Impact of FGGE buoy system data on southern hemisphere meteorology

Although a definitive evaluation of the performance of the FGGE buoy system will take some time, it is already clear that the buoy data have made a major contribution to both operational and research aspects of southern hemisphere meteorology. The buoys have provided a wealth of information on both the surface drift and sea surface temperature characteristics of the Southern Ocean. Their impact on operational synoptic analysis and prediction in the southern hemisphere during the FGGE year was substantial. The buoy pressure data generally provided an adequate basis for delineation of the large scale flow over the middle and high latitude oceans in a way that has not been possible before. Preliminary evaluations of the impact of the buoy data on numerical prediction have indicated small but significant improvements in skill scores. Regional Forecasting Centres in the southern States of Australia have found that the more accurate delineation of synoptic systems over the oceans to the south has contributed significantly to forecast performance in their Regions. Use of the buoy data, and synoptic analyses based on the buoy data, to examine particular problems in southern hemisphere meteorology is now underway.     

Tracking and communication in long-duration flights

Balloon location techniques have developed along the same lines as ship and aircraft navigation systems. Early NCAR balloon flights were located by sun angle measurements versus time and magnetic field measurement, much the same way that Captain Cook used to navigate his sailing vessel. Others have used radio systems developed for ship and aircraft location such as Omega, Loran, radio direction finding, Variable Omnidirectional Radio (VOR) and radar transponders.     

Radio emissions from Uranus

The Voyager Planetary Radio Astronomy Experiment detected strong 40 kHz to 850 kHz radio emissions from Uranus after closest approach and somewhat weaker emissions, but none above 100 kHz before closest approach, on the dayside of Uranus. The time variations of these emissions closely match Uranus' rotation, in a period of 17.24 h, and are evidently controlled by the strength and shape of its magnetic field. Throughout the entire encounter the polarization of the emission was approximately lefthand, corresponding to extraordinary mode. The emission associated with the nightside pole was a relatively smooth continuum (free of bursts) with a Gaussian-shaped rise and fall at low frequencies, 200 kHz for example, but a Gaussian with a central dip nearly to zero lasting a little less than two hours at frequencies above 400 kHz. Half a rotation later, when Voyager was near the magnetic equator of Uranus and farthest from the nightside dipole tip, the continuum emission was absent, but very strong, narrowband impulsive bursts appeared. Voyager successfully acquired one brief (24 seconds long) record of high time resolution radio observations in the range 500 to 700 kHz. This record, which was made near closest approach, shows a hierarchy of fast variations. Several days after closest approach, at the times of bowshock crossings outbound, the continuum emissions were modulated strongly in a manner suggestive of the presence of waves in the bowshock regions.

The instrument also recorded possible Uranian electrostatic discharges, vertex early arcs occurring in sequences of more than a dozen events with approximately ten-minute period, and, as early as several days before closest approach in the frequency range below 100 kHz, very intense isolated bursts lasting tens of minutes.     

Observations of the profiles of solar UV emission lines and their analysis in terms of the heating and production of the corona

Observations of the solar spectrum have been made between 1200–2200 with high spectral resolution. The results were obtained with an all-reflecting echelle spectrograph carried by a stabilized Skylark rocket launched in April 1970. Measurements of the profiles of a number of emission lines due to Siii, Cii, Siiii and Civ formed in the temperature range 10⁴-10⁵ K, indicate ion energies which are considerably in excess of the electron temperatures derived from the ionization balance. Since the ion/electron relaxation time is very short the observed ion energies cannot correspond to an ion temperature and hence a non-thermal mechanical energy component exists in the transition zone.It is postulated that the non-thermal energy component represents the actual mechanical energy responsible for the heating of the corona, and, that, it is propagated as an acoustic wave. On this basis and with a preliminary estimate of the reflection from the transition zone, a flux of 3 × 10⁵ erg cm ^-2 s ^-1 is established as entering the corona. This value is in agreement with estimates of the total energy loss from the corona due to conduction, radiation and the solar wind, thus establishing a gross energy balance.Theoretical calculations are currently underway to establish the physical nature of the atmosphere which would result from such a propagating flux. At the present time this has been carried out for an atmosphere in hydrostatic equilibrium and the energy balance equation solved. A preliminary temperature structure which results is shown in Figure 1, together with the derived distribution in electron density. This gives a corona of the right temperature and density but the observed structure deviates in detail from those derived from an analysis of the solar XUV spectrum.     

Optimum Windows for Image Registration

Two-dimensional cross-correlation techniques are applied to the problem of image registration under the assumption of small geometric distortion. Optimum window functions are derived for two performance measures of interest: peak-to-sidelobe ratio and mean-square registration error. The latter is examined in terms of the contribution caused by noise and the contribution caused by geometric distortion. A generalized Lagrange multiplier approach is used to derive approximate solutions assuming random images. The case of Gaussian autocorrelation functions is examined in detail. Results of applying the theoretically derived window functions to real data are presented, showing significant improvement in correlator performance.     

Detection and range/Doppler estimation for colocated sensors

The problem of multisensor detection and high resolution signal state estimation using joint maximum a posteriori detection and high order nonlinear filtering techniques is addressed. The model-based fusion approach offers the potential for increased target resolution in range/Doppler/azimuth space. The approach employs joint detection/estimation filters (JDEF) for target detection and localization. The JDEF approach segments the aggregate nonlinear model over the entire target resolution space into a number of localized nonlinear models by partitioning the resolution space into a number of resolution subcells. This partitioning leads to extremely accurate state estimation. The proposed JDEF approach has a built-in capability for automatic data alignment from multiple sensors, and can be used for centralized, decentralized, and distributed data fusion.     

Thermospheric signature of magnetospheric energy dissipation

Dissipation of magnetospheric energy leads to an upper atmospheric disturbance zone whose extent varies with local time. A statistical analysis of ESRO 4 data reveals that (1) in the afternoon/evening sector the boundary location is determined by the region of electric current dissipation along the auroral oval; (2) in the midnight/early morning sector dynamical effects extend the disturbance zone to lower latitudes; and (3) in the late morning sector direct heating effects are superimposed on the residuals of the early morning disturbance.     

Potential experiments with superconducting magnets in Earth orbit

Several experiments that can be performed in Earth orbit with a superconducting magnet are discussed. They are divided into 2 classes, pure plasma physics experiments that can be performed in near Earth orbit and planetary magnetosphere simulation experiments that are best conducted in weak background fields distant from the Earth. The later are all based on the Minimag concept where plasma is directed toward a large dipolar magnet in Earth orbit to form a model miniature magnetosphere. Several experiments that cannot be performed in ground based laboratories and tests that cannot be made in the real magnetosphere can be carried out in Earth orbit. The creation of a miniature model of the magnetosphere (Minimag) forms the basis for several of these experiments.     

Analysis of a Multiplicative Feed System for Monopulse Tracking Applications

In angle tracking antenna applications, the angle sensing boresight accuracy capabilities are important. The ability of an antenna to precisely determine the bearing angle to a point source is determined by the slope of the control function pattern at boresight. In the presence of extraneous interference, the magnitudes of the sidelobe and backlobe responses are important. Control pattern slope (angular sensitivity) is primarily a function of aperture illumination. It can be described by a current distribution in intensity and phase at every point. Once distribution is defined, lobe structure is defined by the associated transform. When more than one feed is used, the distribution will be a vector sum of the individual feed distributions. The resulting secondary pattern can be defined in terms of the amplitude distribution and the phase center locations of the contributing feeds. With a four-horn monopulse configuration, the feed phase centers are displaced from the boresight axis. Placing the phase centers on the boresight axis by rotating the feeds through 45 degrees results in a different set of intensity and phase values. A quite different secondary pattern results. The control function obtained by the subtraction of the powers from a paired set of on-axis feeds results in a lower sidelobe level than that obtained with a conventional monopulse combiner for a given feed taper.