The implantation of life on Mars: feasibility and motivation.

Environmental conditions on Mars are extremely hostile, and would be destructive to any organisms which might arrive there unprotected to-day. However, it is a biocompatible planet. Its unalterable astrophysical parameters would allow the maintenance of a much thicker, warmer carbon dioxide atmosphere than that which currently exists. Though very cold (averaging about -60 degrees C), highly oxidizing and desiccated, Mars may possess substantial quantities of the materials needed to support life--in particular, water and carbon dioxide. A general scenario for implanting life on Mars would include three main phases: (1) robotic and human exploration to determine whether sufficiently large and accessible volatile inventories are available; (2) planetary engineering designed to warm the planet, release liquid water and produce a thick carbon dioxide atmosphere; and (3) if no indigenous Martian organisms emerge as liquid water becomes available, a program of biological engineering designed to construct and implant pioneering microbial communities able to proliferate in the newly clement, though still anaerobic, Martian environment. The process of establishing an ecosystem, or biosphere, on a lifeless planet is best termed 'ecopoiesis.' This new word, derived from Greek, means 'the making of an abode for life.' It is by no means clear whether ecopoiesis on Mars is scientifically possible or technologically achievable. Thus we urge that it be one of the objectives of space research during the next century to assess the feasibility of ecopoiesis on Mars.     

Exact Detection Performance for Broadband Correlators

The detection of a broadband plane wave in an isotropic noise field is considered. The detection statistic used is the cross correlation of the sampled output from two sensors where the sampling rate equals the Nyquist rate and the time delay is an integer multiple of the sampling period. By restricting the number of points in the cross correlation to be even, the detection and false-alarm probbilities are obtained in closed form. Numerical results are presented for several special cases.     

Measurements of LET spectra and comparison to models.

We present measurements of LET spectra for near earth orbits with various inclinations and altitudes. A comparison with calculated LET spectra shows that the contribution from direct ionizing galactic cosmic rays is well described by the models. An additional contribution to the spectra originates from stopping protons and from nuclear interactions of particles with material. In the case of an interaction a large amount of energy is deposited in a small volume by target recoils or target fragments. These events will be called short range (SR) events. For a low inclination orbit radiation belt protons are the main source of these events while galactic protons become more important when increasing the inclination to near polar orbits. We show that the contribution of SR events for orbits with low altitude (324 km) and 57 degrees inclination is comparable to that for an orbit with 28 degrees inclination at a high altitude (510 km).     

Review of basic medical results of the Salyut-7--Soyuz-T 8-month manned flight.

This paper presents the results of medical investigations performed in the Salyut-7 8-month mission in which a professional physician took part. The paper contains anthropometric measurements, results of investigating the vestibular function, cardiovascular function at rest and in response to multi-step tests (with emphasis on echocardiographic measurements), metabolic parameters and hormonal status. It also discusses medical aspects of the extravehicular activity. The medical investigations, although some new methods were applied, provided the continuity of methodical approaches and data accumulated in previous missions.     

Can late effects of neutron irradiation in man be estimated from early responses?1

Slowly-developing tissue changes after neutron irradiation should be more easily predicted from acutely-developing injury than is the case with X rays. The difference between tissue responses to neutrons and X rays is that cell survival in both rapidly and slowly responding tissues is a direct logarithmic function of neutron dose, at least up to about 3 Gy, whereas the X-ray dose-survival relationship differs between the two types of tissue: the target cells for late injury are more susceptible to killing from accumulation of sub-lethal X-ray injury and hence the survival curve diverges from its initial essentially linear region more rapidly than does that for the target cells for acute injury.     

Advanced communications satellite technology

Technology drivers for commercial communications satellites are examined based on the efficient use of spacecraft mass which is to be accomplished by increasing the efficiency of the microwave power amplifiers and antenna feed systems used for communications satellites, such as the INTELSAT series. The history of the INTELSAT series of satellites, the late 1980s market and available technology, and future directions of development are considered. Emphasis is on multibeam solid-state antennas, microwave switch matrices, solid-state power amplifiers, and the use of several filter modes in one physical cavity. By using quasimonolithic solid state techniques in a class B amplification mode they have achieved 40-60% efficiencies, compared with 20% for the conventional travelling wavetube amplifiers. It is concluded that technology directed towards improving the economics of satellite communications will continue to be a major driver of future communications satellite payloads. Through their use and their extension, the authors foresee more than doubling the telephone channels per satellite from the current 80000 to perhaps 200000 by the turn of the century     

The electrolytical processes in dirty ices: implications for origin and chemistry of minor bodies and related objects.

Many moonlike bodies (M approximately or = 1 Moon) beyond the Martian orbit contain large amounts of dirty ice (approximately 50%) forming thick mantle with the solid phase thermal convection. When a body moves through the inter- or nearplanetary magnetized plasma, electric current is generated in the body and its environment. The current passing through a dirty ice containing up to 10% of organic admixtures produces a lot of electrochemical effects which have a profound impact on its composition. At this stage one can hardly say something definite concerning changes experienced by organics. The changes must occur inevitably and can be of a rather unexpected and far-reaching nature, so deserving a close study. Another obvious effect is a volumetric electrolysis of ice containing alien inclusions. The electrolysis products accumulate in ice in the form of a solid solution which is capable of detonation at 15-20 wt.% of 2H2 + O2. If M > or = 1 Moon (Galilean satellites, Titan), the body loses in explosion a part of its mass in the form of vapor and ice fragments (=short-period comet nuclei), whereas if M < or = 0.2 Moon, the body breaks up totally (the Main Belt asteroids origin approximately 3.9 Byr ago). 2H2 + O2 containing cometary nuclei are capable of burning or suffer new explosions when receiving an additional energy. The combustion in the sublimation products containing also light organics and 2H2 + O2 explains unexpected energetics and nearnuclear chemistry of Comet P/Halley (e.g. great abundances of negative and positive ions, atomic carbon, CO over CO2, origin of CHON particles etc) and its distant outbursts correlated, possibly, with the Solar activity. Thus the electrochemical processes in the dirty ice with organics, along with its subsequent thermal, radiative etc. processing, open up new potentials for explanation and prediction of quite unexpected discoveries.     

Dynamic dissipative compensators for multibody flexible spacestructures

The stability characteristics of dynamic dissipative compensators are investigated for multibody flexible space structures having nonlinear dynamics. The problem addressed is that of proving asymptotic stability of dynamic dissipative compensators. The stability proof uses the Lyapunov approach and exploits the inherent passivity of such systems. For such systems these compensators are shown to be robust to parametric uncertainties and unmodeled dynamics. The results are applicable to a large class of structures such as satellites with multiple payloads and space-based manipulators     

Corotating interplanetary streams and associated ionospheric disturbances at Venus and Earth

During the summer of 1979, solar coronal structure was such that a sequence of recurrent regions produced a corresponding sequence of corotating solar wind streams, with pronounced downstream signatures. One of these stream events passed Earth on July 3, and was observed later at Venus late on July 11th, with similar characteristics. Corresponding in-situ measurements at Earth from the Atmospheric Explorer-E satellite and at Venus from the Pioneer Venus Orbiter are examined for evidence of comparable perturbations of the planetary ionospheres. The passage of the stream shock front is found to be associated with pronounced fluctuations in n(0⁺) which appear as pronounced local depletion of ion concentrations in both ionospheres. The ionosphere disturbances appear to be closely associated with large variations in the solar wind momentum flux. The implied local ionospheric depletions observed at each planet are interpreted to be the consequence of plasma redistribution, rather than actual depletions of plasma.     

On Increasing Usable MTI Filter Bandwidth by Removing Linear-Phase Constraint

It has been shown in the literature that the linear-phase constraint of finite-duration impulse-response (FIR) digital filters can, under certain circumstances, be effectively traded either for a better filter amplitude response or a reduction in the number of filter coeficients. It is shown that such a tradeoff can be exploited for moving target indicator (MTI) radar signal processors to increase the usable bandwidth for target detection. Although it is demonstrated that the increase is significant for narrowband (ground) clutter, it is negligible for wideband (weather) clutter.