An image orthicon technique for recording meteors, developed some years ago by Hemenway at the Dudley Observatory, has recently been used at the Springhill Meteor Observatory, Ontario, for the recording of meteor spectra and combined with three other observational techniques—meteor radars, spectrographs, and a team of visual observers. Fifteen meteors, observed with the image orthicon during the August campaign in 1969, are here discussed out of a total of more than forty. Apparent visual magnitudes range from −1 to +3 and all 14 Perseid spectra in this group exhibit the oxygen green line at 5577 Å as well as other atomic lines normally found in the spectra of members of this shower. At the beginning of their trails all meteors show either a strong continuum, or evidence of band structure where the 1st and 2nd positive systems of N2 have been identified with reasonable certainty, while the first negative systems of N2+ and O2+, and the visible system of OH, are possible contributors.Measures of the 5577 Å line indicate a height spread from 120 to 95 km with a maximum near 106 km. After initial formation the intensity of this line increases for 0.2 to 0.5 s, after which it decays over periods up to 2 s. The decay constant for the 1S metastable state of neutral atomic oxygen is 0.76 s−1.The two chief advantages of the image orthicon technique are: its ability to record meteor spectra down to fainter thresholds of luminosity than in the case of conventional spectrography, and the time-resolution given by a recording of 15 complete frames per second.

Sampling of noctilucent cloud particles by means of sounding rockets has been successfully carried out from northern Sweden in the Summer of 1962. Two successful flights were achieved, one in the presence of noctilucent clouds and one when no such clouds could be visually observed from the ground or from aircraft. The collecting surfaces were exposed between the altitudes of approximately 75 and 98 kilometers during ascent only. The particle concentration in a vertical column through the noctilucent cloud display is found to be greater than 8 x 1Olo particles per square meter which is at least one thousand times greater than in the case when no clouds were observed. The integral size distribution of the cloud particles is of the formN = Ad-P where 3 < p < 4. A significant fraction of the collected cloud particles had a volatile coating prior to collection. The particles were analyzed by electron diffraction, neutron activation, and electron beam microprobe techniques. Electron-beam microprobe analysis has given evidence for iron particles with high nickel content. Calcium films were used as indicators of moisture associated with the collected particles. Study of the exposed and unexposed films flown in the sampling experiments has revealed evidence for moisture. Laboratory simulation of a ringor halo-patterns found in the electron microscopic examination of the noctilucent cloud particles has been attempted. This was done by impacting ice-coated nickel particles on collecting surfaces similar to those used in the sampling experiment. Ring patterns similar to those observed on the rocket sampling surfaces have been produced. The primary conclusions are that the cloud particles are probably of extraterrestrial origin and that a significant fraction appears to have been coated with terrestrial ice. Plans for future experiments are briefly outlined.

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