Telerobotics: problems and research needs

With major emphasis on simulation, a university laboratory telerobotics facility permits problems to be approached by groups of graduate students. Helmet-mounded displays provide realism; the slaving of the display to the human operator's viewpoint gives a sense of `telepresence' that may be useful for prolonged tasks. Using top-down 3-D model control of distant images allows distant images to be reduced to a few parameters to update the model used for display to the human operator in a preview model to circumvent, in part, the communication delay. Also, the model can be used as a format for supervisory control and permit short-term local autonomous operations. Image processing algorithms can be made simpler and faster without trying to construct sensible images from the bottom. Control studies of telerobots lead to preferential manual control modes and, in this university environment, to basic paradigms for human motion and thence, perhaps, to redesign of robotic control, trajectory path planning, and rehabilitation prosthetics. Speculation as to future industrial drives for this telerobotic field suggests efficient roles for government agencies such as NASA     

Geometric aspects of long-term noncoherent integration

Long-term integration is defined as integration, perhaps interrupted, over time periods long enough for targets to move through volumes in space resolvable by the radar. Because the motion of the target is unknown prior to detection, long-term integration must be performed along multiple paths representing plausible target paths. The geometry of such a set of integration paths affects detection performance in several ways. The simplest implementation of long-term integration, using constant radial velocity paths, is investigated. The effects of path geometry on detection is quantified and optimized for a target whose motion is nearly radial but otherwise unknown     

A noise insensitive solution to an ambiguity problem in spectralestimation

The instantaneous frequency measurement (IFM) receiver is capable of measuring the center frequency of single frequency pulses over a wide range (bandwidth) of center frequencies. Because of various constraints, the frequency resolution requirement results in long correlator delay times that reduce the single correlator bandwidth. A large bandwidth can be achieved only if two or more correlators are used. The problem of estimating frequency is then reduced to the simultaneous congruence problem of number theory. A design procedure is presented for solving the congruence problem for a given amount of noise protection, a stated frequency resolution, a minimum bandwidth, and a fixed level of precision (bits) in the IFM receiver     

Spectroscopic study of plasma parameters for solar active regions and flares

Results are given of the study of active regions and flares by a high resolution Mg XI ion spectra obtained aboard rockets and a satellite. It is shown that there is a noticable similarity in the physical conditions in the plasma of active regions and flares. Plasma of both sources consists okf a thermal component with the temperature T ～ 2.?3.10⁶K for active regions and T ～ 1.5?2.5.10⁷K for flares and in both cases of a relatively small number (～ 1–5%) of suprathermal electrons with an energy E ～ 3–6 kT.     

Effects of prolonged exposure to space flight factors for 175 days on lettuce seeds

We have studied the effects of prolonged (up to 175 days) exposure of $\text{Lactuca sativa}$ seeds to space flight factors, including primary cosmic radiation heavy ions. The data obtained evidence a significant fourfold increase ofs pontaneous mutagenesis in seeds both with regard to the total number of aberrant cells as well as the formation of single cells with multiple aberrations. Comparison of the present experiment with earlier works shows that the frequency of such aberrations increases with the duration of the flight.     

What auroral electron and ion beams tell us about magnetosphere-ionosphere coupling

The electron and ion beams which have been detected on many rockets and satellites are of particular interest because beam particles carry information about both the ionosphere and the magnetosphere out to the distant tail. Stability analyses have shown that even the most dramatic beams have evolved until the particle distribution functions are only weakly unstable. The shortest plasma wave growth lengths in the auroral region are usually comparable to the size of an arc. The resulting clearest electron beams generally are relatively minor features of distribution functions which are dominated by plateaus, loss cones, broad or stretched out field aligned features, and hot or cold isotropic components. The true electron beams therefore represent a small fraction of the total electron number density. Ion beams carry a much larger fraction of all ions, but also are only weakly unstable. The electron beams seen at low altitudes can drive whistlers (both electromagnetic and electrostatic, including lower hybrid waves) and upper hybrid waves, which may be particularly intense near electron gyroharmonics. Ion beams can drive low frequency electromagnetic waves that are related to gyrofrequencies of several ion species as well as ion acoustic and electrostatic ion cyclotron waves. These latter waves can be driven both by the drift of ion beams relative to cold stationary ions and by the drift of electrons relative to either stationary or drifting ions. Abrupt changes or boundaries in the electron and ion velocity space distribution functions (e.g. beams and loss cones) have been analyzed to provide information about the plasma source, acceleration process, and regions of strong wave-particle interactions. Fluid analyses have shown that upgoing ion beams carry a great deal of momentum flux from the ionosphere. This aspect of ion beams is analyzed by treating the entire acceleration region as a black box, and determining the forces that must be applied to support the upgoing beams. This force could be provided by moderate energy (10's of eV) electrons which are heated near the lower border of the acceleration region. It is difficult to use standard particle detectors to measure the particles which carry electric current in much of the magnetosphere. Such measurements may be relatively easy within upgoing ion beams because there is some evidence that few of the hard-to-measure cold plasma particles are present. Therefore, ion beam regions may be good places to study fluid or MHD properties of magnetospheric plasmas, including the identification of current carriers, a study of current continuity, and some aspects of the substorm and particle energization processes. Finally, some of the experimental results which would be helpful in an analysis of several magnetospheric problems are summarized.     

Organisation of a unified system of energetic calibration of X-ray experiments

X-ray data obtained by the Prognoz 5,6,7 and 8 hard X-ray photometers are compared with the measurements carried out by similar instruments aboard the Solrad 11, ISEE 3, SMM and Hinotori satellites. Using the method of relative amplitude analysis, the apparent disagreement in the energy discrimination level calibration between the instruments is pointed out. The results of the comparison and the possible sources of disagreement are given. We suggest an international effort be made to develop a system of uniform pre-launch calibration of photometers based on a reference calibration source.     

CCRS C/X-airborne synthetic aperture radar: An Rand D tool for the ERS-1 time frame

The airborne synthetic-aperture radar (SAR) system developed for the Canada Centre for Remote Sensing (CCRS) is described. It consists of two radars, at C-band and X-band. Each radar incorporates the following features: dual-channel receivers and dual-polarized antennas; a high quality, 7-look, real-time processor; a sensitivity time control for range-dependent gain control; a motion-compensation system for antenna steering in azimuth and elevation; and baseband I and Q signal phase rotation. The system also uses a high-power transmitter with a low-power back-up. The SAR maps to either side of the aircraft, at high or low resolution, at incidence angles which in high resolution span 0° to 80°. Radar operating parameters, data products, key specifications and the motion compensation scheme used are presented. Properties of the real-time imagery are discussed and examples of C-band SAR data in the three operating modes are given