Modified gradiometer technique applied to Double Star (TC-1)

On TC-1 (Tan Ce 1), the equatorial spacecraft of the Double Star mission, a strong spin-synchronized magnetic interference from the solar panels was observed. In-flight correction techniques for spinning spacecraft that are based on minimizing spin tones in the spin-aligned component and in the magnitude of the ambient magnetic field are therefore not possible in this case. However, due to the fortunate situation that the spacecraft carries two flux-gate magnetometers on the same boom (at 0.5 m distance from each other), the spacecraft field effects could be removed from the spin-averaged data to achieve 0.2 nT relative accuracy, by using a gradiometer technique. Methodology and results are presented. The obtained accuracy allows the use of the data in multi-spacecraft studies together with the Cluster satellites.     

Noise-correlating radar based on retrodirective antennas

A new retrodirective antenna-based search radar system has been introduced. The suggested system uses a noise correlation technique to detect the presence and the direction of the target. Simulation and analytical results show an order of magnitude improvement in acquisition time of the radar when compared with a phased array antenna-based radar system with the same specifications, except transmit power. To the best knowledge of the authors, no radar of a comparable acquisition time has been designed to this date. Power versus acquisition time tradeoff has been compared with a phased array radar for evaluating performance of the system. The radar is self-tracking due to retrodirectivity of the antenna array, and is much easier to implement, as it does not require any phase shifters etc.     

Experiments Involving a Microwave Beam to Power and Position a Helicopter

This paper describes two different experiments involving a microwavebeam and a helicopter. The first experiment utilized a CW microwavebeam to supply a small helicopter with all of the power that it neededfor its propulsion. The second experiment utilized an unmodulated CW microwave beam for supplying a position reference to the helicopterer with respect to roll, pitch, yaw, and horizontal translation. Thesecond experiment also involved the construction of a fully articulatedhelicopter and a complete control system carried on board theli-helicopter. The paper also attempts to relate the small scale experimentsand the present state of component technology to practical, full scalemicrowave-powered helicopter systems that can operate at altitudesof up to 50 000 feet.     

Circumnutation augmented in clinostatted plants by a tactile stimulus

Dark-grown, 4-day old, $\text{Helianthus annuus}$ seedlings were rotated for 20 hr on horizontal clinostats to minimize the amplitude of circumnutation. Then a Plexiglas sheet was placed gently against the tip of the cotyledons. By time-lapse video imaging (using intermittent IR illumination to which the plants were insensitive) movements of the clinostatted plants were observed before, during, and after the period of mechanical contact. Immediately after the Plexiglas sheet was removed residual nutation increased in amplitude almost three-fold, then declined over the next 7 hr to the prestimulation level. This demonstration of enhancement of circumnutation by mechanical contact is consistent with the model of an endogenous oscillator that can be stimulated by factors other than gravity.     

Simulated microgravity does not alter epithelial cell adhesion to matrix and other molecules.

Microgravity has advantages for the cultivation of tissues with high fidelity; however, tissue formation requires cellular recognition and adhesion. We tested the hypothesis that simulated microgravity does not affect cell adhesion. Human colorectal carcinoma cells were cultured in the NASA Rotating Wall Vessel (RWV) under low shear stress with randomization of the gravity vector that simulates microgravity. After 6-7 days, cells were assayed for binding to various substrates and compared to cells grown in standard tissue culture flasks and static suspension cultures. The RWV cultures bound as well to basement membrane proteins and to CEA, an intercellular adhesion molecule, as control cultures did. Thus, microgravity does not alter epithelial cell adhesion and may be useful for tissue engineering.     

Tetrahedral Robotics for Space Exploration

A reconfigurable space filling robotic architecture has a wide range of possible applications. One of the more intriguing possibilities is mobility in very irregular and otherwise impassable terrain. NASA Goddard Space Flight Center is developing the third generation of its addressable reconfigurable technology (ART) tetrahedral robotics architecture. An ART-based variable geometry truss consisting of 12 tetrahedral elements made from 26 smart struts on a wireless network has been developed. The primary goal of this development is the demonstration of a new kind of robotic mobility that can provide access and articulation that complement existing capabilities. An initial set of gaits and other behaviors are being tested, and accommodations for payloads such as sensor and telemetry packages are being studied. Herein, we describe our experience with the ART tetrahedral robotics architecture and the improvements implemented in the third generation of this technology. Applications of these robots to space exploration and the tradeoffs involved with this architecture will be discussed.