Apollo Experience Report Flight Anomaly Resolution

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N A S A TE C H N IC A L N O T E NASA TN 0 -7968

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APOLLO EXPERIENCE REPORT -FLIGHT ANOMALY RESOLUTIONJohn D. LobbLyndon B. Johnson Space CenterHoztston, Texas 77058N A T I O N A L A E R O N A U T I C S A N D S P AC E A D M I N I S T R A T I O N W A S H I N G T O N , D . C. J U L Y 1975


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1 . Report No.NASA TN D-7968

4. Tltle and SubtitleAPOLLOEXPERIENCEREPORTFLIGHT ANOMALY RESOLUTION

2. Government Accession No. 3. Recipient's Catalog No.

5. Report DateJuly 1975JSC-07733

17. Key Words (Suggested by Author(s)).Space -FlightIrregulari t ies .Quality Control.Performance Deviations . rr or -Correcting. ailur e Analysis Devices.Flight Hazards .Malfunctions

.Operational Problems

7. Authorls)John D. Lobb

18 . Distribution StatementSTAR Subject Cat egory :12 (Astronautics, General)

8. Performing Organization Report No.1 JSC S-412

Unclassified

10. Work Unit No.914-89-00-00-72. Performing Organization Name and Address

Unclassified 74 $4.25

Lyndon B. Johnson Space C enterHouston, Texas 77058

11. Contract or Grant No .

13. Type of Report and Period CoveredTechnical Note2. Sponsoring Agency Name and Address

14. Sponsoring Agency CodeNational Aeronautics and Space AdministrationWashington, D. C. 20546I15. Supplementary Notes

16. AbstractThe identification of flight anomalies, the determination of their cause s, and the approachestaken for corrective action a re described. Interrelatio nships of the broad ran ge of d isciplinesinvolved with the complex s ys tem s and the team concept employed to ens ur e timely andaccur ate resolutio n of anomalies ar e discussed . The dynamic nature of the prog ram req uireda rig orou s effor t in documenting all proced ures for the use of progra m management, flightcontrol, engineer ing design, and scientific investigation person nel. . The documentationtechniqu es and the techniq ues for management of anomaly resolut ion a r e included. Exam plesof specific anomalies a r e presented in the original form of th eir pr ogres sive documentation.Flight anomaly resolution functioned a s a par t of the real-tim e mission support and post-flight testing, and re su lt s were included in the postflight documentation. However, thisreport re fe rs to these activities only insofar a s they affect, or ar e affected by, the pro-gre ssi ve activit ies of flight anomaly resolution. The detai ls of real- time mission support,postflight te sting, and postflight documentation a r e discussed under these headings inseparate reports.


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CONTENTS

SectionSUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PERSONNEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .IDENTIFICATION O F ANOMALIES . . . . . . . . . . . . . . . . . . . . . . . .

Insufficient Ground Test Data . . . . . . . . . . . . . . . . . . . . . . . . . .Insufficient Flight Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Obvious Component Fa ilure . . . . . . . . . . . . . . . . . . . . . . . . . . .Crew Observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Extensive Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Limited Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Returned Flight Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . .Unreturned Flight Hardware . . . . . . . . . . . . . . . . . . . . . . . . . .

TYPICAL CAUSES O F ANOMALIES . . . . . . . . . . . . . . . . . . . . . . .

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8Manufacturing Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Hardware Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Operational Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

DOCUMENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10During Flight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10After Flight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Continuing Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

CONCLUDING REMARKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

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Section P a g eR E F E R E N C E S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

ANOMALY RESO LUTION . . . . . . . . . . . . . . . . . . . . 15APPENDIX- XAMPLES O F PROGRESSIVE DOCUMENTATION OF

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APOLLO EXPER IENCE REPORTF L IGHT ANOMAL Y RESOL UT ION

B y J o h n D. LobbL y n d o n B . J o h n s o n Space C e n t e rS U M M A R Y

The frequency of the Apollo missions demanded that flight anomalies be quicklyidentified and resolved so that prompt corrective action could be taken. Analyses of thedata for problems and anomalies had to be compressed into a relatively short timeframe.

Timely resolution of flight anomalies was achieved during the Apollo Prog ra mso that corrective actions necessary for crew safety, mission success , and programsu cc es s were completed during each mission and between missions. This success wa slargely due to a team of engineers who understood the deta ils of hardware design, te sthistory, and operational charac teri stic s of their respective systems. A working rela-tionship that ensured quick responses and concurrence of this team with programmanagement and flight operations personnel contributed equally to program success.The analysi s team had acc es s to the support of any other special ists o r facilitie s neededto the extent justified by the natu re of the par ticu lar problem. Team understanding ofthe mechanism associated with the cause of the problem w a s required for resolvingeach anomaly. Complete understanding of an anomaly often requi red postflight dataanalysi s, crew debrief ings, and testing of spacecraft hardware.The efficient documentation system established a definite point on which to focusdirect ion and continuity of effort f or more effective anomaly resolution. The flexibilityof some of the documentation provided continuous updating by the analys ts and ens ureda common understanding of the current status of each system problem by the analys isteam and by program management and flight control personnel.Of course, the complexity of the spacecraft configuration and of the complement

of experiments taken on the lunar-landing missions incr eased the probability of a widevariety of anomalies. The same general procedure was used to properly identify andunderstand each problem, analyze the cause, and determine the proper cour se of action.Examples of actual flight anomalies illu strate the gen era l types of causes identified,the levels of analysis r equired, and differences in the nature and extent of the cor re c-tive actions justified.


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I NTRODUCTI ONFlight anomaly resolution was the mission evaluation task that covered space-craft and experiment problems and deviations from expected or predicted performance.This task included not only the resolution of t rue fa ilu res and malfunctions, but also theresolution of i tems that appeared to be problems o r discrepancies at first but that, on

further investigation, proved to be incor rectly identified as anomalies. Thus, the te rm"resolution, '' as used in this repor t, includes the proper identification of the anomalyas we l l a s the determination of the cause and the proper cour se of action to be takenboth during the mission in progress at the time and before subsequent missions.The flight anomaly resolution system used during the Apollo Program was an out-growth and further development of the miss ion evaluation procedures used on the pr e-vious manned space flights of Project Mercury and the Gemini Program. Missionevaluation ensured that maximum information wa s obtained from each Apollo flight fo ruse in managing and planning later flights and future programs .

also provided to the scientif ic community and to the public s o that they could be we l linformed on the ac tivi ties of U. S. space exploration.The information w a s

It was necessary that anomaly resolution be completed in a timely manner forthe interim in-flight course of action. J u s t as important w a s the need for a t ime fra methat would enable completing the proper corrective action for subsequent missions with-out requiring changes in the scheduled launch dates for lunar -landing miss ions , whichwere limited to specific lift-off times and calendar dates for each lunar exploration si te.This report contains a discussion of the primary charac teristic s of the succ es s-ful resolution of Apollo flight anomalies. Typical experiences have been used toillustrate how the system w a s actually implemented. In addition to the examples offlight anomal ies discussed in the body of the repor t, ex tra cts from actual anomalyresolution repo rt s for four problems a r e presented in the appendix. These extracts

have been included to illustr ate that changes from issue to issue of the reporting syst emreflect the progress made in resolving anomalies. The four anomalies selected reflectdifferent combinations of causes, so ur ce s of data for analysis, correc tive actions, andreporting his or es.PERSONNEL

Essent ial to the successful performance of anomaly resolu tion w a s the makeupand interaction of the mission evaluation team. Each of the many disciplines involvedwas represented on the team by a group of s pecial ist s managed by a NASA team leaderwho w a s also a specialist in the sam e discipline. Each specialist had a thorough under-standing of system characteri stic s, operations, and limitations gained from experiencewith his particular systems from initial design through development and testing of thehardware. Team members were selected from NASA and contrac tor personnel.Each team leader was the analysis manager for anomaly resolution'within hi spar ticular range of responsibility. For example, the Apollo 14 team included an

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analysis manager for each of the following: telecommunications, crew syst ems , elec-tronic syst ems, propulsion and power, guidance and control, st ru ctur es and mechanics,thermal control, flight crew support, trajectory, and lunar surface experiments.The responsibi liti es of each team leader included coordination with the other team

le ad er s to ensure that any solution or recommended cours e of action would not jeopard-iz e other systems. The team lea der s reported to an evaluation team manager whowa s responsible for the overa ll operation of the team, reviewed and integrated the inputsfr om the team leader s, and communicatedwi th the Mission Control Center as the singlepoint of contact. In addition, an anomaly engineer was responsible to the team managerfor following through on each anomaly to completion of the resolution. There was ananomaly engineer for command and serv ice module problems, one for lunar moduleproblems, and one fo r experiments and Government-furnished-equipment problems.Continuity to completion of the activity was enhanced because some team me mber s ineach discipline were also responsible for the detailed implementation of hardwarechanges required fo r subsequent missions. The mission evaluation team provideddirect support to the flight control organization in the Mission Control Center for in-flight resolutions and to program management for resolutions requiring action on theground before subsequent missions.

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The premission planning and training of flight operations personnel with the cr ew-men covered many possible fa ilu res and malfunctions of s ys te ms and components.These fai lure modes and corre ctive contingency procedures were thoroughly exercisedduring simulations. Nevertheless, it was not surprisi ng that unpredicted problems anddiscrepancies were encountered with a complex configuration such as the spacecraftand the complement of experiments taken to the Moon.evaluation team were to properly identify and understand these problems, to perf ormthe investigations and analyses required, to determine the causes, and to recommendthe proper co ur se s of action.

The prime tasks for the mission

In support of the team effort a t the NASA Lyndon B. Johnson Space Center (JSC)(formerly the Manned Spacecraft Center (MSC)), he pri me cont ractors maintainedsim ila r teams of specia lists at 'their facilities during the mission for analyses, tes ts,and related activities as they were required. These tea ms also reported to the missionevaluation team management at MSC.

Many tim es during Apollo flights, the support team personnel at the prime con-tr ac to r facility provided tes t information that w a s invaluable fo r understanding a prob -lem and fo r determining the be st course of action. For example, during lift-off of theApollo 12 spacecraft, a lightning discharge r esul ted in tumbling of the inerti al platformand lo ss of inertial reference. The support team at the Massachusetts Institute ofTechnology in Cambridge, Massachusetts, performed a te st simulating the condition inan attempt to unders tand how the potential discharge had caused the platform to tumble.It was important to quickly verify that the platform had not been damaged. A promptresponse w a s received by the evaluation team, and the mechanism that had caused theconditions in flight w a s determined.

The choice of team personnel f or Apollo flight anomaly resolution w a s a majorcontribution to the succes s of the missions, Many of the analysi s manager s continued

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in that capacity fo r the ent ire program and, thus, provided continuity to the anomalyresolution and corrective action effort as well as exceptionally good intrateam under -standing. The team manager, who was also chief of the MSC Apollo Spacecraft Pro-gr am Office Tes t Division, led the mission evaluation and anomaly resolution operat ionfo r the Apollo Program, beginning with the Apollo 6 flight.IDENTI F ICAT1 ON OF AN OMA LIES

The first task of the mission evaluation team was to identify the anomaly. Thistask required the team 's constant awareness of the total system performance as themission progressed. Individuals monitored telemetry data that were received by thetracking stations, transmitted to and processed by the Mission Control Center, anddisplayed on closed-circuit television rece iv er s in the Mission Evaluation Room. Inaddition, the air -ground voice communications and television coverage of crew activi-ti es were closely monitored. Selected telemetry data, which were not on the televisiondisplays, were provided to team m em be rs in the form of computer tabulated printoutcopies several hours after trans miss ion fo r analysis of system performance. Identifi-cation of flight anomalies continued after completion of the mission through crewdebriefings and additional individual conferences between special is ts and the crewmen,re sul ts of the ana lyses of in-flight photography, and re sul ts of the analyses of reduceddata from the mission.

Identification of anomalies for the lunar surface equipment operating at the fiveApollo science s tations will continue for the remaining data -gathering lifetime of eachinstallation. When indications of a problem appear in the telemetry data, vari oustroubleshooting command sequences a r e transmi tted to the affected station to helpidentify the poss ible anomaly. Initial indicat ions somet imes are evident in the real-time data; at other times, the anomaly may not be evident until the mo re detailed dataprocessed by the principal investigator have been analyzed se vera l months l ate r.

I n s u f f i c i e n t G r o u n d T es t D ataSystem performance w as usually determined by comparing the flight data withperformance predictions and with data from ground tests and from other flights. Data

comparison was also a pr im e method of detecting anomalies . However, in the mostdifficult identification problems, the available data were not sufficient fo r completeunderstanding of all normal operating char acte rist ics of the system.A typical example of this condition occurred on the Apollo 7 mission. The com-

mand module entry battery recharging ch ar ac te ri st ic s were below predicted levelsthroughout the flight, and the planned charge leve ls could not be maintained. Availableground test data were insufficient to explain the condition.ted during postflight tests, and a detailed analys is was made. Results of the analysisshowed that the charger to battery line impedances, which were not evaluated previously,were l ar ge enough to cause a significant reduction in the charge voltage applied at thebattery. Results of the system analysi s als o showed that the cha rge r output voltage w a swithin specifications, but on the low side, and that the cha ra ct er is ti cs of an experimen-tal plate-divider mate rial used in the batteri es could re su lt in a condition, at zero g,that could limit the recharge capacity of the batte ry,

The condition was duplica-

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As a re su lt of the anomaly investigation, cha rge rs with the highest voltage out-put were selected for subsequent missions, and integrated sys tem s test s were per -formed to establish the overall system characte rist ics of each installation and, thereby,to ensure adequate recharge capability. In addition, fo r Apollo 11 and subsequentmissions, the charger w a s modified fo r a higher output voltage setting, and conven-tional plate -divider mater ial w as used in the batteries. Performance on subsequentmissions was satisfactory. Additional detail on this anomaly is contained inreference 1.

I nsufficient Flight DataSometimes, the flight data wer e insufficient for immediate identification of aspecific problem.

system th rust light, located on the entry monitor system panel, was illuminatedshortly after transposition and docking at a time when no engine-firing command w a spresent. Because the problem could not be accurately identified by using available data,the crewmen were provided with special troubleshooting procedures to better pinpointthe problem. Application of the fault isolation procedures resulted in isolation of themalfunction to a shor t circuit in bank A of the se rvice propulsion system ignition ci r -cuitry. The re su lt s of the next special procedure - to manually initiate ignition forthe first midcourse correction th rust firing by closing the pilot-valve main A circuitbreaker - fur ther verified that the s ho rt circuit existed on the negative side of these rv ice propulsion system pilot-valve solenoids, and also indicated that subsequentmaneuvers could be controlled by manual control of bank A. Resu lt s of postflighttests and examination of the returned hardware showed that the intermittent shortcircuit was caused by a freefloating strand of contaminating w i r e inside the system Adifferential-velocity thrust switch. A ll switches of this type wer e subjected to addi-tional sc reening procedures for subsequent missions.

For example, during the Apollo 15 miss ion, the ser vice propulsion

Obvious Component FailureMany anomalies were recognized simply because a specific component was

obviously not functioning. For example, during the init ial deployment of the Apollo 1 2color television camera on the lunar surface, the picture was lost because the camerawas inadvertently pointed at the Sun. The direct sunlight had caused a light ove rstr ess,which damaged the image se ns or to the extent that a usable picture could no longer beattained. For further details, se e the appendix and re fe re nc e 2.

Crew ObservationSometimes, the init ial indication of an anomaly resul ted from observation of anoff-nominal condition by a team member o r by a crewman, reported either at the timethe problem occurred o r later if the problem w a s not crit ical . An example was the

postflight r ep or t by the crewmen concerning the fai lur e of the primary floodlights inthe command module lower equipment bay during the Apollo 7 mission. Subsequentinvestigation revealed that the lamps had been operated excessively in the dimmedmode before flight. For additional information, see the appendix.

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ANALY S I STwo basi c techniques were used to determine the cause of a problem and therequir ed corrective action. The first technique was the experimental testing of theactual or identical hardware under actual or simulated flight conditions or under labo-

ra tor y ambient conditions. The us e of breadboard s ys te ms when requ ired was anothertype of experimental testing available to the mission evaluation team. The secondtechnique w a s analytical, generally in the class ical sense.included the use of computerized mathematical models, the application of physical l aw s ,and the use of established engineering formulas.The analytical technique

The choice of technique depended on the nature of the problem. The most expe-dient approach was sought; however, attention to detai l w as al so of pri me importancebecause the analys is had to be sufficiently rigorous to establish the cause and, then,to develop and prove the necessary corr ecti ve action to prevent future occurr ences.Of course, corr ecti ve action sometimes w a s unnecessary.

Extens ive An a lys isThe extent of the analysis vari ed considerably and depended on the significanceand nature of the problem. Extensive analysis sometimes was required,on the Apollo 6 mission, a structural failure occurred in the adapter that housed thelunar module during launch and provided the structural connection between the servicemodule and the launch vehicle.designed and developed for any application to that time. Photographs from missionsupport ai rcraf t and ground-based long-range ca me ra s showed that much of the honey-comb sandwich facesheet had separ ated abruptly from one of the four circumferent ialsect ions of the adapter during launch. The effects of the separation were indicated on

many measurements in the command and se rv ic e module, the lunar module, and thelaunch vehicle. The adapter continued to sustain the requ ired loads, however.

For example,

This adapter had the largest honeycomb structure

The seriousness of the problem because of its possible effect on the integr ity ofthe s pace vehicle and impact on the Apollo Prog ra m requir ed an extensive analysis.The investigation of th is anomaly included testing full-scale hardware under dynamicand stat ic conditions, performing many experimental ,t es ts on smal le r tes t art ic le s,and performing extensive structural analyses at various NASA cent er s and contractorfacilit ies. To determine the cause of this anomaly, analy ses were made of the struc-tural dynamics of the launch vehicle, the dynamic loads of the lunar module, thedynamic modes of the adapter itself, the effect of the rmal and pr es su re environmentsduring launch, and the assembly techniques and quality control procedure s used in themanufacture of the adapter structure.

The investigation w a s focused first on an understanding of the coupled vibrat ionmodes and vibration character isti cs of the launch vehicle, the spacecra ft, and theadapter. Results of extensive vibrat ion tests showed that the fa ilure s had not beencaused by vibration. Investigations of the the rmal and pres su re conditions, whichincluded full-scale simulations, revealed that the press ur e buildup within the honeycomb

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R e t u r n e d F l i g h t H a r d w a r eSometimes, the analysis and resolution could not be completed until the re turnedhardware had been examined in detail. Examples of dependence on flight hardware foranomaly resolution were the fa ilu re of the Apollo 12 color television c am er a on thelunar surface and the failure of the primar y lower equipment bay floodlights on theApollo 7 mission (ref. 2 and appendix). The floodlights were returned because theywere par t of the command module equipment. However, the televis ion camera wasretu rned because of the anomaly resolut ion requirement.nally been listed for return stowage.gram, see reference 3.

The cam er a had not origi -For deta ils of the Apollo postflight testing pro-

Un eturn e d F i h H a r d w a r eIn general, two types of malfunctioning equipment were not returned. One typew a s hardware that had been deployed and was operating as pa rt of a lunar surfacescience station, such as the Apollo 14 active se is mi c experiment geophone that w a sproducing erratic data (appendix). Testing to resolve the problem was accomplishedby using breadboard equipment in the laboratory and by transmitting commands to thescience station on the lunar surface.The other type of problem equipment that could not be returned was equipmentlocated in the lunar module o r in the service module. Oscillation of fuel cell condenserexit tempera tures during the Apollo 10 and 11 missions w a s a good example. See re f-erence 4 and the appendix. The fuel cel l condenser was mounted in the ser vi ce module,which separates from the command module at the time of entry and is not recoverable.Extensive review and analysis of the flight data for all previous missions were neces-sa ry because the condition had been observed on se ve ra l missions.

T Y P I C A L C A U SE S O F A N O M A L IE SThe causes of mos t anomalies were re lated to manufacturing quality, hardwaredesign, or operational procedures or to a combination of these.

M a n u a c t urin g Q u a l i t yThe structu ral failure of the Apollo 6 adapter w a s primarily a manufacturingquality problem because of the failure to adequately inte rpre t the ultrasonic scan

record. If the r eco rd had been interpreted properly and the fault confirmed by X-ray;the c or re ct struc tura l rep ai r would have been implemented. In addition, the re hadbeen manufacturing process difficulty in properly alining all stru ctur al part s when theassembly was prepared for bonding in the autoclave. Manufacturing quality anomaliesal so included irregularities such as improperly torqued screws, incorrectly solderedjoints, and improperly potted components which resu lted from deficient manufacturingprocedures.

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Hardware DesignSystem anomalies caused by hardware design deficiencies sometimes occurredbecause all fa ct or s that would influence the performance of the system were notincluded in the design criteria or specifications. Because component and system te st -ing w a s based on these cr ite ria or specifications, the deficiency could go unnoticed

during development and qualification t es ts and not be detected until ac tual flight condi-tions were encountered. A typical illustration w a s fogging between the panes of theApollo 7 command module windows caused by deposits from the outgassing products ofthe room -tempera ture -vulcanizing sealing material around the windows. The designof the assembly had not required that the sealing material be cured at the operatingtempe ratu re and pressure . Such a curing process would have reduced the amount ofoutgassing during flight. For further discussion of this problem, se e reference 5.Other types of design deficiency anomalies we re those in which the state of theart ha6 advanced o r additional knowledge and experience in space had been acquiredfollowing the design and manufacture of the component o r assembly. An example ofthis type w a s the cracking solder phenomenon that occur red on electronic hardware

designed and manufactured before 1967. An investigation, per formed at that timebecause of problems with spacecraft and launch vehicle electronics , revealed thatexisting design practi ces f or printed circuit board assembl ies did not allow for occur -rence of thermal expansion of the assemblies during normal operations. Differencesin the the rma l expansion proper tie s of the board mater ial s, coating materi als , pot-ting materia ls, and component lead materials caused st r e ss and cracking in thesoldered connections. The program al so resulted in development and publication oftested, acceptable design configurations and guidelines fo r printed circuit boardassemblies . See refe rences 6 and 7. Many non-mission-critical elec tronic ass emblieshad been built before that time. Although the assembli es were subjected to additionaltesting and screening, some anomalies did occur as a result of this design weakness.For example, during the Apollo 1 2 mission, a failure occurred in the mission timertuning fork cir cuit because of a cracked solder joint in the cordwood construction.Elec trical components such as re si stor s, capacitors, and diodes had been solderedbetween two circui t boards, and the void between the boards had been filled with pottingcompound.component leads resulted in solder joint cr acks at a board-to-lead connection. Designof a new clock, developed for subsequent missions, did not include the cordwoodconstruction.

The thermal expansion differential between the potting compound and the

Operational P rocedu esProcedura l problems in operating the various syst em s and equipment wereusually eas y to cor rect. An example of a procedural problem occurred during the entryand landing sequence on the Apollo 1 2 mission. A crewman w a s struck by a16-millimeter camer a that was dislodged from the mounting bracket near the rendez-vous window at splashdown. The ca mera was to have been stowed before landing becausedesign of the mounting bracke t did not include retention under landing forces. Designa-tion of the ca me ra for stowage in the flight plan and the crew checklist on subsequent

flights precluded r ec ur re nc e of this incident.

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The correct ion of some procedural problems involved both crew training andhardware design changes. This type of correc tion was required af ter the l os s of lunarsurface television transmission during the Apollo 1 2 mission (appendix and ref. 2) .It w a s found that high-intensity light inputs were received not only during direct point-ing at the Sun, but also during normal pointing as a re su lt of specular refle ctions fromobjects in the field of view. This problem hastened completion of the development ofnew burn-resistant image sensor s. The newly developed tubes we re used with suc ce sson subsequent missions. Operational procedure on la te r missions was established toavoid pointing the television camera at speci fied light sources. Also, with the additionof the l u n a r roving vehicle having a television camera mount on the Apollo 15 mission,remote pointing control from the Mission Control Center freed the flight crew frommost of this responsibility.

Another type of procedural problem was illu strated by the sh or t in-flight life ofthe floodlights in the Apollo 7 command module lower equipment bay (appendix).Here, the preflight procedures wer e modified to ensure sufficient floodlight lifetimefor mission operations,

DOCUMENTATIONDocumentation provided, in fir m and visible form, definitive information for a

bet ter understanding of each anomaly throughout the resolution process . Clear lywritten explanations, accompanied by illustrations and data when required to clarifyo r back up a point, ensured a common understanding of the status, findings, and finalresolution of anomal ies by management, engineering, and operations personnel. Thecharacter of the documentation and the scheduling of the documentation al so forcedanalys ts to organize the work so that the results and conclusions wer e concur red uponby the working groups and repor ted in an understandable for mat and in a timely manner.

During F lightDuring flight, the anomaly resolution activity of the miss ion evaluation team wasdocumented in several different formats , each serving a specif ic purpose and eachsupporting the other. Communications between the Mission Control Center and theMission Evaluation Room about questions, ans wers , and speci fic information concern-ing the spacecraft and experiments hardware w ere documented on a spacecraft-analysis/mission-evaluation action request form. This documentation w a s often thewritten confirmation of concurrent verbal understandings between the two groups,sometimes containing additional detail backing up the verbal action.

of an anomaly was frequently documented for the first time in one of these messages.The identification

The request fo rm s issued by the mission evaluation team, in the form of ques-tions, responses, or information, wer e signed by the originating specia list, by theanalysis manager o r managers for the system o r sy st em s affected, by the contractorrepresentative to indicate concurrence from the team a t the contractor facility, and bythe evaluation team manager to indicate that the contents covered all affected systems.Copies of these messages were al so forwarded by wire to the contrac tor, and contrac-tor inputs to the team at MSC were documented on sim il ar f orms .10


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Because the actions covered by these communications were for real-time deci-Sometimes, an immediate

sions, response time was kept to a minimum. Sometimes, the answer was almostinstantaneous and requi red close -knit, alert team action.reply required action to achieve a sa fe standby condition until the r es ul ts of expedited,special ground tests and analysis provided a more permanent, longer range procedure.The team handled an average of 325 of these requests for each lunar-landing mission.In addition, anomalies were noted briefly in the 2 -hour status r epor ts preparedby the analysi s mana ger s during the mission. In these repor ts, the status of eachspacecraft syst em and experiment was presented fo r each 2-hour period during themission. As a result, a problem would sometimes be described s ev er al places in thesam e re por t because of its effect on mor e than one system.tional assurance that team members were aware of problems and trends in other sys-tems as well as in the ir own.2-hour re po rt s for the preceding 24 hours.

This re po rt provided addi-The da i l y report was , in essence, a summary of the

As problems were identified, they were documented on a problem -tracking list,which included a statement of the problem as it w a s understood at the time, identifica-tion of the responsible analysis manager o r managers, and a brief discussion of theproblem, including the action in pro gr es s and the schedule sta tus of the resolution.This list, distributed to team members and posted in the Mission Evaluation Room,established a definite point on which to focus direction and continuity of effor t so thatanomaly resolution would be more efficient and effective. Items that had been incor -rectly identified as problems because of insufficient o r misinter preted information werequickly recognized as normal operations, and efforts were directed toward resolvingthe authentic anomalies.

After FlightAfter flight, the documentation was changed to su it the postmission test ing andanalysis required for anomaly resolution.the Problem and Discrepancy 'List. report s, which included se pa ra te documentation fo r.each anomaly. Examples of the Problem and Discrepancy Lis t format for individual

problems are included in 'the appendix.example of the final format for the program.

The problem -tracking list w as expanded into

The extract from the Apollo 14 mission is an

The Problem and Discrepancy List was updated frequently as the fast-movingresolution process prog ress ed, Statements in each issue of the re po rt were subject tochange as the analysis continued and were based on indications at the time the list waspublished. As a resul t, discuss ions and conclusions could change significantly fromissue to iss ue until final closeout. The changes reflec ted the pr og re ss in the analysi sand resolution. Because of the frequency of the Apollo miss ions and the need for co r -rective actions befo re the next flight, this frequently updated format w a s a definiteadvantage.

The Problem and Discrepancy L ist included problems f rom the problem -trackinglist; problems identified during crew debriefings, particularly those pertaining to crew-operated equipment; and problems identified during the analysis of the in-flight photog-raphy and processe d data. There wa s an average of 72 Problem and Discrepancy Listit ems f o r each lunar -landing mission.11


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A report w a s published by MSC 30 days af te r each flight. In the 30-day report,the anomalies were identified, the analyses discussed, and the corrective actionsexplained when determined.The mission report, published by MSC approximately 9 0 days after each mission,included sections in which each flight anomaly was discussed. Ext rac ts from three

mission repor ts ar e included in the appendix. An average of 35 anomalies were dis-cussed in each lunar -landing -mission repor t.

Updating and publishing of the Problem and Discrepancy List was continued af te rCor-ublication of the mission re po rt until all problems could be considered closed.rective action was always taken for cr iti cal failur e modes. When the cause of a criticalfai lure could be isolated to no less than two o r more possibilities, corrective actionw a s taken for each possible cause. A closed problem w a s usually one for which thecause had been determined and the corr ective action w a s being implemented. A sepa-rate anomaly report w a s published for each anomaly that w a s not r esolved and closedbefore publication of the mission report. Examples of anomaly re po rt s are included inthe appendix. '

Continuing DocumentationScientific data-gathering equipment and re la ted communications and power equip-ment were deployed on the lunar surface by the crewmen on each of the six Apollolunar-landing missions from July 20, 1969 (Apollo l l ) , to December 12, 1972(Apollo 17).return of the crewmen to Earth; therefore, from the standpoint of the experiments

hardware specia lis t, the lifetime of each of these miss ions extends considerablybeyond splashdown.

The deployed equipment w a s designed to continue to provide data after

Transmission of data from the Apollo 1 1 station ended on December 14 , 1969 .However, the other five stations were designed for considerably longer lifetimes, andcommunications with all five stations a r e continuing. Almost all the experiments thatwere deployed and activated continue collecting data, and analysis of the scient ific datacontinues.The spacecraft-analysis/mission-evaluationaction reques t form is being usedto provide the documentation of communications between the flight controllers and thehardware engineers and scien tist s in much the s am e way as during the flight. Problemidentifications, investigative actions and result s, resolutions, and cor rec tive actionsare documented in th is system. The Apollo Pr og ra m Lunar Surface Equipment StatusReport has replaced the Problem and Discrepancy List. This re po rt is issu edat approxi-mately 3-month intervals; interim re po rt s a r e issued i f an ea rl ie r update is requiredfor a specific purpose.Anomaly resolution documentation w a s handled in the sam e manner f or the twoparti cles and fields subsate llites that were launched into lunar o rbi t from the Apollo 15

and 16 service modules, TheApollo 15 subsatellite mission ended August 23, 1973 .The Apollo 1 6 subsatellite mission ended May 29, 1972.

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CONCLUDING REMARKSThe flight anomaly resolution s ystem, developed and implemented during theApollo Program, w a s used successfully for identifying and resolving problems and fordetermining the proper course of action within the relatively sh or t time f ra me allowedby the Apollo Program schedule of missions. The s ucce ss of this operation contributedto the over all succ es s of the Apollo Program. The prim ary re as on s fo r the degree ofsu cc es s achieved in flight anomaly resolution a re as follows.1. The application of the concept of a mission evaluation team that was knowl-edgeable in all hardware syst ems serving as an integral pa rt of t he mission teamwhile retaining the freedom to pursue problem solution to the extent requir ed formission and program success2. The selection of the proper personnel for this team, including the specialists,the team leaders, and the team manager3. The recognition that this team assignment was the pr im e activity for eachmember during the mission anomaly resolution period4. The establishment of an effective interface level for the evaluation team withothe r segments of the overall mission team5. The provision to the evaluation team of displays, data, and communicationsnecessary for maintaining constant awareness of total system performance as themission progressed6. The establishment of a definite point on which to focus direction and continuity

of effort through a timely documentation system7. The implementation of a flexible updating system for problem resolutiondocumentation to ensure a common understanding of problem statu s by me mb ers of theoveral l miss ion team, including projec t management8. The consistent application of the premise that, before any anomaly was con-sidered resolved, it was necessary

a. That the details of how each affected system, component, o r circuit func-tioned normally, and .its purpose, be understoodb. That the detail s of the anomalous condition be understoodc. That the relationship of the affected function with other sys tem functionsand with the total mission be understood

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A P P E N D I XEXAM PLES OF PROGRESSIVE DOCUMENTATION OF ANO M ALY RESO LUTI O N

Extracts from the anomaly resolution documentation system a r e included becausethe changes in the documentation fr om issue to issue reflect the pr og re ss made in theanomaly resolution process. The se ri es of repo rts also il lust rate s some of the manyconditions that influence the resolution proc ess. The re po rt s included a r e as follows.1. Extracts from Problem and Discrepancy List reports

a. Apollo 12, December 5, 1969, GFE-1b. Apollo 12, December 16, 1969, GFE-1c. Apollo 14, April 12, 1971, ALSEP-18d. Apollo 14, May 14, 1971, ALSEP-18e. Apollo 14, July 15, 1971, ALSEP-18

2. Extracts from mission re por tsa. Apollo 12 Mission Report, March 1970, Section 14. 3 . 1b. Apollo 14 Mission Report, April 1971, Section 1 4 . 4 . 7c. Apollo 7 Mission Report, December 1968, Section 1 1 . 2 1

3. Complete Reportsa. Apollo 14 Mission Anomaly Report No. 6, December 1972b. Apollo 7 Mission Anomaly Report No. 3, February 1969C. Apollo 10 and 11 Missions Anomaly Report No. 1, April 1970

The four problems selected wer e among the l e ss complex examples available.Resolution of the Apollo 12 lunar surf ac e television camera problem involved examina-tion of the flight hardware, which w as returned as a result of the problem. It was anobvious component fa ilure and w a s resolved quickly. The problem hastened completionof the development of an improved image sensor .Resolution of the Apollo 14 active seismic experiment geophone problem requiredtesting by telemetry uplink commands to the experiment and breadboard bench tests onth e ground because the flight hardware had been deployed on the lunar sur face . Theprob lem occ ur re d af ter completion of the flight and was not resolved before publicationof the mission report. The pr og re ss made in the resolution pr oc es s, including changesin the conclusions fr om issue to issue, is apparent in the extracts from the reports.

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Resolution of the Apollo 7 command module floodlight problem involved examina-tion of the flight hardware as well as testing to determine expected lamp life and todevelop proper preflight procedures. The flight hardware was available since it w a spar t of the retu rned command module.A s described in the anomaly report, the fuel ce ll condenser exit- temperature

oscillat ions encountered on the Apollo 11 mission had been observed on seve ralmissions. Analysis in great er depth was requ ired to understand the condition. Theresolut ion included a detailed analys is of the flight data.

APOLLO 12 LUNAR SURFACE COLOR TELEVI S l O N CAM ERA FA1 LUREThe loss of the Apollo 12 color television picture occurred when the camerawas inadvertently pointed toward the Sun while being tr an sf er re d to the lunarsur fac e from the modular equipment stowage assembly of the lunar module. Thepermanent lo ss resulted f ro m both a crew operational procedure problem and adesign weakness because the image sensor was susceptible to almost immediate

damage i f exposed to high-intensity light. Ground te s ts performed on si mi la requipment and on the re turned hardware revealed the following.1. That light overstress from direct sunlight would immediately damage the

image sensor2. That high-intensity light from highly specular reflections, as well as directsunlight, would damage the image sens or3. That an image sen sor more resi stan t to damage by high-intensity light wasnecessary4. That improved pointing procedures and controls were needed

The cause of the problem wa s closed out in the documents that follow. The correct iveaction, which continued af te r the publication of these documents, produced a satis-factory image se nso r and a remote-control camera-pointing system for subsequentmissions.

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EXTRACT

TIME :DESCRIPTION:

DISCUSSION:

I N PROGRESS:

Apollo 12 Problem and Discrepancy ListD e c e m b e r 5, 1969

D ur in g f i r s t ex t r a v eh i c u la r a c t i v i t y a t 116 hoursLunar s u r f a c e c o l o r t e l e v i s i o n c am er a d i d n o t o p e r a t ea f t e r deployment f rom lunar module.The c am er a p r o v id e d s a t i s f a c t o r y t e l e v i s i o n c ov er ag e f o rapproximate ly 40 minu te s .t i o n , t h e p i c t u r e f a i l e d when t h e t u be w a s appa ren t ly ex -p os ed t o d i r e c t s u n l i g h t o r d i r e c t r e f l e c t i o n f rom h i g h l ys p e c u l a r lunar module surfaces.Camera i s now i n Lunar Receiving L abora tory and w i l l bereleased on December 6 , 1969.t e s t i n g w i l l be performed a t MSC:1. Determine whether th e co l or whee l i s r o t a t i n g ; i f p os-2. D i s ab l e t h e au t o ma t i c l i g h t c o n t r o l c i r c u i t a nd e v a l u a t e

When moved t o a d i f f e r e n t l o c a -

Afte r r e l e a s e , t h e f ol lo w in g

s i b l e , wi thout removing th e camera case .

t h e t o t a l v id e o s i g na l t o d et er mi ne t h e e x t e n t o f v i d i co ndamage.

3. Perform a mechan ica l fv i sua l in spec t ion o f the equ ipmen tt o de te rm in e i f any other damage was incurred and i fextreme he at in g had been expe rienc ed by t he camera.

T h i s t a s k w i l l be comple ted wi th in two weeks a f t e r re ce ip tof camera.

COMPLETION : January 21 , 1970ASSIGNED TO : Kingsley

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EXTRACTApol lo 12 Problem and Discrepancy L is tDecem ber 16 , 1969

TIME : During f i r s t e x t r a v eh i c u l a r a c t i v i t y a t 116 hour sDESCRIPTION: Lunar sur f ac e col or te le v i s i o n camera di d not op er at e

a f t e r dep loyment f rom lun ar module.DISCUSSION: The camera provided sat is fa ct oy : te le v is i o n coverage fo r

approximately 40 minutes .t i o n , t h e p i c t u r e f a i l e d when t h e t u be w a s a p p a r e n t l y ex -p osed t o d i r e c t s u n l i g h t o r d i r e c t r e f l e c t i o n from h i g h lys pe c u l a r l u na r m odule s u r f a c e s .A f t e r decontamina t ion and c le an ing , t he camera w a s i n s p e c t e da nd t h e n o p e r a t e d . The p i c t u r e t h a t r e s u l t e d w a s the sameas t h a t r e c e i v e d at t he e nd o f t he A pol lo 12 t r a ns m i s s i on .The c ol or wheel could be he a r d t u r n i ng w i t h i n t he c am er a,and when th e l en s wa s r emoved , t he tu r n i ng w a s viewedd i r ec t l y . The power t o th e camera was tu rne d on and of fs e v e r a l t i me s t o s e e t h e w he el start and s top . By c u t t i n gone w i r e , t he A u toma ti c L i ght L e ve l c on t r o l c i r c u i t wasd i s a b l e d , a nd t he c am era t u r ne d t a c k on. A w e l l d e f i n e dimage WBS v i s i b l e i n t h e p i c t u r e i n t h e a rea which w a sformerly b lack . This b lac k r e p r e s e n t e d t h e undmaged a r e ao f t h e i mage s e n s o r t a r g e t . T h i s t e s t pr ov ed c o n c l u s i v e l yt h a t t h e A po ll o 12 f a i l u r e was due t o a damaged i m a g e sen-s o r .I n a d d i t i o n , t h e c m e r a c o n t r a c t o r d e l i b e r a t e l y damaged as i m i l a r im age s e n s o r by a p p ly i n g b r i g h t l i g h t l e v e l s . Ther e s u l t i n g p i c t u r e w a s similar t o t h a t o f t h e A po ll o 12camera.S u b j e c t t o A p o ll o CCB approval on December 12 , 1969, a l e z scover w i l l be p r ov i de d f o r t he A pol lo 13 camera . Opera t iona lp r oc e du r e s a nd t r a i n i ng w i l l a l so be improved t o r educe prob-a b i l i t y of e xp o su re .are a l s o be i ng e va l ua t e d .

When moved t o a d i f f e r e n t l o ca -

A ut om at ic p r o t e c t i ve de s i gn a pp r oa c hes

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EXTRACTApollo 12 Mission ReportMarch, 1970

l k . 3 GOVERNMENT FURNISHED EQUIPMENT

14.3.1 C ol o r T e l e v i s i on F a i l u r eThe c o l o r t e l e v i s i o n c am era p r ov i de d s a t i s f a c t o r y t e l e v i s i o n c o ve r -

age fo r approximate ly 40 minutes a t t h e be g i nn i n g o f t h e f i r s t e x t r a ve -h i c u l a r a c t i v i t y . T h e r e a f t e r , t h e v i de o d i s p l a y showed o n ly w h i t e i n ani r r e g u l a r p a t t e r n i n t h e u pper p a r t of t h e p i c tu r e and b la ck i n t h e re -maind er. The camera w a s t u r n e d o f f a f t e r r e p e a t ed a t t e m p t s by t h e crewt o r e s t o r e a s a t i s f a c t o r y p i c t u r e .

Ground t e s t s us in g an Apol lo-type image senso r ( secondary e l ec t r onconduc t ing v id ico n tu be ) exposed th e camera sys tem t o extreme l i g h tle ve ls . The r e su l t in g image on a monitor w a s v er y s i m i l a r t o t h a t s ee na f t e r t h e f l i g h t c amera fa i lure .

After d e c o n t m i n a t i o n and c l e an i n g, t h e f l i g h t ca mera w a s i n s p e c t e dand power w a s ap pl ie d. The image, as viewed on a moni tor , w a s t h e same ast h a t las t s e e n from t h e l u n a r s u r f a c e . The a u t om a t ic l i g h t - l e v e l c o n t r o lc i r c u i t w a s d i s a b l e d by c u t t i n g on e wire. The camera then reproduced goods ce ne d e t a i l i n t h a t area of t h e p i c t u r e w h ic h ha d p r e v i ous l y bee n b l a c k ,v e r if y i n g t h a t t h e b l ac k a r e a of t h e t a r g e t w a s undamaged, as shown i nf igure 14-39 . T h i s f i nd i n g a l s o pr oved t h a t t h e c om bina t ion o f nor ma la ut om at ic l i g h t c o n t r o l a c t i o n and a damaged image-tube t a rg e t caused t h eloss of p i c t u r e . I n t h e p r oc e s s o f moving t h e c am er a on t h e l una r sur-f a c e , a p o r t i o n of t h e t a r g e t i n t h e s e c on d a ry - e le c t ro n c o n d u c t i v i t yv id iccn mus t have r ece ived a h i gh solar i n p u t , e i t h e r d i r e c t l y from t h esun o r fro m some h i g h l y r e f l e c t i v e s u r f a c e . T ha t p o r t i o n o f t h e t a r g e twas de s t r oye d , a s w a s evidenced by th e whi te appearance of th e upperp a r t o f t h e p i c t u r e .

T r a i n i ng a nd ope r a t i on a l p r oc e du r e s, i nc l ud i ng t h e u se of a l e n s c a p ,are be i ng c hange d t o r e duc e t he p os s i b i l i t y o f e xpos i ng t h e i mage s e ns o r .t o e xt re m e l i g h t l e ve l s . I n a dd i t i on , de s i gn c ha nges a r e be i ng cons i de r e dt o i nc l ude a u t o ma t ic p r o t e c t i o n , such as t h e use of an image se ns or whichis less s u s c ep t i b le t o dacage f r c z i n t e n se light l e v e l s .

T h i s anamaly i s c l o s e d .

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EXTRACTApollo 12 Mission Report

March, 1970N A S A - S - 7 0 - 1 4 3 4

optics Photoelectrons

Videosignal

Dischargecurrent

+V d

r Aluminum oxide

-Potassium ch lor ideburned o f f an daluminum andaluminum oxideruptured

Good potassium chloridetarget areaTarget3ide view Targ et front viewFigure 14-39. - S ec on da ry e l e c t r o n c o n d u c t i v i t y t u b e i n t h ec o l o r t e l e v i s i o n .

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APOLLO 14 A C T I V E S E I S M I C EXPERIMENT - ERRATl C DATAFROMNUMBER3 GEOPHONEThe number 3 geophone data from the Apollo 14 active seismic experiment becameerratic. These data had been satisfactory during crew thumper operation on the lunarsurf ace and also during high-bit-rate listening periods during the first 49 days afterdeployment at the lunar surf ace site. Tes ts of the emplaced flight hardware were per-

formed by transmitting selected command sequences to the experiment, and the telem-etry data and experiment cir cuit s were analyzed,breadboard bench tests. Components taken from the lot that included the malfunctioningcomponent were tested for a possible generic problem that would req uir e corr ectionbefore the next mission.

The problem was duplicated by

The prog ress ive ste ps in the analyses ar e apparen t in the documents that follow.They reflect a better understanding of th e cause as more r esul ts of t est s and analysesbecame available. A s indicated in the final anomaly report , the resolut ion also includedan analysis of how the data from the number 3 sen sor could be used i f required for theanalysis of a specific event.

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EXTRACTApollo 1 4 Problem and Discrepancy ListApri l 12 , 1971

Italics indicate change from previous issue.P R O B L E M A N D D l S C R E P A N C Y L I S T N ~ .LSEP- I 8

St at ement o f Problem:Active seismic experiment no. 3 geophone data became erratic.

D i s c u s s i o n :On March 26, the experiment was turned on i n the list enin g mode (h igh b i tratel and Geophone #3 was spikin g t o off -s cal e high.was transmi tted to a l l thr ee geophone channels.scale high simultaneous with the application of the calibration pulse andstayed off-scale high for the remainder of the listening period.one second period when the ca li br at io n pul se was present, Geophone #3 datashowed four negative going pulses from off-scale high.shorter than corresponding oscillations on Geophones 1 and 2 and decreasedfrom the f i r s t t o the fourth. The characteris t ics of these pulses indicatedthat Geophone # 3 channel was ope rating a t a higher gain than Geophones 1 and2 during the cali brat ion period.had to be i n the logarithmic compressor i n t he Geophone #3 amplifier chain.Signals are coupled into the logarithmic cwnpressor through an input couplingcapacitor which would block any dc vol tage which would have t o b.e pr es en t t odrive the output voltage off -s cal e high fo r long periods (more than 1 or 2minutes).The logarithmic compressor i s bas ical ly an inve rti ng ampl ifie r wit h exponen-tial negative feedback.

The calibration commandGeophone #3 channel went of f -During the

Pllse widths were

Circuit an alysis indicated that the problem

Two diode connected transistors between the output(see continuation sh eet)

N o t e s : 1 . Th i r d lunar day data. 5 t o 1 5 minutes of high b i t ra te data da i ly ,April 4 - 1 2Preliminary analysis A p r i l 1 - 8 - Complete.3. Bench checks and analysis.

Personnel Assigned:J . Harris , Be nd k, Geo tech, Gadbois

Conclus ions:*

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EXTRACTApollo 14 Problem and Discrepancy ListApril 12, 1971

Italics indicate change from previous issue.P R O B L E M A N D D I S C R E P A N C Y L I S T N,, . .ALSEP-l8C O N T I N UA T ION S H E E T

D iscuss ion :

and inpu t of the ampli fie r supply the feedback.f o r pos it iv e going and the second f o r negative going input signals.diodes for all three geophone channels 12 per c.hanne1) are physically lo-cated i n an oven which contr ols th ei r temperature at 105OC.Analysis ind ica tes tha t the most probable cause of the problem i s . an in -ter mit ten t open ci rc ui t in th e diode feedback path. This would allow theamplifier input tran sist or t o saturate, driving the output off- scale high.men signals large enough to drive the input stage act of saturation werepresent, the output would then respond and ampl if ie r gain would not becompressed.l'uo copper paths conduct the feedback diodes to the logarithmic compressoramplifier.characteristics.phones by energizing 3 rela ys, the rela y contact t ran sfe r shock could thendisturb the solder crack and either open or close the feedback path.The problem was detected during the lunar night at the experiment location.Under lunar night conditions the thermal gradient between the oven (105C)and the re st of the electroni cs ( 4 . 4OC ) was m a x i m .di en ts cause mechanical s tr ess es by di ff er ent ia l thermal expansion, t helarge temperature gradient between the oven and the rest of the experimentel ec tr on ic s probably caused the crack.A breadboard of the logarithmic compressor w i l l be constructed and thediode feedback loop w i l l be opened to duplicate the experiment data.

The f i r s t diode i s usedThe

A solder crack i n either path would then re su lt i n the dataSince the cal ibrat ion uoltage i s applied to the 3 geo-

Since thermal gra-

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EXTRACTApol lo 14 M iss ion ReportApri l 1971

14 . 4 . 7 Act ive Se ismic Geophone 3 E lec t ron ic Ci r cu i t Er r a t icThe experiment was tu rned on i n th e l i s t en in g mode on March 26 ,1971, and geophone 3 d a t a were s p i k i ng o f f - s c a l e h i gh ( f i g . 14 - 34 ) .

When th e geophone c ha nn el s were ca l i b r a t ed , th e geophone 3 channe l wento f f - s c a l e h i gh s i m ul t a neous l y w i t h t h e s t a r t o f t h e c a l i b r a t i o n p u l seand s t a ye d o f f - s c a l e h i gh f o r t h e r em ai nd er o f t h e l i s t e n i n g p e r i o d .Dur ing th e 1-second per iod when the ca l i b r a t io n pu ls e w a s p r e s e n t , d a t afrom geophones 1 and 2 showed t h e normal 7-her tz r i ng in g caused by th eca l i b ra t i on pul se . However, geophone 3 data showed four negat ive-goings p i k es c o in c i d en t w it h t h e f i r s t f o u r n e g a t i v e h a l f c y c l e s of t h e r in g -ing on th e o the r two channe ls . The sp ik es decreased in dur a t i on fromt h e f i r s t t o t h e l a s t , t h e l a s t having an ampli tude of 90 perc ent off u l l s c a l e ( p l u s 2.5 v o l t s t o minus 2 .0 v o l t s ) . Dur ing the t i m e t h a tth i s pu lse was pr ese n t , t he s i gn a l on channe l 2 changed f rom minus 2 .2v o l t s t o minus 2.35 v o l t s , i n d i c a t i n g t h a t c h a n ne l 3 w a s o p e r a t i n g a tan apparen t ga i n of 30 times the channe l 2 ga in .

A s shown i n f ig ur e 14-35, each geophone channe l c on s i s t s o f a geo-phone , an input p rea mpl i f ie r , a lo w-pass f i l t e r , a nd a logar i thmic com-p r e s s o r a m p l i f i e r .ins t rum enta t ion sys tem. The loga r i th mic compressor i s b a s i c a l l y a n i n -ve r t i n g a m p l i f i e r w i t h e xpone n t i a l ne ga t i ve f e edba ck .ne c t e d t r a n s i s t o r s be tw ee n t h e ou t pu t and i npu t o f t h e a m p l i f i e r s upp l ythe f eedback .f o r ne ga ti ve- goi ng i npu t s i g na l s .channe ls ( two per channe l ) are phy s i c a l l y l o c a t e d i n a n ove n w hi ch con-t r o l s t h e i r t e m pe ra tu re a t 105' C .

The ou t pu t o f the l oga r i t hm i c c om pr es so r f e e ds t heTwo diode-con-

The f i r s t diode i s used fo r pos i t ive -going and th e secondThe diodes for a l l three geophone

NASA-S-7 1-1703Cal ibaw

= +JI +2.4v dcI-.- I ID lCcophom I- . 1 - Premplificr Tolelcnyvy

Figure 14-35.- Ty pi ca l geophone 'chann el .

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EXTRACTApol lo 14 Miss ion ReportApr i l 1971

I t i s b e li e ve d t h a t t h e f a i l u r e i s i r l the logar i thmic compress iona m p l i f i e r be ca use s i gn a l s a r e c oup le d i n t o i t th rough an input coupl ingc a p a c i t o r .ceding s tag es which would be re qu ired t o dr i v e t h e out pu t o f f - s c a l e h i gh .Ana lys i s ind ica te s t h a t th e most p robable cause of th e problem i s ani n t e r m i t t e n t open c i r c u i t i n t h e d io de fe ed ba ck p a th .t h e a m p l i f ie r i n p ut t r a n s i s t o r t o s a t u r a t e , d r i v i n g t h e o u t p u t o f f - s c a l eh igh . When s i gn a l s l a rg e enough t o drive th e input s t ag e ou t o f sa t ura -t i o n were pre sen t , th e ou tput would then r espond and th e ou tput s ig na lwould not be com pressed.

This cap ac i t o r would b lock any of f s e t vo l t age s f rom the pre -

This would allow

The exper iment e le ct ro ni cs u ses l lcordwoodl' co ns tru ct i on of t he typ ewhich has caused sol de r cracks i n other equipment. Two copper pat hs con-duc t t he f eed-back d iodes t o th e logar i thmic compressor am pl i f i e r , As o l d e r c ra c k i n e i t h e r p a t h would t he n r e s u l t i n t h e d a t a c h a r a c t e r i s t i c s .

There are 1 0 s uc h s o l de r j o i n t s f o r e a ch ge ophone ( f i g . 14-36):fou r on th e oven te rmin a l boara , f our on th e mother board , one on thet op boar d o f t he l o g compressor module, and one on the bottom board oft h e l o g comp ressor module. The one mo s t l ik e l y t o f a i l f i r s t i s on theto p board of th e lo g compressor module. Co nti nui ty a t t h e j o i n t re -cover s as long as t he c r a c k c l o s e s du r ing t he l un a r da y .

NASA-S-7 1-17047ost l ikely cracked joint

Oventerminalboard-Motherboard

' Log compressorto p board

- Log compressorbottom b o a d

Figure 14-36.- S uspe ct e d cr ac ke d s o l d e r j o i n t s i n a m p l i f i e r .

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EXTRACTApollo 14 Mi s s i on R e p ortApri l 1971

m

CCI

8it

N

4 00 v ! ? 0

N l nv!N

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EXTRACTApollo 14 Mission ReportApril 1971

The loe; compressor modules f o r geophones 1 and 2 ar e of th e samet y p e c o ns t r u c ti o n . S in c e t h e s e a r e l o c a t e d s l i g h t l y f u r t h e r from t h eoven tha n t h e one fo r geqphone 3, t h e maximum temperature may not beq u i t e a s h i gh . As a r e s u l t , i t may take long er f o r them t o c r ack , ifa t a l l .

S ys te ms t e s t i n g i nc l ude d ope r a t i ona l the r m al c yc l i ng t e s t s ove r t h etempera ture r ange fo r luna r day and n i gh t .a r e a f u n c t i o n o f t i m e as w e l l as t empera ture, and appa ren t ly th e groundt e s t cyc le d id not a l low enough t ime fo r a c r e e p f a i l u r e . T h is e qu ipme ntw a s d es ig ne d and b u i l t p r i o r t o t h e t i n e when it w a s found t h a t cordwoodc ons t r u c t i on w i t h s o l de r e d j o i n t s was uns a t i s f a c t o r y .

However, c r acked so ld er jo i n t s

A breadboard of t h e logar i thmic compressor has been cons t ru c ted ,and th e d iode f eedback loop w i l l be ope ne d t o dup l i c a t e t h e e xper im e ntdat a . The mechanical des ign of t he log ar i thm ic compressor w i l l be re -viewed t o determine th e 'changes th a t must b e made t o prevent so l de rcracks on Apollo 1 6 . The a ct iv e se ismic exper iment i s no t c a r r i e d onApollo 15.

Procedura l changes under con s ide ra t ion i nc lud e opera t ion of t h eme n t o main ta in compressor module tempera ture because t h e so lde r j o i n twhich i s most l ik e l y c r acked i s i n conlpress ion ( s t ro ng er ) a t t h e h i g h e rtempera ture .

This anomaly i s open.

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EXTRACTApollo 14 Problem and Discrepancy L is tMay 14, 1971

Italics indicate change from previous issue.P R O B L E M A N D D I SC R E P A N C Y LIST N ~ . LSEP-18

St at ement o f Problem :Active seismic exper iment no. 3 geophone dat a became er r a t i c .

Discussion:On March 26, t he exper imen t w a s t u r n e d on i n t h e l i s t e n i n g mode ( h i g h b i tr a t e ) and geophone #3 w a s s p i k i n g t o o f f -s c a l e h i g h .was t r a n s m i tt e d t o a l l three geophone channels .s c a l e h ig h s i mu lt an e ou s w it h t h e a p p l i c a t i o n of t h e c a l i b r a t i o n p u l s e a nds t a y ed o f f - s c a l e h i g h f o r t h e r em a in de r o f t h e l i s t e n i n g p e r i o d .one second per iod when th e ca l i b r a t io n pu l s e was presen t , geophone # 3 d a t ashowed four nega t ive go ing pu l s es f rom of f - sc a le h igh . Pu l se wid ths weresh or t e r than cor respond ing os c i l l a t io ns on geophones 1 and 2 and decreasedfrom t h e f i r s t t o t h e f o u r th . The c h a r a c t e r i s t i c s o f t h e s e p u l s e s i n d i c a te dthat geophone # 3 channe l w a s o p e r a t i n g at a high er ga in than geophones 1 an d2 d u r in g t h e c a l i b r a t i o n p e ri o d . C i r c u i t a n a l y s i s i n d i c a t e d t h a t t h e pro ble mh ad t o b e i n t h e l o g a r i t h m i c c om p re ss or i n t h e g eo ph on e # 3 a m p l i f i e r c h a i n .S i g n a l s are coup led in to th e loga r i thmic compressor th rough an inp u t coup l in gcap aci tor which would block any dc vol tag e which would have t o be prese nt t od r i v e t h e o u t p u t v o l t a g e o f f - s c a l e h i g h f o r l o n g p e r i o d s (more than 1 o r 2minutes ) .

The ca li b ra ti o n commandGeophone # 3 channel went of f -

Dur ing the

The logarithmic compressor i s b a s i c a l l y a n i n v e r t i n g a m p l i f i e r w i t h e xp on en -t i a l nega t ive f eedback . Two d i o d e c on n ec t ed t r a n s i s t o r s b e t we en t h e o u t p u t

( s e e c o n t in u a t i o n s h e e t )

Schedule:

N o t e s : 1. Thi rd lun ar day da ta . 5 t o 1 5 m in ut es o f h i g h b i t r a t e d a t a d a i l y ,2.3. Bench checks and analysis

A p r i l 4 - 12P r e li m i n ar y a n a l y s i s A p r i l 1 - 8 - complete

Per sonnel Ass igned:J . Harr is , Bendix, Geotech, Gadbois

C o n c l u s i o n s :

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EXTRACTApollo 14 Problem and Discrepancy ListMay 14, 1971

Italics indicate change from previous issue.P R O B L E M A N D D IS C R E PA N C Y L I S T N ~ . LSEP-18C O N T I N U A T I O N S H E E T. Discussion:

and inpu t o f the ampl i f i e r supp ly th e feedback . The f i r s t d iode i s usedfo r po s i t ive go ing and th e second fo r nega t ive go ing inpu t s ig na l s . Thed iodes fo r a l l three geophone channels ( 2 per channe l ) are p h y s i c a l l y l o -ca te d i n an oven which c on t ro l s t h e i r t empera tu re a t 105OC.Analys i s in d ic a te s th a t t h e mos t p robab le cause o f th e p rob lem i s an in-t e r mi t t e n t open c i r c u i t i n th e diode feedback pa th . Th i s would a l low th ea m p l i f i er i n p u t t r a n s i s t o r t o s a t u r a t e , d r i v i n g t h e o u t pu t o f f- s c a l e h ig h .When s ig na l s l a rg e enough t o d r iv e the inpu t s t age ou t o f sa tu r a t i on werepre sen t , th e ou tput would then respond and amp l i f i er g ain would not be com-pressed.The experiment ele ct ro ni cs used "cordwood" con st ru cti on of the t y p e whichhas caused solde r cracks i n othe r equipment.feedback diodes t o the logarithmic compressor ampli fie r.eit her path would then re su lt i n the data charact eris tics .There are ten suck solder joints for each geophone:m i n a l board, four on the mother board, one on the top board of the log com-pressor module and one on th e bottom board of th e log compressor module.The one most li ke ly t o f a i l f i r s t i s on the top board of the log compressormodule.ing the lunar day.The log compressor modules fo r geophones 1 and 2 are of the same type con-struction.one for geophone 3, the mmimwn temperature may not be quite as high.a result , i t may take longer fo r them to crack, i f a t al l .A breadboard of the logarithmic compressor has been constructed and the diodefeedback loop w i l l be opened t o duplicate the exp erine nt data.The active seismic experiment i s not on Apollo 1 5 .

Two copper paths conduct theA solder crack i n

four on the oven ter-

Continuity at the jo in t recovers as long as the crack clos es dur-

Since these are located slightly further from the oven than theAs

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EXTRACTApollo 14 Problem and Discrepancy ListJuly 15, 1971

Italics indicate change from previous issue. = Closure da te .P R O B L E M A N D D I S C R E P A N C Y L I ST N o . U E P - 1 8

S ta tement o f P rob lem:Active seismic exper iment no . 3 geophone d at a became e r r at ic . CLOSED

Discussion:On March 26, the experiment w a s t u r n e d on i n t h e l i s t e n i n g m ode ( h i g h b i trate) and geophone no. 3 w a s s p i k i n g t o o f f - s c a l e h i g h . The c a l i b r a t i o ncommand w a s t r a n s m it t e d t o a l l th r e e geophone chann els. Geophone no . 3 chan-n e l w en t o f f - s c a l e h i gh s i m u lt a ne o u s w i t h t h e a p p l i c a t i o n o f t h e c a l i b r a t i o np u ls e a nd s t a y ed o f f - s c a l e h i gh f o r t h e r e m ai n de r of t h e l i s t e n i n g p e r i o d .Dur ing the one second per iod when th e c a l ib r a t io n pu l se w a s present , geophoneno. 3 dat a showed fou r nega t ive going pulses . from off - sca le high. Puls ewidths were sh or t e r than cor r espond ing os c i l l a t io ns on geophones 1 and 2 an dd ec re as ed from t h e f i r s t t o t h e f o u r t h . The c h a r a c t e r i s t i c s o f t h e s e p u ls e sindicated that geophone no. 3 channel was o p e r a t i n g a t a high er ga in than geo-phones 1 and 2 d u r in g t h e c a l i b r a t i o n pe r io d . C i r c u i t a n a l y s i s i n d i c a t ed t h a tthe p roblem had t o be in th e logar i thmic compressor i n th e geophone no . 3ampl i f i e r cha in .S igna ls a r e coup led in to t he lo gar i thmic compressor through an inpu t c oup l ingcapa ci to r which would block .any dc vol tag e which would have t o be p res ent t od r ive th e ou tpu t vo l t age o f f - sca le h igh fo r long per iods (more than 1 o r 2minutes ) .

( s e e c o n t i n u at i o n s h e e t )

S c h e d u l e :D a ta R ev iew C ompleteA n a l y s i s C o m p l e t eT e s t s ( I d en t if y i n N o t e ) C o m p l et eC hanges ( Iden t ify in N o te )

Noten: 1. Third lunar day data . 5 t o 15 m in ut es o f h i gh b i t r a t e d a t a d a i l y ,A p r i l 4 - 12

2. Mathematical a na ly si s, May 113. Bench checks and an al ys is . Breadboard t e s t s , May 314 . Review. June 3

P ersonn e l A ss igned:J. Harris, Bendix, Geotech, Gadbois

COnClUSiOnS: Problem w a s caused by un intermittent f ail ure (open) i n the posit ive 'goingdiode wired trans istor i n the log compressor fo r the no. 3 geophone.is to r failu re appears t o be an isolated case rather than a generic condition.Trans-

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EXTRACTApollo 14 Problem and Discrepancy ListJuly 15, 1971

Italics indicate change from previous issue.P R O B L E M A N D D IS C R E PA N C Y L I S T N ~ . LSEP-18C O N T I N U A TI O N S H E E T

Discussion :

The logarithmic compressor i s ba s i ca l ly an inver t in g a mpl i f i e r wi th exponen-t i a l negat ive feedback.and inpu t of th e ampl i f i e r supp ly th e feedback . The f i r s t diode i s usedf o r po s i t ive go ing and the second fo r nega tive go ing inpu t s ig na l s . Thediodes f o r a l l three geophone channels ( 2 per channe l ) are p h y s i c a l l y lo -ca ted in an oven which co n t ro l s th e i r t empera tu re a t 105OC.Mathematical analy si s and breadboard t es t s show tha t th e cause of the prob-lem i s an int erm itt ent failu re (open) i n the posit ive going diode wiredtransis tor .ing the output off-scale high.put stage out of satur ation are present, the output responds, and amplifiergain w i l l not be compressed.No previous fa il ur es of t hi s type have been experienced during th e develop-ment and t e s t program.(2if2484-2B) i s connected directly to the case without a lead.and base are connected from pi n t o chip by small alwninum leads which couldpossibly break and again make contact with temperature changes or by mechan-ical shock from nearby relay actuation.The experinent el ec tr on ic s uses "cordWood" cons tru ctio n of the type that hascaused solde r cracks i n other equipment however, a cracked sold er j o i n t i nthe cordwood construction, i n t h i s case, w i l l not produce the f l i gh t re-su l t s .wood construction has averted a cracked solder joint, - a t l e ast , f o r thetime being.The next mission scheduled fo r the active seismic experiment i s Apollo 1 6 .

Two d iode connec ted t r an s i s t o r s between th e ou tpu t

This allows the amplifier input tran sis tor t o saturate, driv-When sig nal s large enough t o dri ve the in -

The collector of the intermittent trans istorThe emitter

Apparently some inadvertent st rai n r el i ef configu ration i n the cord-

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M S C - 0 7 6 3 8

APOLLO 14 MISSIONA n o n a l y R e p o r t N o . 6

A C T I V E S E I S M I C E X P E R I M E N T G EO P H O NE 3 D A T A E R R A T I C

P R E P A R E D B YFlission Evalua t ion T e a m

A P P R O V E D B Y

O w e n G . M o r r i sManager, A p o l l o Sp a c e c r a f t P r o g r a m

N A T I O N A L A E R O N A U T I C S AND S P A C E A D M I N I S T R A T I O NMANNED S P A C E C R A F T C E N T E R

H O U S T O N , T E X A SD e c e m b e r 1972

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ACTIVE SEISMIC EXPERIMENT GEOPHONE 3 DATA ERRATIC

STATEMENT OF ANOMALY

During th e high- bi t - ra t e l is te n in g mode pe r io d on March 26, 1971, h egeophone 3 da ta showed in te rm it te nt spikes going of f -s ca le high. When th ec a l i b r a t i o n s i g n a l was a p p li e d t o a l l three geophones, t h e geophone 3 d a t aw en t o f f -s c a l e h i z h f o r t he r e ma inder o f t h e l i s t e n i ng pe r i o d .r esponse w a s observed dur i ng th e succeeding weekly l i s t en in g mode per iods .A s imi la r

SYSTEM DESCRIPTION

The ac t i ve se i smic exper iment cons i s t s o f a n a r r a y o f t h r e e g eo-phones , a thumper w i t h 2 1 i n i t i a t o r s ( d e t o n a t o r s ) , a mortar package withfou r rocke t- launched grenades , a c e n t r a l e l e c t r on i c s a s se m b ly , a nd con-nec t in g cabl ing . The th re e geophones are de pl oye d on t he l u na r s u r f a c ei n a s t r a i g h t l i n e a t 150-foot in te rva l s and are u se d t o t r a n s l a t e p hy si -c a l s u r f a c e movement i n t o e l e c t r i c a l s i gna l s . The thum pe r i n i t i a t o r s ,f i r e d a t i n t e r v a l s along a p a t h p a r a l l e l t o t h e g eo phone l i n e , an d t h emor ta r g r enades , p rope l led t o d i s tan ces of 500 t o 5000 f e e t away from thegeophone l i n e , a r t i f i c i a l l y p roduc e s e i sm i c waves w hi ch a re d e t e c t e d b yth e geophones. I n ad di t io n , t he geophones monitor na t ur a l ly produced lu -n a r s ei sm ic a c t i v i t y i n t h e 3 t o 250 Hz range.

The cons t ruc t io n of a geophone i s shown i n f i gu re 1. A c o i l of cop-pe r w i r e ( se i smic mass) i s suspended i n a m ag ne ti c f i e l d by f l a t c a n t i -l e v e r s p r i n g s which a l s o g u id e t h e c o i l v e r t i c a l l y . The m ag n et ic f i e l di s produced by a permanent magnet frame.c o i l a nd t h e f ra me g e n e ra t e s a n o u tp u t v o l t a g e a cr o s s t h e c o i l , and t h i sv o l t a g e i s s u p p l i e d t hr ou g h c o n t a c t s of t h e c a l i b r a t e r e l a y ( f i g . 2 ) t ot h e i n p u t o f a p r e a m p l i f i e r . The preampl i f ie r ou tput i s t he n f e d t h r ougha low-pass f i l t e r t o a l oga r i t hm i c c om pr es si on c i r c u i t . S i gna l s a re cou-p l e d i n t o t h i s c i r c u i t t h r ough a n i npu t c oup l i ng c a p a c i t o r w hic h w ou ldno rm a ll y b loc k a ny d-c vo l t a ge t h a t m ust be p r e s e n t t o d r i ve t he o u t pu tvo l t a ge o f f - s c a l e h i gh f o r l ong pe ri ods (more than 1 o r 2 min ute s) . Theou t pu t s i gn a l f rom t h e l oga r i t hm i c c om pr es si on c i r c u i t ( t h e l oga r i t hm o ft h e i n p u t s i g n a l ) i s s u p p l i e d t o t h e t e l e m e t ry s y s te m .

Rela t ive mot ion be tween the

The logar i thmi c compress ion c i r cu i t p rov ides adequa te r eso lu t io n whens m a l l s i g n a l s a r e p re s e n t , b u t a l s o has t h e c a p a b i l i t y t o re sp on d t o t h eexpected 60- t o 8 0 - d ~ i gna l r a nge . T he c i r c u i t i s b a s i c a l l y an i n v e r ti n ga m pl i f i e r w i t h e xpone n t i a l n e ga t i ve f e edbac k . Two diode-connected t ran-s i s t o r s , i n p a r a l l e l , b e tw ee n t h e o ut pu t and i n p u t o f t h e a m p l i f i e r s up p ly

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Cable

Spike'k rFigure 1.- Cutaway view of geophone.

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t h e f ee db ac k s i g n a l ( f i g . 2 ) .i t i v e - g o i n g i n p u t signals , a nd t h e o t h e r i s used f o r t h e nega tiv .e -go inginp ut s i gn al s . The feedback t rai- sis tors fo r a ll th r ee geophone channe ls( two per channe l ) are p h y s i c a l l y l o c a t e d i n a n o ve n t h a t m a i n t a i n s t h e i rt e m pe r a t u r e a t 105' C.

One o f t he t r a n s i s t o r s i s u se d f o r t h e pos-

The geophone i s c a l i b r a t e d by app l y i ng a f ixed-ampl i tude , 1 - secondc u r r e n t p u l s e t o t h e geo pho ne c o i l .t o a new ba lan ce po s i t io n . The co i l w i l l o s c i l l a t e a bou t t he new pos i -t i on u n t i l t h e o s c i l l a t i o ns damp ou t . The geophone r e s ona n t f r e que nc y ,se ns i t iv i t y , and damping f ac to r can then be de te rmined f rom t h e dampedo s c i l l a t i o n w aveform g e ne r a te d w i t h i n t h e c o i l .

The c u r r en t f o r c e s t h e c o i l t o move

DISCUSSION

The ac t i ve se i smic exper iment w a s i n i t i a l l y t u r n e d on i n t h e t humpermode w it h t h e c e n t r a l s t a t i o n i n t h e high -b i t - r a te mode dur i ng lun ar sur-f a c e e x t r a v e h i c u l a r a c t i v i t i e s on Fe br ua ry 5 , 1971. Vibr at io ns f rom eachof 13 thumper f i r in g s were r ece iv ed by each of th e th r e e geophones andt h e data were t r a n s m i t t e d t o e a r t h . The e xpe ri m en t was then commandedt o t h e s tandby mode, and w a s to r emain i n th a t mode except fo r 30 minutesof op era t io n each week i n th e l i s te n in g mode and th e h igh-b i t - r a te mode.System operat ion w a s norm al du r i ng t h e f i r s t s i x w ee ks ; howe ve r, du r i n gth e seventh-week monit or ing cy cle (March 26, 19711, a t a bou t l una r mid-n i g h t , t h e geophone 3 da t a w ere s p i k i ng o f f - s c a l e h i gh .

All th r e e geophone channe ls were ca l i b ra te d , and th e geophone 3 chan-n e l went o f f - s c a l e h ig h s i m u lt a ne o u sl y w i t h t h e a p p l i c a t i o n o f t h e c a l i -b r a t i o n p u ls e ( f i g . 3 ) . The channe l s tayed of f - sc a le h igh f or th e r emain-d e r o f t h e l i s t e n i n g p e r i o d . D uri ng t h e 1-second per iod when th e ca l ib r a -t i o n p u l se w a s p r e s e n t , the geophone 3 da ta showed fo ur negat ive-g oingpul ses from of f - sca le h igh . Pu lse w id ths were sh or t e r than cor r espond ingos c i l l a t i o ns on ge ophone s 1 and 2 , a n d de c r e a s e d i n w i d th from t h e f i r s tt o t h e f o u r t h p u l se . The c h a r a c t e r i s t i c s o f t h e s e p u l s e s i n d i c a t e t h a tthe geophone 3 channe l was op era t in g a t a higher ga in than geophones 1and 2 d u ri n g t h e c a l i b r a t i o n p er i o d , a nd t h a t i t s ou t pu t was b i a s e d o f f -s c a l e h i g h .

A f a i l u r e i n t h e g eo ph on e, p r e a m p l i f ie r , o r f i l t e r c o u ld p ro du ce ab i a s o f f s e t ; however, th e compressor input coupl in g cap ac i to r vo uld b lockt h e b i a s o f f s e t and t h e ou tpu t s i gna l would no t r em ai n o f f - s c a l e h i gh .Had t h e i npu t c a pa c i t o r s ho r t e d , t he ou tpu t woul d be s h i f t e d , bu t no t o f f -s c a l e - h i gh . The f a u l t , t h e r e f o r e , must have bee n w i t h i n t he l oga r i t hm i cc o m p r e s s o r c i r c u i t ( f i g . 2 ) .

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-08m

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T he f a i l u r e was dup l ic a ted by opening the pos i t iv e -going d iode-wiredt r a n s i s t o r . T h is s a t u r a t e d t h e a m p l i f i e r i n p ut t r a n s i s t o r , and d ro v e t h eoutput o f f - sca le h igh .o u t o f s a t u r a t i o n were pr e s e n t , t h e ou t pu t r es ponde d and t h e a m p l i f i e rgain w a s no t c ompre ss ed un t i l t he ou t pu t v o l t a ge was d r i v e n t o z e ro . Thep a r t o f t h e signal which went below zero voltage w a s then compressed bythe negat ive-going feedback diode and th e narrow puls es shown in f i gu re 3were produced.

When s i gn a l s l a r ge enough t o d r i ve t he i npu t s t a g e

T h e t r a n s i s t o r emitter and base are connected f rom p i n t o ch ip bysmall aluminum wires ( f i g . 4. ) . A br e ak i n one o f t he s e wires, o r a par -t i a l o r complete bond f a i lu r e between t h e wire and th e c hip would causeth e open c i r c u i t . The e lements could a l so make contac t a g a i n - t o produceth e in t e rm i t t en t con di t ion when mechanica l ly shocked by nearby r e l ayac tua t ion .

No f a i l u r e s o f t h i s t ype oc c u r re d du r i ng t he devel opme nt a nd t e s tprogram. To determine i f a ge ne r i c de f e c t e x i s t e d , a group o f t e n t r a n -s i s t o r s f rom t h e same l o t w ere e xam ined i n t e r n a l l y a nd s u b j e c t e d t o t h e r -m a l shock and bond p u l l t e s t s as w e l l as e l e c t r i c a l t e s t s . The t r ans i s -t o r s were t e s t e d w i t h i n t h e ma n uf a ct u re r' s s p e c i f i c a t i o n l i m i t s and a l sobeyond spec i f ica t ion l i m i t s an d were fou nd t o be s a t i s f a c t o r y .

With a s i g n i f i c a n t e v e n t , s uc h as f i r i n g t h e m o rt a r, t h e n e ga ti v es i d e of geophone 3 i s c a pa b le o f d i s t i n g u i s h i n g t h e a r r i va l o f t h e e v e n ts i gna l . C a l c u l a t i ons o f new c i r c u i t c ons t a n t s f o r a n ope n i n t h e pos i-t i ve- go ing t r a ns i s t o r make t he c ha nnel u s a b l e f o r i n t e r p r e t a t i on o f d i s -ce rnable nega t ive da ta .

The experiment w a s flown on Apollo 16 w i t hou t a ny c hanges t o t h e ac-t iv e se i smic de t ec t io n system, and

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Apollo Experience Report Flight Anomaly Resolution