Optical coating in space

A technological appraisal of the steps required to approach the goal of in-situ optical coating, cleaning and re-coating the optical elements of a remote telescope in space is reported. Emphasis is placed on the high ultraviolet throughput that a telescope using bare aluminum mirrors would offer. A preliminary design is suggested for an Orbital Coating Laboratory to answer basic technical questions

Test for contamination of MgF2 - coated mirrors

Graphs show preflight and postflight reflectivities in percent for exposed and covered mirrors carried on the OSS-1 payload pallet during STS-3. No changes greater than 1.8 sigma were observed except for a fingerprint. Weak evidence for degradation at 1216 A and 1600 A was found in several samples. There was no difference between flight mirrors and control mirrors. Covered samples suffered more than samples exposed to the Sun, but the differences are barely significant. The exposed side of the flight mirrors were somewhat dusty. No evidence was found for permanent solar-induced or shuttle-induced deterioration. There also was no evidence on oil-pumped vacuum versus oil-free vacuum during coating

Highest Energy Cosmic Rays and results from the HiRes Experiment

The status of the field of ultrahigh energy cosmic rays is summarized, from the point of view of the latest results of the High Resolution Fly's Eye (HiRes) Experiment. HiRes results are presented, and compared with those of the Akeno Giant Air Shower Array (AGASA), plus the Telescope Array and Pierre Auger experiments. The HiRes measurements of the cosmic ray spectrum, and the observation of the GZK cutoff are presented. HiRes results on composition, searches for anisotropy, measurement of the proton-air total cross section, and shapes of shower profiles are presented.Comment: 31 pages, 18 figures, submitted to Journal of Physics

The Extremely High Energy Cosmic Rays

Experimental results from Haverah Park, Yakutsk, AGASA and Fly's Eye are reviewed. All these experiments work in the energy range above 0.1 EeV. The 'dip' structure around 3 EeV in the energy spectrum is well established by all the experiments, though the exact position differs slightly. Fly's Eye and Yakutsk results on the chemical composition indicate that the cosmic rays are getting lighter over the energy range from 0.1 EeV to 10 EeV, but the exact fraction is hadronic interaction model dependent, as indicated by the AGASA analysis. The arrival directions of cosmic rays are largely isotropic, but interesting features may be starting to emerge. Most of the experimental results can best be explained with the scenario that an extragalactic component gradually takes over a galactic population as energy increases and cosmic rays at the highest energies are dominated by particles coming from extragalactic space. However, identification of the extragalactic sources has not yet been successful because of limited statistics and the resolution of the data.Comment: The review paper including 21 figures. 39 pages: To be published in Journal of Physics

A Front-Tracking Method for the Computations of Multiphase Flow

International audienc

First Coordinated Campaign of X-ray and ground based observations of X-Persei=3U 0352+30

A coordinated campaign of simultaneous X-ray and ground-based photometric and spectroscopic observations of X Persei = 3U 0352 + 30 was organized from February 14 to March 2, 1977. The optical observations show little photometric activity, a less marked Balmer excess than in 1971-72, weaker emission than in 1970, and a nearly normal intrinsic color. The H-alpha emission is double with R about equal to V. No clear correlation with the X-ray emission was found, except for the lower intensity probably related to a lower 'activity' of the optical source. A best-fit heliocentric X-ray period of 835.05 + or - 0.15 is found