Multiple Target Effects on Monopulse Signal Processing

Analysis of a typical amplitude-comparison monopulse angle-tracking radar shows that gain variation and bias in the radar error signal can occur under certain conditions involving multiple targets. The general behavior depends on the Doppler separation of the targets relative to system bandwidths; for a specific situation, the gain variation and bias are functions of the relative strengths of the targs. The analysis is shown to be consistent with experimental observations.     

Evidence for a shock wave in visible light and radio observations of the 1980 June 29 event

Shock waves, as evidenced by type II radio bursts, often accompany flares and coronal mass ejection transients. At present, the density enhancements observed by coronagraphs are believed by some to be ejected matter from the low corona, and by others to be the compressed material behind a shock front. If the former is correct, one would expect in some cases to see a density enhancement, associated with the compression region of the shock, some distance ahead of the transient ejecta. Such a density enhancement has not been previously reported.The coronal transient of 1980 June 29 (0233 UT) was observed with the High Altitude Observatory's Coronagraph/Polarimeter aboard SMM. This flare-associated coronal transient event was well observed with the Culgoora Radioheliograph, including a well-developed type II burst. Visible on the coronagraph images is a faint circular arc moving out well ahead of the transient loops. This arc is moving at more than 900 km s^?1 while the transient itself is moving at a speed of about 600 km s^?1. Both the arc and transient appear to have originated either prior to the X-ray flare or at some height above the flare at the time of the flare. The type II burst observed at Culgoora is associated with the transient loops, and no type II emission is identified with the faint arc.Due to its great speed, we interpret the faint arc as a manifestation of a shock wave, but also envision a separate shock wave associated with the transient loops as evidenced by the type II emission. Preliminary density measurements are consistent with this interpretation, and show the outer shock wave associated with the faint arc to have a Mach number M_A ≤ 1.7. At present we have no convincing explanation for the lack of a type II burst in association with the arc.This work was supported in part by NASA through grants NSG-7287 and NAGW-91 to the University of Colorado, Boulder, and S-55989 to the High Altitude Observatory, National Center for Atmospheric Research. The National Center for Atmospheric Research, NCAR, is sponsored by the National Science Foundation.     

A retarding potential analyzer for rocket experiments

A Retarding Potential Analyzer (RPA) is designed using a micro-channel plate in front of the collector as a flow amplifier, which makes it possible to detect ion species with very low concentration (<0,5 cm.^?3). A technique is described for using the micro-channel plate at abnormally high pressure (>0.01 N/m²). This allows the precise determination of the mass composition of the low ionosphere. An adaptive retarding potential consisting of 2048 steps is used to increase the sensitivity. This retarding potential is applied in the range where dI/dU ≠ 0. The sensor is hermetically sealed and opens on command.     

Potential starter/generator technologies for future aerospaceapplications

This paper presents a search and comparative review of the literature available on variable speed constant frequency (VSCF) technologies. In particular, most of the progress made in the past ten years, using power electronics and electric machines for VSCF systems, is reported. Two VSCF systems, based on induction and switched reluctance machine technologies are presented. The research on the singly- and doubly-fed induction machines has focused on VSCF for wind power generation, whereas that on switched reluctance machines has been directly studied as a VSCF technology in aircraft systems. Results obtained so far favor the switched reluctance machine over the induction machine. Based on the foregoing comparative review, it is recommended that the induction machine be fully investigated as a VSCF drive for aircraft systems. The findings should then be compared with the counterpart SRM system. Issues of comparison may include fault tolerance and redundancy, power density, torque requirements, overload ratings, temperature range and cooling, efficiency and stability over expected operating speed range     

An assessment of the Qualified Manufacturer List (QML)

The Qualified Manufacturer List (QML) approach, detailed in MIL-I-38535, General Specification for Integrated Circuits (Microcircuit) Manufacturing, embraces many of the commercial practices employed by high volume microcircuit suppliers. Nevertheless, with the availability of highly reliable and lower cost commercial parts, the QML approach becomes unnecessary and undesirable. In this paper we attempt to show why US government support of the QML program is leading the military and government to unaffordable access to out-dated technologies, damaging our country's military and avionics position. We will present information to show why we support the retraction of MIL-PRF-38535 and any other documents which imply that QML parts are superior to commercial parts, including those of QPL, MIL-STD-454, and MIL-HDBK-217 (now prohibited from use in all new Army programs)     

Spatial variation for flares observed with the gamma ray spectrometer aboard the SMM satellite

We have searched for anisotropic X-ray bremsstrahlung photon production from relativistic electrons by studying the heliocentric angular dependence of 53 flares detected at energies above 300 keV. We have found no evidence for a higher rate of detectable flares near the limb at the 80% confidence level. This result implies that the X-ray directivity as defined by the ratio of photon intensity at 75° and 0° of heliocentric angle is less than 1.5 above 300 keV and strongly rejects any flare model predicting X-ray production from a radial “beam” of energetic electrons.     

Maneuvering target tracking using extended Kalman filter

A numerically well-conditioned, quasi-extended Kalman filter is proposed. The filter is numerically described. The simulation results presented show that the estimation performance of the quasi-extended filter is superior, for short distances, compared with the widely used linear tracking filters. In addition, the simplicity of the quasi-extended filter makes it very easy to implement     

On the origin of the grooves on Phobos

L-grooves are the consequence of layered structure of Phobos, which are made up of parallel layers of different composition or hardness.     

Performance of a blood chemistry analyzer during parabolic flight

We have tested the performance of the VISION System Blood Analyzer, produced by Abbott Laboratories, during parabolic flight on a KC-135 aircraft (NASA 930). This fully automated instrument performed flawlessly in these trials, demonstrating its potential for efficient, reliable use in a microgravity environment. In addition to instrument capability, we demonstrated that investigators could readily fill specially modified test packs with fluid during zero gravity, and that filled test packs could be easily loaded into VISION during an episode of microgravity.     

Programmable ultrawideband signal generator for electromagnetic susceptibility testing

Under Phase I of the Defense Advanced Research Projects Agency (DARPA) Networking in Extreme Environments (NETEX) initiative, Multispectral Solutions, Inc. (MSSI) was tasked with the development of a general-purpose, ultrawideband hardware simulator capable of reproducing a wide variety of ultrawideband (UWB) waveforms. The simulator, with UWB outputs from baseband through millimeter wave, was to be used for the purpose of electromagnetic susceptibility testing of legacy military radio, radar, and positioning systems. The ultimate goal of this portion of the Phase I program was the quantitative determination of those UWB parameters (e.g., frequency, power, pulse rate, pulse shape, dithering, etc.) which had the least impact on the operational performance of legacy designs. This describes the development of the MSSI NETEX UWB simulator (BFP1000).