New Data Bus Interface Technique

Data bus systems as defined in MIL-STD-1553B are widely used in aerospace instrumentation systems for digital data transmissions between units on the bus. Although the bus is protected against a short circuit which may occur in the remote unit electronics or transformer, it has no protection against a cable termination failure. Open or short failure along main bus cable results in failure of the entire bus system. A new data bus interface technique is described which is insensitive to cable termination failure. The central feature of this new interface circuit is that communication between main unit and remote units is not affected by the cable termination failure. In applications such as multistage missiles, no provisions need be made for retermination in the cable characteristic impedance after stage separation. The key to this new technique is a directional coupling transformer which is only slightly more complicated than standard interface transformers. Design equations for directional coupling transformer and experimental results of new data bus systems are presented.     

Modified input estimation technique using pseudoresiduals

An adaptive tracking filter for maneuvering targets is proposed using modified input estimation technique. Pseudoresiduals are defined using measurements and the velocity estimate at the hypothesized maneuver onset time. With the pseudoresiduals and a new target model representing transitions of nominal accelerations, a new input estimation method for tracking a maneuvering target is derived. Since the proposed detection technique is more sensitive to maneuvers than previous work, the shorter window length can be employed to detect and compensate target maneuvers. Also shown is that the tracking performance of the proposed filter is similar to that of interacting multiple model method (IMM) with 3 models, while computational loads of our method are drastically reduced     

Total solar irradiance measurements by ERB/Nimbus-7. A review of nine years

The advent of reliable extraterrestrial solar irradiance measurements from satellites has supplied the impetus for new research in solar physics and solar-terrestrial relationships. The records for the principal experiments now extend beyond nine years. The Nimbus-7 measurements began in November 1978 and the Solar Maximum Mission (SMM) results started in February 1980. Both the ERB experiment of Nimbus-7 and the ACRIM experiment of SMM are still operational as of this writing (June 1988). We describe the nine-year Nimbus-7 total solar irradiance data set and compare it with similar data sets from the SMM and other satellite solar monitoring programs. Long-term downward trends of less than 0.02 % per year had been noted during the decaying portion of solar cycle 21 with indications that a leveling off and possible reversal of the trend was being experienced as we enter the new cycle. It had been demonstrated that fluctuations in the data over shorter periods corresponded to solar activity, from a primary discovery of irradiance depletions in times of building large sunspot groups to more subtle effects on the scale of solar rotation. Studies of the frequency spectra of the measurements have advanced the interest in helioseismology or mode analysis. Studies of photospheric activity have advanced by modelling of the sunspot blocking and photospheric brightening versus the measured irradiance. The theories are being extended to longer time-scales which indicate that solar irradiance is higher near solar cycle maximum, as defined by activity, and somewhat lower during the period between cycles. While measurements of total solar irradiance, the solar constant, alone cannot be employed to answer all of the questions of solar physics or helioclimatology, these long-term, high-precision data sets are valuable to both disciplines. The continuation of such measurements to more meaningful, longer time-scales should have a high priority in the international space community.     

用二阶矩两相湍流模型模拟鼓泡床内气泡—液体湍流两相流动

建立了二阶矩气液两相湍流模型，模拟了不同工况下二维矩形断面气液鼓泡床中气泡－液体湍流两相流动，给出了气泡和液体的速度场、气泡体积分数和两相雷诺应力分布，基本工况的模拟结果与美国俄亥俄州立大学PIV测量结果符合较好。文中研究了不同气体表观速度对两相流场的影响。模拟结果显示了鼓泡床内液体的回流流动和气泡的上升运动、各向异性的上湍流，气泡湍流脉动比液体的强，以及气泡体积分数和两相湍流强度随着气体表观速度的增大而增大等规律。     

Corotating Interaction Regions at High Latitudes

Ulysses observed a stable strong CIR from early 1992 through 1994 during its first journey into the southern hemisphere. After the rapid latitude scan in early 1995, Ulysses observed a weaker CIR from early 1996 to mid-1997 in the northern hemisphere as it traveled back to the ecliptic at the orbit of Jupiter. These two CIRs are the observational basis of the investigation into the latitudinal structure of CIRs. The first CIR was caused by an extension of the northern coronal hole into the southern hemisphere during declining solar activity, whereas the second CIR near solar minimum activity was caused by small warps in the streamer belt. The latitudinal structure is described through the presentation of three 26-day periods during the southern CIR. The first at ∼24°S shows the full plasma interaction region including fast and slow wind streams, the compressed shocked flows with embedded stream interface and heliospheric current sheet (HCS), and the forward and reverse shocks with associated accelerated ions and electrons. The second at 40°S exhibits only the reverse shock, accelerated particles, and the 26-day modulation of cosmic rays. The third at 60°S shows only the accelerated particles and modulated cosmic rays. The possible mechanisms for the access of the accelerated particles and the CIR-modulated cosmic rays to high latitudes above the plasma interaction region are presented. They include direct magnetic field connection across latitude due to stochastic field line weaving or to systematic weaving caused by solar differential rotation combined with non-radial expansion of the fast wind. Another possible mechanism is particle diffusion across the average magnetic field, which includes stochastic field line weaving. A constraint on connection to a distant portion of the CIR is energy loss in the solar wind, which is substantial for the relatively slow-moving accelerated ions. Finally, the weaker northern CIR is compared with the southern CIR. It is weak because the inclination of the streamer belt and HCS decreased as Ulysses traveled to lower latitudes so that the spacecraft remained at about the maximum latitudinal extent of the HCS. This revised version was published online in August 2006 with corrections to the Cover Date.     

发动机维修:成本与性能的平衡

在燃油价格上涨时,航空公司所期望的性能改进多与节省燃油有关;在燃油价格冲高回落、世界经济大衰退的今日,各航空公司关心的是如何获得最佳的运营成本.     

Generation of satellite tracking profile: Problems and validation algorithms

Recently, as a satellite mission becomes complicated, it has been required to generate the schedule of satellite antenna movements automatically without relying upon operator’s ad hoc knowledge. To generate the satellite antenna schedule autonomously, this paper first addresses geometrical problems associated with the antenna scheduling and mission planning problems that can be formulated from satellite navigation and antenna orientation information. Then, based on the solutions of the geometrical problems, a set of antenna azimuth and elevation angles that enables the antenna to point towards the desired ground station is obtained systematically. Using the computed azimuth and elevation angles, the satellite tracking profile (TP) is generated, and to validate it, TP validation algorithms are developed.     

The Upgraded CARISMA Magnetometer Array in the THEMIS Era

This review describes the infrastructure and capabilities of the expanded and upgraded Canadian Array for Realtime InvestigationS of Magnetic Activity (CARISMA) magnetometer array in the era of the THEMIS mission. Formerly operated as the Canadian Auroral Network for the OPEN Program Unified Study (CANOPUS) magnetometer array until 2003, CARISMA capabilities have been extended with the deployment of additional fluxgate magnetometer stations (to a total of 28), the upgrading of the fluxgate magnetometer cadence to a standard data product of 1 sample/s (raw sampled 8 samples/s data stream available on request), and the deployment of a new network of 8 pairs of induction coils (100 samples per second). CARISMA data, GPS-timed and backed up at remote field stations, is collected using Very Small Aperture Terminal (VSAT) satellite internet in real-time providing a real-time monitor for magnetic activity on a continent-wide scale. Operating under the magnetic footprint of the THEMIS probes, data from 5 CARISMA stations at 29–30 samples/s also forms part of the formal THEMIS ground-based observatory (GBO) data-stream. In addition to technical details, in this review we also outline some of the scientific capabilities of the CARISMA array for addressing all three of the scientific objectives of the THEMIS mission, namely: 1. Onset and evolution of the macroscale substorm instability, 2. Production of storm-time MeV electrons, and 3. Control of the solar wind-magnetosphere coupling by the bow shock, magnetosheath, and magnetopause. We further discuss some of the compelling questions related to these three THEMIS mission science objectives which can be addressed with CARISMA.     

An introduction to the lunar and planetary science activities in Korea

Korea is planning a series of lunar space programs in 2020 starting with a lunar orbiter and a lander with a rover. Compared to other countries, Korea has a relatively brief history in space and planetary sciences. With the expected Korean missions on the near-term horizon and the relatively few Korean planetary scientists, Korea Institute of Geoscience and Mineral Resources (KIGAM) has established a new planetary research group focusing on development of prospective lunar instruments, analysis of the publicly available planetary data of the Moon, organizing nationwide planetary workshops, and initiating planetary educational programs with academic institutions. Korea has also initiated its own rocket development program, which could acquire a rocket-launch capability toward the Korean lunar mission. For the prospective Korea’s lunar science program, feasibility studies for some candidate science payloads have been started since 2010 for an orbiter and a lander. The concept design of each candidate instrument has been accomplished in 2012. It is expected that the development of science payloads may start by 2014 as Phase A. Not only developing hardware required for the lunar mission but also educational activities for young students are high priorities for Korea. The new plan of the Korean lunar mission can be successfully accomplished with international cooperative outreach programs in conjunction with internationally accessible planetary data system (PDS). This paper introduces the KIGAM’s international cooperative planetary research and educational programs and also summarizes other nationwide new developments for Korean lunar research projects at Kyung Hee University and Hanyang University.