swh:1:snp:92f3f585b9ae79620ad8c41a332d6329b31fd381
Tip revision: 078c79d8734a9ed2860303a7c1662004284fe853 authored by Ron Burkey on 07 August 2022, 15:04:04 UTC
Fixed a potential string-overflow bug in yaASM. Removed timestamps from
Fixed a potential string-overflow bug in yaASM. Removed timestamps from
Tip revision: 078c79d
INFLIGHT_ALIGNMENT_ROUTINES.agc
### FILE="Main.annotation"
## Copyright: Public domain.
## Filename: INFLIGHT_ALIGNMENT_ROUTINES.agc
## Purpose: A section of Sunburst revision 37, or Shepatin revision 0.
## It is part of an early development version of the software
## for Apollo Guidance Computer (AGC) on the unmanned Lunar
## Module (LM) flight Apollo 5. Sunburst 37 was the program
## upon which Don Eyles's offline development program Shepatin
## was based; the listing herein transcribed was actually for
## the equivalent revision 0 of Shepatin.
## 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. 322-341
## Assembler: yaYUL
## Contact: Ron Burkey <info@sandroid.org>.
## Website: www.ibiblio.org/apollo/index.html
## Mod history: 2017-05-24 MAS Created from Sunburst 120.
## 2017-06-06 HG Transcribed
## 2017-06-22 RSB Proofed comment text with
## octopus/ProoferComments.
## 2021-05-30 ABS Aligned IAW to field boundary.
## Page 322
BANK 15
EBANK= XSM
# CALCGTA COMPUTES THE GYRO TORQUE ANGLES REQUIRED TO BRING THE STABLE MEMBER INTO THE DESIRED ORIENTATION.
# THE INPUT IS THE DESIRED STABLE MEMBER COORDINATES REFERRED TO PRESENT STABLE MEMBER COORDINATES. THE THREE
# HALF-UNIT VECTORS ARE STORED AT XDC, YDC, AND ZDC.
# THE OUTPUTS ARE THE THREE GYRO TORQUING ANGLES TO BE APPLIED TO THE Y, Z, AND X GYROS AND ARE STORED DP AT IGC,
# MGC, AND OGC RESPECTIVELY. ANGLES ARE SCALED PROPERLY FOR IMUPULSE.
CALCGTA ITA DLOAD # PUSHDOWN 00,02,16D,18D,22D-26D,32D-36D
S2 # XDC = (XD1 XD2 XD3)
XDC # YDC = (YD1 YD2 YD3)
PDDL PDDL # ZDC = (ZD1 ZD2 ZD3)
ZERODP
XDC +4
DCOMP VDEF
UNIT
STODL ZPRIME # ZP = UNIT(-XD3 0 XD1) = (ZP1 ZP2 ZP3)
ZPRIME
SR1
STODL SINTH # SIN(IGC) = ZP1
ZPRIME +4
SR1
STCALL COSTH # COS(IGC) = ZP3
ARCTRIG
STODL IGC # Y GYRO TORQUING ANGLE FRACTION OF REV.
XDC +2
SR1
STODL SINTH # SIN(MGC) = XD2
ZPRIME
DMP PDDL
XDC +4 # PD00 = (ZP1)(XD3)
ZPRIME +4
DMP DSU
XDC # MPAC = (ZP3)(XD1)
STADR
STCALL COSTH # COS(MGC) = MPAC - PD00
ARCTRIG
STOVL MGC # Z GYRO TORQUING ANGLE FRACTION OF REV.
## Page 323
ZPRIME
DOT
ZDC
STOVL COSTH # COS(OGC) = ZP . ZDC
ZPRIME
DOT
YDC
STCALL SINTH # SIN(OGC) = ZP . YDC
ARCTRIG
STCALL OGC # X GYRO TORQUING ANGLE FRACTION OF REV.
S2
## Page 324
# ARCTRIG COMPUTES AN ANGLE GIVEN THE SINE AND COSINE OF THIS ANGLE.
# THE INPUTS ARE SIN/4 AND COS/4 STORED DP AT SINTH AND COSTH.
# THE OUTPUT IS THE CALCULATED ANGLE BETWEEN +.5 AND -.5 REVOLUTIONS AND STORED AT THETA. THE OUTPUT IS ALSO
# AVAILABLE AT MPAC.
ARCTRIG DLOAD ABS # PUSHDOWN 16D,18D,20D,22D-26D
SINTH
DSU BMN
QTSN45 # ABS(SIN/4) - SIN(45)/4
TRIG1 # IF (-45,45) OR (135,-135)
DLOAD SL1 # (45,135) OR (-135,-45)
COSTH
ACOS SIGN
SINTH
STORE THETA # X = ARCCOS(COS) WITH SIGN(SIN)
RVQ
TRIG1 DLOAD SL1 # (-45,45) OR (135,-135)
SINTH
ASIN
STODL THETA # X = ARCSIN(SIN) WITH SIGN(SIN)
COSTH
BMN
TRIG2 # IF (135,-135)
DLOAD RVQ
THETA # X = ARCSIN(SIN) (-45,45)
TRIG2 DLOAD SIGN # (135,-135)
HALFDP
SINTH
DSU
THETA
STORE THETA # X = .5 WITH SIGN(SIN) - ARCSIN(SIN)
RVQ # (+) - (+) OR (-) - (-)
## Page 325
# SMNB TRANSFORMS A STAR DIRECTION FROM STABLE MEMBER TO NAVIGATION BASE COORDINATES.
# THE INPUTS ARE 1) THE STAR VECTOR REFERRED TO PRESENT STABLE MEMBER COORDINATES STORED AT LOCATION 32D OF THE
# VAC AREA. 2) THE GIMBAL ANGLES (CDUY,CDUZ,CDUX) STORED AT ALTERNATING LOCATIONS RESPECTIVELY. THE ANGLES ARE
# USUALLY STORED AT LOCATIONS 2,4, AND 6 OF THE MARK VAC AREA. THEY CAN BE STORED AT LOCATIONS 20,22, AND 24 OF
# YOUR JOB VAC AREA. 3) THE BASE ADDRESS OF THE GIMBAL ANGLES STORED SP AT LOCATION S1 OF YOUR JOB VAC AREA.
# THE OUTPUT IS THE STAR VECTOR REFERRED TO NAVIGATION BASE COORDINATES STORED AT 32D OF THE VAC AREA. THE OUTPUT
# IS ALSO AVAILABLE AT MPAC.
SMNB ITA CLEAR # PUSHDOWN 00,02,04-10D,30D,32D-36D
S2
NBSMBIT # SET NBSMBIT = 0
SMNB1 AXT,1 AXT,2 # ROTATE X,Z, ABOUT Y
4
0
CALL
AXISROT
AXT,1 AXT,2 # ROTATE Y,X ABOUT Z
2
4
CALL
AXISROT
AXT,1 AXT,2 # ROTATE Z,Y ABOUT X
0
2
CALL
AXISROT
GOTO
S2
## Page 326
# NBSM TRANSFORMS A STAR DIRECTION FROM NAVIGATION BASE TO STABLE MEMBER COORDINATES.
# THE INPUTS ARE 1) THE STAR VECTOR REFERRED TO NAVIGATION BASE COORDINATES STORED AT LOCATION 32D OF THE VAC
# AREA. 2) THE GIMBAL ANGLES (CDUY,CDUZ,CDUX) STORED AT ALTERNATING LOCATIONS RESPECTIVELY. THE ANGLES ARE
# USUALLY STORED AT LOCATIONS 2,4, AND 6 OF THE MARK VAC AREA. THEY CAN BE STORED AT LOCATIONS 20,22, AND 24 OF
# YOUR JOB VAC AREA. 3) THE BASE ADDRESS OF THE GIMBAL ANGLES STORED SP AT LOCATION S1 OF YOUR JOB VAC AREA.
# THE OUTPUT IS THE STAR VECTOR REFERRED TO PRESENT STABLE MEMBER COORDINATES STORED AT LOCATION 32D OF THE VAC
# AREA. THE OUTPUT IS ALSO AVAILABLE AT MPAC.
NBSM ITA SET # PUSHDOWN 00,02,04-10D,30D,32D-36D
S2
NBSMBIT # SET NBSMBIT = 1
NBSM2 AXT,1 AXT,2 # ROTATE Z,Y ABOUT X
0
2
CALL
AXISROT
AXT,1 AXT,2 # ROTATE Y,X ABOUT Z
2
4
CALL
AXISROT
AXT,1 AXT,2 # ROTATE X,Z, ABOUT Y
4
0
CALL
AXISROT
GOTO
S2
## Page 327
# AXISROT IS UTILIZED BY THE SMNB AND NBSM ROUTINES. SEE REMARKS ON THESE ROUTINES FOR INPUTS AND OUTPUTS.
AXISROT XSU,1 SLOAD*
S1 # SMNB . NBSM
4,1 # IG MG OG . OG MG IG
RTB XAD,1
CDULOGIC
S1
STORE 30D
ACCUROT COS
STORE 8D,1 # COS(ANGLE)
DLOAD SIN
30D
STORE 10D,1 # SIN(ANGLE)
DMP* SL1
32D +4,2
PDDL* DMP* # PD0
8D,1 # S3SIN S1SIN S2SIN . S2SIN S1SIN S3SIN
32D +4,2
SL1 PDDL* # PD2
10D,1 # S3COS S1COS S2COS . S2COS S1COS S3COS
DMP* SL1 # MPAC
32D +4,1 # S1SIN S2SIN S3SIN . S3SIN S2SIN S1SIN
BOFF
NBSMBIT
AXISROT1
BDSU STADR # . PD2 - MPAC
STORE 32D +4,2 # . S2 S1 S3
DLOAD*
8D,1
DMP* SL1 # . MPAC
32D +4,1 # . S3COS S2COS S1COS
DAD STADR # . PD0 + MPAC
STORE 32D +4,1 # . S3 S2 S1
VLOAD RVQ
32D
AXISROT1 DAD STADR # MPAC + PD2 .
STORE 32D +4,2 # S3 S1 S2
DLOAD*
8D,1
## Page 328
DMP* SL1 # MPAC .
32D +4,1 # S1COS S2COS S3COS .
DSU STADR # MPAC - PD0 .
STORE 32D +4,1 # S1 S2 S3
VLOAD RVQ
32D
# CALCGA COMPUTES THE CDU DRIVING ANGLES REQUIRED TO BRING THE STABLE MEMBER INTO THE DESIRED ORIENTATION.
# THE INPUTS ARE 1) THE NAVIGATION BASE COORDINATES REFERRED TO ANY COORDINATE SYSTEM. THE THREE HALF-UNIT
# VECTORS ARE STORED AT XNB,YNB, AND ZNB. 2) THE DESIRED STABLE MEMBER COORDINATES REFERRED TO THE SAME
# COORDINATE SYSTEM ARE STORED AT XSM, YSM, AND ZSM.
# THE OUTPUTS ARE THE THREE CDU DRIVING ANGLES AND ARE STORED SP AT THETAD, THETAD +1, AND THETAD +2.
CALCGA VLOAD VXV # PUSHDONW 00-04,16D,18D
XNB # XNB = OGA (OUTER GIMBAL AXIS)
YSM # YSM = IGA (INNER GIMBAL AXIS)
UNIT PUSH # PD0 = UNIT(OGA X IGA) = MGA
DOT ITA
ZNB
S2
STOVL COSTH # COS(OG) = MGA . ZNB
0
DOT
YNB
STCALL SINTH # SIN(OG) = MGA . YNB
ARCTRIG
STOVL OGC
0
VXV DOT # PROVISION FOR MG ANGLE OF 90 DEGREES
XNB
YSM
SL1
STOVL COSTH # COS(MG) = IGA . (MGA X OGA)
YSM
DOT
XNB
STCALL SINTH # SIN(MG) = IGA . OGA
ARCTRIG
STORE MGC
ABS DSU
.166...
BPL
GIMLOCK1 # IF ANGLE GREATER THAN 60 DEGREES
## Page 329
CALCGA1 VLOAD DOT
ZSM
0
STOVL COSTH # COS(IG) = ZSM . MGA
XSM
DOT STADR
STCALL SINTH # SIN(IG) = XSM . MGA
ARCTRIG
STOVL IGC
OGC
RTB
V1STO2S
STCALL THETAD
S2
GIMLOCK1 EXIT
TC FLAG1UP # SET GIMBAL LOCK FLAG
OCT 200
TC ALARM
OCT 00401
TC INTPRET
GOTO
CALCGA1
## Page 330
# AXISGEN COMPUTES THE COORDINATES OF ONE COORDINATE SYSTEM REFERRED TO ANOTHER COORDINATE SYSTEM.
# THE INPUTS ARE 1) THE STAR1 VECTOR REFERRED TO COORDINATE SYSTEM A STORED AT STARAD. 2) THE STAR2 VECTOR
# REFERRED TO COORDINATE SYSTEM A STORED AT STARAD +6. 3) THE STAR1 VECTOR REFERRED TO COORDINATE SYSTEM B STORED
# AT LOCATION 6 OF THE VAC AREA. 4) THE STAR2 VECTOR REFERRED TO COORDINATE SYSTEM B STORED AT LOCATION 12D OF
# THE VAC AREA.
# THE OUTPUT DEFINES COORDINATE SYSTEM A REFERRED TO COORDINATE SYSTEM B. THE THREE HALF-UNIT VECTORS ARE STORED
# AT LOCATIONS XDC, XDC +6, XDC +12D, AND STARAD, STARAD +6, STARAD +12D.
AXISGEN AXT,1 SSP # PUSHDOWN 00-22D,24D-28D,30D
STARAD +6
S1
STARAD -6
AXISGEN1 VLOAD* VXV* # 06D UA = S1
STARAD +12D,1 # STARAD +00D UB = S1
STARAD +18D,1
UNIT # 12D VA = UNIT(S1 X S2)
STORE STARAD +18D,1 # STARAD +06D VB = UNIT(S1 X S2)
VLOAD*
STARAD +12D,1
VXV* VSL1
STARAD +18D,1 # 18D WA = UA X VA
STORE STARAD +24D,1 # STARAD +12D WB = UB X VB
TIX,1
AXISGEN1
AXC,1 SXA,1
6
30D
AXT,1 SSP
18D
S1
6
AXT,2 SSP
6
S2
2
AXISGEN2 XCHX,1 VLOAD*
30D # X1=-6 X2=+6 X1=-6 X2=+4 X1=-6 X2=+2
0,1
VXSC* PDVL* # J=(UA)(UB1) J=(UA)(UB2) J=(UA)(UB3)
## Page 331
STARAD +6,2
6,1
VXSC*
STARAD +12D,2
STOVL* 24D # K=(VA)(VB1) J=(VA)(VB2) J=(VA)(VB3)
12D,1
VXSC* VAD
STARAD +18D,2 # L=(WA)(WB1) J=(WA)(WB2) J=(WA)(WB3)
VAD VSL1
24D
XCHX,1
30D
STORE XDC +18D,1 # XDC = L+J+K YDC = L+J+K ZDC = L+J+K
TIX,1
AXISGEN3
AXISGEN3 TIX,2
AXISGEN2
VLOAD
XDC
STOVL STARAD
YDC
STOVL STARAD +6
ZDC
STORE STARAD +12D
RVQ
## Page 332
# TRANSPSE COMPUTES THE TRANSPOSE OF A MATRIX (TRANSPOSE = INVERSE OF ORTHOGONAL TRANSFORMATION).
# THE INPUT IS A MATRIX DEFINING COORDINATE SYSTEM A WITH RESPECT TO COORDINATE SYSTEM B STORED IN STARAD THRU
# STARAD +17D.
# THE OUTPUT IS A MATRIX DEFINING COORDINATE SYSTEM B WITH RESPECT TO COORDINATE SYSTEM A STORED IN STARAD THRU
# STARAD +17D.
TRANSPSE DXCH STARAD +2 # PUSHDOWN NONE
DXCH STARAD +6
DXCH STARAD +2
DXCH STARAD +4
DXCH STARAD +12D
DXCH STARAD +4
DXCH STARAD +10D
DXCH STARAD +14D
DXCH STARAD +10D
TCF DANZIG
# SMD/EREF TRANSFORMS STABLE MEMBER DESIRED COORDINATES FROM STABLE MEMBER DESIRED (DESIRED = PRESENT HERE) TO
# EARTH REFERENCE COORDINATES TO ALIGN THE STABLE MEMBER TO SPECIFIED GIMBAL ANGLES.
# THE INPUTS ARE 1) THE MATRIX DEFINING THE EARTH REFERENCE COORDINATE FRAME WITH RESPECT TO THE NAVIGATION BASE
# COORDINATE FRAME. 2) SAME AS 2) AND 3) OF SMNB.
# THE OUTPUT IS THE DESIRED STABLE MEMBER COORDINATES WITH RESPECT TO THE EARTH REFERENCE COORDINATE FRAME. THE
# THREE UNIT VECTORS ARE STORED AT XSM, YSM, AND ZSM.
SMD/EREF ITA VLOAD # PUSHDOWN 00,02,04-10D,30D,32D-36D
12D
XUNIT
STCALL 32D
SMNB # STABLE MEMBER TO NAVIGATION BASE
MXV VSL1
STARAD # THEN TO EARTH REFERENCE
STOVL XSM
YUNIT
STCALL 32D
SMNB # STABLE MEMBER TO NAVIGATION BASE
MXV VSL1
STARAD # THEN TO EARTH REFERENCE
STOVL YSM
ZUNIT
STCALL 32D
## Page 333
SMNB # STABLE MEMBER TO NAVIGATION BASE
MXV VSL1
STARAD # THEN TO EARTH REFERENCE
STCALL ZSM
12D
270DEG 2DEC -.25
QTSN45 2DEC .1768
HALFDP 2DEC .5
ZUNIT 2DEC 0
YUNIT 2DEC 0
XUNIT 2DEC 0.5
ZERODP 2DEC 0
2DEC 0
2DEC 0
.166... 2DEC .1666666667
## Page 334
# AOTNB CONVERTS THE AOT RETICLE ROTATION ANGLE (YROT AND SROT) AND
# THE DETENT SETTING TO A HALF UNIT STAR VECTOR REFERRED TO THE
# NAVIGATION BASE FOR NON-FLIGHT ALIGNMENT MODES
#
# THE INPUTS ARE
#
# Y RET. LINE RATATION S(YROT) STORED IN LOC 3 OF THE MARK VAC AREA
# SPIRAL ROTATION ANGLE S(SROT) STORED IN LOC 5 OF MARK VAC AREA
# ANGLE OF CENTER OF FIELD OF VIEW S(ELV) STORED IN LOC 9 OF MARK VAC
# AOT ASZIMUTH ANGLE S(DET) STORED IN LOC 8 OF MARK VAC AREA
# THE COMPLEMENT OF BASE ADDRESS OF MARK VAC IS STORED AT X1
# COMPENSATION FOR FIELD OF VIEW TILT IN LOC 10D
# THE ABOVE STORAGE IS DONE BY AOTMARK
#
# THE OUTPUT IS A HALF UNIT STAR VECTOR IN NB COORDINATES STORED
# AT 32D AND AVAILABLE IN VAC ON RETURN TO THE CALLING PROGRAM
AOTNB SETPD SLOAD*
0
10D,1 # AOT FOV TILT COMPENSATION ANGLE
SR1 PUSH # RESCALE TILT TO 2PI
SLOAD* RTB
3,1
CDULOGIC
STORE 14D # STORE UNCOMPENSATED YROT FOR S COMP
DAD PUSH # YROT NOW CORRECTED FOR TILT
COS PDDL # 1/2 COS(YROT) PD 0-1
SIN PUSH # 1/2 SIN(YROT) PD 2-3
SLOAD* RTB
5,1
CDULOGIC
STORE 16D # STORE S IF S AND Y ARE ZERO, S=0
BZE GOTO # S NOT ZERO
SISZ # S=0
SCOMP
SISZ DLOAD BZE # IS Y ZERO
14D
YISZ # Y=0
GOTO
SCOMP
YISZ DLOAD GOTO
ZERODP
SGOT
SCOMP DLOAD DSU
14D
16D # Y-S
BDSU
NEARONE # S=360-(Y-S)
SGOT DMP PUSH
## Page 335
DP1/12
COS PDDL
SIN PUSH
DMP SL1
0
STODL 0
2
DMP STADR
STORE 2
SLOAD* RTB
9D,1
CDULOGIC
PUSH SIN
PDDL COS
PUSH DMP
0
PDDL DMP
4
6
DAD SL1
STADR
STODL 32D
DMP
4
STODL 4
DMP BDSU
0
PUSH SLOAD*
8D,1
RTB PUSH
CDULOGIC
COS PDDL
SIN
STORE 0
DMP PDDL
4
6
DMP DAD
2
SL2
STODL 34D
DMP STADR
STODL 36D
## Page 336
DMP
BDSU SL2
36D
STOVL 36D
32D
RVQ
DP1/12 2DEC .0833333333
NEARONE 2DEC .999999999
## Page 337
# AOTSM CALCULATES A HALF UNIT STAR VECTOR IN STABLE MEMBER COORDINATES
# FROM TWO PLANES CONTAINING THE STAR REFERRED TO NB
# THE INPUTS ARE
# AOT AZIMUTH AND ELEVATION STORED IN 8D AND 9D RESP. OF VAC AREA
# CDUY, CDUZ AND CDUX FROM A YMARK STORED AT 3, 5, AND 7 OF VAC AREA
# CDUY, CDUZ AND CDUX FROM A XMARK STORED AT 2, 4, AND 6 OF VAC AREA
# COMPENSATION FOR FIELD OF VIEW STORED AT 10D OF VAC AREA
# THE BASE ADDRESS OF THE CDUS IS STORED AT LOCATION S1
#
# THE OUTPUT IS A STAR VECTOR REFERRED TO STABLE MEMBER AT LOC 32D
# AND AVAILBLE IN MPAC
#
AOTSM STQ SETPD
29D # SET UP RETURN
0
LXC,1 SLOAD*
S1 # COMPLEMENT OF CDU ADR FOR XMARK
8D,1 # LOAD APPARENT TILT ANGLE,ONES COMP
SR1 # RESCALE TILT TO 2PI
PUSH COS
PDDL SIN # 1/2 COS(TA) 0-1
PUSH SLOAD* # 1/2 SIN(TA) 2-3
6,1 # LOAD AZIMUTH, 2S COMP
RTB PUSH
CDULOGIC
COS PDDL # 1/2 COS(AZ) 4-5
SIN PUSH # 1/2 SIN(AZ) 6-7
DMP PDDL
0
DMP PDDL
2
4
DMP PDDL
0
4
DMP PUSH
SLOAD* RTB
7,1 # LOAD ELEVATION, 2S COMP
CDULOGIC
PUSH SIN
PDDL COS # 1/2 SIN(ELV) 14-15
PUSH DMP # 1/2 COS(ELV) 16-17
0
SL1
STODL 32D # X COMPONENT OF X-PLANE VECTOR
DMP SL1 # UP 16-17
2
## Page 338
DCOMP PDDL # X COMPONENT OF Y-PLANE VECTOR 16-17
14D
DMP SL1
6
BDSU SL1
12D
STODL 34D # Y COMPONENT OF X-PLANE VEC
14D
DMP SL1
10D
DAD SL1
8D
DCOMP
STODL 36D # Z COMPONENT OF X-PLANE VECTOR
14D
DMP SL1
8D
DAD SL1
10D
PDDL DMP # Y COMPONENT OF Y-PLANE VECTOR 18-19
14D
12D
DSU SL1
6
STCALL 20D # Z COMPONENT OF Y-PLANE VECTOR 20-21
NBSM # TRANSFORM TO SM
STOVL 10D # STORE X-PLAVE VECTOR (SM)
16D # LOAD Y-PLANE VECTOR (NB)
XCHX,1 INCR,1
S1 # INCREMENT CDU BASE ADR TO YMARK CDUS
1
XCHX,1 # PUT IT BACK IN S1
S1
STCALL 32D
NBSM # GET Y-PLANE IN SM
VXV VSL1 # YP CROSS XP
10D
VCOMP UNIT # UNIT (XP CROSS YP)
STORE 32D # STAR VECTOR IN SM COORDINATES
GOTO
29D # RETURN
## Page 339
# THE FOLLOWING ROUTINE TAKES A HALF UNIT TARGET VECTOR REFERRED TO NAV BASE COORDINATES AND FINDS BOTH
# GIMBAL ORIENTATIONS AT WHICH THE RR MIGHT SIGHT THE TARGET. THE GIMBAL ANGLES CORRESPONDING TO THE PRESENT MODE
# ARE LEFT IN MODEA AND THOSE WHICH WOULD BE USED AFTER A REMODE IN MODEB. THIS ROUTINE ASSUMES MODE 1 IS TRUNNION
# ANGLE LESS THAN 90 DEGS IN ABS VALUE WITH ARBITRARY SHAFT, WITH A CORRESPONDING DEFINITION FOR MODE 2. MODE
# SELECTION AND LIMIT CHECKING ARE DONE ELSEWHERE.
# THE MODE 1 CONFIGURATION IS CALCULATED FROM THE VECTOR AND THEN MODE 2 IS FOUND USING THE RELATIONS
# S(2) = 180 + S(1)
# T(2) = 180 - T(1)
RRANGLES DLOAD DCOMP # SINCE WE WILL FIND THE MODE 1 SHAFT
34D # ANGLE LATER, WE CAN FIND THE MODE 1
SETPD ASIN # TRUNNION BY SIMPLY TAKING THE ARCSIN OF
0 # THE Y COMPONENT, THE ASIN GIVING AN
PUSH BDSU # ANSWER WHOSE ABS VAL IS LESS THAN 90 DEG
HALFDP
STODL 4 # MODE 2 TRUNNION TO 4.
ZERODP
STOVL 34D # UNIT THE PROJECTION OF THE VECTOR IN THE
32D # X-Z PLANE.
UNIT BOVB # CALL FOR S/C MANEUVER ON GIMBAL LOCK.
DESRETRN +1
STODL 32D # PROJECTION VECTOR.
32D
SR1 STQ
S2
STODL SINTH # USE ARCTRIG SINCE SHAFT COULD BE ARB.
36D
SR1
STCALL COSTH
ARCTRIG
## Page 340
PUSH DAD # MODE 1 SHAFT TO 2.
HALFDP # (OVERFLOW DOESNT MATTER SINCE SCALED REV
STOVL 6
4
RTB # FIND MODE 2 CDU ANGLES.
2V1STO2S
STOVL MODEB
0
RTB # MODE 1 ANGLES TO MODE A.
2V1STO2S
STORE MODEA
EXIT
CS RADMODES # SWAP MODEA AND MODEB IF RR IN MODE2.
MASK BIT12
CCS A
TCF +4
DXCH MODEA
DXCH MODEB
DXCH MODEA
TC INTPRET
GOTO
S2
## Page 341
# GIVEN RR TRUNION AND SHAFT (T,S) IN TANG,+1, FIND THE ASSOCIATED
# LINE OF SIGHT IN NAV BASE AXES. THE HALF UNIT VECTOR, .5(SIN(S)COS(T),
# -SIN(T),COS(S)COS(T)) IS LEFT IN MPAC AND 32D.
RRNB SLOAD RTB
TANG
CDULOGIC
SETPD PUSH # TRUNNION ANGLE TO 0
0
SIN DCOMP
STODL 34D # Y COMPONENT
COS PUSH # .5 COS(T) TO 0
SLOAD RTB
TANG +1
CDULOGIC
PUSH COS # SHAFT ANGLE TO 2
DMP SL1
0
STODL 36D # Z COMPONENT
SIN DMP
SL1
STOVL 32D
32D
RVQ
