Observations of the Sun are always complicated by the thermal influence of the integral flux of its radiation on the optical-mechanical and photo-detecting units of the telescope. This influence manifests itself especially strong and can be even amplified while observing the Sun from the space, and mostly while observing its full disk. However, the existing optical solar telescopes produce an image of either full disk of the Sun or only one individual region. In the latter case, the radiation of almost full disk of the Sun is cut off from the telescope, and emission from a small region on its surface propagate through a small aperture on the optical axis of the telescope (see, for example, Popov (1988); Stix (1991). The third variant is a solar coronagraph, which constructs an image of the solar corona, cutting off radiation of the whole disk of the Sun, thus imitating a total solar eclipse (Lyott, 1939; Nikolsky 1966; Smartt 1998). This solution determines success of the solar experiment in the space, particularly, if it is connected with long-term high-precision photometric and coordinate measurements of temporal variations of the diameter and shape of the solar disk limb.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html