Review of primary spaceflight-induced and secondary reloading-induced changes in slow antigravity muscles of rats.

We have examined the light and electron microscopic properties of hindlimb muscles of rats flown in space for 1-2 weeks on Cosmos biosatellite flights 1887 and 2044 and Space Shuttle missions Spacelab-3, Spacelab Life Sciences-1 and Spacelab Life Sciences-2. Tissues were obtained both inflight and postflight permitting definition of primary microgravity-induced changes and secondary reentry and gravity reloading-induced alterations. Spaceflight causes atrophy and expression of fast fiber characteristics in slow antigravity muscles. The stresses of reentry and reloading reveal that atrophic muscles show increased susceptibility to interstitial edema and ischemic-anoxic necrosis as well as muscle fiber tearing with disruption of contractile proteins. These results demonstrate that the effects of spaceflight on skeletal muscle are multifaceted, and major changes occur both inflight and following return to Earth's gravity.     

Cardiovascular effects of simulated zero-gravity in humans

Head-down and head-up [correction of heat-up] tilted bedrest (5 degrees) and head out water immersion (HOWI) for 6 hr were compared. Parameters: Cardiac output (rebreathing method), blood pressure (arm cuff), forearm blood flow (venous occlusion plethysmography), total peripheral (TPR), and forearm vascular (FVR) resistances, Hct, Hb, relative plasma volume (PV) changes, and plasma catecholamines (single-isotope assay). During HOWI there was as expected a decrement in TPR, FVR, Mean arterial pressure (MAP, from 100 to 80 mmHg), Hct, and PV, and--as a new finding--catecholamines, which were 30-50% lower compared with both +5 and -5 degrees bedrest. During head down tilt, MAP was elevated (to 100-110 mmHg) and catecholamines did not fall, while TPR and EVR slowly decreased over 6 hr. HOWI is a stronger stimulus than -5 degrees bedrest, probably because HOWI elevates central venous pressure more markedly emptying the peripheral veins, while bedrest permits a distension of veins, which induces an increase in sympathetic nervous activity.     

The past and future of the earth-moon system

The lunar orbit is presently expanding due, we believe, to tidal friction, i.e. the attraction of the moon for the tides it raises on the rotating Earth. The Moon may therefore have been significantly closer to the Earth in the distant past, a point of great interest to those studying the lunar origin. This work presents the results of the integration of the equations which govern the rates of change of the lunar orbit elements and the angular momentum of the Earth. Results are presented for both the past and future of the Earth-Moon system.     

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.     

A three-dimensional plasma and energetic particle investigation for the wind spacecraft

This instrument is designed to make measurements of the full three-dimensional distribution of suprathermal electrons and ions from solar wind plasma to low energy cosmic rays, with high sensitivity, wide dynamic range, good energy and angular resolution, and high time resolution. The primary scientific goals are to explore the suprathermal particle population between the solar wind and low energy cosmic rays, to study particle accleration and transport and wave-particle interactions, and to monitor particle input to and output from the Earth's magnetosphere.Three arrays, each consisting of a pair of double-ended semi-conductor telescopes each with two or three closely sandwiched passivated ion implanted silicon detectors, measure electrons and ions above 20 keV. One side of each telescope is covered with a thin foil which absorbs ions below 400 keV, while on the other side the incoming <400 keV electrons are swept away by a magnet so electrons and ions are cleanly separated. Higher energy electrons (up to 1 MeV) and ions (up to 11 MeV) are identified by the two double-ended telescopes which have a third detector. The telescopes provide energy resolution of E/E0.3 and angular resolution of 22.5°×36°, and full 4 steradian coverage in one spin (3 s).Top-hat symmetrical spherical section electrostatic analyzers with microchannel plate detectors are used to measure ions and electrons from 3 eV to 30 keV. All these analyzers have either 180° or 360° fields of view in a plane, E/E0.2, and angular resolution varying from 5.6° (near the ecliptic) to 22.5°. Full 4 steradian coverage can be obtained in one-half or one spin. A large and a small geometric factor analyzer measure ions over the wide flux range from quiet-time suprathermal levels to intense solar wind fluxes. Similarly two analyzers are used to cover the wide range of electron fluxes. Moments of the electron and ion distributions are computed on board.In addition, a Fast Particle Correlator combines electron data from the high sensitivity electron analyzer with plasma wave data from the WAVE experiment (Bougeretet al., in this volume) to study wave-particle interactions on fast time scales. The large geometric factor electron analyzer has electrostatic deflectors to steer the field of view and follow the magnetic field to enhance the correlation measurements.     

Some active galactic nuclei as cosmological probes

A method of using AGNs as cosmological probes and some recent results are discussed. The method is based on fitting the Hedgehog model to observations of spectra, structure and polarization of AGN radio emission and time variations of the observed quantities. If red shifts of selected AGNs are known, extragalactic distances, the Hubble constant and the deceleration parameter of the Universe can be measured using only radio observations. Recent results may give new strong arguments for the basic model to be in agreement with observations of variable spectra and structure of many AGNs, and may allow preliminary selection of AGNs for further use.     

Observation of fundamental magnetoplasma emissions excited in magnetosphere by modulated electron beams

There were several cases when modulated electron beam had been injected from APEX satellite into an otherwise unmodified ionospheric plasma. The beams were formed from 2 μs pulses repeated at a rate of 40kHz. Injections took place in the altitude range 400–1100km over Europe. The onboard receiver connected to the dipole antenna swept the frequency interval 1–10 MHz in 1 sec. Due to a relatively narrow receiver bandwidth (15 kHz), moderate frequency step (50 kHz), slow changes of f_n and f_c (local electron plasma and gyro frequencies) fine structure of excited emissions was detected. In many cases, a very prominent doublet could be convincingly identified as a (f_n,f_u=sqrt(f_n^*f_n+f_c^*f_c)) band, with f_n practically equal to the local plasma frequency in the unperturbed ionosphere. Determination of plasma frequency is of prime importance in analysis of complex structures composed from various harmonics f_n,f_c,f_u. Complexity is manifested as coalescing of various harmonics with maxima shifted from nominal frequencies or splitting them into components due to mixing of local and propagation effects. Despite the existence of strong emissions on frequencies characteristic for the unperturbed ionosphere, very strong broadcasting transmissions are frequently cut off, even when the beam is directed upward. Most typical spectra are discussed.     

Response of the electron energy distribution to an artificially emitted electron beam: Apex experiment

The paper is based on the electron and ion energy spectra measurement on board the main spacecraft of the APEX mission. During the active phase of the experiment an intense electron beam was emitted from the main satellite. The basic cycle of the electron injection is formed by current pulses of different frequencies, duration and intensity. The spacecraft potential changes due to the gun operation were compensated by a low energy Xe plasma generator. The data show that the response of the environment to the beam emission depends not only on injection parameters but on the spacecraft position and orientation with respect to the magnetic field as well. The typical response is an increase of the intensity of the low energy (less than 1 keV) electrons in all directions. In addition, strong field aligned fluxes of electrons and/or ions are observed with energies below the gun energy. An attempt to classify different types of response and to find possible mechanisms which can explain the observed phenomena is made in the present paper.     

Ionospheric wave processes during HF heating experiments

Effects of ionospheric modification produced by powerful high frequency radio waves are studied using the method of field-aligned scattering of diagnostic HF radio signals. Observations of scattered HF signals have been made by the Doppler spectrum method. Analysis of the experimental data shows the appearance of quasiperiodic variations in Doppler frequency shift f_d, with periods 30–60 s during the heating cycles. Powerful HF waves are assumed to excite the Alfvén resonator generating oscillations of the magnetic field lines in the heated region and giving rise to f_d artificial variations and magnetic pulsations. In the case of continuous action of the powerful HF transmitter ionospheric waves are sometimes observed with periods 12–25 min, typical of medium-scale travelling ionospheric disturbances.     

Generation of artificial ionospheric plasma density irregularities with prescribed spectra

The creation of artificial plasma density irregularities (AI) with prescribed spectra in the ionospheric heating experiments is discussed. We show that periodic successions of powerful pulses, pumped into the F-region of the ionosphere lead to obtaining AI with the controlled stationary spatial spectrum and allow us to change power low spectral index 2β at least from 2β = 2.2 to 2β = 3.4 by changing of the powerful pulse time schedule.