Proceeding of the 6th International Symposium on Artificial Intelligence and Robotics & Automation in Space: i-SAIRAS 2001, Canadian Space Agency, St-Hubert, Quebec, Canada, June 18-22, 2001. FULLY AUTOMATIC AND OPERATOR-LESS ANOMALY DETECTING GROUND SUPPORT SYSTEM FOR MARS PROBE "NOZOMI" NAOMI NISHIGORI Fujitsu Limited 9-3, Nakase 1-chome, Mihama-ku, Chiba-shi, Chiba 261-8588, Japan Phone: 81-43-299-3248 Email: [email protected] MASASHI HASHIMOTO Institute of Space and Astronautical Science (ISAS) 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan Phone: 81-42-759-8352 Email: [email protected] AKINARI CHOKI Institute of Space and Astronautical Science (ISAS) 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan Phone: 81-42-759-8386 Fax: 81-42-759-8387 Email: [email protected] MITSUE MIZUTANI Fujitsu Advanced Solutions Limited 1-2-4, Shinkoyasu, Kanagawa-ku, Yokohama-shi, Kanagawa 221-0013, Japan Phone: 81-45-438-2082 Email: [email protected] Keywords: expert system, GEOTAIL, Mars probe, ISACS-DOC has caught many abnormalities including monitoring and diagnostic expert system, NOZOMI, serious problems which actually happened to satellite abnormalities, scientific satellite, spacecraft “NOZOMI” and warned to “NOZOMI” operators abnormalities, rule-based reasoning, heuristic about them immediately at SSOC. ISACS-DOC for classification problem. “NOZOMI” will be continuously used until the end of the “NOZOMI” mission to keep the operation safe Abstract under strict limitation of the operation budget at ISAS. In this paper, the process of ISACS-DOC development, This paper describes a fully automatic and operator- the improvement points that were performed, and less anomaly detecting ground support system named some actual examples of abnormalities that were ISACS-DOC for Japan’s first Mars probe “NOZOMI”. detected by ISACS-DOC will be reported as well as This system is the second application of expert the outline of ISACS-DOC itself. technique to daily operation of scientific spacecraft at the Institute of Space and Astronautical Science 1. Introduction (ISAS) in Japan. Many improvements are achieved based on the experiences of the first expert application The study of diagnostic expert system has been to monitoring and diagnosis system for geomagnetic becoming active since the second half of 1980s and observation satellite “GEOTAIL”. ISACS-DOC is also been applied to the space field. The first stage now used to keep the safer operation of “NOZOMI” as of diagnostic expert system treated problems as well as the first system for “GEOTAIL” at ISAS’ ‘heuristic classification problem’, namely, the Sagamihara Spacecraft Operation Center (SSOC). diagnosis was conducted by forward or backward inference engines referring the knowledge database 2.2 Four Steps on GEOTAIL System Development that was previously defined using specialists’ knowledge or experiences. ISAS also decided to It was the first trial for ISAS to develop diagnostic apply rule-based reasoning diagnostic expert system to system for the actual scientific spacecraft, and we perform the safe operation of the spacecraft control on developed the system in following four steps: the ground with small number of operators. This (1) Prototype system for the limited subsystem : We system was named Intelligent SAtellite Control developed a prototype system to evaluate the Software -DOCtor (ISACS-DOC) and its first version effectiveness of the rule-based reasoning was developed and has been used to geomagnetic diagnostic system targeting to the spacecraft observation satellite “GEOTAIL” for almost nine commutation system only. We decided to use a years. Although model-based reasoning diagnostic commercially available application software to expert system has been very active and many reports reduce the development cost. This diagnostic have been able to find nowadays, ISAS decided to expert tools package running on the OS/2 apply the same technique to the second version of environment had three standard functions of the ISACS-DOC and successfully developed the fully knowledge database editor, the forward inference automatic and operator-less anomaly detecting ground engine, and the rule-based knowledge database. support system for Japan’s first Mars probe (2) Diagnostic system operated in manual mode : We “NOZOMI”. Two ISACS-DOCs for “GEOTAIL” developed the second-step prototype system and “NOZOMI” are both backing up daily spacecraft targeting the whole subsystems of the spacecraft. operations powerfully in ISAS. This paper reports The necessary data for diagnosis was manually on many trials and ideas on developing ISACS-DOC input to the system as we did not have much and also the latest status of ISACS-DOC for confidence that the system was useful to the “NOZOMI”. spacecraft operation. (3) Diagnostic system operated in on-line data 2. Process of ISACS-DOC Development feeding mode : It took 30-40 minutes to input necessary data to the system in manual mode, 2.1 Basic Concept of ISACS-DOC though it was recognized that the system could diagnose the spacecraft status almost correctly. Following is the basic concept in designing ISACS- The system was revised to the on-line data feeding DOC. Although these ideas were discussed at the system as almost all necessary data was input on a beginning of the first version of ISACS-DOC for real time basis from telemetry data. “GEOTAIL” launched in 1992, they were not changed (4) Diagnostic system cycled automatically : It was throughout the second version of system development strongly required to watch whole spacecraft status for “NOZOMI” launched in 1998 . all the time automatically during the real time (1) Operators can easily recognize abnormalities of operation and to warn operators of the spacecraft satellites/spacecraft by being provided appropriate abnormality when some trouble happened. The monitoring and abnormality detection capability system upgraded to repeat the diagnosis every even if they do not have enough knowledge. three minutes during the real time operation. (2) Workload on operators to use ISACS-DOC should be minimized. In a spacecraft operation, a significant amount of data (3) Knowledge database can be easily modified to is produced and several pages of quick look screens correspond to an unexpected situation after launch. are necessary to display them. The operator would (4) A fatal damage of the satellites/spacecraft can be be flustered without the appropriate knowledge on avoid even if the operator fails to find a complete how to deal with the identified trouble. We noticed solution to the trouble by taking first aid action. through the actual spacecraft operation that ISACS- (5) The necessary information for diagnosing DOC was very useful to avoid overlooking the satellites/spacecraft can be obtained not only from spacecraft contingencies as the system automatically the telemetry data but also from the ground checking 570 items of spacecraft health condition tracking stations. every few minutes. ISACS-DOC for “GEOTAIL” found several spacecraft contingencies in the Page 2 Figure 1 Monitor Screen of Solar Particle Monitor (SPM) Including Reproduced Data communication subsystem, control subsystem and following reasons, though the model-based reasoning scientific instruments and helped the spacecraft technique becoming active: operators to cope with them. l It would have been very hard and difficult to verify the diagnoses model of “NOZOMI” before 2.3 New Ideas on NOZOMI System Development spacecraft launch with low cost, if the model-based Learned from GEOTAIL experiences reasoning technique was applied to the system. l Many experiences and knowledge obtained from It is possible to accumulate statistical data of the the system development of ISACS-DOC for diagnostic knowledge for cars, electric appliances for “GEOTAIL” seemed to be useful and applicable to home use because there are plenty of exactly the same other future satellite operations by relatively little or almost the same products on the market. It is very efforts. easy to obtain the information about what kind of troubles happens at what rate. Using this information, ISACS-DOC for “NOZOMI” is developed according it is possible to analyze the troubles statistically. to the following ideas. Some of them are introduced However, there is no exactly the same scientific based on lessons learned from ISACS-COD for spacecraft. So the knowledge database for a “GEOTAIL". scientific spacecraft mainly depends on the design knowledge. For this reason, a wide variety of design (1) Wide range of information can be gathered knowledge for developing spacecraft has to be through an on-line network to realize extensive and accumulated in the diagnostic expert system. The reliable diagnosis , and all data used for diagnosis knowledge database of the ISACS-DOC for are saved in the system and can be used for “GEOTAIL” was made using a lot of design checking a long-term trend of the data. knowledge obtained by interviewing 30 or more (2) Only reliable results should be shown in order to experts. We also decided to apply the rule-based avoid giving operators unnecessary concerns. reasoning diagnostic system for “NOZOMI” from the Only related facts should be shown if the Page 3 coordinate the differences between actual status of “NOZOMI” after launch and the preset-knowledge database before launch, to add insufficient knowledge and tune the data collection function. It took another 5 months to finely adjust the knowledge database through daily operations of ISACS-DOC. After that, operation of ISACS-DOC was placed under the control of the “NOZOMI” operation team on June of 1999. Furthermore, following new functions were added to ISACS-DOC for “NOZOMI” according to the actual spacecraft operation until now. (1) Diagnosis for Data from Onboard Data Recorder “NOZOMI” is operated using only one tracking antenna at Usuda Deep Space Center (UDSC) of ISAS usually. SSOC cannot make contact with “NOZOMI” during the invisible time for long hours. In addition to that, “NOZOMI” lost its S-band telemetry capability after launch because of the TMS malfunction that happened on July 5, 1999.