Results of TV imaging of Phobos (Experiment VSK-Fregat).

From February to March 1989 the Phobos 2 spacecraft took 37 TV images of Phobos at a distance of 190-1100 km. These images complement Mariner-9 and Viking data by providing higher-resolution coverage of a large region West of the crater Stickney (40-160 degrees W) and by providing disk-resolved measurements of surface brightness at a greater range of wavelengths and additional phase angles. These images have supported updated mapping and characterization of large craters and grooves, and have provided additional observations of craters' and grooves' bright rims. Variations in surface visible/near-infrared color ratio of almost a factor of 2 have been recognized; these variations appear to be associated with the ejecta of specific large impact craters. Updated determinations of satellite mass and volume allow calculation of a more accurate value of bulk density, 1.90 +/- 0.1 g cm-3. This is significantly lower than the density of meteoritic analogs to Phobos' surface, suggesting a porous interior perhaps containing interstitial ice.

Carbon dioxide laser beam control for corneal surgery.

Precise control of output power and beam divergence of a CO2 laser resulted in focused beam diameters down to 25 microns and essentially continuous control of energy deposition on target. Application of controlled laser beams on cow, hog, and human eye-bank reject corneal tissue give evidence of well-defined, narrow cuts. The controllable penetration depth and width of the CO2 laser incisions seem to make the laser an ideal "knife" for such corneal modifications as radial keratotomy and epikeratophakia. Our results indicate that the CO2 laser, when successfully integrated with the standard slit lamp, may be a safer and useful tool in laser surgery of the cornea.