The infrared imaging channel of the IKS instrument for detection of Comet Halley nucleus

The imaging Channel of the IKS Instrument placed on board the Vega fly-by probes will perform measurements of the infrared emission of the central region of Comet Halley at distances in the 10⁴ ? 10⁵ km range. An encoding wheel analyses one spatial frequency of the infrared image during the whole fly-by. Inversion of this measurement will give low resolution brightness profiles of the nucleus and its immediate surroundings, in two wave-length bandpasses and in two directions of analysis.     

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.     

Shock sensitivity of nitromethane with well defined hot spots distribution

The behavior of nitromethane under the action of a plane shock wave presenting local overpressures is experimentally analysed. The role of hot spots and the successive activation of new reaction sites are clearly evidenced. The optical observations made during the build-up to detonation and the measured shock sensitivities support a model of initiation for heterogeneous explosives.     

Planetary radio astronomy experiment for Voyager missions

The planetary radio astronomy experiment will measure radio spectra of planetary emissions in the range 1.2 kHz to 40.5 MHz. These emissions result from wave-particle-plasma interactions in the magnetospheres and ionospheres of the planets. At Jupiter, they are strongly modulated by the Galilean satellite Io.As the spacecraft leave the Earth's vicinity, we will observe terrestrial kilometric radiation, and for the first time, determine its polarization (RH and LH power separately). At the giant planets, the source of radio emission at low frequencies is not understood, but will be defined through comparison of the radio emission data with other particles and fields experiments aboard Voyager, as well as with optical data. Since, for Jupiter, as for the Earth, the radio data quite probably relate to particle precipitation, and to magnetic field strength and orientation in the polar ionosphere, we hope to be able to elucidate some characteristics of Jupiter auroras.Together with the plasma wave experiment, and possibly several optical experiments, our data can demonstrate the existence of lightning on the giant planets and on the satellite Titan, should it exist. Finally, the Voyager missions occur near maximum of the sunspot cycle. Solar outburst types can be identified through the radio measurements; when the spacecraft are on the opposite side of the Sun from the Earth we can identify solar flare-related events otherwise invisible on the Earth.     

Rocket measurements of mesospheric ionization irregularities

The Langmuir-probe technique for measurement of electron concentration in the mesosphere is capable of excellent altitude resolution, of order 1 m. Measurements from nine rocket flights frequently show small-scale ionization structures in the altitude region 60–90 km. These are believed to be identical with regions of strong coherent backscatter seem by VHF radars at Jicamarca, Peru and Urbana, Illinois. They are believed to represent intermittent turbulence attributable to nonlinear interaction of waves in the mesosphere. Parameters of the turbulent regions are estimated.     

Compensating a Recursive MTI Filter for Missing Pulses

Four methods of compensating a recursive, double-delay movingtarget indictor (MTI) cltter-cancellation filter for missing pulses were simulated and compared. One technique involving feedback from the delay outputs gave an average frequency response closely approximating that of the unperturbed filter.     

An Implementation of the Multidimensional Modified LMS Algorithm

An implementation of the multidimensional modified LMS algorithm is provided from its relationship to a recently developed class of lhyperstable adaptive filters.