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111.
G. J. Peters 《Space Science Reviews》1989,49(3-4):9-22
The circumstellar plasma that produces H emission in Algol binaries has been investigated using phase-resolved, high dispersion data acquired from CCD and image tube detectors. Results are summarized in this paper, including discussions of the disk geometry and size, asymmetry in the distribution of material, long-term or non-phase dependent variability, mass outflow, the mean electron density, and how the latter properties vary with the system's period or location in the r-q diagram. Five systems which display permanent emission with periods ranging from 4.5 to 261 days (SW Cyg, UX Mon, TT Hya, AD Her, and RZ Oph) are intercompared. If P < 4.5 days, no permanent disks are observed, while if P > 6 days, stable disks with only slight long-term variations in their H brightness are seen. The most variable systems appear to be those in the 5 – 6 day range, but the star's position in the r-q diagram has the largest influence on its behavior. The trailing side of the accretion disk, where the gas stream impacts the inner disk, is usually brighter, and the leading side is often times more extended. The disk extends out to at least 95% of the Roche surface of the primary and is highly flattened (RP). Mass outflow near phase 0.5 is commonplace. 相似文献
112.
Dabbous T.E. Ahmed N.U. McMillan J.C. Liang D.F. 《IEEE transactions on aerospace and electronic systems》1988,24(1):85-102
A refined stochastic model for the errors of the Loran-C radio navigation aid is described, and it is shown how this model can be used to improve the performance of integrated navigation systems. In addition to the usual propagation errors, Loran-C time of arrival measurements are occasionally plagued with sudden intermittent errors of a particular magnitude and caused by receiver cycle selection errors. These result in sudden large jumps in the calculated position solution. The Loran-C error has been modeled as the sum of a diffusion process, representing the normal propagating errors, and a pure jump process of Poisson type, representing the cycle selection errors. A simple integrated navigation system is then described, based on the Loran-C model and the standard dead reckoning (heading and speed) system model. Assuming that the observed process is governed by a linear stochastic difference equation, a recursive linear unbiased minimum variance filter is developed, from which the Loran-C and dead reckoning errors, and hence position and velocity, can be estimated 相似文献
113.
The Galileo spacecraft was launched by the Space Shuttle Atlantis on October 18, 1989. A two-stage Inertial Upper Stage propelled Galileo out of Earth parking orbit to begin its 6-year interplanetary transfer to Jupiter. Galileo has already received two gravity assists: from Venus on February 10, 1990 and from Earth on December 8, 1990. After a second gravity-assist flyby of Earth on December 8, 1992, Galileo will have achieved the energy necessary to reach Jupiter. Galileo's interplanetary trajectory includes a close flyby of asteroid 951-Gaspra on October 29, 1991, and, depending on propellant availability and other factors, there may be a second asteroid flyby of 243-Ida on August 28, 1993. Upon arrival at Jupiter on December 7, 1995, the Galileo Orbiter will relay data back to Earth from an atmospheric Probe which is released five months earlier. For about 75 min, data is transmitted to the Orbiter from the Probe as it descends on a parachute to a pressure depth of 20–30 bars in the Jovian atmosphere. Shortly after the end of Probe relay, the Orbiter ignites its rocket motor to insert into orbit about Jupiter. The orbital phase of the mission, referred to as the satellite tour, lasts nearly two years, during which time Galileo will complete 10 orbits about Jupiter. On each of these orbits, there will be a close encounter with one of the three outermost Galilean satellites (Europa, Ganymede, and Callisto). The gravity assist from each satellite is designed to target the spacecraft to the next encounter with minimal expenditure of propellant. The nominal mission is scheduled to end in October 1997 when the Orbiter enters Jupiter's magnetotail.List of Acronyms ASI
Atmospheric Structure Instrument
- EPI
Energetic Particles Instrument
- HGA
High Gain Antenna
- IUS
Inertial Upper Stage
- JOI
Jupiter Orbit Insertion
- JPL
Jet Propulsion Laboratory
- LRD
Lightning and Radio Emissions Detector
- NASA
National Aeronautics and Space Administration
- NEP
Nephelometer
- NIMS
Near-Infrared Mapping Spectrometer
- ODM
Orbit Deflection Maneuver
- OTM
Orbit Trim Maneuver
- PJR
Perijove Raise Maneuver
- PM
Propellant Margin
- PDT
Pacific Daylight Time
- PST
Pacific Standard Time
- RPM
Retropropulsion Module
- RRA
Radio Relay Antenna
- SSI
Solid State Imaging
- TCM
Trajectory Correction Maneuver
- UTC
Universal Time Coordinated
- UVS
Ultraviolet Spectrometer
- VEEGA
Venus-Earth-Earth Gravity Assist 相似文献
114.
Meteorological control of the D region 总被引:1,自引:0,他引:1
J. Taubenheim 《Space Science Reviews》1983,34(4):397-411
After a short review of the characteristics of ionized state and meteorology of the mesopause region, the winter anomaly of the D region electron density and its variability are described as manifestations of meteorological control. A major mechanism is the redistribution of nitric oxide, another important mechanism is the strong temperature dependence of cluster ion formation rates. The meteorological control can be described either in a ‘concerted’ scenario of more or less independently acting mechanisms, or in a ‘unitary’ scenario where all mechanisms are regarded as effects of a common cause, viz., the strong winter vortex circulation of the middle atmosphere. 相似文献
115.
Susan M. P. McKenna-Lawlor 《Space Science Reviews》1982,32(1-2):235-250
McMath Plage 15266, which transited the solar disk during Carrington Rotation 1667, gave rise during its passage to a spectacular sequence of five proton producing flares. Solar circumstances leading up to the formation of the active plage are described. An account is given of the magnetic affiliations and optical characteristics of the flares themselves, and it is suggested that four of these events might be interpreted as two twin phase flares displaying secondary maxima and minima such that the second phase in each case could in some sense be deemed a consequence of phenomena initiated during the first phase. Those particle phenomena associated with the observed activity are reviewed, and it is suggested that the azimuthal propagation of solar cosmic rays in the corona may occur more efficiently for flares at eastern longitudes in which the magnetic axis is aligned in a roughly north to south rather than an east-to-west direction.An invited paper presented at STIP Workshop on Shock Waves in the Solar Corona and Interplanetary Space, 15–19 June, 1980, Smolenice, Czechoslovakia. 相似文献
116.
117.
A methodology for addressing support equipment obsolescence 总被引:2,自引:0,他引:2
The rapid growth of technology over the last twenty years is providing vastly improved capabilities for both avionics and avionics test systems. Unfortunately, an environment of rapid technological growth breeds a corresponding environment of rapid technological obsolescence. Test systems developed fifteen years ago are becoming increasingly more difficult to support due to obsolescence issues and, additionally, such a test system does not reflect the current state-of-the-art for automatic test equipment. The ability of a test system to evolve is essential to providing cost-effective support systems for electronic systems. The F-15 Tactical Electronic Warfare System (TEWS) Intermediate Support System (TISS) was developed under the Modular Automatic Test Equipment (MATE) guidelines to support the suite of F-15 electronic warfare LRUs. MATE imposed hardware architecture constraints, which were factors that contributed to its abandonment. However, the modular aspect of MATE has provided a system that can easily evolve with technological advancements. Modularity is the cornerstone of modern software systems and this is the aspect that has been exploited in the evolution of the TISS 相似文献
118.
A new family of constant false alarm rate (CFAR) processors is introduced. An Ll-CFAR forms its noise power estimate by linearly filtering ranked samples from the reference set; the weights of this combination, however, depend not only on the rank, but also on the relative proximity of the sample to the cell under test. From the class of Ll-CFARs may be chosen members which effectively censor spurious targets; members which exhibit impressive control of false alarm in the presence of a clutter edge; and members which are robust against both such inhomogeneities. While the design of such schemes is involved, their implementation is not significantly more burdensome than that of plain ordered statistic CFAR (OS-CFAR). After a discussion of the stochastic training of Ll-CFAR, the performance is thoroughly assessed under the most commonly encountered instances of environmental conditions, and compared with those of classical CFAR techniques 相似文献
119.
Investigation of corona initiation voltage at reduced pressures 总被引:1,自引:0,他引:1
Karady G.G. Sirkis M.D. Li Liu 《IEEE transactions on aerospace and electronic systems》1994,30(1):144-150
The results of an experimental study of the 60 Hz ac corona inception voltage at reduced pressures for a cylindrical conductor and a parallel ground plane are presented. Several spacings and bare and insulated conductors of several diameters are considered. Empirical expressions from which a reasonably accurate prediction of the corona inception voltage (CIV) may be made have been inferred from experimental data 相似文献
120.