The Earth Atmospheric Solar-Occultation Imager (EASI) is a proposed interferometer with 5 telescopes on an 8-meter boom in a 1D Fizeau configuration. Placed at the Earth-Sun L2 Lagrange point, EASI would perform absorption spectroscopy of the Earth’s atmosphere occulting the Sun. Fizeau interferometers give spatial resolution comparable to a filled aperture but lower collecting area. Even with the small collecting area the high solar flux requires most of the energy to be reflected back to space. EASI will require closed loop control of the optics to compensate for spacecraft and instrument motions, thermal and structural transients and pointing jitter. The Solar Viewing Interferometry Prototype (SVIP) is a prototype ground instrument to study the needed wavefront control methods. SVIP consists of three 10 cm aperture telescopes, in a linear configuration, on a 1.2-meter boom that will estimate atmospheric abundances of O2, H2O, CO2, and CH4 versus altitude and azimuth in the 1.25 - 1.73 micron band. SVIP measures the Greenhouse Gas absorption while looking at the sun, and uses solar granulation to deduce piston, tip and tilt misalignments from atmospheric turbulence and the instrument structure. Tip/tilt sensors determine relative/absolute telescope pointing and operate from 0.43 - 0.48 microns to maximize contrast. Two piston sensors, using a robust variation of dispersed fringes, determine piston shifts between the baselines and operate from 0.5 - 0.73 microns. All sensors are sampled at 800 Hz and processed with a DSP computer and fed back at 200 Hz (3 dB) to the active optics. A 4 Hz error signal is also fed back to the tracking platform. Optical performance will be maintained to better than λ/8 rms in closed-loop.
One basic robotics task is to position a robot tool point over the geometric center of a symmetric object. This paper presents a fully autonomous control command development technique of linear complexity that solves the robot tool point centering and alignment problem. It is based on non-visual sensor imaging and starts with only a partial image of the target in its field of view. A new capacitive proximity and imaging sensor, called a capaciflector, is being used to obtain 2D discrete images of objects with moderate surface complexity. Considered are spacecraft parts whose imaged surfaces are flat with a simple geometrical shape such as a solid rectangle or a circle.
The Capaciflector, a capacitive proximity sensor, is being developed by NASA for collision avoidance. Capaciflector provides a single output value as measure of altered base frequency. This value is a characteristic of an external object in the sensor''s field of view. An attempt is made to use the Capaciflector for imaging with operating range from 1 to 2 inches. By positional arangement of sensors in a grid pattern and electronic activation of sensors over the grid one at a time an object characteristic image is obtained. The article describes the Capaciflector experimental imaging system and preliminary results obtained by the system.