Scientific ballooning services

The services available for scientific ballooning are described with special emphasis on the facilities of the NCAR Balloon Flight Station at Palestine, Texas. The preparations for a typical launching, the operations during the launch, the flight and the recovery are described for illustrative purposes. Considerations on the future development of scientific ballooning are given; technological problems for extended flights are considered to be less serious than the political problems.     

Postdetection Integration Loss for Logarithmic Detectors

The effect of a logarithmic receiver on the detection performance of a radar has been determined by Green by numerical computations for up to 100 pulses integrated. It was further suggested that the loss in decibels as compared to a square-law detector would appear to be proportional to the logarithm of the number of pulses integrated. In this correspondence we show that this ?conjecture? is false, and that the additional loss when N becomes very large approaches a constant value of 2.2 dB.     

A Hybrid Navigation Concept Using a Spinning Satellite?Borne Interferometer and Self?Contained Equipment

This paper analyzes a hybrid navigation concept that uses signals from a radio interferometer mounted on a spinning geostationary satellite, preliminary position estimates from self-contained equipment, and stored a priori information on the past performance of this equipment. The craft-borne processor, optimum in the maximum a posteriori (MAP) sense, is designed to estimate position coordinates using only the incoming radio signals, although improved estimates result if the other two items are available. An error analysis starts with the derivation of an estimation error covariance matrix, whose elements depend on additive receiver noise and the physical parameters of the system. A minimum 1? estimation error in position is obtained by trading off these parameters. The effects of other major error sources, such as tropospheric phase fluctuations, multipath, and craft altitude uncertainty, are added to the estimation error to give a total 1? position error on the order of 3.7 to 5.6 km.     

Susan: A New Doppler Radionavigation System

SUSAN is a novel electronic Doppler navigation system which can be used with moving vehicles including aircraft, missiles, satellites, and ships. The system uses a technique of time delays and frequency multiplication to determine the rates of change of the Doppler frequency component present on a signal received from a moving vehicle. From this information the range and velocity of the vehicle can be determined with respect to a transmitting station whose position or ephemeris is known.     

小卫星的自适应姿态控制

分析了小卫星的姿态动力学及运动学方程；利用姿态动力学方程为一动力学参数矢量的线性函数这一事实，考虑存在参数不确定性，提出了一种自适应控制方法；证明了这种方法可以保证控制系统全局渐近稳定。仿真结果验证了该方法的有效性。