By the mid 1990's, high definition television (HDTV) is likely to be widely available to the American public. Also by this time, construction of the Space Station is expected to have begun. NASA's statutory mandate includes being able to transmit information, often in the form of video images, from the space station for distribution to the media for public viewing. Eight-bit encoding of full-bandwidth digitized HDTV images for transmission would require a bit-rate of about 1.2 Gigabits. The available bit-rate, however, is a factor of 10 less than this. Thus, bit-rate reduction schemes will be needed that compress the image, without impairing its quality. This requires a good understanding of the basic psychophysics of image sampling, in both spatial and temporal domains. In the spatial domain, we have conducted a series of two-alternative forced choice experiments to compare the sharpness of televised moving images sampled using cardinal or diagonal patterns, with reference images of varying resolution. Considerable savings in bit-rate transmissions is possible if the same apparent sharpness can be obtained with diagonal as with cardinal sampling. Studies are underway to determine the optimal sampling patterns and pre-and-post filtering characteristics to maximize sharpness with minimum sampling artifacts. Digital transmission also requires images that are sampled in time. Such sampling as well as scan conversion between different frame rates, can produce motion artifacts, such as "jutter". In the laboratory, we have studied discriminability of jutter using the drifting sine-wave gratings with known spatial and temporal characteristics.