### FILE="Main.annotation" ## Copyright: Public domain. ## Filename: S-BAND_ANTENNA_FOR_LM.agc ## Purpose: A section of Luminary 1C, revision 131. ## It is part of the source code for the Lunar Module's (LM) ## Apollo Guidance Computer (AGC) for Apollo 13. ## This file is intended to be a faithful transcription, except ## that the code format has been changed to conform to the ## requirements of the yaYUL assembler rather than the ## original YUL assembler. ## Reference: pp. 490-493 ## Contact: Ron Burkey . ## Website: www.ibiblio.org/apollo/index.html ## Mod history: 05/14/03 RSB. Began transcribing. ## 05/14/05 RSB Corrected website references above. ## 2017-01-06 RSB Page numbers now agree with those on the ## original harcopy, as opposed to the PDF page ## numbers in 1701.pdf. ## 2017-02-24 RSB Proofed comment text using octopus/ProoferComments. ## Page 490 # SUBROUTINE NAME: R05 - S-BAND ANTENNA FOR LM # # MOD0 BY T. JAMES # MOD1 BY P. SHAKIR # # FUNCTIONAL DESCRIPTION # # THE S-BAND ANTENNA ROUTINE, R05, COMPUTES AND DISPLAYS THE PITCH AND # YAW ANTENNA GIMBAL ANGLES REQUIRED TO POINT THE LM STEERABLE ANTENNA # TOWARD THE CENTER OF THE EARTH. THIS ROUTINE IS SELECTED BY THE ASTRO- # NAUT VIA DSKY ENTRY DURING COASTING FLIGHT OR WHEN THE LM IS ON THE MOON # SURFACE. THE EARTH OR MOON REFERENCE COORDINATE SYSTEM IS USED DEPENDING # ON WHETHER THE LM IS ABOUT TO ENTER OR HAS ALREADY ENTERED THE MOON # SPHERE OF INFLUENCE, RESPECTIVELY. CAN BE CALLED ANY TIME EXCEPT WHEN # ANOTHER EXTENDED VERB IS IN USE. DISPLAY IS MEANINGLESS WITH IMU OFF. # # TO CALL SUBROUTINE, ASTRONAUT KEYS IN V 64 E # # SUBROUTINES CALLED - # INTPRET # LOADTIME # LEMCONIC # LUNPOS # CDUTRIG # *SMNB* # BANKCALL # B5OFF # ENDOFJOB # BLANKET # # RETURNS WITH # PITCH ANGLE IN PITCHANG REV. B0 # YAW ANGLE IN YAWANG REV. B0 # # ERASABLES USED # PITCHANG # YAWANG # RLM # VAC AREA BANK 41 SETLOC SBAND BANK EBANK= WHOCARES COUNT* $$/R05 SBANDANT TC INTPRET ## Page 491 SETPD RTB 0D LOADTIME # PICK UP CURRENT TIME STCALL TDEC1 # ADVANCE INTEGRATION TO TIME IN TDEC1 LEMCONIC # USING CONIC INTEGRATION SLOAD BHIZ X2 # X2 =0 EARTH SPHERE, X2 =2 MOON SPHERE CONV4 VLOAD RATT STODL RLM TAT CONV3 CALL LUNPOS # UNIT POSITION VECTOR FROM EARTH TO MOON VLOAD VXSC VMOON REMDIST # MEAN DISTANCE FROM EARTH TO MOON VSL1 VAD RLM GOTO CONV5 CONV4 VLOAD RATT # UE = -UNIT(RATT) EARTH SPHERE CONV5 SETPD UNIT # UE = -UNIT((REM)(UEM) + RL) MOON SPHERE 0D # SET PL POINTER TO 0 VCOMP CALL CDUTRIG # COMPUTE SINES AND COSINES OF CDU ANGLES MXV VSL1 # TRANSFORM REF. COORDINATE SYSTEM TO REFSMMAT # STABLE MEMBER B-1 X B-1 X B+1 = B-1 PUSH DLOAD # 8D HI6ZEROS STORE PITCHANG STOVL YAWANG # ZERO OUT ANGLES CALL *SMNB* STODL RLM # PRE-MULTIPLY RLM BY (NBSA) MATRIX(B0) RLM +2 PUSH DSU RLM DMP 1OVSQRT2 STODL RLM +2 DAD DMP RLM 1OVSQRT2 STOVL RLM # R B-1 RLM UNIT PDVL RLM VPROJ VSL2 # PROJECTION OF R ONTO LM XZ PLANE ## Page 492 HIUNITY BVSU BOV # CLEAR OVERFLOW INDICATOR IF ON RLM COVCNV COVCNV UNIT BOV # EXIT ON OVERFLOW SBANDEX PUSH VXV # URP VECTOR B-1 HIUNITZ VSL1 VCOMP # UZ X URP = -(URP X UZ) STORE RLM # X VEC B-1 DOT PDVL # SGN(X.UY) UNSCALED HIUNITY RLM ABVAL SIGN ASIN # ASIN((SGN(X.UY))ABV(X)) REV B0 STOVL PITCHANG URP DOT BPL HIUNITZ NOADJUST # YES, -90 TO +90 DLOAD DSU HIDPHALF PITCHANG STORE PITCHANG NOADJUST VLOAD VXV UR # Z = (UR X URP) URP VSL1 STODL RLM # Z VEC B-1 PITCHANG SIN VXSC HIUNITZ PDDL COS PITCHANG VXSC VSU HIUNITX # (UX COS ALPHA) - (UZ SIN ALPHA) DOT PDVL # YAW.Z RLM RLM ABVAL SIGN ASIN STORE YAWANG SBANDEX EXIT CA EXTVBACT MASK BIT5 # IS BIT5 STILL ON EXTEND BZF ENDEXT # NO CAF PRIO5 TC PRIOCHNG CAF V06N51 # DISPLAY ANGLES ## Page 493 TC BANKCALL CADR GOMARKFR TC B5OFF # TERMINATE TC B5OFF # PROCEED TC ENDOFJOB # RECYCLE CAF BIT3 # IMMEDIATE RETURN TC BLANKET # BLANK R3 CAF PRIO4 TC PRIOCHNG TC SBANDANT # YES, CONTINUE DISPLAYING ANGLES. V06N51 VN 0651 1OVSQRT2 2DEC .7071067815 # 1/SQRT(2) UR EQUALS 0D URP EQUALS 6D SBANK= LOWSUPER