Spatial structure of Pc5 waves in the outer magnetosphere according to observations onboard the THEMIS satellites

We have analyzed oscillations in the Pc5 range recorded in the outer region of the evening magnetosphere onboard 5 THEMIS satellites when all vehicles were moving with a small distance along one and the same orbit. Gradients of the spatial structure of oscillations and fluxes of energetic protons are determined. The observed phase shifts of the oscillation field between the satellites are presumably caused by their sunward (westward) propagation with azimuthal wave numbers m ～ 30–60. According the data of particle detectors, non-equilibrium character of the distribution of protons is found: their non-monotonous distribution in energy and sharp spatial heterogeneity. The calculated parameters of plasma and oscillations are not consistent with the assumption on drift-mirror instability as a source of the oscillations. A complete theory of these waves should include effects of the finite Larmor radius and simultaneous existence of two types of nonequilibrium plasma.     

Application of laser diode beacons for determination of coordinates of space and ground objects

We consider the principles of constructing measurement schemes with optical autonomous laser diode beacons for space and ground objects. The structure, functional scheme, and cyclogram of operation of such beacons are described. Possible scenarios of application of the beacons for providing high-precision localization of space and ground devices are analyzed.     

Spacecraft “Foton-M” in-flight thermal conditions

The problem of thermal conditions aboard the “Foton-M” spacecraft during its orbital flight is under consideration in this paper. The problem is very acute for performing microgravity experiments onboard of the orbital platform, because on one hand, many experiments need a definite temperature range to be performed, and on the other hand all electrical devices aboard radiate heat. To avoid uncontrolled heating of the environment special heat exchangers are used. To transport heat from different places of the capsule to heat exchanger special fans are installed given definite orientation. All the heat exchange facilities should be designed in advance being adjusted to current capsule loading and heat radiation by equipment. Thus special tools are needed predicting the capsule thermal conditions being function of equipment placement.The present paper introduces a new developed prognostic mathematical model able to forecast temperature distribution inside the capsule with account of fan induced air flows, thermal irradiation by scientific equipment and heat losses due to cooling system.     

Using radiation risk for assessment of space radiation hazard

Radiation hazard caused by exposure during a spaceflight is characterized by radiobiological consequences at all levels of organism. These consequences have a stochastic nature. Even deterministic effects are basically random quantity having all attributes of such mathematical values. The radiation risk is defined in this case as an additional probability of health damage or as a death probability in extreme case. For the manned spaceflight additional peculiarity of a human’s exposure is added. A natural space radiation environment has a stochastic character because solar particle events and crew of a spacecraft can be exposed to dose from background level up to lethal one.The report presents a procedure of radiation risk assessment for quantitative expression of radiation hazard level during a flight and using this value for developing protection recommendations. It is emphasized that the risk value is connected specifically with the time interval of possible hazard’s existent. The form of risk representation must be chosen depending on a time scale of radiobiological processes induced by the exposure (expressing in fact the radiation hazard model). Surviving function specified for the crewmember mortality rate changed by the professional exposure must be used for risk calculation. Solar particle events determine a stochastic character of radiation environment in space that must be taken into account for a risk assessment. The reliability of radiation risk assessment can be used for this goal.     

Through optimization of branching injection trajectories by the Pontryagin maximum principle using stochasticmodels

A problem of the through optimization of aerospace vehicle branching ascent trajectories in view of atmospheric disturbances (wind and thermodynamic parameters variations) and constraints on admissible areas of separated parts fall points is considered. The problem solution is based on the Pontryagin maximum principle. The problem with a continuum of branches corresponding random disturbances was reduced to the more standard one with a finite set of branches being the most critical (at the given event probability) with regard to the functional considered. The analytical synthesis of such critical disturbances profiles is obtained on basis of the Bliss formula, connecting a functional change with variations of right parts of motion equations. The developed technique and its efficiency are demonstrated by an example for a typical launcher.     

Calculation of resultant vector and principal moment of light pressure forces acting upon the spacecraft with a solar sail

Two methods of calculating the resultant vector and principal moment of light pressure forces, having an effect on a spacecraft with a composite solar sail, are compared. The first method is based on analytical formulas obtained without regard to shading of some parts of the sail by others. The second method uses a detailed geometrical model of the sail, which allows one to take such shading into account. Some part of photons falling on a sail is supposed to be reflected from it in a mirror manner, while the others are completely absorbed. The range of variation of sail orientation parameters with respect to incident solar light streams, where the first method turns out to be accurate enough, is found.     

Power law distribution in statistics of failures in operation of spacecraft onboard equipment

The possibility of using the statistics of recurrence time for extreme events is studied in this paper having in mind the problems of control and prediction of failures in spacecraft operation. The information about failures onboard satellites of various types presented by the US National Geophysical Data Center was analyzed. It was found that the probability density of recurrence intervals followed a power law of the Pareto type with an index equal to 2.3. The obtained result is consistent both with the theory of normal catastrophes and with the principle of self-organization of criticality for metastable active heterogeneous environment. A practical consequence of the obtained result consists in the fact that predictions of these extreme events should not rely on traditional models with the second-order Pearson statistics. To make predictions, the models are necessary that take into account the power law distribution of recurrence intervals for failures on satellites. The failures should be considered in these models as extreme events connected with manifestation of the space environment factors.     

Navigation support for the RadioAstron mission

A developed method of determination of orbital parameters allows one to estimate, along with orbit elements, some additional parameters that characterize solar radiation pressure and perturbing accelerations due to unloadings of reactiion wheels. A parameterized model of perturbing action of solar radiation pressure on the spacecraft motion is described (this model takes into account the shape, reflecting properties of surfaces, and spacecraft attitude). Some orbit determination results are presented obtained by the joint processing of radio measurements of slant range and Doppler, laser range measurements used to calibrate the radio measurements, optical observations of right ascension and declination, and telemetry data on spacecraft thrusters’ firings during an unloading of reaction wheels.     

Comparative Utilization of Limited Energy for Continuous and Pulse Operations

Comparative utilization of a limited amount of energy for continuous and pulse operations was investigated. Under a restriction that the amount of available energy was limited, general equations for operational hours of the energy source for given power output were derived for both continuous and pulse mode operations. This paper points out that due to various adjustable parameters available for pulse mode operation, if properly designed pulse mode operation produces longer utilization of available energy for required output power than continuous mode operation.     

Conical Scanning System for Pioneer Jupiter Spacecraft

The concept, operation, and predicted performance of an RF tracking control system used to point the Pioneer F/G spacecraft at the Earth is described. This system employs a modified conical scanning technique called Conscan. The signal processor, the most interesting unit of the system, is described in detail to show that it approximates a maximum likelihood estimator. The dynamic behavior of the spacecraft and the stability analysis of the system are presented, demonstrating that the system performance is basically determined by the open-loop phase and amplitude errors introduced by the antenna, receiver, and signal processor. A detailed error budget shows that the phase and amplitude errors are small. Finally, closed-loop simulation and test data are presented to verify the error budget.