Broadband light source for fiber-optic measurement system in spaceborne applications

Measuring temperatures, mechanical loads and derived quantities precisely and reliably play an important role in spaceflight. With spacecraft becoming increasingly complex, upscaling of present telemetry techniques can become cumbersome. Additionally, there are entirely new sensory requirements, resulting from emerging technologies such as smart structures, active vibration damping and composite material health monitoring. It has been demonstrated in preceding studies that these measurements can be advantageously and efficiently carried out by means of fiber-optic systems. The most prominent fiber-optic strain and temperature sensor is the fiber Bragg grating. Typically, multiple fiber Bragg gratings are used to translate entire temperature and strain fields into an optical wavelength information. For the interrogation of these sensors, a broadband or scanning light source is required. Additional requirements with respect to the light source are high intensity and unpolarized illumination of the gratings. These constraints can be met by a light source that is based on amplified spontaneous emission in a rare-earth-doped fiber. In the presented work, a compact light source, adapted for measurement applications and targeted towards space applications, has been developed. The design of this light source is presented, as well as its implementation. The light source has been designed and tested for selected core aspects of space robustness and the results of these tests are summarized.     

Cosmic Rays From Supernova Remnants: a Brief Description of the Shock Acceleration of gas and Dust

Space Science Reviews - We summarize our model of galactic cosmic-ray (GCR) origin and acceleration, wherein a mixture of interstellar and/or circumstellar gas and dust is accelerated by a...     

Earth–Moon libration point orbit stationkeeping: Theory,modeling, and operations

Collinear Earth–Moon libration points have emerged as locations with immediate applications. These libration point orbits are inherently unstable and must be maintained regularly which constrains operations and maneuver locations. Stationkeeping is challenging due to relatively short time scales for divergence, effects of large orbital eccentricity of the secondary body, and third-body perturbations. Using the Acceleration Reconnection and Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) mission orbit as a platform, the fundamental behavior of the trajectories is explored using Poincaré maps in the circular restricted three-body problem. Operational stationkeeping results obtained using the Optimal Continuation Strategy are presented and compared to orbit stability information generated from mode analysis based in dynamical systems theory.     

PowerCore combining structure and batteries for increased energy toweight ratio

Much of the mass of a battery is comprised of nonreactive materials. In an NiH₂ battery, this includes the pressure vessel and 50% of the positive electrode. PowerCore reconfigures the battery materials to serve as a structural sandwich panel. The effective specific energy of the new device can exceed 100 Wh/kg. PowerCore is intended to handle power demands of low Earth orbiting communications satellites such as IRIDIUM. This paper describes the concept and development progress     

Effect of track structure and radioprotectors on the induction of oncogenic transformation in murine fibroblasts by heavy ions

The oncogenic potential of high-energy ⁵⁶Fe particles (1 GeV/nucleon) accelerated with the Alternating Gradient Synchrotron at the Brookhaven National Laboratory was examined utilizing the mouse C3H 10T1/2 cell model. The dose-averaged LET for high-energy ⁵⁶Fe is estimated to be 143 keV/μm with the exposure conditions used in this study. For ⁵⁶Fe ions, the maximum relative biological effectiveness (RBE_max) values for cell survival and oncogenic transformation were 7.71 and 16.5 respectively. Compared to 150 keV/μm ⁴He nuclei, high-energy ⁵⁶Fe nuclei were significantly less effective in cell killing and oncogenic induction. The prostaglandin E₁ analog misoprostol, an effective oncoprotector of C3H 10T1/2 cells exposed to X rays, was evaluated for its potential as a radioprotector of oncogenic transformation with high-energy ⁵⁶Fe. Exposure of cells to misoprostol did not alter ⁵⁶Fe cytotoxicity or the rate of ⁵⁶Fe-induced oncogenic transformation.     

The Segmented Aperture Synthetic Aperture Radar (SASAR)

A new concept in synthetic aperture radar, called SASAR, which uses a segmented aperture, is described. Use of the segmented aperture allows appreciable extra receiving antenna gain to be realized. Each subarray of the receive antenna is equal in length to the transmit antenna; the system performance is increased approximately by a factor equal to the number of subarrays. To allow array combination of the subarray signal outputs requires a phase-shift factor (varying with azimuth) to be applied to each subarray signal. A digital implementation of this preprocessor is sketched out; it uses a push-down storage stack to store the range histories for a synthetic aperture from each subarray. Appropriate phase shifts are added to the stacks and a sum of stack values then provides the combined output range history sequence. Possibilities of using analog delay lines for preprocessing are also discussed. Pattern errors due to subarray size and receive array near field are examined and constraints are given.     

Software replacement of test module adapters for depot instrumentation due to obsolescence

Depot-level automatic test equipment has been used over the years by various facets of both the government and commercial industry. Over time, the instrumentation used in the depot will need to be repaired or replaced and, oftentimes, the older instruments are no longer serviceable or manufactured. This paper discusses how to replace the obsolete instrument and its associated hardware. Test module adapter with a software module and driver that allows compatibility between the original test executive and the modern instrument without re-hosting existing test program sets. Systems & Electronics, Inc. has implemented this procedure for a digitizer and precision DC power supply on a depot that utilizes the IEEE-488 general purpose interface bus (GPIB) for communication between the control computer and instrumentation.     

On the fundamental acoustic mode in variable area,low Mach number nozzles

We consider the propagation of sound in nozzles of substantially varying cross-section, taking into account reflections from the tapering walls and non-uniform convection by the axially accelerated or decelerated mean flow. Exact solutions of the acoustic equations are obtained for the simplest case of the fundamental longitudinal mode in quasi-one-dimensional, low Mach number nozzle flow. The effects of non-uniform mean flow on sound are demonstrated by comparing horns with nozzles, and 15 properties (stated in italics and labelled P1, P2 ... P15 in the text) are proved and discussed, viz. concerning (1) relations between acoustic pressure and velocity; (2) equipartition or biasing of kinetic and compression energies; (3) conservation or evolution of wave action; (4) existence of elementary or special solutions and (5) cut-off frequencies, and amplitude and phase laws. We conclude with a simple formula for the approximate calculation of the acoustic fields; the formula can be made more accurate by using a correction factor for amplitude and phase, which is plotted against area ratio for propagation upstream or downstream in diffusers and convergent nozzles.