Radiation noise in a high sensitivity star sensor

An extremely accurate attitude determination was developed for space applications. This system uses a high sensitivity star sensor in which the photomultiplier tube is subject to noise generated by space radiations. The space radiation induced noise arises from trapped electrons, solar protons and other ionizing radiations, as well as from dim star background. The solar activity and hence the electron and proton environments are predicted through the end of the twentieth century. The available data for the response of the phototube to proton, electron, gamma ray, and bremsstrahlung radiations are reviewed and new experimental data is presented. A simulation was developed which represents the characteristics of the effect of radiations on the star sensor, including the non-stationarity of the backgrounds

Planned improvements to the Owens Valley frequency-agile interferometer

Three small antennas will be added to the OVRO interferometer to form a five-element solar-dedicated array. This would provide up to 7 or 10 baselines (compared to the present 1 or 3). This would be sufficient to apply microwave diagnostics to most active region and burst sources. By using frequency-synthesis it would also provide an imaging capability comparable to that of an approximately 100 baseline interferometer. Expansion of the array is discussed

Arthur M. Okun, 1928-1980

tribute, rememberance

Collisional damping of surface waves in the solar corona

The damping of surface waves by viscosity and heat conduction is evaluated. For the solar corona, it is found that surface waves dissipate efficiently only if their periods are shorter than a few tens of seconds and only if the background magnetic field is less than about 10 Gauss. Heating of quiet coronal regions is possible if the coronal waves have short periods, but they cannot heat regions of strong magnetic field, such as coronal active region loops

A New Technique for System-to-system Transfer of Surface Data

The purpose is to describe a recently developed technique aimed at providing a universal interface between surface types. In brief, a software package was developed which functions a common denominator of CAD/CAM surface types. This software enable one to convert from any given surface representation to any other target representation. The tiles maintain the same slope continuity as the target surface gram, bicubic patches are used since they allow one to match point, slope, and twist vectors to the target surface. Thus, slopes can be continuous or discontinuous as they are on the target surface. The patches can be of lower order if desired. For example, if only point information is available, the patches produced will be bilinear; however, the number of patches required is likely to increase correspondingly. The patches can be of higher order although many systems will not accept patches of more than order four. The final result of the program is a rectangular grid of bicubic patches. The patches fit the target surface exactly at their corners. Also, the patch corners have the same tangent and twist vectors. Adjacent patches will have slope continuity, unless a discontinuity was indicated by the target surface

Catastrophe Design - Or How To Behave Like a Worm

The number of accidents which are caused by the existence of defects in engineering structures can be reduced in two ways, By diminishing the number and size of the defects, either by making the structure more carefully in the first place or by using better inspection methods in service - or by some combination of the two. By designing structures which are inherently safer - that is to say less susceptible to the presence of defects. An \u27ideal\u27 structure could be shot full of holes and still not break. In fact there will always be some defects in every structure for no manufacturing process and no inspection procedure can be perfect. Furthermore defects will accumulate in a structure between inspections due to fatigue, corrosion, accidental impacts, bad servicing, enemy action and so on. This paper is therefore about the philosophy of the imperfect structure. Since Nature has to deal with similar problems - because no plant or animal is perfect - I am making no apology for using analogiffi and examples from the new and expanding and exr.iting discipline of biomechanics. That is to say from the science of the mechanical strength of living structures