Parametric Identification of a Return Space Vehicle during Vertical Landing

Real values of parameters for a space vehicle and its steering devices are specified by using the motion parameters measured in flight based on solving the differential equations of motion.     

Near-infrared study of open clusters Teutsch 10 and Teutsch 25

The astrophysical parameters have been estimated for two unstudied open star clusters Teutsch 10 and Teutsch 25 using the Two Micron All Sky Survey ($2\mathit{MASS}$) database. Radius is estimated as 4.5 arcmin for both clusters using radial density profiles. We have estimated proper motion values in both RA and DEC directions as $2.28\pm 0.3$ and $-0.38\pm 0.11$?mas?yr^?1 for Teutsch 10 and $0.48\pm 0.3$ and $3.35\pm 0.16$?mas?yr^?1 for Teutsch 25 using $\mathit{PPMXL}$¹ catalog. By estimating the stellar membership probabilities, we have identified 30 and 28 most likely members for Teutsch 10 and Teutsch 25 respectively. We have estimated the reddening as $E(B-V)=0.96\pm 0.3$?mag for Teutsch 10 and $0.58\pm 0.2$?mag for Teutsch 25, while the corresponding distances are $2.4\pm 0.2$ and $1.9\pm 0.1$?kpc. Ages of $70\pm 10$?Myr for Teutsch 10 and $900\pm 100$?Myr for Teutsch 25 are estimated using the theoretical isochrones of metallicity Z?=?0.019. The mass function slopes are derived as $1.23\pm 0.30$ and $1.09\pm 0.35$ for Teutsch 10 and Teutsch 25 respectively. Estimated mass function slope for both the clusters are close to the Salpeter value ($x=1.35$) within the errors. Estimated values of dynamical relaxation time are found to be less than cluster’s age for these objects. This concludes that both objects are dynamically relaxed. The possible reason for relaxation may be due to dynamical evolution or imprint of star formation or both.     

Observation of a 27-day solar signature in noctilucent cloud altitude

Previous studies have identified solar 27-day signatures in several parameters in the Mesosphere/Lower thermosphere region, including temperature and Noctilucent cloud (NLC) occurrence frequency. In this study we report on a solar 27-day signature in NLC altitude with peak-to-peak variations of about 400?m. We use SCIAMACHY limb-scatter observations from 2002 to 2012 to detect NLCs. The superposed epoch analysis method is applied to extract solar 27-day signatures. A 27-day signature in NLC altitude can be identified in both hemispheres in the SCIAMACHY dataset, but the signature is more pronounced in the northern hemisphere. The solar signature in NLC altitude is found to be in phase with solar activity and temperature for latitudes $?70°$N. We provide a qualitative explanation for the positive correlation between solar activity and NLC altitude based on published model simulations.     

Order out of Randomness: Self-Organization Processes in Astrophysics

Self-organization is a property of dissipative nonlinear processes that are governed by a global driving force and a local positive feedback mechanism, which creates regular geometric and/or temporal patterns, and decreases the entropy locally, in contrast to random processes. Here we investigate for the first time a comprehensive number of (17) self-organization processes that operate in planetary physics, solar physics, stellar physics, galactic physics, and cosmology. Self-organizing systems create spontaneous “order out of randomness”, during the evolution from an initially disordered system to an ordered quasi-stationary system, mostly by quasi-periodic limit-cycle dynamics, but also by harmonic (mechanical or gyromagnetic) resonances. The global driving force can be due to gravity, electromagnetic forces, mechanical forces (e.g., rotation or differential rotation), thermal pressure, or acceleration of nonthermal particles, while the positive feedback mechanism is often an instability, such as the magneto-rotational (Balbus-Hawley) instability, the convective (Rayleigh-Bénard) instability, turbulence, vortex attraction, magnetic reconnection, plasma condensation, or a loss-cone instability. Physical models of astrophysical self-organization processes require hydrodynamic, magneto-hydrodynamic (MHD), plasma, or N-body simulations. Analytical formulations of self-organizing systems generally involve coupled differential equations with limit-cycle solutions of the Lotka-Volterra or Hopf-bifurcation type.     

Behavior of tethered debris with flexible appendages

Active exploration of the space leads to growth of a near-Earth space pollution. The frequency of the registered collisions of space debris with functional satellites highly increased during last 10 years. As a rule a large space debris can be observed from the Earth and catalogued, then it is possible to avoid collision with the active spacecraft. However every large debris is a potential source of a numerous small debris particles. To reduce debris population in the near Earth space the large debris should be removed from working orbits. The active debris removal technique is considered that intend to use a tethered orbital transfer vehicle, or a space tug attached by a tether to the space debris. This paper focuses on the dynamics of the space debris with flexible appendages. Mathematical model of the system is derived using the Lagrange formalism. Several numerical examples are presented to illustrate the mutual influence of the oscillations of flexible appendages and the oscillations of a tether. It is shown that flexible appendages can have a significant influence on the attitude motion of the space debris and the safety of the transportation process.     

Thick galactic cosmic radiation shielding using atmospheric data

NASA is concerned with protecting astronauts from the effects of galactic cosmic radiation and has expended substantial effort in the development of computer models to predict the shielding obtained from various materials. However, these models were only developed for shields up to about 120 g/cm² in mass thickness and have predicted that shields of this mass thickness are insufficient to provide adequate protection for extended deep space flights. Consequently, effort is underway to extend the range of these models to thicker shields and experimental data is required to help confirm the resulting code. In this paper empirically obtained effective dose measurements from aircraft flights in the atmosphere are used to obtain the radiation shielding function of the Earth's atmosphere, a very thick, i.e. high mass, shield. Obtaining this result required solving an inverse problem and the method for solving it is presented. The results are shown to be in agreement with current code in the ranges where they overlap. These results are then checked and used to predict the radiation dosage under thick shields such as planetary regolith and the atmosphere of Venus.     

System of maintaining the thermal regime of a space radio telescope

We present the results of developing a system of thermal regime maintenance for the onboard complex of scientific instruments of the space radio telescope installed on the Spektr-R spacecraft. The structure of the system of thermal regime maintenance is presented that includes a set of autonomous systems of constructive elements of the radio telescope. Basic schemes and composition of aggregates are presented, and main principles of operation of the autonomous systems supporting the thermal regime of the radio telescope are considered.     

Three dimensional temperature field in a conducting sphere due to an arbitrarily located split ring heating source

Thermal control of spacecrafts plays an important role in space missions. In the design stage the preliminary thermal analysis of the spacecraft requires an estimate of the conductive thermal resistance between the various spacecraft components. With this in mind, the fully three dimensional problem of determining the thermal field in a conducting sphere with an asymmetric split ring current carrying heating source is resolved in an analytical or almost analytical form, implying either a closed form solution or utmost expressions involving a simple numerical integration. This has immediate application for evaluation of thermal resistance in spacecrafts. Green's function integral techniques are used. Comparisons are made with series solutions and also with purely numerical solutions to contrast the simplicity and highlight the elegance of the present method. Parametric studies reveal expected behavior.     

New one-axis one-sensor magnetic attitude control theoretical and in-flight performance

New one-axis magnetic attitude control is proposed. Only one attitude sensor providing any inertial direction measurements is necessary, magnetometer is not used. The control may be used as a backup capability in case main actuators or some attitude sensors fail. Sun pointing is achievable using only three-axis Sun sensor, so the control may be used to lower the power consumption during battery charging. Asymptotic stability of different equilibria depending on the satellite inertia tensor is summarized. In-flight results from “Chibis-M” microsatellite are provided proving general control performance.