Leveling of Analytic Platforms

Use of an analytic platform or strapdown system requires that the system em be initially leveled just as a conventional multigimbaled platform must be leveled. The process of leveling involves the determination of the orientation between the local vertical and an instrumented reference nce frame. With a conventional platform it is quite common to use a pair of servo loops to precess the inner gimbal until gravity signals are nulled on two orthogonally mounted accelerometers. The input axes of these two accelerometers thus define the horizontal plane and the platform is said to be leveled. A strapdown system, however, lacks the physical entity of the inner gimbal and consequently cannot be physically precessed into verticality. The method of leveling is nonetheless analogous if we consider the computational reference frame of the analytic platform to be the "alter ego" or counterpart of a physical inner gimbal. In general, strapdown leveling techniques can be divided into two categories: closed-loop leveling and open-loop leveling. These two techniques are quantitatively developed and discussed in this paper.     

Preliminary calibration results of VEGA 1 and 2 SIGMA-3 gas chromatograph

SIGMA - 3 gas chromatograph on board VEGA 1 and 2 landing probes has been operated successfully in the 60 - 50 km altitude range, providing several in - situ chemical analysis of the gas and the aerosols of Venus cloud layers. Post flight calibration required to derive atmospheric abundancies from gas chromatograms were carried out using the SIGMA - 3 spare model. A Venus atmospheric aerosol simulation chamber was used in which sulfuric acid droplets were generated. Preliminary results of these calibration experiments indicate that the concentration of sulfuric acid in the upper part of the clouds ( 60 to 55 km) is about 1 mg/m³ and suggest that an additional constituant must be present in noticeable amount in the aerosols. From these experiments the mixing ratio upper limits of SO₂ is 100 ppmV and of H₂S and COS is few 10 ppmV.     

Coronal Observations of CMEs

CMEs have been observed for over 30 years with a wide variety of instruments. It is now possible to derive detailed and quantitative information on CME morphology, velocity, acceleration and mass. Flares associated with CMEs are observed in X-rays, and several different radio signatures are also seen. Optical and UV spectra of CMEs both on the disk and at the limb provide velocities along the line of sight and diagnostics for temperature, density and composition. From the vast quantity of data we attempt to synthesize the current state of knowledge of the properties of CMEs, along with some specific observed characteristics that illuminate the physical processes occurring during CME eruption. These include the common three-part structures of CMEs, which is generally attributed to compressed material at the leading edge, a low-density magnetic bubble and dense prominence gas. Signatures of shock waves are seen, but the location of these shocks relative to the other structures and the occurrence rate at the heights where Solar Energetic Particles are produced remains controversial. The relationships among CMEs, Moreton waves, EIT waves, and EUV dimming are also cloudy. The close connection between CMEs and flares suggests that magnetic reconnection plays an important role in CME eruption and evolution. We discuss the evidence for reconnection in current sheets from white-light, X-ray, radio and UV observations. Finally, we summarize the requirements for future instrumentation that might answer the outstanding questions and the opportunities that new space-based and ground-based observatories will provide in the future.     

Multipath-adaptive GPS/INS receiver

Multipath interference is one of the contributing sources of errors in precise global positioning system (GPS) position determination. This paper identifies key parameters of a multipath signal, focusing on estimating them accurately in order to mitigate multipath effects. Multiple model adaptive estimation (MMAE) techniques are applied to an inertial navigation system (INS)-coupled GPS receiver, based on a federated (distributed) Kalman filter design, to estimate the desired multipath parameters. The system configuration is one in which a GPS receiver and an INS are integrated together at the level of the in-phase and quadrature phase (I and Q) signals, rather than at the level of pseudo-range signals or navigation solutions. The system model of the MMAE is presented and the elemental Kalman filter design is examined. Different parameter search spaces are examined for accurate multipath parameter identification. The resulting GPS/INS receiver designs are validated through computer simulation of a user receiving signals from GPS satellites with multipath signal interference present The designed adaptive receiver provides pseudo-range estimates that are corrected for the effects of multipath interference, resulting in an integrated system that performs well with or without multipath interference present.     

Missile Electronic System Hardness Assurance Program

A hardness assurance program suitable for a retaliatory or deterrent missile system is discussed. The program consists of three phases: the establishment of suitable controls and screens to ensure piece part hardness, a supplier data monitoring program to measure hardness related parameters in a timely fashion to obtain advanced warning of potential problems, and a hardness assurance verification testing (HAVT) program to periodically measure the radiation response of parts, circuits, subsystems, and systems on a sample basis to ensure proper functioning in simulated radiation environments. All of the data relevant to hardness assurance is stored in computer memory and routinely interrogated with programs which compare current results with the engineering baseline data and other data from preceding lots. Other computer programs enable statistical estimation of system response to the radiation environment with confidence based on the expanding data base provided by the HAVT program.     

Evaluating the economic impact of design alternatives on domestic communication satellite ventures

What are the economic consequences of establishing a domestic communication satellite venture? Has the best design alternative been selected? Should investments be made to develop new technology? How much should be invested? These are but some of the questions facing those concerned with providing domestic communication satellite services. Because of the demand, performance and cost uncertainties and the unpredictability of the need for and timing of large capital expenditures (due to less than perfect reliability of transportation systems and satellites) providing answers to these and other related questions is a complex process.This paper describes a methodology for providing answers to the above questions. The methodology, by explicitly considering demand, performance and cost uncertainties and satellite and transportation system reliability, develops probabilistic pro forma financial analyses of domestic communication satellite system ventures. In so doing, the risk dimension is quantified and alternative courses of action can be evaluated and compared taking into account expected values, risk and risk aversion preferences. It is also important to quantify and consider the risk dimension since many R &; D projects are specifically aimed at risk reduction.     

Economy of modular low-technology launch vehicles

The paper comprises an assessment of the design and the economics of so-called “low-cost” simple modular launch vehicles. It is shown that the performance is very marginal and that the cost per launch cannot compete with technically more advanced fully reusable vehicles. Especially a private-funded development cannot be amortized economically in case of an expendable launch vehicle.     

基于LabVIEW平台的数字抽取滤波器的设计与应用

介绍了基于LabVIEW平台的数字抽取滤波器的设计。该方法是对高采样率的数据进行低通数字滤波，然后对结果用1／K倍重新采样，将数字信号频带压缩K倍，从而实现动态测试较大的动态范围要求和划分频带要求，数字抽取滤波器的设计包含调制，数字滤波和抽取三方面，LabVIEW是一种基于图形编程语言（G语言）的开发环境，采用交互界面设计，模块化编程，该滤波器也是作者正在研制的动态测试分析虚拟仪器的一个重要组成部分。本文给出了在LabVIEW平台上所进行数字抽取滤波器的设计原理，仿真结果和在动态数字信号分析中的应用。