GB1380144A - Apparatus for determining the direction of luminous radiation - Google Patents

Abstract

1380144 Encoding angular position SOC ANON D'ETUDES ET REALISATIONS NUCLEAIRES-SODERN 13 March 1972 [12 March 1971 21 Jan 1972] 11583/72 Heading G4H [Also in Division H4] Apparatus for determining the direction of a distant light source comprises at least one rectilinear slit producing a luminous line on a coding system formed by at least two tracks, perpendicular to the slit, of opaque and transparent segments covering photo-cells, the slit and coding system being supported by two parallel spaced sheets. As applied to a satellite altitude senser, the light from the sun passes through slit 15 delineated by a mask on quartz sheet 10. Varying directions of the sun correspond to different positions of luminous line L on coding system 25 and hence different binary words produced collectively by cells 23A to 23G. The coding system is formed by metal deposition on quartz sheet 20, masks being placed on the underside of the sheet so that the transparent portions of the coding system are profiled to compensate for variations in light intensity with angle of incidence #. The cell outputs are fed to comparator circuits (45A) to (45G) (Fig. 7, not shown) and give logic outputs at S. A reference cell 40 always illuminated by line L through transparent track 22R, provides a variable threshold so that spurious signals below this threshold do not cause outputs at S. For a large range of values of # two slits may be used (Fig. 5, not shown). The sheets may be held in an asembly (Fig. 6, not shown) having a compartment (37) for the electronic circuits. Additional cells (53A), (53B) (Fig. 8, not shown), may be provided to inhibit the outputs when the light source is in such a position that line L does not cut across all the tracks. For satellites with spin the additional cells may also furnish a signal to indicate that the sun is orthogonal to the apparatus (angle α=0, Fig. 1, not shown). In another embodiment (Fig. 11, not shown), for use in satellites with spin, a slit (50) and cell (53) indicate when the sun is orthogonal and produce a signal to enable the outputs to indicate the attitude angle # at only this instant. In a further embodiment (Fig. 15, not shown), cell (53) is illuminated by two slits (50A), (50B) at its ends and reference cell (40) is illuminated by slits (65A), (65B), at 45 degrees to the slit (15).