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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, TSP

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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, TSP

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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, TSP

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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, TSP

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Automated Counting of Particles To Quantify Cleanliness

A machine vision system, similar to systems used in microbiological laboratories to count cultured microbes, has been proposed for quantifying the cleanliness of nominally precisely cleaned hardware by counting residual contaminant particles. The system would include a microscope equipped with an electronic camera and circuitry to digitize the camera output, a personal computer programmed with machine-vision and interface software, and digital storage media.

Posted in: Physical Sciences, Briefs

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