The number of new couples available for the Space Telescope can be estimated through the study of prior surveys and observational selection.

Surveys realized at the beginning of this century, as well as actual surveys being recalled, show that couples remain to be discovered. A method is developed showing the importance of instrumental selection by the difference of magnitude between the components, this way can be estimated the number of couples inaccessible by earth observations due to differences of magnitudes.

Limiting ourselves to the magnitude 10, we show that the Space Telescope will permit to discoverer mostly close couples with a small difference of magnitude and a short period (P 20 y). They represent several thousands of stars.