The small satellite KAGAYAKI (SORUNSAT-1)

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1 SpaceOps 2008 Conference (Hosted and organized by ESA and EUMETSAT in association with AIAA) AIAA The small satellite KAGAYAKI (SORUNSAT-1) Yusuke Murata, Katsuyoshi Yamamoto, Hiroshi Saegusa, Yuzoh Tomabechi, and Mariko Higuchi SORUN Corporation, Tokyo, , Japan Fumio Tohyama Tokai University, Hiratsuka, Kanagawa, , Japan and Kazuki Watanabe Wel Research Co., Ltd, Kashiwa, Chiba, , Japan SORUNSAT-1 is a small satellite in Japan, named KAGAYAKI and was co-launched on JAXA H-II vehicle in It was selected for the JAXA s public collection in May The main purpose of SORUNSAT-1( KAGAYAKI ) is a societal contribution program which merged two matters. One is a family support program SORUN KIDS that SORUN Corporation supports the family of children having intractable diseases or disabilities. The other is for the demonstrations of SORUN's space technology. (Remark: KAGAYAKI is Japanese. It means brightness and hope.) I. Introduction ecently, the launching of small satellites has been increasing worldwide. JAXA has publicly collected the R small satellites that are co-launched with H-IIA rocket from private companies and universities since May, 2006 for the purpose of Making people feel the space is closer to them. SORUN Corporation cooperated with Tokai University and WEL RESEARCH Co., Ltd. to design a small satellite KAGAYAKI, which is the first Japanese small satellite designed by private companies and applied to this plan. As a result of JAXA examination, KAGAYAKI was selected as the first satellite for co-launched with H-IIA rocket on May 16, SORUN Corporation implements a family support program SORUN KIDS that supports the families of children with incurable diseases and disabilities. SORUN Corporation employees participate as volunteers in a family camp held every year. SORUN Corporation provides a hot-air balloon that is wheelchair accessible. SORUN Corporation plans to connect the dreams of children with incurable diseases and disabilities and their families to space by developing small satellites using the opportunity of co-launching with the H-IIA rocket offered by JAXA. This is the mission of KAGAYAKI. II. Satellite Overview KAGAYAKI has a mass of 28kg, 15W of power and 31cm 31cm 35cm in size. It is categorized as an ultra small satellite among the JAXA co-launching small satellites. The gravity-gradient method is adopted for attitude control so that entire length of KAGAYAKI is almost 3 m when the boom deploys. Mission instruments mounted in KAGAYAKI observe aurora current and space debris and shoot aurora, and measure satellite remnant magnetism in orbit after the measures to reduce remnant magnetism moment is taken on the ground. A deployment boom for gravity-gradient stabilization altitude control is made of triaxial woven-fabric CFRP (Carbon Fiber Reinforced Plastic). It is stored, wound around a spool, when the satellite is launched, and deploys using an inflatable method in orbit. Its mechanism is simple and the number of parts is minimal, in addition, deployment parts weigh only 8g per meter, which classifies it as ultra-light weight. Copyright 2008 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

2 Mass : 28kg Power : 15W Size : 31cm 31cm 35cm Orbit : Altitude: 666Km Orbit Inclination: Approx 98º Sun-Synchronous Sub-Recurrent orbit Figure 1. Image of KAGAYAKI flying in orbit III. Development system A. SORUN Corporation SORUN Corporation became engaged in the development of the spacecraft control systems of the application satellites in Japan from At that time, the name of SORUN Corporation was SDCJ Co., Ltd. Then, in 2001, the company name became SORUN Corporation after merging with other companies. In the development of KAGAYAKI, SORUN Corporation developed a spacecraft control system that is SORUN Corporation expertise and manufactured an onboard control system (E-MAX: Embedded tlm Monitor And cmd execute system) to be mounted in KAGAYAKI. SORUN Corporation also played a coordinating role in this project. B. Tokai University Many educators in the Department of Aeronautics and Astronautics of Tokai University have participated in space development in Japan from the initial stage, and they have many past records centering on magnetic measurement. They have results in the field of the space magnetic field observation, and have results of the magnetic moment measurement of small satellite which is easy to be affected by the geomagnetic field. Tokai University is in charge of development pro-observation systems of KAGAYAKI. To contribute to education in universities and to develop human resources, Tokai University asked for observation themes are from the students of the university and the students developed items to be mounted in the satellite. C. WEL RESEARCH Co., Ltd. WEL RESEARCH Co., Ltd. designs, analyzes and tests satellite systems and develops various kinds of instruments to utilize space environment such as space stations and for aviation and ground instruments. SORUN Corporation specializes in software development, so that WEL RESEARCH Co., Ltd. manufactures hardware for the satellites. IV. Mission of KAGAYAKI A. Creating mission For engineers who engage in space development in private companies, launching the satellites designed by the engineers themselves was a long awaited dream. However, when the dream was nearly achieved of co-launching satellite offered by JAXA, there were questions such as why is the satellite being launched? As for the current space development in Japan, a project in which cutting-edge technology is collected has been advanced. Therefore, the reasons for the private companies to launch a satellite have not been found. In such situations, even if the private companies plan a project with the purpose of a cutting-edge study or technological development, it cannot be expected that the companies exercise these characteristics. Therefore, we deliberated on creating a mission from a viewpoint of the application side, which is activities performed by private companies that can be connected with space, but not from the traditional approach which searches for cutting-edge technology.

3 SORUN Corporation has an activity called SORUN KIDS which supports families who have children with incurable diseases and disabilities, and SORUN Corporation s employees volunteer to plan and operate family camps held in the summer. This activity provides opportunities where children with disabilities, their brothers and sisters and the children of volunteers, can communicate without prejudice. By setting this activity, which is seemingly not related to the space, as a main mission, we hope that we may think of Making people feel the space is closer to them from a different way from how we see it now. We suggested performing various kinds of activities from the satellite development stage to get children interested in the space. This is named as Communication mission, and activities after the launch is named Satellite application mission. B. Communication mission We plan to children known satellite development sites through satellite manufacturing and ground experiments where people usually do not have opportunities to see, and become familiar with space through space center excursions. 1) Kids Seminar The space center excursions and study sessions are planned to encourage the children s interest in space. Children visited the Tsukuba space center on December 16, 2006 in time for ETS-VIII launching. Since the weather in Tanegashima was bad on that day, the launching was postponed. However, the children made a courtesy call on the center president and had a tour of the facility. In the pavilion, volunteers brought the children in wheelchair up to see inside the Japanese Experiment Module of the International Space Station. When we lifted the children up, we were impressed when they said In space this work would be much easier wouldn t it? We have had the Kids Seminar 4 times so far. Figure 2. The first Tsukuba space center excursion 2) Kids Factory The children can see the satellite manufacturing processes at the manufacturing site and experience the satellite functions by operating sub systems and components. On July 29, 2007 children visited the study development room at WEL RESEARCH Co., Ltd. where the satellite is manufactured and saw the engineering model of KAGAYAKI. There was also an explanation of the operation principles of KAGAYAKI while they monitored an installation camera operated by hitting light to the solar power panels on television, and deployed the boom using nitrogen gas. Such demonstrations using actual instruments were very well received. Participating adults watched the demonstration and were as interested as the children were. Figure 3. The first Kids Factory 3) Kids Launching Member The children with disabilities selected from the SORUN KIDS are appointed as launching members of the small satellite KAGAYAKI and are dispatched to the Tanegashima space center for the satellite inspection before launching and to experience the launching. 4) Introducing KAGAYAKI and making the space canvas at the family camp

4 A family camp was held with 33 families of children with incurable diseases and disabilities (112 persons) and 151 volunteers at Kawaguchi lake front from August 31 to September 2, During the camp, we introduced KAGAYAKI and with the children, performed tests on the instruments to be installed in KAGAYAKI. A drawing that is to be decaled on space canvas in the satellite application mission was made. Since it is not easy for children with disabilities to make drawings, healthy children drew the designs first and the children with incurable diseases and disabilities colored the design with hand prints. The drawing was decaled on the parachute for deorbit to be installed in the satellite, and its pictures are taken with the backdrop of the earth using a camera on the boom tip. These pictures will be sent to the earth from KAGAYAKI on amateur radio band. Figure 4. Rough drawing of the space canvas. C. Satellite application mission We plan to have various kinds of missions with the children after KAGAYAKI is launched. 1) Aurora shooting Pictures of aurora are taken with cameras installed in the boom tip and at the lower part of the structure of KAGAYAKI and headed toward the earth. The pictures taken are received from the satellite in the sky above Japan and distributed to the children who want them. 2) Space bottle Children s voices are recorded in KAGAYAKI on the ground and are sent from orbit to be received by amateur radio operators. This has the romantic connotations of a message in a bottle released into the ocean 3) Space canvas Pictures of drawings by the children on a parachute for deorbit are taken using the camera on the boom tip with the backdrop of the earth when the parachute deploys. Novel space display Figure 5. Image of space canvas deployment

5 V. Scientific feature Some missions have been prepared to arouse the children s interest in space such as the Space application mission. The new technologies below are applied to realize these missions. A. Ultra light deployment boom (WEL RESEARCH Co., Ltd.) A long boom is mounted as the gravity-gradient stabilization method adopted as the attitude control for KAGAYAKI. The boom and its deployment mechanism heavily affect the small satellites. For KAGAYAKI, the boom made of triaxial wovenfabric CFRP mesh is belt-like and stored, wound around a spool, and the method deployed by inflatable structure with nitrogen gas in orbit is adopted. With this system, significant savings of simplification and weight of the deployment mechanism can be expected. This is the first time the deployment function of this method is seen in orbit. Figure 6. Ultra-right inflatable structure method deployment b B. Onboard control system (SORUN Corporation) Autonomous onboard control system (E-MAX: Embedded tlm Monitor And cmd execute system) collects data from the instruments in the satellites, edits and sends the data as telemetry via communication instruments to ground. The system also controls the instruments according to commands sent from ground and has mechanism for autonomous operation in orbit. Such controller was developed to be applied to each satellite, however, E-MAX was developed as a universal controller that can be used in any satellite applying the ground satellite control system. C. 3-axis fluxgate magnetometer (Tokai University) A 3-axis fluxgate magnetometer that observes field aligned current is mounted in KAGAYAKI to observe magnetic field around the earth. Aurora occurs when charged electron particles (plasma), which come in electrode area of the earth, clash with the earth atmosphere. Flow of the charged electron particles (current) generates magnetic fields. Therefore, the current structures that generate aurora are analyzed observing the magnetic field. To avoid influence of magnetic field from the satellite, the magnetometer sensor is installed at the tip of the deployment boom and an electric circuit is installed in the satellite. The magnetometer is measurable with 5nT accuracy, which is equivalent to parts per 10,000 of the earth s magnetic field and parts per 100 of variation of magnetic field due to current system. The students of the Tokai University manufactured the 3-axis fluxgate magnetometer. D. Remnant magnetism moment control (Tokai University) Small satellites are more likely to be affected by the earth s magnetic field in orbit. The remnant magnetism is controlled to be minimized during the KAGAYAKI assembly. Also, as the first experiment, the 3-axis fluxgate magnetometer installed at the tip of the boom measures magnetic moment of the satellite when a boom for gravitygradient control deploys and obtains data to be compared with ground tests. E. Observing debris (Tokai University) Many space objects fly in space, which may crash into the spacecrafts. The space objects that may crash are Micro Meteoroid (MM) and Orbital Debris (OD). The objects of 10cm or more in diameter can be tracked with the radar observational networks on the ground. Tracking MM and OD of 10 cm or less in diameter is more difficult. A debris detection instrument, MOIS (Micro meteoroid / Orbital debris Impact Sensor) consists of 3 sensors, which are an antenna, coil and PVDF (PolyVinyliDene Fluoride) sensor, and detect electromagnetic radiation and shock-wave propagation generated by ultra high speed crash of MM/OD of 100 micrometer or more. KAGAYAKI is launched to a circular orbit at 666km of altitude and 98º of orbit inclination. As a result of the analysis using the MASTER99 model of European Space Agency (ESA), it is estimated that probability of signal detection by each sensor of the MOIS is 1.1 a month. In fact, we think that signals will be obtained several times a month when considering debris is increasing day by day. This observation results are expected to be important data for worldwide satellite groups.

6 F. Space parachute (WEL RESEARCH Co., Ltd.) As a guideline set by Inter-Agency Space Debris Coordination Committee (IADC) and other committees, it is recommended that the low orbit satellites shall be scraped after 25 years of mission completion by atmosphere reentry. Mounting fuel for deorbit on KAGAYAKI is not allowed, therefore, a space parachute in which attenuated atmosphere is used is mounted. As for orbit change after the parachute deployment, it is expected to create various kinds of study themes from GPS data and other data. VI. Ground facilities 3 tracking control stations for KAGAYAKI are located in Japan (Tokyo, Miyazaki and Matsumoto). Telemetry is received with a transceiver shown in Fig. 8 and processed with the spacecraft control systems at the stations after through Terminal Node Controller (TNC). The telemetry can be received by the ham operators. The commands are sent to the satellites via the spacecraft control systems TNC- transmitter at the stations. Matsumoto Sengakuji (Tokyo) Miyazaki Figure 7. Location of earth station Figure 8. Ground facilities at earth station

7 A spacecraft control system Space-MAX (Space tlm Monitor And cmd execute system) monitors and controls KAGAYAKI at the stations. The Space-MAX is the one where a spacecraft control system (SMACS: Spacecraft MAnagement and Control System) designed and manufactured by SORUN Corporation for JAXA is applied to private satellite control systems. Space-MAX has main functions listed in Table 1. Telemetry Command Planning Function Telemetry receiving Telemetry conversion Telemetry evaluation Telemetry display Command setting Command sending Pre-checking Success verifying Satellite operation procedure Semiautomatic operation Stored command creation E-MAX parameter creation Table 1. Overview of satellite control system (Space-MAX) function Overview Receiving telemetry sent from the stations and recording the received telemetry on a disk. Converting engineering values of received telemetry and recording the converting results Evaluating the limit of converted telemetry. Displaying the converted telemetry on a screen in real time. Trend display and block diagram display. Displaying telemetry in the past. Entering commands to be sent and setting them in chronological order. Sending the set commands to the satellites sequentially. Checking command status if they are ready to be sent. Verifying the command execution results after the commands are sent. Sending the commands and checking telemetry according to prepared satellite operation procedures. Automatically sending the commands and checking telemetry by the systems according to set time in advance. Creating the stored commands that are executed in the satellites following the operation requests. Creating the table rewriting commands to operate E-MAX. VII. Operation A. Critical operation phase KAGAYAKI operation sequence after the satellite separation is as follows: 1) Antenna deployment 2) 1 st SAP deployment 3) 2 nd SAP development 4) Attitude control boom deployment The sequence of 1) is automatically executed. After SAP deployment and rate damp are executed, the attitude control boom deploys at visible range of the tracking control stations for KAGAYAKI. During the boom deployment, the 3-axis fluxgate magnetometer sensor on the boom tip measures the satellite magnetic moment and sends the measured data to the ground in real time. 1 st SAP deployment 2 nd SAP deployment Antenna deployment Attitude control boom deployment and deorbit mast primary deployment Launching Figure 9. Operation sequence after the satellite separation

8 B. Nominal operation phase Various experiments and their data collection will be executed in the steady operation as well as HK operation. This report describes the overview of aurora shooting and attitude control. 1) Aurora shooting Since there is no wide-range tracking station for small satellites, the events outside visible range have to be performed without operators. KAGAYAKI has the same GPS as the one used in JAXA satellite REIMEI. The GPS obtains position information and the 3-axis fluxgate magnetometer on the boom tip measures aurora current. E- MAX mounted in the satellite analyzes, evaluates the information and automatically shoots aurora. Data process systems of KAGAYAKI consist of Integrated Controller Unit (ICU) and autonomous onboard control system (E-MAX: Embedded tlm Monitor And cmd execute system). ICU enables KAGAYAKI to have monitoring and control functions through communication with the ground, therefore, ICU sends telemetry, receives commands and control the instrument in real time, furthermore, accepts the stored commands and the attitude stabilization control can be executed with mounted algorithm. ICU has measures against failure with ICU redundant configuration. TX TX RX RX ICU ICU sub sub ICU ICU main main Bus and Mission Bus and Mission instruments instruments E-MAX E-MAX Figure 10. Logical configuration of data process for KAGAYAKI E-MAX has a universal autonomous operation system as well as ICU functions. In the steady operation, E-MAX interfaces data via ICU, monitors and controls KAGAYAKI. E-MAX monitors the satellite state with raw data. When it cannot monitor the satellite with raw data, processes which are specialized in monitoring items are executed with algorithm library. If monitoring is performed with either of raw data or algorithm, event detection conditions (threshold value) are parameterized, and the operation procedures (series of command) specified for the case where the threshold value is exceeded can be executed if needed. When latitude becomes 70 or more degrees, KAGAYAKI monitors aurora current. KAGAYAKI obtains latitude information from GPS data, and automatically starts and completes monitoring of aurora current with these systems and takes photos when aurora current is detected. 2) Attitude control Attitude control is performed with the deployment boom for gravity-gradient stabilization attitude control. Its attitude error toward the earth direction shall be within ± 5º for aurora current observation. The satellites may rotate due to earth magnetism. To accept this, attitude supplementary and control sequences shown in Fig.11 are prepared. During accuracy control mode, the satellites attitude is kept with the attitude control logic shown in Fig.12. This logic is installed in both ICU and E-MAX, and it automatically keeps the attitude. The 3-axis fluxgate magnetometer is used for earth magnetism sensor.

9 Statellite separation Coarse control mode1(rate dumping Gravity-gradient stabilization mast deployment Coarse control mode 2 (Rate dumping) Nominal operation mode Fine control mode (Gravity-gradient stabilization control) Reverse control mode Uncontrolled mode Earth magnetism sensor GPS Latitude/longitude/altitude Coarse control mode2 (Rate damp) GAS Z Bref z Earth magnetism map data Position calculation on orbit Tumbling control + - Field aligned control Figure 11. Attitude supplementary and control sequence Difference process Magnetic torquer Energizing polarity ON_OFF Time Intermittent ON_OFF Timing control Time Dead band/saturation logic Timer Software process Bref_z : Earth magnetism vector zenith component GAS_Z : Earth magnetism sensor output Z-axis direction component Figure 12. Attitude control logic

10 VIII. Foresight KAGAYAKI is launched with the dreams and hopes of children. We have plans to bring space closer to children through Communication mission before the launch and to get children exited through Satellite application missions such as aurora shooting after the launch. There are rough plans for the entire KAGAYAKI project, however, detail missions will be created together with the children. When a dream that handicapped children could freely move in space was suggested during the space center excursion in December 2006, we honestly thought that it was impossible. However, an English astrophysicist, Stephen Hawking, achieved experimental flying in a gravity on April 26, 2007 in Florida, USA, and we saw an article in the newspaper that he would go to space in This is one of the motivators that brought us to plan the KAGAYAKI project. As children grow, their weight becomes heavier, which is one of the difficulties in nursing care. We image that if the nursing-care facilities and hospitals are built on the moon in the future, the nursing of growing children will become easier. Several years later, when the children grow up, they can share their dream to go to the moon with each other while watching KAGAYAKI whose space canvas is outspread in the earth orbit. We would like to create further missions of KAGAYAKI with children. IX. Conclusion One year has past since the Communication mission for KAGAYAKI was started. People who initially thought of space as a different world have started feeling that space is closer to them by participating in volunteer activities such as Kids Seminar and Kids Factory. By developing these activities, it can be expected that the initial plan of Seeing space in a different way from how we see it now can be realized.