XXI. Astronomical observations on the periodical star in Collo Ceti
This remarkable star, we are told, "was first observed by David Fabricus, the 13th of August, 1596, who called it the stella mire, or wonderful star; which has been since found to appear and disappear, periodically, seven times in six years, continuing in the greatest lustre for fifteen days together, and is never quire extinguished." My own observations on this wonderful star are but few, yet sufficiently verify the surprizing appearances that have been ascribed to it.
Abstract Many human operations have created a large population of small orbital debris in near Earth environment. The threat they represent for satellites is a major factor for the preparation of future space missions. Several experiments devoted to the study of this environment, as well as various materials exposed to space, have been retrieved in the past few years. The analysis of the results shows some differences with previous modeling. Comparison with data from LDEF and from EURECA give some insight in the long term evolution of particle size distribution. Chemical identification of particle remnants inside craters is difficult but provides valuable information on the origin of the impactors. Permanent monitoring of environment is obviously needed, especially for the type of orbits where data are presently scarce ie. heliosynchronous and geostationary orbits.