Differential Lobing in Sidelobe Suppression Systems

The sidelobe suppression function in the secondary surveillance radar system is analyzed when separate main and control antenna are used. Their vertical lobing structures are not matched with each other, so a differential lobing pattern comes out whose maxima and minima are enveloped by smooth curves depending on vertical displacement of phase centers and horizon cutoff rates. The developed analysis provides a method for the evaluation of the system performance for any antenna configuration and for the determination of design guidelines.     

The face inversion effect in microgravity: is gravity used as a spatial reference for complex object recognition?

Complex objects are better recognized under a specific orientation. When presented upside down, a face, even very familiar, is recognized with greater difficulty than when presented upright ("Inversion effect"). Up to now it was not possible to decide whether the direction provided by gravity or the one provided by the retina and the body constitutes the spatial reference involved in this "Inversion effect". Three cosmonautes learned photographed faces on the ground and had to recognize them both on ground and on flight. Other photographed faces were learned in flight and where presented for recognition on flight. Results show that the Inversion effect is still present on flight for faces that have been learned on ground as well as for those learned on flight. Persistence of the inversion effect in 0-G shows that gravity is not involved as a spatial reference in recognition of faces. Learning and recognition performances of faces learned in flight were significantly lower than performances for faces learned on ground. A possible role of gravity in configural processing, but not in the Inversion effect, is suggested.     

Internal Gravitational Field of a Thin Homogeneous Ring

The potential of gravity forces is found inside a thin homogeneous ring when the ring’s mean radius is much larger than the diameter of its cross section. Rings with elliptic and almost circular cross sections are considered.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 4, 2005, pp. 260–268.Original Russian Text Copyright © 2005 by Kasatkin.     

Quantization and Saturation Noise Due to Analog-to-Digital Conversion of Radar Returns from Targets with Log-Normal Radar Cross-Section Distributions

An analysis of the saturation and quantization noise generated by analog-to-digital (A/D) conversion of radar returns from targets with log-normal radar cross sections is presented. The results of the analysis show that the high-cross-section tails of the log-normal distribution require higher saturation levels to be set in the A/D converter. The setting of the higher saturation level in the converter results in an increase in quantization noise. Thus the minimum achievable distortion in the output of the A/D converter signal is considerably higher than that for radar targets if their radar cross section had an exponential power distribution.     

Humans and robots: hand in grip

As we move boldly forward into the 21st century, there has rarely been a more exciting time in which to contemplate the future of space exploration. The President of the United States has made a new and ambitious commitment to exploration of the solar system and beyond. Robotic partners will play a vital role in ensuring that the Vision is truly "sustainable and affordable". Relevant science and technology will be discussed with particular emphasis on expertise from NASA Ames Research Center of which the author is Director. The likely evolution of the balance between human explorers and robotic explorers will be addressed.     

Autopoiesis and the origin of bacteria.

"Autopoiesis" is the explanatory principle for the organization of living systems, a concept directly applicable to the problematic issues surrounding the origins of life. Because it provides criteria by which a system may be judged as living, autopoiesis can be used to characterize a minimal living system. Once these defining characteristics have been established, we can extrapolate the conditions which would have made possible the emergence of earliest life. Because autopoiesis is a principle of organization, it provides a definition of living systems not restricted to specific molecules or structures--that is, to those nucleic-acid/protein/lipid cellular life forms with which we are familiar. Autopoiesis provides the conceptual and systematic framework within which any living system may be identified. In examining living systems, then, autopoiesis gives us a literally "meta-physical" view of life.