The IMF pile-up regions near the Earth and Venus: lessons for the solar wind - Mars interaction

The Mars Global Surveyor mission has revealed that localized crustal paleomagnetic anomalies are a common feature of the Southern Hemisphere of Mars. The magnetometer measured small-scale magnetic fields associated with many individual magnetic anomalies have magnitudes ranging from hundreds to thousands nT at altitude above 120 km. That makes Mars globally different from both Venus and Earth. The data collected by Lunar Prospector near the Moon were interpreted as evidence that above regions of inferred strong surface magnetic fields on the Moon the SW flow is deflected, and a small-scale mini-magnetosphere exists under some circumstances. With a factor of 100 stronger magnetic fields at Mars and a lower SW dynamic pressure, those conditions offer the opportunity for a larger size of small `magnetospheres' which can be formed by the crustal magnetic fields. Outside the regions of the magnetic anomalies, the SW/Mars interaction is Venus-like. Thus, at Mars the distinguishing feature of the magnetic field pile-up boundary most likely varies from Venus-like to Earth-like above the crustal magnetic field regions. The observational data regarding the IMF pile-up regions near Venus and the Earth are initially reviewed. As long as the SW/Mars interaction remains like that at Venus, the IMF penetrates deep into the Martian ionosphere under the `overpressure' conditions. Results of numerical simulations and theoretical expectations regarding the temporal evolution of the IMF inside the Venus ionosphere and appearance of superthermal electrons are also reviewed and assessed.     

Highly accurate, noncoherent technique for spacecraft Dopplertracking

A two-way, noncoherent spacecraft navigation technique has been developed to provide velocity accuracy comparable to that available from a deep space coherent transponder (0.1 mm/s). The technique is compatible with the normal tracking procedures of the Deep Space Network (DSN) ground stations and does not require the use of a highly stable oscillator on-board the spacecraft. The measurement technique, potential error sources, and test results obtained with prototype hardware are described     

Displacement simulation for spacecraft structure

The paper presents a technique of forming and evaluating the allowable clearance between a launch vehicle fairing and spacecraft.     

Organic chemistry by irradiation in space

The irradiation of grains and/or ices by particles from solar or stellar winds, as well as cosmic rays, induces the synthesis of molecular species. We have shown by in-situ infrared spectroscopy of irradiated samples that this chemistry may be responsible for the presence of organic compounds in a large variety of astrophysical sites such as: lunar and asteroidal regoliths, cometary nucleus, rings and satellites of outer planets, circumstellar shells, interstellar clouds. We present our experimental results concerning the nature and efficiency of C and N irradiation chemistries, and give plausible astrophysical implications.     

Transient Nonstationary Behavior of a Delay Line Discriminator

The development of numerical methods for studying the transient nonstationary behavior of a delay line discriminator is presented. Expressions are developed for the mean and the variance of the output noise process. For the cases where the output is stationary, power density spectra are found.     

应用限制编程的信息模型内在检查方法

提出了一种基于限制编程(Constraint programmmg)的信息模型内在一致性检查方法,重点描述了EXPRESS信息模型的一致性及其检查。EXPRESS语言,作为标准制造数据交换的一个重要部分,广泛地应用于制造与信息业。中提到的一致性检查包括三个步骤：EXPRESS模型形式化,限制满足性问题(CSP)从形式化模型中的抽取和CSP的可满足性测试。本同时揭示了限制编程的一个新的应用领域：模型验证。     

Analysis of towed decoys

Recent advances in RF missile systems have reduced the effectiveness of conventional on-board electronic countermeasures (ECM) to defend friendly aircraft. To provide the much needed defense, off-board ECM techniques are being developed. The effectiveness of off-board RF ECM is analyzed, and specific observations are made about the effectiveness of such ECM when used to defend friendly aircraft     

Extensions of the Discrete-Average Models for Converter Power Stages

An improved power converter model is developed by combining the average and discrete modeling techniques. The parameter determination of the proposed discrete-average model is shown to be dependent on the type of duty cycle control law and the nature of the error processor used in the feedback loop. Furthermore, the paper pinpoints deficiencies of the conventional loop gain measurement technique which is widely used in industries.     

A comparative and numerical study of effects of gravity waves in small miss-distance and miss-time GPS radio occultation temperature profiles

The Global Positioning System (GPS) Radio Occultation (RO) technique has global coverage and is capable of generating high vertical resolution temperature profiles of the upper troposphere and lower stratosphere with sub-Kelvin accuracy and long-term stability, regardless of weather conditions. In this work, we take advantage of the anomalously high density of occultation events at the eastern side of the highest Andes Mountains during the initial mission months of COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate). This region is well-known for its high wave activity. We choose to study two pairs of GPS RO, both containing two occultations that occurred close in time and space. One pair shows significant differences between both temperature profiles. Numerical simulations with a mesoscale model were performed, in order to understand this discrepancy. It is attributed to the presence of a horizontal inhomogeneous structure caused by gravity waves.