Determination of the Microacceleration Quasisteady Component onboard the International Space Station

A comparison of two methods of determination of the microacceleration quasisteady component arising onboard the International Space Station was performed. In the first method the acceleration was calculated using the relative motion of the station reconstructed on the basis of telemetry data. The second method was a direct measurement of the microacceleration by a low-frequency accelerometer and a smoothing of the data obtained. The used measurements were made by the American accelerometer MAMS. The above comparison can theoretically be used to refine the position of the station center of mass relative to its body.     

Optimization of imperfect stiffened cylinders under destabilizing loads

A design procedure is outlined for optimizing stiffened, thin circular, cylindrical shells subject to a given set of destabilizing loads, in the presence of a specified initial geometric imperfection. The procedure incorporates two distinct steps (a) optimization based on linear buckling analyses and (b) imperfection sensitivity studies of the optimum design point from (a) as well as of the surrounding design space. A comparison of all these designs yield the true optimum in the presence of the specified geometric imperfection. The present methodology is fully demonstrated through two illustrative examples, one dealing with an axially loaded stiffened cylinder and one with a torsionally loaded one.     

Gathering news from space

Developments in remote-sensing technology have prompted suggestions that the news media could soon make routine use of newsgathering from space. A satellite system dedicated to this purpose (a ‘Mediasat’) could supply critical information. Government policy makers, however, fear that the media's use of such technology could affect national security, foreign relations and personal privacy. This article assesses US government policy on current and future newsgathering from space, and the technical potential for a Mediasat system. The authors raise doubts about the commercial viability of Mediasat, and point out that existing media sources already provide information on news stories. They conclude that concerns over the use of data from space will have to be met on a case-by-case basis as the media gain experience, using the same criteria now applied to balance the right of freedom of information with the need for national security.     

Leadership in space transportation

Rather than aiming at overall preemenence in space, as in the past, it is important for the USA now to specify goals and objectives for its space programme. In the space transportation market, the USA faces long-term competition. Planned properly, the Space Shuttle, Space Station and transfer stages can be used as a unique transport system, forcing other suppliers to compete on US terms. Such a total transport service system could also include ELV support. In entering into international space agreements, the government must take into account the objective of maintaining the competitiveness of the US commercial sector.     

Empirical model of the high-latitude boundary of the Earth’s outer radiation belt at altitudes of up to 1000 km

An empirical model of the high-latitude boundary of the outer Earth’s radiation belt (ERB) has been presented, which is based on the measurement data of electron fluxes on the polar low-orbit CORONAS-Photon, Meteor-M1, and Meteor-M2 satellites. The boundary was determined by a sharp decrease to the background level of the flux of trapped electrons with energies of 100 or 200 keV in the polar part of the profile of the outer radiation belt. A numerical algorithm has been implemented to determine the time moment, when the fastest flux changes are recorded. The primary search was carried out, first, on 30 s averaged data, then repeated on data with a higher resolution. A functional dependence was obtained in order to approximate the obtained set of intersections of the boundary by elliptical curve. The empirical model constructed using the CORONAS-Photon measurement data in the epoch of anomalously low geomagnetic activity reflects the longitude structure of the high-latitude boundary of the outer radiation belt associated with the internal Earth’s magnetic field (MF), as well as its dependence on the universal time. Based on the data of intersections of the high-latitude boundary of the outer ERB (OERB) in the epoch of 2014–2016, the latitudinal shift of the boundary to the equator dependent on geomagnetic activity has been determined, as well as the nightside shift of the boundary due to the diurnal rotation of the Earth.     

Plasma irregularities in unstable outer ionosphere according to the Intercosmos-Bulgaria-1300 satellite data

The results of the satellite low-latitude and mid-latitude measurements of the disturbed plasma concentration, electron temperature, and quasi-stable electric field at heights of ～900 km after sunset are discussed. It is shown that the sharp fronts of changes in the electron temperature and plasma density observed in the experiment onboard the Intercosmos-Bulgaria-1300 satellite in the low-latitude (and equatorial) outer ionosphere can be related to damping of the oscillations of plasma electrons at local decreases of the plasma density (plasma “pits”) and formation of the vortex plasma structures at density and temperature gradients, which promotes conservation of ionosphere irregularities and makes the fronts of concentration variations steeper. Nonmonotonic variations in the plasma conductivity for the ionosphere currents in unstable plasma can be a cause of observed nonmonotonic disturbances of the vertical component of the “constant” electric field.     

Features of whistling electromagnetic wave propagation descending from above upon the night ionosphere

The results of numerical solution of the wave equations for the oblique incidence of whistling electromagnetic waves upon the night ionosphere from above have been obtained and analyzed. In the studied region of altitudes, within the wavelength scale, charged particle concentration varies drastically, and damping caused by collisions between the charged and neutral particles decreases considerably. Below, the sharp lower boundary of the ionosphere, the refractive index of the whistler wave approaches unity, and plasma turbulence transform into atmospheric electromagnetic waves. The dependences of the whistler reflection factor are found in terms of energy and horizontal magnetic component of the electromagnetic wave near the Earth’s surface on the frequency and the wave vector transverse component for the plain-layered medium model at two values of latitude. Strong dependences have been found on the wave angle of incidence and frequency. At rather small angles of incidence, the wave disturbances reach the Earth’s surface, and the module of reflection coefficient logarithm is in the range of 0.4–1. At large angles of incidence, the reflection coefficient module varies over a wide range depending on specific conditions. The obtained results explain the absence of oscillation modes of plasma magnetosphere maser in the night magnetosphere.     

Modes of uncontrolled rotational motion of the <Emphasis Type="Italic">Progress M-29M</Emphasis> spacecraft

We have reconstructed the uncontrolled rotational motion of the Progress M-29M transport cargo spacecraft in the single-axis solar orientation mode (the so-called sunward spin) and in the mode of the gravitational orientation of a rotating satellite. The modes were implemented on April 3–7, 2016 as a part of preparation for experiments with the DAKON convection sensor onboard the Progress spacecraft. The reconstruction was performed by integral statistical techniques using the measurements of the spacecraft’s angular velocity and electric current from its solar arrays. The measurement data obtained in a certain time interval have been jointly processed using the least-squares method by integrating the equations of the spacecraft’s motion relative to the center of mass. As a result of processing, the initial conditions of motion and parameters of the mathematical model have been estimated. The motion in the sunward spin mode is the rotation of the spacecraft with an angular velocity of 2.2 deg/s about the normal to the plane of solar arrays; the normal is oriented toward the Sun or forms a small angle with this direction. The duration of the mode is several orbit passes. The reconstruction has been performed over time intervals of up to 1 h. As a result, the actual rotational motion of the spacecraft relative to the Earth–Sun direction was obtained. In the gravitational orientation mode, the spacecraft was rotated about its longitudinal axis with an angular velocity of 0.1–0.2 deg/s; the longitudinal axis executed small oscillated relative to the local vertical. The reconstruction of motion relative to the orbital coordinate system was performed in time intervals of up to 7 h using only the angularvelocity measurements. The measurements of the electric current from solar arrays were used for verification.     

Control of the Onboard Microgravity Environment and Extension of the Service Life of the Long-Term Space Station

The problem of control of the on-board microgravity environment in order to extend the service life of the long-term space station has been discussed. Software developed for the ISS and the results of identifying dynamic models and external impacts based on telemetry data have been presented. Proposals for controlling the onboard microgravity environment for future long-term space stations have been formulated.