Noncontact reconstructing 3-D objects surface profile on base of projection-shadow method is investigated in this paper. It is shown that this method in contrast to known techniques allows reconstructing a shape of object with vertical sides. Optimal parameters for measuring are proposed. The dependence of relative error of reconstructing on angle of light beam propagating is obtained.
A micro-satellite, designed to aid ground-based laser imaging, ranging, and sensing systems as a calibration target, has been constructed and is scheduled to be launched in the fall of 2000. This low-earth orbit satellite carries a set of retro- reflectors (for visible and near-infrared wavelengths) that present a spatially extended target to sites on the ground. Several of the reflectors also impart a polarization signature to the reflected laser light. This paper discusses the specifications of the retro-reflectors, positioning of the reflectors on the satellite structure, passive control of the vehicle orientation, and ground-pattern characteristics of the reflected light.
For many years, the United States Air Force Research Laboratory (AFRL) has developed algorithms and researched methods for optical tracking and imaging space objects. This effort has been partly limited by the lack of a calibrated on- orbit 'proof' object that can be used to reliably compare predictions to observations. In 1996, AFRL scientists began discussing this problem with the Scientific Research Institute for Precision Device Engineering of the Space Device Engineering Corporation (SDEC), Moscow, Russia. SDEC's own research in this area has been similarly limited. As a result of these discussions, and as a spin-off from related research conducted under AFRL contract, SDEC has constructed a small instrument that can fulfill the role of a non-orbit proof instrument. This free-flying passive satellite, named REFLECTOR, is designed using 32 corner cube retro-reflectors on a simple aluminum frame to ensure reliable return when illuminated from any angle. It is approximately 2 m high and 1 m wide at the base with a mass of only 6 kg. The REFLECTOR satellite has been built and is scheduled for launch as a secondary payload in December 1999. Once deployed, into its near sun-synchronous orbit, it will be observable from any location on Earth. It will be possible to passively acquire and track the satellite (using reflected sunlight) with a telescope as small as 10 cm in diameter. Because the retro- reflectors on the satellite return a large signal, laser tracking and imaging experiments can be done from the ground using small, laboratory-sized lasers. REFLECTOR will provide a 'proof instrument' that will allow the U.S. Air Force and others to test various atmospheric correction techniques.