Modeling the sodium potassium droplet interactions with the low earth orbit space debris environment

The NASA/JSC sodium potassium (NaK) RORSAT coolant source and propagation model has been extended to 1 mm in diameter via a size distribution, which is an inverse power law fit that has been modified to damp out in the large size regime. This function matches the observed Haystack NaK population down to diameters of about 6 mm. The extrapolated function takes the population to arbitrarily small sizes all the while retaining the mass dominance of the 1–3 cm droplets that is observed in the Haystack data. This result is physically satisfying since the mechanism of NaK ejection appears to be a nonviolent release at low relative velocities. We propose that any NaK particles smaller than about 1 mm that exist would not be due to that mechanism. Instead, we show that such a population could be the result of subsequent collisions of NaK droplets with larger resident space objects and the micrometeoroid population. Our preliminary analysis shows that collisions between these populations are likely in the time period of 1980 through present-day. Though the result of such collisions is generally unknown it is probable that some ejecta of NaK enter the low Earth orbit (LEO) environment as a result. It is these secondary NaK droplets/particles that we contend are the likely impactors noted on returned surfaces.     

Optimization of Bi-Elliptic transfer with plane change—Part I

We introduce a more advanced analysis than that of Roth concerning the following two points of view: (1) We attempt to find an analytical solution of the optimization problem instead of Roth's iterative solution. That means a stress is operated on the analytical approach. (2) We consider the terminal orbits to be elliptic and not circular as Roth assumed. This is a generalization of the problem. We shall complete the solution of this Bi-Elliptic transfer with plane change problem in the second part of the present research paper (I).     

Stability of resonance rotation of a satellite with respect to its center of mass in the orbit plane

The stability of resonance oscillations and rotations of a satellite in the plane of its orbit in the case when the difference of the moments of inertia with respect to the principal axes lying in the orbit plane is small is determined at a given rotation number m by the sign of function Φ_m(e), introduced by F.L. Chernous’ko in 1963. In this paper, convenient analytical representations of functions Φ_m(e) are described in the form of integrals and series of Bessel functions regular at e → 1^?. Values of Φ_m(1) are calculated in explicit form. A theorem about the double asymptotic form of functions Φ_m(e) at m → ∞ and e → 1^? is proved by the saddlepoint method.     

行波管在轨可调高压数字化隔离控制电路设计方案

为了实现星载行波管放大器在轨功率和频率可调,需要遥控改变行波管的阴极电流和螺旋极电压。为了精准控制行波管的阴极电流和螺旋极电压以及控制灵活性,提出了用变压器隔离的串行数字化高压控制参考电压产生电路,电路通过传输两路脉冲信号：一路为开始和时钟复合脉冲,用于识别和准备接收数据以及分离时钟信号;另一路为数据信号,它是数字化的高电压值(对应螺旋极或阳极电压)。详细介绍了电路的组成、原理和参数设计方法,并用PSpice进行了仿真验证。仿真结果证明：电路能正确识别、接收和完成数据传输和转换功能。串行数字化高压隔离电路完全可以实现控制电压的精准传输,输出电压无纹波,控制方式灵活,易于调试。     

Diurnal change of MW and IR thermal emissions from lunar craters with relevance to rock abundance

Abnormal “hot spots” during a total eclipse on the lunar surface were revealed by using a ground based infrared (IR) scanner and visible telescope in the early 1960s, which turned out to be “cold spots” on the microwave (MW) brightness temperature distribution at night according to the Chang'E (CE)-1 radiometer's observations. In this paper, a theoretical analysis of radiative transfer is presented to explain this abnormal phenomenon of diurnal changes. Two typical craters, representing the abnormal fresh craters rich in rock abundance and an old one almost free of rocks located at similar latitudes are chosen for comparison of the diurnal temperature change. Using the measurements of CE-1 multi-channel microwave radiometer, brightness temperatures from these two craters are presented and applied to inversions of the physical temperatures of lunar regolith media, based on a three-layer radiative transfer model. The correlation between the diurnal MW and IR thermal changes of the lunar surface and the rock abundance is discussed.