trackers, which are commercially available, a stellar gyroscope would capture and process images of stars to determine the orientation of a spacecraft in celestial coordinates. Star trackers utilize charge coupled devices as image detectors and are capable of tracking attitudes at spin rates of no more than a few degrees per second and update rates typically <5 Hz. In contrast, a stellar gyroscope would utilize an active pixel sensor as an image detector and would be capable of tracking attitude at a slew rate as high as 50°/s, with an update rate as high as 200 Hz. Moreover, a stellar gyroscope would be capable of measuring a slew rate up to 420°/s. Whereas a Sun sensor and a three-axis mechanical gyroscope are typically needed to complement a star tracker, a stellar gyroscope would function without them; consequently, the mass, power consumption, and mechanical complexity of an attitude-determination system could be reduced considerably.

Posted in: Physical Sciences, Briefs

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Fault-Tolerant Heat Exchanger

A single-point leak would not cause mixing of heat-transfer fluids.

Posted in: Physical Sciences, Briefs

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Optical Design of an Optical Communications Terminal

This airborne system would keep itself aimed at a ground station. An optical communications terminal (OCT) is being developed to enable transmission of data at a rate as high as 2.5 Gb/s, from an aircraft or spacecraft to a ground station. In addition to transmitting high data rates, OCT will also be capable of bidirectional communications. The OCT is meant to incorporate all of the design features of a prior apparatus denoted the Optical Communications Demonstrator (OCD), plus some improvements.

Posted in: Physical Sciences, Photonics, Briefs

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Atomic Clock Based on Opto-Electronic Oscillator

This apparatus would afford spectral purity plus long-term stability and accuracy.

Posted in: Physical Sciences, Briefs

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Microfocus/Polycapillary-Optic Crystallographic X-Ray System

This system generates an intense, nearly collimated beam suitable for crystallography.

Posted in: Physical Sciences, Briefs

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Depth-Penetrating Luminescence Thermography of Thermal-Barrier Coatings

Temperatures at depths can be measured by luminescence decay of suitable thermographic phosphors.

Posted in: Physical Sciences, Briefs

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