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179-73225
BELLCOMM, INC. 955 L'ENFANT PLAZA NORTH, S.W. WASHINGTON, D. C. 20024
SUBJECT: Distribution of t h e Final Report .DATE: October 7, 1968 a of the Apol lo Guidance Software
Task Force - Case 310 FROM: W. G. Heffron
IJIEMOHANDUM FOR FILE
This memorandum has been prepared to distribute
the Final Report of the Apollo Guidance Software Task
Force.
The Final Report has been reviewed by Task Force
members and signed by t h e Task Force's chairman, Dr. G. E.
Mueller--Associate Administrator for Manned Space Flight.
2014-WGH-bjh
Attachment
F I N A L R E P O R T
A P O L L O G U I D A N C E S O F T W A R E T A S K F O R C E
September 23, 1968
A P P R O V E D
/ C h a i r m a n
FINAL REPORT
APOLLO GUIDANCE SOFTWARE TASK FORCE
1. I n t r o d u c t i o n
T h i s i s t h e f i n a l r e p o r t o f t h e Apol lo Guidance
S o f t w a r e Task F o r c e , which was e s t a b l i s h e d by D r . G . E .
M u e l l e r , A s s o c i a t e A d m i n i s t r a t o r f o r Manned Space F l i g h t ,
NASA, a t t h e r e q u e s t o f L t . Gene ra l S. C . P h i l l i p s , USAF,
Apol lo Program D i r e c t o r .
The pu rpose o f t h e Task Force was s t a t e d i n a
l e t t e r d a t e d December 1 8 , 1967 from Dr. Muel l e r t o D r . R . R .
G i l r u t h , D i r e c t o r , Manned S p a c e c r a f t C e n t e r , as " t o d e t e r -
mine whe the r t h e r e are any a d d i t i o n a l a c t i o n s which cou ld be
t a k e n to improve t h e s o f t w a r e development and v e r i f i c a t i o n
p r o c e s s and o u r v i s i b i l i t y and c o n t r o l of i t . "
The Task Force was c h a i r e d by D r . Mue l l e r : member-
s h i p i s g i v e n i n E n c l o s u r e 1. F o u r t e e n mee t ings were h e l d
a t l o c a t i o n s and dates g iven i n E n c l o s u r e 2 . Minutes o f
t h e mee t ings were p u b l i s h e d and a c t i o n i tems were a s s i g n e d
and accompl ished . A l l are a v a i l a b l e from t h e s e c r e t a r i e s
o f t h e T a s k F o r c e ( g i v e n i n E n c l o s u r e 1).
T h i s f i n a l r e p o r t p r e s e n t s , b r i e f l y , t h e major
t o p i c s of d i s c u s s i o n , t h e Task F o r c e ' s recommendations f o r
f u r t h e r Apol lo Program a c t i o n and f o r t r e a t m e n t o f s o f t w a r e
i n advanced programs, and t h e c o n c l u s i o n s drawn b y t h e Task
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F o r c e as a r e s u l t of t h e p r e s e n t a t i o n s made t o i t by t h e
o r g a n i z a t i o n s i n v o l v e d . The minu tes and a c t i o n i tems s e r v e
as a f u l l r e p o r t on t h e Task F o r c e ' s a c t i v i t i e s .
2 . Major T o p i c s o f D i s c u s s i o n
Although t h e T a s k Force rev iewed a l l a s p e c t s of
s o f t w a r e development from i n i t i a l e s t a b l i s h m e n t o f r e q u i r e -
ments t o p o s t f l i g h t a n a l y s i s , t h e major t o p i c s o f d i s c u s s i o n
were as f o l l o w s :
1. The a s s i g n m e n t s o f r e s p o n s i b i l i t y and p a r t i c i p a t i o n
by t h e numerous o r g a n i z a t i o n s i n v o l v e d i n o r a f f e c t i n g
s o f t w a r e .
2 . C o o r d i n a t i o n and c o n t r o l , i n f o r m a l l y and th rough
documents and s p e c i f i c a t i o n s , as t h e y a f f e c t i n t e r f a c e s between
s o f t w a r e and hardware, s o f t w a r e and crew p r o c e d u r e s , r e q u i r e -
ments f o r s o f t w a r e , d e s i g n data r e q u i r e d f o r s o f t w a r e d e v e l -
opment and v e r i f i c a t i o n , and c o m p a t a b i l i t y between t h e
Pr imary Guidance Computer and t h e Abort Guidance System i n
t h e Lunar Module.
3. S o f t w a r e cod ing t e c h n i q u e s , p r o c e d u r e s and
management.
4 . S o f t w a r e s c h e d u l e per formance and v i s i b i l i t y .
5. S o f t w a r e t e s t i n g r e q u i r e m e n t s and ph i losophy .
6 . A p p l i c a t i o n of t r a i n e r s and h y b r i d s i m u l a t o r s t o
s o f t w a r e v e r i f i c a t i o n .
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3. Recommendations f o r t h e Apol lo Program
S e v e r a l recommendations o f t h e Task Force have
a l r e a d y been a c t e d upon. The f o l l o w i n g a d d i t i o n a l recom-
mendat i o n s a re made.
I. The d i f f i c u l t i e s i n s o f t w a r e development
r e f l e c t t h e c o m p l e x i t i e s o f t h e Apol lo m i s s i o n s and w i l l
c o n t i n u e t o r e q u i r e t o p l e v e l management a t t e n t i o n a t MSC
and MSFC. Management p r o c e d u r e s and working ar rangements
as p r e s e n t e d appear s a t i s f a c t o r y . S i n c e s o many o r g a n i z a -
t i o n s are i n v o l v e d , it i s recommended t h a t MSC and MSFC
p r o v i d e f o r m a l d e f i n i t i o n of t h e o r g a n i z a t i o n i n t e r f a c e s
and r e s p o n s i b i l i t i e s between MSC and MSFC, and i n t e r n a l l y t o
t h o s e c e n t e r s .
11. C o n t r o l o f c o n s t a n t s , c o o r d i n a t e s y s t e m s , ope ra -
t i o n a l data, d e f i n i t i o n o f s o f t w a r e v a r i a b l e s , was i d e n t i f i e d
as a c o n t i n u i n g problem i n s o f t w a r e development . The com-
p l e x i t y o f t h e Apol lo Sof tware i n t e n s i f i e s t h e Task F o r c e ' s
conce rn . The Task Force makes t h e f o l l o w i n g recommendations:
1. M S C , MSFC and K S C management s h o u l d s u p p o r t u s e o f Apo l lo Program S t a n d a r d s f o r P h y s i c a l C o n s t a n t s , Env i ronmen ta l Data and C o o r d i n a t e Axes, amending and e x t e n d i n g them as becomes n e c e s s a r y .
2 . The MSC Apol lo S p a c e c r a f t Program O f f i c e O p e r a t i o n a l Data C o n t r o l a c t i v i t y s h o u l d r e c e i v e c o n t i n u i n g management a t t e n t i o n and s u p p o r t . MSFC and K S C s h o u l d r ev iew t h i s e f f o r t i n a n a c t i v e e f f o r t t o improve t h e i r c u r r e n t data c o n t r o l methods.
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3. Working w i t h i n t h e p r e s e n t s i t u a t i o n , MSC and MSFC s h o u l d encourage s t a n d a r d i z a t i o n o f t h e symbols and names o f s o f t w a r e v a r i a b l e s , and promote unde r s t and- i n g o f t h e s e q u a n t i t i e s by r e q u i r i n g a p p r o p r i a t e t a b l e s of nomenc la tu re , d i c t i o n a r y - l i k e l i s t i n g s , e t c .
111. I n d e v e l o p i n g s o f t w a r e , MSC and MSFC shou ld
r e q u i r e c l e a r i d e n t i f i c a t i o n of a l l c o n d i t i o n s which c a u s e
s o f t w a r e program i n t e r l o c k s , e r r o r i n t e r r u p t s , r e d l i n e r e s t r i c -
t i o n s , e t c . , p r e f e r a b l y b y t h e s o f t w a r e programmer. These
s h o u l d b e rev iewed f o r a p p l i c a b i l i t y by o p e r a t i o n a l sys tem
g r o u p s .
I V . The Task Force e n d o r s e s t h e p l a n s f o r i n c r e a s e d
u s e o f h y b r i d s i m u l a t o r s and t r a i n e r s i n ha rdware / so f tware /
crew i n t e r f a c e v e r i f i c a t i o n and recommends Apol lo Program
O f f i c e c o n t i n u e d s u p p o r t o f t h i s a c t i v i t y .
V. The Task Force f e e l s t h a t s o f t w a r e t e s t i n g a t
K S C s h o u l d emphasize v e r i f i c a t i o n of i n t e r f a c e s , and o f t h e
i n t e g r i t y of t h e program. KSC s c h e d u l e s shou ld pe rmi t d e l i v -
e r y o f f l i g h t programs f o r b o t h t h e l aunch v e h i c l e and t h e
s p a c e c r a f t as l a t e as t h e Countdown Demonst ra t ion T e s t or t h e
F l i g h t Readiness T e s t , whichever i s e a r l i e r .
4 . Recommendations f o r Advanced Programs
F o r Space programs such as Apol lo A p p l i c a t i o n s ,
P l a n e t a r y Miss ions , e t c . , t h e Task Force draws t h e f o l l o w i n g
recommendations from Apol lo Program e x p e r i e n c e .
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1. Exper i enced p e r s o n n e l shou ld be a s s i g n e d t o t h e
advanced program as q u i c k l y as p o s s i b l e , r a the r t h a n u s e t h e
e a r l y s t a g e s of a n advanced program t o t r a i n i n e x p e r i e n c e d
p e o p l e .
2 . T e c h n i c a l o r g a n i z a t i o n s s h o u l d spend some 1 0 % o f
t h e i r t i m e on advanced programs, s o as t o promote t h e c a r r y
o v e r o f e x p e r i e n c e .
3. A t h o r o u g h , e a r l y , e f f o r t a t s y s t e m s e n g i n e e r i n g
i s as i m p o r t a n t f o r t h e crew/computer/spacecraft s y s t e m as
i t i s for hardware . The e f f o r t shou ld produce :
a. A d e t a i l e d System S p e c i f i c a t i o n , s u i t a b l e as a basis f o r s o f t w a r e and hardware development . Design r e q u i r e m e n t s s h o u l d b e d e t a i l e d and s p e c i f i c , accu racy and per formance r e q u i r e m e n t s s h o u l d be g i v e n , and i n t e r f a c e s p e c i f i c a t i o n s s h o u l d be tho rough and comple te .
b . An O p e r a t i o n s Handbook f o r t h e crew.
c . A d e t a i l e d m i s s i o n t i m e l i n e .
To i n s u r e these are r e a l i s t i c , t h e y shou ld be based
on m i s s i o n development and rehearsa l work i n a s u i t a b l e f u l l
s c a l e t r a i n e r , as w e l l as on a n a l y s i s .
4. There shou ld be a de l ibera te p o l i c y o f maximum
c a r r y o v e r of g u i d a n c e t e c h n i q u e s from e a r l i e r programs.
5. There s h o u l d be a s i m i l a r l y d e l i b e r a t e e f f o r t t o
promote s i m p l i c i t y .
6 . I n choos ing a computer , p a r t i c u l a r l y i n d e t e r m i n i n g
t h e q u a n t i t y of and t h e r a t i o between erasable and non-e rasab le
memory, t h e d i f f i c u l t i e s i n s o f t w a r e development shou ld weigh 0
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as heavily as the more traditional hardware aspects. While
a computer and its software do lend an element of flexibility,
experience teaches that software is more difficult to develop
than hardware, that, verification of software, in particular,
is a time consuming task.
7. In designing software, particular effort should be
placed on avoiding or mitigating redline restrictions, error
interrupts, program interlocks, etc. Those that remain should
be clearly identified.
8 . Present standardization of physical constants, envi-
ronmental data and coordinate axes should be extended to
include symbolic names and mathematical symbols for software
variables.
9 . Organizational structure and assignments should
stress accountability for performance as well as scope of
authority and responsibility. Panels, committees, e t c . ,
should be used to promote coordination and to formalize
agreements, but not as replacements for line organizations.
6. Conclusions
The Task Force draws the following conclusions:
1. It is in basic agreement with the present software
situation.
2. No major improvements remain to be made.
3. Software complexity requires a high level of com-
munication and participation by the many organizations
involved.
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4 . There i s a d e q u a t e s o f t w a r e s c h e d u l e c o n t r o l and
v i s i b i l i t y a t p r e s e n t , a l t h o u g h s c h e d u l e s and f l i g h t d a t e s
w i l l make s o f t w a r e a s u b j e c t o f c o n t i n u a l concern .
5. I n d e v e l o p i n g c o n f i d e n c e i n s o f t w a r e , f u l l advan tage
s h o u l d be t a k e n o f t h e s e v e r a l h y b r i d s i m u l a t o r s and t r a i n e r s .
C o o r d i n a t i o n o f a c t i v i t y and fo rma l f a i l u r e and d i s c r e p a n c y
r e p o r t i n g s y s t e m s must be c o n t i n u e d .
And, as a g e n e r a l c o n c l u s i o n , t h e Task F o r c e f e e l s
i t i s i m p o r t a n t t o r e c o g n i z e t h a t s o f t w a r e r e q u i r e m e n t s w i l l
a lways be dynamic. A s s u c h , s p e c i f i c a t i o n s and r e q u i r e m e n t s
w i l l n e v e r b e a v a i l a b l e i n a comfor t ab ly e a r l y t i m e frame.
T h i s w i l l a lways c a u s e a c c e l e r a t e d development s c h e d u l e s .
Apo l lo Program management must r e c o g n i z e , t h e r e f o r e , t h a t
s o f t w a r e w i l l r e q u i r e c o n t i n u a l a t t e n t i o n and e f f o r t t o
i n s u r e t i m e l i n e s s and s t a b i l i t y . And Advanced Programs s h o u l d
a t t e m p t , as e a r l y as p o s s i b l e , t o d e f i n e these r e q u i r e m e n t s
and s p e c i f i c a t i o n s s o as t o m i t i g a t e these problems.
7. Acknowledgment
The Task F o r c e f e e l s t h a t i t has been f u r n i s h e d f u l l
c o o p e r a t i o n and cand id t e s t i m o n y . The s i n c e r i t y and d e d i c a t i o n
of a l l members of t h e NASA team was a p p a r e n t . The i r de te rmi-
n a t i o n t o meet t h e c h a l l e n g e o f t h e Apol lo Program i s recog-
n i z e d , a p p r e c i a t e d , and commended.
BELLCOMM, INC.
ENCLOSURE 1
APOLLO GUIDANCE SOFTWARE TASK FORCE MEMBERSHIP
APOLLO GUIDANCE SOFTWARE TASK FORCE
CHAIRMAN:
Dr. George E. Mueller Associate Administrator for Manned Space Flight National Aeronautics and Space Administration 600 Independence Avenue, S. W. Washington, D. C. 20546
MEMBERS :
Mr. Kenneth F. Steffan Head, Guidance Dynamics Department Building A3-2093 Aerospace Corporation P. 0. Box 95085 Los Angeles, California 90049
Dr. D. R. Hagner Director, Apollo Applications Division Bellcomm, Inc. 955 L'Enfant Plaza North, S.W. Washington, D. C. 20024
(213) 648-6117
0
(202) 484-7654
Mr. James S. Martin, Jr Head, Advanced Space Projects Office (Unmanned) Langley Research Center (Mail Stop 159) National Aeronautics and Space Administration Langley Station Hampton, Virginia 23365 (703) 722-7961 - Ext. 3265 Mr. John P. Mayer Chief, Mission Planning and Analysis Division (FM) Manned Spacecraft Center National Aeronautics and Space Administration Houston, Texas 77058 (713) 483-3301
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(Members Cont'd.)
Mr. Ludie G. Richard Director, Technical Systems Office (R-TO-DIR) George C. Marshall Space Flight Center National Aeronautics and Space Administration Huntsville, Alabama 35812 (204) 877-3760
Mr. A. P. Boysen, Jr. Director, Mission Assignments Division Bellcomm, Inc. 955 L'Enfant Plaza North, S. W. Washington, D. C. 20024 (202) 484-7894
Mr. Leon R. Bush Director, Flight Operations, MOL Project Building 100-2061 Aerospace Corporation P. 0. Box 95085 Los Angeles, California 90049 (213) 648-5936
SUPPORTING MEMBERS:
Dr. Richard H. Battin Associate Director Instrumentation Laboratory Massachusetts Institute of Technology 75 Cambridge Parkway (MS73) Cambridge, Massachusetts 02142 (617) 864-6900 - EXt. 1295
Mr. Richard B. Hanrahan RTCC Project Manager International Business Machine Corporation 1322 Space Park Drive Houston, Texas 77058 (713) 591-3300 Mr. Clarence W. Pittman Manager, Mission Trajectory Control Program TRW Systems Group (Hl-2009) Space Park Drive Houston, Texas 77058 (713) 488-3530 - Ext. 2411
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SECRETARIES:
M r . Rober t V . Spe r ry Head, Guidance and C o n t r o l Department Bellcomm, I n c . 955 L 'Enfan t P l a z a North, S. W . Washington, D . C . 20024 ( 2 0 2 ) 484-7968
M r . W . Gordon Hef f ron Head, Guidance Program Ana lys i s Department Bellcomm, I n c . 955 L 'Enfant P l a z a North, S . W . Washington, D . C . 20024 ( 2 0 2 0 484-7970
ENCLOSURE 2
PLACES AND DATES OF TASK FORCE MEETINGS
APOLLO G U I D A N C E SOFTWARE TASK FORCE MEETINGS
Meet ing P l a c e Date
1 Manned S p a c e c r a f t C e n t e r , Houston, Texas Dec. 2 0 , 1967
2 . C h a r t e r h o u s e H o t e l , Cambridge, Mass. J a n . 4 , 1968
3 . M a s s a c h u s e t t s I n s t i t u t e o f Technology, J a n . 5 , 1 9 6 8
4 . NASA H e a d q u a r t e r s , Washington, D . C . J a n . 1 6 , 1968
5. TRW Sys tems, Redondo Beach, C a l i f . J a n . 2 4 , 1368
6 . North American Rockwell C o r p o r a t i o n , J a n . 2 5 , 1 9 6 8
Cambridge, Mass.
Downey, C a l i f o r n i a
7 . Grumman A i r c r a f t E n g i n e e r i n g C o r p o r a t i o n , Feb. 3, 1 9 6 8 Bethpage , N . Y .
8 . NASA H e a d q u a r t e r s , Washington, D . C . Feb. 9 , 1 9 6 8
9. J . F. Kennedy Space C e n t e r , Cape Kennedy, F l o r i d a
Feb. 1 8 , 1968
1 0 . G . C . M a r s h a l l Space F l i g h t C e n t e r , Feb. 2 3 , 1 9 6 8 H u n t s v i l l e , Alabama
11. Hol iday I n n , Nassau B a y , Texas March 1, 1968
1 2 . Manned S p a c e c r a f t C e n t e r , Houston, Texas March 2&3, 1968
1 3 Manned S p a c e c r a f t C e n t e r , Houston, Texas May 2 0 , 1968
1 4 . Manned S p a c e c r a f t C e n t e r , Houston, Texas J u l y 1 2 , 1968
BELLCOMM, INC. SUBJECT: Distribution of the Final Report FROM: W. G. Heffron
of the Apollo Guidance Software Task Force - Case 310
DISTRIBUTION
Task Force Members Messrs. R. H.
NASA
MSC -
MSFC
KSC -
A. P. L. R. D. R. R. B. J. P. J. S. G. E. c. w. L. G. R. V. K. F.
R. 0. L. D. J. K. T. A. J. R. H. T. s. c. J. B. G. C.
R. G. c. c. L. c. R. A. T. F. R. R. G. M. J. C.
Battin - MIT Boysen, Jr. - Bellcomm Bush - Aerospace Corporation Hagner - Bellcomm/MLS Hanrahan - IBM Mayer - MSC/FM Martin - NASA/Langley Station Mueller - NASA/M Pittman - TRW Richard - MSFC/R-TO-DIR Sperry - Bellcomm/MAS Steff'an - Aerospace Corporation
Aller/MAO Day/MAT Holcomb/MAO K e e gan/MA Kuba t /MP Luskin/ML Phillips/MA Skaggs/MAP White, Jr./MAR
Chilton/EG Kraf t/FA Dunseith/FS Gardiner/EG Gibson/FS5 Gilruth/AA Low/PA Stokes/FS5
E. O'Cennor/I-DIR L. B. James/I-V-MGR F. A. Speer/I-140-MGR W. von Braun
K. H. Dehcs H. F. Gruene/LV R. 0. Middleton/AP R. A. Petrone/LO J. Williams/LS
BELLCOMM, INC.
D i s t r i b u t i o n c o n t i n u e d
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Bellcomm, I n c . Messrs. D. A . Chisholm
D. A . DeGraaf I . M . Ross J . W . Timko R. L . Wagner
C e n t r a l Files 4 CODY TO
Department 1 0 2 4 F i l e L i b r a r y