Maximum Likelihood Elevation Angle Estimates of Radar Targets Using Subapertures

The maximum likelihood estimates of the elevation angles of two closely spaced targets within the beamwidth is considered. For an array divided into three subapertures, a simple, closed form solution is found whose accuracy compares favorably to the maximum likelihood estimate which uses all the individual elements. Simulation results are presented for the case of a radar target located over a smooth reflecting surface.     

Flow of material at the Chromosphere-Corona transition zone of the Sun

Early models of the Chromosphere-Corona transition zone of the Sun considered it to be a static plane-parallel region. From these it became clear that the layer was extremely thin and had an important role in the conduction of energy from the Corona. More recent observations show mass motions of order 10 km s^-1, which means that heating and cooling of the moving plasma has an important affect on the energy balance, while transient effects producing far higher velocities are also common. Studies of plasma motion through the zone are clearly relevant to the initial heating of material which enters the solar wind.Paper presented at the IX-th Lindau Workshop The Source Region of the Solar Wind.     

Ureilites

Ureilites are a rare group of five stony meteorites — feldsparless achondrites containing diamonds of preterrestrial origin the total weight of them being 315 carats. The whole carbon content in ureilites makes up 1.5–4.1%. Ureilites substantially differ from the other stony meteorites. In comparison with chondrites they are enriched in Mg but depleted in metal, troilite, alkaline elements. All ureilites are very similar by their structure. They contain elongated cavities generally stretched in the same direction. The structure of ureilites is an achondritic porphyric one. These meteorites consist of large olivine grains, there is less clinopyroxene (pigeonite). They contain kamacite (Ni content being 1.5–4%), troilite FeS, chromite. Carbon material is represented by diamond, graphite and organic material being present in a disequilibrium state. Two ureilites (North Haig and Dingo Pup Donga) were considerably oxidized during terrestrial weathering and contain secondary iron oxides.Diamonds are present in ureilites in thin intergrowths with graphite being disposed between silicate grains more or less evenly in the meteorite. The sizes of such black diamond-graphite aggregates are 0.3–0.9 mm. The sizes of the micromonocrystals of diamond and graphite are less than 1. The diamond-graphite aggregates contain dispersed particles of kamacite, troilite, chromite, nickelchrome, being present in very thin intergrowths with one another. Besides the usual diamond there is an admixture of lonsdaleite in the aggregates representing a hexagonal diamond with a würtzite-like structure. Lonsdaleite has been identified in the ureilites Novo Urei, Goalpara, North Haig. The diamonds of ureilites are characterized by inhomogeneities in the crystalline structure which are at least partly caused by the presence of donor nitrogen. According to the isotopic carbon composition the diamond in the meteorite Novo Urei has the value C¹³ = -5.7.The structure peculiarities of ureilites bear witness of the fact that these meteorites had been subject to the action of dynamic pressure about 300–600 kbar. The impact had taken place in cosmic space. All ureilites subdivide into two types: the first type are Novo Urei, Dyalpur, Dingo Pup Donga, the second type are Goalpara, North Haig according to the following signs: (1) olivine grains are finer in ureilites of the second type; (2) twinning is more typical of clinopyroxenes of ureilites belonging to the first type; (3) in ureilites of the first type a net-like iron distribution is observed, in ureilites of the second type kamacite plates are chiefly present between silicate grains; (4) the size of diamondgraphite intergrowths in ureilites of the first type does not exceed 0.3 mm, in ureilites of the second type it reaches 0.9 mm. Ureilites of the first type have undergone a less intensive impact than ureilites of the second type. Certain similarity of the material composition of ureilites and of the material composition of carbonaceous chondrites, the distinction of these two groups of meteorites from all other meteorites bear witness of the fact that ureilites have formed from carbonaceous chondrites during a collision of asteroid bodies in cosmic space, diamonds having been formed from the carbon material of carbonaceous chondrites.     

Missile Electronic System Hardness Assurance Program

A hardness assurance program suitable for a retaliatory or deterrent missile system is discussed. The program consists of three phases: the establishment of suitable controls and screens to ensure piece part hardness, a supplier data monitoring program to measure hardness related parameters in a timely fashion to obtain advanced warning of potential problems, and a hardness assurance verification testing (HAVT) program to periodically measure the radiation response of parts, circuits, subsystems, and systems on a sample basis to ensure proper functioning in simulated radiation environments. All of the data relevant to hardness assurance is stored in computer memory and routinely interrogated with programs which compare current results with the engineering baseline data and other data from preceding lots. Other computer programs enable statistical estimation of system response to the radiation environment with confidence based on the expanding data base provided by the HAVT program.     

Submicron lunar ejecta in the magnetosphere associated with meteor showers

Recent studies of the lunar ejecta from lunar impacts of interplanetary dust particles indicate that during favorable lunar phases, over 80% of the submicron ejecta enters the earth's magnetosphere. This “pulse” of lunar ejecta produced by the sporadic meteor background will follow the random variations of the sporadic flux. An additional enhancement of this flux can be related to major meteor showers. Since the annual periods of these showers occur during varying lunar phase angles, magnetosphere ejecta flux associated with major showers will vary depending on the coincidence of shower periods and favorable lunar phase angles. The results of an analysis of the “pulse” of ejecta flux in the magnetosphere during the Quadrantids, Geminids, Leonids, and Perseids meteor showers are presented. These results are compared to the satellite measurements of 1959 Eta and HEOS II.     

Bars — A dual bistatic auroral radar system for the study of electric fields in the Canadian sector of the auroral zone

One instrument of the Canadian Auroral Network for the Open Program Unified Study (CANOPUS) is a pulsed dual bistatic auroral radar system (BARS) for the mapping of ionospheric electric fields, using the STARE technique originated by R.A. Greenwald [14]. The Canadian system is presently in the specification and design phases, with the objective of being operational by mid-1984. This paper describes the geometry of the BARS system, the design considerations, and the planned data and control network.     

Scientific results from the pioneer Saturn infrared radiometer

The Pioneer 11 Infrared Radiometer instrument made observations of Saturn and its rings in broadband channels centered at 20 and 45 μm and obtained whole-disk information on Titan. A planetary average effective temperature of 96.5±2.5 K implies a total emission 2.8 times the absorbed sunlight. Correlation with radio science results implies that the molar fraction of H₂ is 90±3% (assuming the rest is He). Temperatures at the 1 bar level are 137 to 140 K; regions appearing cooler may be overlain by a cloud acting as a 124 K blackbody surface. A minimum temperature averaging 87 K is reached near 0.06 bars. Ring boundaries and optical depths are consistent with those at optical wavelengths. Ring temperatures are 64–86 K on the south (illuminated) side, ～54 K on the north (unilluminated) side, and at least 67 K in Saturn's shadow. There is evidence for a south to north drop in ring temperatures. Titan's 45 μm brightness temperature is 75±5 K.     

Slope Coding of Coherent Pulse-Burst Waveforms

Useful new properties are obtained with a coherent pulse-burst waveform if the FM slopes are allowed to change from pulse to pulse. A design feature using such a "slope-coded" waveform is the ability to transfer, in a controllable manner, ambiguity volume from the range ambiguity peaks to regions located between the peaks (in the frequency direction). Slope coding thus provides a useful mechanism for matching the waveform to the environment; i. e., it permits the signal designer to make some compromise between range ambiguity-peak heights and low-velocity clutter rejection.