A technique for estimating the probability of radiation-stimulated failures of integrated microcircuits in low-intensity radiation fields: Application to the Spektr-R spacecraft

In developing radio-electronic devices (RED) of spacecraft operating in the fields of ionizing radiation in space, one of the most important problems is the correct estimation of their radiation tolerance. The “weakest link” in the element base of onboard microelectronic devices under radiation effect is the integrated microcircuits (IMC), especially of large scale (LSI) and very large scale (VLSI) degree of integration. The main characteristic of IMC, which is taken into account when making decisions on using some particular type of IMC in the onboard RED, is the probability of non-failure operation (NFO) at the end of the spacecraft’s lifetime. It should be noted that, until now, the NFO has been calculated only from the reliability characteristics, disregarding the radiation effect. This paper presents the so-called “reliability” approach to determination of radiation tolerance of IMC, which allows one to estimate the probability of non-failure operation of various types of IMC with due account of radiation-stimulated dose failures. The described technique is applied to RED onboard the Spektr-R spacecraft to be launched in 2007.     

On stability of a rotating spacecraft partially filled with liquid: The case of a single cavity

The problem of stability of a rotating spacecraft with a cavity partially filled with liquid to a small depth is considered with regard to the distinction in angular velocities of spacecraft and liquid rotation and their variability (the modes of the spacecraft’s stationary rotation, spin-up, and rotation deceleration). The regions of stability (in space of the characteristic parameters of an object) are found, and mathematical simulating of the disturbed motion is carried out.     

Need and effect of reconditioning of nickel/hydrogen batteries

There has been a debate about the need for reconditioning nickel/hydrogen batteries in geosynchronous satellites. A study was done as part of life cycling, to determine the necessity of reconditioning and its effect on the cell performance. A 36 Ah nickel/hydrogen cell was put on a GEO simulated cycling at 15°C without reconditioning up to four eclipse seasons. The effect of reconditioning on the fifth and sixth eclipse seasons was studied. The study has conclusively proven the need for reconditioning and has shown the benefits of a high rate reconditioning. It has also been possible to draw some conclusions about the effect of a long duration trickle charge on the positive electrode     

Monitoring power supply current and using a neural network routineto diagnose circuit faults

As a circuit is tested, the current drawn from a power supply can vary as different functions are invoked by the test. The current draw can be plotted against time, showing a characteristic trace for the test performed. Sensors in the ATS power supply can be used to monitor the current flow during test execution. Defective components can be classified using a Neural Network according to the pattern of variation from the “trace” of a good card. This can be performed as a background function, with the network gaining in accuracy over time. This paper discusses the Neural Network Routine for diagnosing circuit faults using monitored power supply current     

End-to-End Modeling of the Solar Terrestrial System

Traditionally modeling for space science has concentrated on developing simulations for individual components of the solar terrestrial system. In reality these regions are coupled together. This coupling can be as simple as the driving of the magnetosphere – ionosphere – thermosphere system by the solar wind or as a complicated as the feedback of the ionospheric conductivity and currents on the magnetosphere. As part of the CISM project we are beginning a concentrated effort to compressively model the entire system. This approach includes chains of models. In the first chain physics based numerical models are utilized while in the second chain empirical models are coupled together. The first half of this paper discusses the numerical modeling approach by highlighting the coupling of pairs of regions within the system. In the second section we present results from empirical models which are combined to make long term forecasts of conditions in the geospace environment. It is expected that a validated and reliable forecast model for space weather can be obtained by combining the strongest elements of each chain.     

Discrete-time min-max tracking

The problem of optimal state estimation of linear discrete-time systems with measured outputs that are corrupted by additive white noise is addressed. Such estimation is often encountered in problems of target tracking where the target dynamics is driven by finite energy signals, whereas the measurement noise is approximated by white noise. The relevant cost function for such tracking problems is the expected value of the standard H/sub /spl infin// performance index, with respect to the measurement noise statistics. The estimator, serving as a tracking filter, tries to minimize the mean-square estimation error, and the exogenous disturbance, which may represent the target maneuvers, tries to maximize this error while being penalized for its energy. The solution, which is obtained by completing the cost function to squares, is shown to satisfy also the matrix version of the maximum principle. The solution is derived in terms of two coupled Riccati difference equations from which the filter gains are derived. In the case where an infinite penalty is imposed on the energy of the exogenous disturbance, the celebrated discrete-time Kalman filter is recovered. A local iterations scheme which is based on linear matrix inequalities is proposed to solve these equations. An illustrative example is given where the velocity of a maneuvering target has to be estimated utilizing noisy measurements of the target position.