ISTS 2006-f-25

AUTOMATIC MONITORING AND DIAGNOSTIC SYSTEM FORINFRARED IMAGING SURVEYOR ASTRO-F
Ryoji Takaki, Masashi Hashimoto, Hideyuki Honda, Akinari Choki
Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science
3-1-1, Yoshinodai, Sagamihara, Kanagawa 229-8510, JAPAN(E-mail : ryo@isas.jaxa.jp, masashi@nnl.isas.jaxa.jp, {honda, akinari}@isas.jaxa.jp)
Mitsue Mizutani and Toshinori Hirose
Fujitsu limited
1-9-3 Nakase, Mihama-ku, Chiba, Chiba 261-8588, JAPAN(E-mail : {mizutani.mitsue, hirose.toshi}@jp.fujitsu.com)

Abstract

multiple reports and determine an appropriate action
in a limited time.

ISACS-DOC (Intelligent SAtellite Control SoftwareDOCtor), which is automatic monitoring and diagnostic
system for spacecraft, has been developed and operated
at Institute of Space and Astronautical Science (ISAS)
of Japan Aerospace Exploration Agency (JAXA). It aims
to rapidly and accurately capture important changes andsignals of anomaly during routine operations without thecontinuous presence of specialists. Three ISACS-DOC
systems have been so far constructed for the features ofdeep or semi-deep space missions. This paper presents
overview of the new generation monitoring and diagnostic system for ASTRO-F, which was launched by M-V
rocket No. 8 on February 22, 2006 from Uchinoura Space
Center. ASTRO-F is a low-altitude earth orbiter different
in various aspects from the deep space spacecraft targetedby the past ISACS-DOC systems. There are certainly
many items to discuss about the monitoring and diagnostic system. Improvement items based on past experiences
can also be considered as issues of the new system. This
paper reports the details of the newly developed ISACSDOC system for ASTRO-F.

• It is not difficult to detect an abnormality in eachcomponent, but it is difficult to find the phenomenonof influence between components.
• An apparently true abnormality can be detected bya device but a general judgment must be made not
only from abnormality information but also frommultiple trend information. However, when there isa great volume of information, it is difficult to findand detect abnormal symptoms by human intuition.
• A trained expert may be able to find the signs offault by experience and intuition, but an operator for
regular operations cannot be expected to find suchsigns.
Under these circumstances, a monitoring and diagnostic system for satellite operations is needed for flexible
operations linking satellite operation planning, tracking
control, and data processing. Since 1992, therefore, theInstitute of Space and Astronautical Science of the Japan
Aerospace Exploration Agency (ISAS/JAXA) has been
conducting research and development on a ground system
for monitoring and diagnosing the status of satellites using AI techniques. This system is called Intelligent Satellite Control Software-DOCtor (ISACS-DOC) [1, 2, 3, 4].
The purpose of ISACS-DOC is to accurately grasp serious changes and abnormality signs during regular operation without experts in the satellite control room to enhance the safety of satellite operations. If the cause ofan abnormality cannot be identified from detected signs,
it is preferable to consult an expert by presenting the related information and contact address. If the cause can be
identified with high reliability, it is preferable to present
diagnostic results and solutions.
To do so, information from the satellite to the groundfacilities needs to be integrated and visualized. Therefore, ISACS-DOC can be positioned as a system to support monitoring by an operator in regular operation and

1. Introduction
To satisfy the high-grade observation requirements ofa scientific satellite, the number of devices per satellite isincreasing, software functions are becoming complicatedand enhanced, and the number of operating stations is
also increasing with the enrichment of satellite operating
facilities. To realize accurate and safe satellite operations,the following issues should be resolved.
• Each component has a function to detect and reportan abnormality. Because of various abnormality reports, however, visual checks are substantially impossible.
• It is impossible to identify a true abnormality fromc
Copyright 2006
by the Japan Society for Aeronautical and Space
Sciences and ISTS. All rights reserved1

to support diagnosis by an expert in abnormal operation.
From the general viewpoint of satellite control systems,
ISACS-DOC is considered to implement ordinary satellite control systems. The main purpose of this system
is to improve the probability of abnormality recognition.
To achieve this purpose, the system should be independent of existing satellite control systems and should notaffect their operations. Independence of existing facilities makes post-launch tuning and trial monitoring anddiagnosis easy and more accurate. Especially, the monitoring and diagnostic techniques verified by this system
will contribute to the continuous improvement of satellite
operation technology through their incorporation into thenext satellite control systems.
So far, this system has been applied to the Geomagnetic Observation Satellite GEOTAIL (launched in1992), Mars Explorer NOZOMI (launched in 1998), andsample-return probe HAYABUSA (launched in 2003).
For GEOTAIL, the first ISACS-DOC system was constructed by using a diagnostic expert system construction
tool (packaged software MANADESHIKUN). To date,ISACS-DOC systems for NOZOMI and HAYABUSA
have also been developed and put into service.
The new-generation ISACS-DOC is being developed
for ASTRO-F, which is a low-altitude earth orbiter different in various aspects from the deep space spacecraft
targeted by the past ISACS-DOC systems. There are certainly many items to discuss about the monitoring anddiagnostic system. Improvement items based on past experiences can also be considered as issues of the nextgeneration system. The details of the newly developed
ISACS-DOC system for ASTRO-F is presented.

sitivity imaging and spectroscopic observations covering
more than several tens of square degrees at wavelengths
from 1.7 to 180 microns.
ASTRO-F satellite consists of a cryostat and a bus
module. A telescope and scientific instruments are stored
in the cryostat and cooled by liquid Helium and mechanical coolers. The bus module takes care of house keeping of the satellite, attitude control, data handling, andcommunication with the ground system. The height andweight of the satellite are 3.7 meters and 952 kg, respectively. The cryostat and the bus module have independent
structures so as to decrease heat inflow into the cryostat.
Figure 1 shows ASTRO-F(AKARI) which is ready to beloaded onto the M-V-8 rocket.

2. Infrared Imaging Surveyor ASTRO-F[5]ASTRO-F is the second space mission for infrared astronomy in Japan. It was launched by M-V rocket No. 8
on February 22, 2006 from Uchinoura Space Center. It
is placed in a sun-synchronous polar orbit of 745 km andgiven a nickname of ”AKARI”, which means a ”light” inJapanese.
The ASTRO-F mission is an ambitious plan to makean all-sky survey with much better sensitivity, spatial resolution and wider wavelength coverage than IRAS (Infrared Astronomical Satellite, launched in 1983 by theUnited Kingdom, the United States, and the Netherlands). ASTRO-F has a 68.5cm telescope cooled down
to 6K, and will observe in the wavelength range from
1.7 (near-infrared) to 180 (far-infrared) micron. By theseequipments, ASTRO-F will make a second generation
survey which meets current astronomer’s expectations.
There are a large variety of scientific targets which will
be investigated by ASTRO-F as follows, 1) to understandthe formation and evolution of galaxies, 2) to inquire into
the formation process of stars and planetary systems. In
order to accomplish these aims, ASTRO-F performs thefollowing observations. 1) an unbiased all-sky survey atwavelengths from 50 to 180 microns, and 2) high sen-Figure 1: ASTRO-F (AKARI)

3. Main purpose of ISACS-DOC for
ASTRO-F
ASTRO-F is a low-altitude earth orbiter different invarious aspects from the deep space spacecraft targetedby the past ISACS-DOC systems. The greatest differencein terms of ISACS-DOC for ASTRO-F is the requirement
for high-speed data processing. This is because of theshort visible time (deep space spacecraft HAYABUSA: 8hours, ASTRO-F: 10 min/pass and 4 passes/day) and hightransfer rate of telemetry data (HAYABUSA: 16 Kbps,
ASTRO-F: 4 Mbps). In other words, a large volume ofdata needs to be processed in a short time. For high-speed
data processing, it is necessary to enhance the system processing performance, to set monitor items strictly, and toset priorities. Therefore, the first purpose of ISACS-DOC
for ASTRO-F is to establish monitoring and diagnostic
technology for low-altitude earth orbiters.
Knowledge collection and production vital to this sys2

tem are expected to be more efficient. Therefore, the second purpose is to develop framework of knowledge collection, which consists of knowledge templates about scientific satellites by utilizing the experiences so far, andsupport system to build knowledge base. Many knowledge bases were previously collected almost manually by
experts and those with experience, and then incorporated
into systems. This is expected to be automated to someextent. Therefore, we arranged the knowledge alreadycollected and summarized common knowledge into templates to have many diagnostic rules incorporated into
systems automatically. These templates and support system to build knowledge base are realized by EXCEL files
and macro features of EXCEL, respectively.

spacecraft) as well as real time telemetry data, based on
the knowledge base. Both data processing are independent and they can be executed at the same time when
reproduced telemetry data and real time telemetry data
are received. ISACS-DOC for ASTRO-F can also rediagnose any past data with the newest knowledge base.
ISACS-DOC for ASTRO-F can freely setup cycle ofmonitoring data creation and cycle of conducting monitoring and diagnosing, and data collecting period, according to features of monitoring data, and monitoringand diagnostic items. Figure 3 shows schematic view ofthe data collecting period and the cycle of creation of themonitoring data.

4. Features of ISACS-DOC for ASTRO-F
Figure 2 shows operation image of ISACS-DOC for
ASTRO-F. ISACS-DOC system gets both telemetry data,
real time data and reproduced data, from data distribution
server, and monitors and diagnoses them. Diagnosed results are displayed in a monitor and are sent by e-mail.
ISACS-DOC for ASTRO-F consists of following 6 functions.

Figure 3: Data processing timing
No dedicated client software is required to check monitored and diagnosed results because a Web based interface is used to show them. Users can check monitored
and diagnosed results in anywhere by commonly used
Web browser through the network.
Figure 4 shows the main window of ISACS-DOC for
ASTRO-F. Detected anomalies are listed in the main partof the window, which is the most important region for
ISACS-DOC users. In the left side of the window, there
is a list menu for all monitoring items, which show current status of monitoring data regardless of whether ananomaly is detected.
Each listed item is linked to another window (Fig. 5)
which shows detailed information: 1) current values of
the anomaly data, 2) conditions of anomaly detection,3) setting values of limit checks, 4) time series plots of
not only the anomaly data but also the related other data,
which provides valuable clues to an understanding of thecircumstances, and 5) messages of anomaly descriptions
and the way to response.
Monitored and diagnosed results are notified by the email. Therefore, users can get these results in anywhere.

1. Import : the system imports knowledge base andtelemetry definition database and extracts telemetry
entry, which are required in monitoring and diagnosing.
2. Telemetry reception : the system receives telemetry
data in real time, decomposes them to each telemetry entry, extracts status values, converts to physicalvalues and finally creates primary data, according to
the telemetry definition database.
3. Monitoring data creation : the system creates monitoring data which are necessary for monitoring anddiagnosing, based on the knowledge-base. A filtering procedure and limit check are applied to primarydata, creating secondary data. Complex data are created from multiple data: secondary data and complex data, as needed.
4. Monitoring and diagnosing : the system monitors and diagnoses according to the definition ofknowledge-base.
5. Display : monitored and diagnosed results areshown through a HTTP server.

4.2 Monitoring and diagnosing
ISACS-DOC for ASTRO-F realizes more flexible andeffective monitoring and diagnosing than the quick looksystem of the satellite control system.
Telemetry data rarely have garbled data which arecaused by one-bit errors and so on. The garbled datacauses incorrect alerts which decrease the reliance on thesystem. Therefore, a data filtering technique is used in
the ISACS-DOC for ASTRO-F. The filter deletes incorrect values in primary data and creates appropriate data as
secondary data in order to realize well-established monitoring and diagnosing. Figure 6 shows filtering process

6. Notification by e-mail : monitored and diagnosed
results are notified by the e-mail after the spacecraft
operation or monitoring and diagnosing of reproduced telemetry data are completed.
4.1 System functions
ISACS-DOC for ASTRO-F can automatically monitor
and diagnose reproduced telemetry data which are reproduced from the on-board data-recorder and are sorted according to their TI-time (time by the Time Indicator on
3

Figure 2: Operation image of ISACS-DOC for ASTRO-F

Figure 4: Main window of ISACS-DOC for ASTRO-F
to create secondary data. Secondary data consists of central values which are calculated every collecting cycle.

A central value is calculated for each collecting period
from the collected primary data according to the filter-4

Figure 5: A window which shows detailed information
ing algorithm. Table 1 shows a list of filters which are
implemented in the system. In general, the average2, anaverage of collected data except maximum and minimum
values, is used for analog data and the majority, a mode
value of collected data, is used for status data.

in a free format as a user intrinsic function, calculationof physical value (ex. electrical power from current andvoltage of electricity), predicted value (ex. tank pressure
calculation by Boyle-Charle’s law), reference of past data(ex. change control of counters), comparison between expectancy and actual showing (ex. difference or ratio between them), and historical trend analysis.
4.3 Knowledge base
The framework of knowledge collection consists of aknowledge templates about scientific satellites by utilizing the experiences so far, and support system to build
knowledge base. The framework is constructed by usinga software package EXCEL, and collected knowledge aredescribed in templates which are three kinds of EXCEL
sheet.

Figure 6: Secondary data processing (filtering)

1. Diagnostic input data (status and analog data) : input data which are necessary for monitoring and diagnosing, are defined in this sheet. For example,
telemetry name, limit check values, collecting period and creation cycle of data, filtering type andvalid/invalid condition.

Complex data are created from multiple data: secondary data and complex data. By using these data,
ISACS-DOC for ASTRO-F realizes complex monitoringand diagnosing. The boundary value of the limit checkcan change according to the current value of specified
data. The system can detect continued anomaly by knowing starting time and ending time of specified status. (ex.
it should be anomaly if a calibration light source continues to be ON longer than five minutes.) Moreover,the system has following features, calculating expression

2. Complex data : new data which are calculated frommultiple data, are defined in this sheet.
3. Monitoring and diagnosing definition : monitoring
5

Name
head
end
maximum
minimummajority
identity
average1
average2
average3
average4
extraction

Table 1: Filters for data processing
Description
the oldest data among collected data
the newest data among collected data
the maximum value of collected data
the minimum value of collected dataa mode value among collected dataa value when all data are identicala simple average of collected data
an average of collected data except maximum and minimum values
an average of collected data except a specified range of data
an average of collected data except maximum and minimum values, and specified values
extract a specified value

data typeanalog/statusanalog/statusanaloganalogstatusanalog/statusanaloganaloganaloganalogstatus

5. Conclusions

and diagnosing items are defined in this sheet. Each
entry has conditions of anomaly detection, diagnosing cycle, importance level, time limit for response.
It has also the specification of data which are used
to draw a graph showing time variation of data,
the configuration of the graph, output messages likeanomaly descriptions and the way to response. They
are displayed in the detail description window.

The overview of the monitoring and diagnostic system, ISACS-DOC for ASTRO-F was presented. It wasa first attempt to develop the monitoring and diagnostic
system for low-altitude earth orbiters. Its effectivenesshas been proved through the daily operation even in thetuning stage of the knowledge base in the system. Further efforts will continue to enhance the system. ISACSDOC for ASTRO-F will continue to assist safe operationof ASTRO-F until the end of the mission.

The knowledge base, which is described in EXCEL files,
becomes more easily viewable than previous one. The
knowledge already collected are arranged and are summarized as common knowledge into templates to have
many diagnostic rules for spacecraft. These templates
help to advance the knowledge base which can be used
for monitoring and diagnostic system for future spacecraft.

References[1] Hashimoto M., Nishigori N., Mizutani M., Operating Status of Monitoring and Diagnostic Expert System for Geomagnetic Observation Satellite GEOTAIL, Proceeding of the 2nd International
Symposium on Reducing the Cost of Spacecraft
Ground Systems and Operations, RAL.GS2.73,
pp.73.1-73.8, July 1997

These templates and support system are realized by
EXCEL files and its macro features, respectively.

[2] Hashimoto M., Choki A., Nishigori N., MizutaniM., Operating Status of Monitoring and Diagnostic
Expert System for Mars Probe NOZOMI, Proceeding of the 4th International Symposium on Reducing
the Cost of Spacecraft Ground Systems and Operations, 2001

The support system to build knowledge base is realized by using macro features of EXCEL, decreasing input loading of users and having a function to check consistency of knowledge base. The support system automatically imports the telemetry definition database. Several values which are defined in the telemetry definition
database, are used as a default value or are displayed as areference value for data input. Moreover, following functions are realized in order to ensure consistency of knowledge base, format check (required item, fixed word, letter
type and number of letters) and consistency check (duplication of entry, magnitude relation of limit values, relation between collecting cycle and collecting period of
data, conditional expression for anomaly detection, andlack of required data for diagnosing). They help to build
the knowledge base more certainly and efficiently.

[3] Hashimoto M., Honda H., Nishigori N., Mizutani M., Monitoring and Diagnostic Expert System
for Sample-Return Probe MUSES-C, Proceeding of
the 5th International Symposium on Reducing theCost of Spacecraft Ground Systems and Operations,
2003[4] Takaki R., Hashimoto M., Honda H., Choki A.,
Mizutani M., Nomura, K., Kosaka T., ISACSDOC: Automatic Monitoring and Diagnostic System for Spacecraft, Proceeding of the 6th International Symposium on Reducing the Cost of Spacecraft Ground Systems and Operations, ESA SP-601,
2005

The knowledge base is converted to CSV formatted files, which are directly imported by ISACS-DOC
for ASTRO-F. Therefore, it becomes incredibly easy tochange the knowledge base.

[5] ASTRO-F (IRIS; Infrared Imaging Surveyor),
http://www.ir.isas.jaxa.jp/ASTRO-F/index-e.html
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