Note about P51
From Colossus source code:
# Page 711 # PROGRAM NAME -- PICAPAR DATE: DEC 20 66 # MOD 1 LOG SECTION: P51-P53 # ASSEMBLY: SUNDISK REV40 # BY KEN VINCENT # # FUNCTION # THIS PROGRAM READS THE IMU-CDUS AND COMPUTES THE VEHICLE ORIENTATION # WITH RESPECT TO INERTIAL SPACE. IT THEN COMPUTES THE SHAFT AXIS (SAX) # WITH RESPECT TO REFERENCE INTERTIAL. EACH STAR IN THE CATALOG IS TESTED # TO DETERMINE IF IT IS OCCULTED BY EITHER EARTH, SUN OR MOON. IF A # STAR IS NOT OCCULTED THEN IT IS PARIED WITH ALL STARS OF LOWER INDEX. # THE PAIRED STAR IS TESTED FOR OCCULTATION. PAIRS OF STARS THAT PASS # THE OCCULTATION TESTS ARE TESTED FOR GOOD SEPARATION. A PAIR OF STARS # HAVE GOOD SEPARATION IF THE ANGLE BETWEEN THEM IS LESS THAN 66 DEGREES # AND MORE THAN 40 DEGREES. THOSE PAIRS WITH GOOD SEPARATION # ARE THEN TESTED TO SEE IF THEY LIE IN CURRENT FIELD OF VIEW. (WITHIN # 33 DEGREES OF SAX). THE PAIR WITH MAX SEPARATION IS CHOSEN FROM # THOSE WITH GOOD SEPARATION, AND IN FIELD OF VIEW.
As stated above, the angular difference between the 2 stars should be 40°-66°, a rather tight margin. Greater than 66° isn't working at all, but smaller than 40° is at least possible (i.e. no errors) however less precise.
But the stated max. field of view = max. trunnion angle of 33° seems to be wrong. With trunnion angles greater than 60°, P51 isn't working anymore (as I figured out by testing). But PICAPAR does choose stars with a trunnion angle greater than 33° (current "record" 45°), so restricting the max. trunnion angle to 33° is NO option. AOH 22.214.171.124.1 seems to state a max. trunnion angle of 50°.