From: IAAI-89 Proceedings. Copyright © 1989, AAAI (www.aaai.org). All rights reserved. Applicationsof Artificial Intelligence To SpaceShuttle Mission Control John F. Muratore TroyA. Heindel Terri B. Murphy National Aeronautics and Space Administration Lyndon B. Johnson Space Center Houston Texas Arthur N. Rasmussen MITRE Corporation Robert Z. McFarland Unisys Corporation ABSTRACT Real time expert systems have been developed In the past, the MCChas relied on mainframe- by the National Aeronautics and Space based processing and display techniques which Administration (NASA) to monitor telemetry emphasizedthe use of highly skilled data from the Space Shuttle. These systems personnel knownas flight controllers to have been used during SpaceShuttle flights. monitor data, detect failures, analyze system This represents the first use of expert performance, and makechanges to flight systemsto makeflight decisions in a real plans. Figure 1 shows the working environment space mission. This paper describes the of the MCCand Figure 2 shows an example of requirements that led to the developmentof the displays provided by this system. This the expert system, the architecture used to worked well for programsof short - duration, obtain real - time performance, and the payoffs but as NASAlooks to operating long duration from the system. programs such Space Station Freedom, techniques are being explored to automate mission monitoring, display and analysis INTRODUCTION functions. During the recovery from the Challenger The successful launch of Discovery in accident, two real time expert systems were September 1988 represented a bright new implementedand certified for use in making beginning for NASA.It also represented a flight- critical decisions. This work was bright newbeginning in the Mission Control erformed by a team of flight controllers and Center (MCC)at the Lyndon B. Johnson Space ~nowledge engineers from a combined NASA- Center. For the first time knowledge- based. industry team using commercial hardware and systemswere used at this critical facility software. These two expert systems which which is the focal point for SpaceShuttle monitor Space Shuttle communications and the flight operations. Knowledge- based systems were used to monitor the Space Shuttle, Space Shuttle Main Engines were successfully detect faults and advise flight operations used in the STS- 26 Discoveryflight. personnel. This is the first use of knowledge THE PROBLEM based systems technology in a NASA spaceflight operational environment. Flight The MCCinformation systems are vital to the managementdecisions were madedirectly based safety and success of mannedspace flights on the results of knowledge- based systems. conducted by the United States. The This is a milestone in the application of centralized system currently employed artificial intelligence. presents only raw data to flight controllers with very little interpretation. All processing is contained in a single large Figure 1 - Space Shuttle Mission Control EAST / COM SYNC PL PNL FM PhIL RCVR LCK 0 5OURCE KU PM.. PH" ERR O H U/L RATE DLPU COHERENT ISEARCH D CODE HF D~SP PI~R ANT 5EL ER ’DETECT D D/L RATE 1 GNC @~1~ ON MODE MAN ITR~CK D CODE 2 GNC ~11 ON ELEC KU 0PER D ENCR U/L CLR CLR 3 GNC ~11 ON BEAM Zi6 5YNC D D/L CLR CLR W S OSOFF XPDR 5EL ’DRTA GD D RCDR NSA NSR ¯ FM MODE R/L HDR OFF RCDR Y ~S -113~ PRE AMP LDR OFF ERROR R O.Z O.Z MODE OP’F H~TER ¢ Z B-MODE D --CCTV ANT SEL ER PA OFF OFF ~NGLE D D/L 5EL MODE OPC TEMP -84) °5¢ , , UHF ¯ TEMP 5V5 5EL--’ RFL 2 ¯ 1 O.? MODE ¥CU MN ~SECURE TV~ ~$PC - - TEC-- Z96-6ZZ Z59--979 D~NLIN~ ENA ~DU PNR ? 5M O D ZTS-gB7 Z~3-Z~T GRM SEL NORM TVPE ? BF5 D ~LC OUTPUT ? RECORDER5 DDH 0PS MODE TK ~TP DIR 5PMTN TEHR DDH I ZTI:Z2:¢O:2~ FR.,5 100 I 5TBV I O REV I 5T0P 98 DDH 2 271:18:53:33 FR.S 0 Z 5TBY I 0 REv I 5T0P ~8 DDH 3 Z71:ZZ:lO:20 FR/5 100 P/L STBY i 0 REV’i 5T0P 91 DDH ~ :71:ZZ:iO:ZO FR/5 i~0 FAULT BCE STRG 3 5TKR GPC 1Z3~ TIME 271:OS::S:lO.07 Figure 2 - Typical MCC Mainframe Display 16 mainframe computer with software which is Thefirst task of this project wasto provide difficult to changeand verify. This system an "i ntelligentassociate" to the flight presents data to the flight controllers, but controller monitoring the SpaceShuttle’s not information. It is the job of the flight communications and data systems. The controllers to convert this raw data to associate expert system is namedafter the information that can be used to managethe first flight controller position selected for mission. Teachingflight controllers to automation and is called the Integrated perform this task is a major training problem CommunicationsOfficer (INCO) Expert System. which typically takes two to three years to Development was started in August 1987 and complete. The nature of the mainframe - based the system was placed in the MCCin April MCCsystem, which mostly provides monochrome 1988. Approximately eight person years worth text displays, causes even.the most highly of effort and $400,000 of hardware were trained and motivated flight controllers to required to field this system. This system makeoccasional monitoring errors. In the was placed next to the INCOconsole which problem domain of the MCC,a flight allows operators to compareresults of the controller error can lead to grave conventional console to those of the expert consequences. ~iYuStemnng the(Figure STS- 3).26 flightThis systemof Discoverywas used in The problem of ensuring high -quality September 1988. decisions by the flight control team using this minimal information processing The INCO Expert System was implemented on a capability is further complicated by NASA’s conventional color graphics engineering unique bi - modal age distribution. Dueto the workstation. The Masscomp5600 with the Unix hiring freezes between the Apollo and Space operating system was chosen to be compatible Shuttle programs, the majority of NASA with other workstations in the MCC. personnel fall into two d!stinct groups: the younger "Shuttle- only group under 35 years Automated monitoring was performed by both of age and the more experienced "Apollo - era algorithmic and heuristic techniques. veterans" of greater than 45 years of age. Knowledge was represented both procedurally Theseveterans represent a dwi ndli ng supply in C languagecode and in rules. The of corporate knowledge and experience as they representation for specific knowledge was are promoted, retire or moveon to other driven by the complexity of the knowledge and activities. required rate of execution. In the Masscomp environment, conventional C programming As NASAmoves into the SpaceStation era, it lenerally executes faster than the is further confronted by the requirement to ~nterpreter in a rule - basedsystem. continuously operate the station for its twenty year lifetime. It is not reasonableto The procedural representations were built in expect that we will be able to maintain a a structured natural language and translated large work force of highly skilled flight into C. This was done by a tool created by controllers to perform the demanding the project called Computation Development workloads that are imposed by our current Environment (CODE). CODEallows flight style of systems monitoring over that amount controllers to specify monitoring algorithms ot time. in a high - level language and then generates the C code necessary to perform the NASA’S SOLUTION algorithm. The rule - basedrepresentation for both algorithms and heuristics were built Artificial Intelligence is a natural source using the CLIPSexpert system tool developed of techniques for converting data into by the Mission Planning and Analysis Division information, capturing corporate knowledge, at the Lyndon B. JohnsonSpace Center. and lowering operator training and response time. In 1987, Mission Operations Directorate One of the requirements placed on the INCO at the Lyndon B. Johnson SpaceCenter started Expert Systemis to advise flight controllers a project to apply the techniques and in real time. This typically meansfailure methodologies of AI such as expert systems detection within five secondsof an event. and natural languageinterfaces to real space This requires the expert system to have mission operations problems. direct electronic accessto the real time telemetry from the SpaceShuttle. A major requirement on the INCO Expert System was also that it be isolated from all of the 17 Figure 3 - Expert SystemWorkstation Installed Next To Conventional Console in MCCDuring STS- 26 existing MCCsystems so that problemsin the The third layer uses procedural techniques to stand - alone expert system could not affect implement domain - specific knowledge. This flight critical mainframeprocessing. The knowledgeis entirely algorithmic in nature. combination of these two requirements forced For example, in this layer the system may us to build a completely independentreal monitor a voltage and signal an alarm if the time telemetry processing capability into the voltage is below a required level. These INCOExpert System. algorithms were built using CODE. The stringent demandsof executing processes The fourth layer uses rule - basedtechniques supporting real time telemetry processing to represent both algorithmic and heuristic while operating under an unmodified Unix led knowledge. It is often easier to implement to the developmentof an innovative complexalgorithms, such as those that architecture tot meeting real time knowledge - perform overall systemsanalysis, in the rule based system needs. The architecture was base rather than in the layer three based on a four layer model (Figure 4). Raw procedures. This must be balanced with speed data enters the first layer; as it movesup of execution concerns. Items that had to through the layers, it is converted to higher execute once every second were implemented quality information. using the layer three procedural techniques. Thefirst layer performs basic data Rules execute as an embeddedcomponent of the acquisition tasks such as telemetry entire system.