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SPROUT



    【Overall System】
    The shape of the SPROUT is 20-cm cube. And, this weight is about 7.1-kg. This satellite consists of the 2 systems. First system is bus system which assists in accomplishing the mission. This system makes from 4 subsystems (Thermal and Structural System, Electric Power Supply System, Communication System, Command & Data Handling System). Second system is engineering mission system which performs the missions of the satellite directly. This system is makes from 4 subsystems (Attitude Determination and Control System, Camera System, Inflatable Membrane Structure System, Armature Communication System). This satellite structure is formed by the cube which is connected two boards which is made of aluminum alloy, by truss structure. The Battery Box is placed in center of satellite, each equipments are fixed on satellite structure, solar cells are fixed the outer surface of the satellite. In addition, we developed the separation mechanism for carrying out the separation from the main satellite.

    Bus system

      【Thermal and Structural System】
      The SPROUT will be launched with the main satellite, as the piggy-back satellite. So it is necessary to consider make sure the SPROUT will not disturb main satellite. It is need to be fulfilled “Interface requirement” and “circumstance of the launching”. We have to consider structural factor about the acceleration load and random vibration. In addition we have to pay close attention to the material that is used for the satellite for outgas, air extraction and others. On the other, the Thermal System has to keep the satellite’s inside constant temperature from the launching to the Operation end. The satellite is exposed extremely hot or extremely cold condition. So we have to do heat control. But, in zero-gravity field, there is no convection. So we have to take measures to keep the satellite’s inside constant temperature, by coating the structure surface or by the equipment arrangement that considering heat conduction.






      【Electric Power Supply System】
      EPS is one of SPROUT subsystems that controls battery charging (electric power generated from Solar cells) and power supply to SPROUT subsystems through boosting circuit (3.7V to 5V). This subsystem design weighed satellite’s mission and determined the number of solar cells and batteries, charge and discharge circuit and so on.

    • Function, Feature
    • I. Stable Power Supply to SPROUT subsystems
    • II. Charging control weighed battery and satellite condition (Over charge, discharge, Sunshine etc.)
    • III. 3 inhibit design to prevent malfunction from vibration at Launch
    • IV. Cutoff charging Path at the end of SPROUT Operation
    • Stable Power Supply to subsystems
    • EPS supply stable electrical power through boosting circuit from batteries.
    • Charging control weighed battery and satellite condition
    • EPS monitor batteries voltage and control batteries charge and discharge by EPS Operation Mode (Normal, Power Saving), Shunt circuit (discharging surplus power) from prevent batteries failure.
    • 3 inhibit design to prevent malfunction from vibration at Launch
    • There are cases in launch rocket, satellite break down by vibration and shock, and supply power to satellite and emit radio waves and so on. For this reason, satellite system suppressed the malfunction at launch by 3 inhibit design (3 switches connected in series between subsystems and batteries)
    • Cutoff charging Path at the end of SPROUT Operation
    • After end of SPROUT Operation, satellite system cut off the charging line (from charging IC to batteries) by uplink “latching switch off” so as not to affect radio waves from SPROUT to other satellites.




      【Communication System】
      Communication System on the SRPOUT consists with Fight Management Receiver system which receives and process uplink data from ground station on 140MHz band. And CW (Continuous Wave) system sends the House Keeping data, such as battery voltage, power generation and etc... by morse signal. We call them “communication sub system” (Transmitting from satellite to ground station, we use 430MHz band. And CDH1・2 bear it.).

    • FMR subsystem
    • FMR sub system is receives and process uplink data about engineering and outreach mission from ground station. FMR has two line. The 1st line is FMR1 which works for engineering mission. The 2nd line is FMR2 which works for outreach mission. The function of FMR is,
    • I. Receiving data, analysis and command systems transmitted form ground station.
    • II. Security check for uplink signal
    • III. The redundant design. The FMR1 and FMR2 complement each other.
    • IV. Reset bus subsystem
    • V. Expand the antenna

    • I. Receiving data, analysis and command systems transmitted form ground station.
    • FMR is top MPU at the SPROUT system. Because, FMR does flight management by receiving and analyzing uplink command and ordering to each subsystems. Also, FMR does important management such as reset bus system. So, these system is nearly same with SEEDS-II which is established movement in space.
    • II. Security check for uplink signal
    • Uplink command consists of call sign, security byte, forcibly action, choosing bus system byte, action time, command, and notes data. It is in accordance with uplink format. And, SPROUT decides the uplink from our ground station and other stations by security byte.
    • III. The redundant design. The FMR1 and FMR2 complement each other.
    • SPROUT has 2 line as redundancy for saving failure of communication system. So, SPROUT can substitute each other.
    • IV. Reset bus subsystem
    • When SPROUT manages the uplink command, it transmits conditions of each subsystems. And, when each sub systems are turned off or got uplink command by direct, each subsystems are reset by FMR.
    • V. Expand the antenna
    • By signal from FMR, CW, and RTC subsystems, SPROUT expands four antennas.

    • Uplink format
    • The Uplink form ground station formed "Uplink formant". The "Uplink format" is contain with call sign, security byte, compulsive execution and bus selection byte. The security byte to judgment uplink command send form Nihon University.

    • CW subsystem

    • CW subsystem collects the data of satellite and send House Keeping data to ground station by Morse code.
    • I. Collecting satellite’s HS data and send to Ground station by Morse code.
    • II. Expanding antenna

    • I. Collecting satellite’s HS data and send to Ground station by Morse code.
    • SPROUT decides CW operating mode by uplink command or satellite’s operating mode. And, SPROUT sends telemetry data as Morse signal by each mode.
    • 【First Stage Mode】 After expanding antennas, SPROUT transmits the only voltage of bus system until coming uplink.
    • 【Normal Mode 】Using regularly. Transmitting HK data by CW.
    • 【Conservation of electric power mode】 When the bus system’s voltage is lowered, it becomes. When SPROUT becomes it, it transmits header and voltage of bus system every three minutes.
    • 【Expanding inflatable membrane mode】Normal mode and sending mission data
    • 【Long Mode 】Normal mode and transmitting temperatures and subsystem’s reset counts.
    • 【Custom Mode 】Transmitting data which gets from getting from command’s notes data.

    • II. Expanding antenna
    • SPROUT expands antennas for sending and receiving by FMR, CW, and RTC subsystem’s signal.
      The radio frequency of the SPROUT is 140MHz for uplink and 40MHz for downlink. Also communication separated for mission use and the ham radio mission use. This satellite consists 4 communication lines, uplink line and downlink line for engineering mission also uplink and downlink line for the ham radio service line. The uplink line for engineering mission is 1200bps FM/AFSK line. And, downlink line for engineering mission is CW line, 1200bps FM/AFSK and 9600bps FM/GMSK line. Also uplink for the ham radio service line is 1200bps FM/AFSK line. And, downlink for the ham radio service is 1200bps FM/AFSK line.








      【Command and Data Handling System】
      Command and Data Handling (C&DH) is main control system of the SPROUT. This C&DH systems gets the sensors and photos data from other sub system. The C&DH gets datas from each systems and save memory to send transmitter. And D&DH counts the satellite time (time form the time separation) and share satellite system with other systems.

          

      Technology mission system

        【Attitude Determination and Control】
        The Attitude Determination and Control System is the system to do that analyze the satellite direction or control the satellite’s attitude. “Attitude Determination” is getting to know direction of the satellite. “Attitude Control” is controlling the direction of the satellite.


      • Attitude Determination
      • The SPROUT has some sensors in order to determine the attitude of the satellite. Sensors of the Attitude Determination consist of the sun sensors, the magnetic sensor and the gyro sensors. The sun sensors are the sensor to get the sun direction by measuring the direction of the sunlight. The magnetic sensor is the sensor to get the geomagnetic field vector by measuring geomagnetic field. The gyro sensors are the sensor to measure for angular velocity. The sun sensors of the SPROUT is self-made.
      • Attitude Control
      • The SPROUT uses the self-made magnetic torquers as attitude control actuator. The magnetic torquers are the actuator which makes a coil generate a magnetic field by sending current, and generates torque in an interaction with a geomagnetic field. There are some kinds of magnetic torquer, among them, the SPROUT uses the magnetic torquer which coiled the coil wire around the rod.








        【Camera Module System】
        The SPROUT uses the three cameras. There are the two cameras for the engineering mission. There is the one camera for the outreach mission which is the satellite operation by the ham radio operators, and which is to provide the earth imaging. The engineering mission of the SPROUT is required that the shape of expanding inflatable membrane structure is measured in the third dimensions, and taking the photos of the inflatable membrane structure under deployment and after deployment. The ham radio mission of the SPROUT is required that taking photos of the earth. The SPROUT has five taking photo modes.

        • 1.Inflatable membrane structure mode (engineering missions camera)
          Taking photo at the time which get signal from the Inflatable Membrane Structure System.
        • 2.Specified time mode (engineering missions camera and outreach missions camera)
          Taking photo at the time which get signal from the Command & Data Handling System
        • 3.ADC shutter mode (outreach missions camera)
          Taking photo at the time which the camera is oriented the direction of the earth by determined using only the sun sensor.
        • 4.Attitude Determination mode (outreach missions camera)
          Taking photo at the time which the camera is oriented the direction of the earth by the Attitude Determination.
        • 5.Attitude Determination and Control mode (outreach missions camera)
          Taking photo at the time which the camera is oriented the direction of the earth by the Attitude Determination and the Attitude Control.

          

        In addition to above command, taking the photo after separation from the rocket. The aspect of all photos is 307,200 (640×480) pixels. Also these photos are sent from the SPROUT by full-size, thumbnail (320×240,160×120,…) and SSTV of the Scotti1 format.







        【Inflatable Membrane Structure System】
        The main mission of the SPROUT is deploying inflatable membrane structure. By means of this, we confirm that design of the inflatable membrane structure is proper, and we confirm how behave of the inflatable membrane structure in the space. Also, we have the purpose to be useful for development of a future flexible structure. Inflatable membrane structure consists of the inflatable tubes and the thin film which are flexible structure. The inflatable tubes are deployed by applying the gas pressure to the inside of the metal foil formed in a bag shape. The SPROUT deploys triangle membrane of 1500-mm one side and keeps as the supporting structure which is the inflatable tubes.


        Because inflatable structure consists of the thin membrane, it is able to carried to the space in the folded state. It is possible to be deployed in the space by folding small. Thus, it is possible to construct large structures at a time that compared to the structure of prior. From these reasons, the flexible structure attracts attention as the future space structure, and research is energetically made all over the world in recent years. However, there are few examples which are deployed of the flexible structure in the space. As the cause, the flexible structure has the instability movement which is influenced by disturbance. On the other, launching the large structure to the space is too expensive, so it is required the reliability. Because the inflatable structure is deployed instability, the inflatable structure has few reliabilities. So, there are few results of deploying in the space, and there are not established of design technology. For established as a future structure, it is need to be improved the reliability. To do so, it is important to perform many space demonstrations and continue evaluation of the deployment behavior and design technology.










        【Amateur Radio system】
        The SPROUT gives opportunity to use satellite by people who has never used the ham radio, or the ham radio operators who live all over the world.
        These are the ham radio mission service of the SPROUT.

        • Degi-talker
          To send recoded sound at the satellite to ground station
        • SSTV
          To transform photo to SSTV signal and send this data to ground station. SSTV signal is able to see free software "MMSSTV". The photo data is two types, pre-setting photo and photo is taken by the SPROUT outside camera. The outside camera is able to control such as photo number. or timing.
        • Voice and text message box project
          To save voice or text data which uplink from the ground station and send back to the ground station.
        • Earth mapping project
          The earth mapping by photo is taken by the SPROUT outside camera.

        The SPROUT has two communication lines, This ham radio mission use one line. And, the band rate is 140MHz for uplink and 430MHz for downlink. The line of ham radio use and mission use is separated so we would like to give privilege for some command to control the satellite.
        ※The information of this service will be introduce this link"Amateur satellite operation".





        Satellite Separation System

          【Satellite Separation System】
          The purpose of developing the self-made separation system is for reducing the design demand on given to the satellite. Therefore, it is possible to raise the size of the satellite and the flexibility of the structure. Also, the technology is accumulated in the individual or the laboratory and built the foundation or the technology to contribute the space development in the future by constructing the separation system, without diversion of the existing technology or the manufacture request to the company.


          The SPROUT was developed not standard size which is 10-cm cube in conventional the Cube sat Project but 20-cm cube. Therefore, we developed the Satellite Separation System to suit the 20-cm cube by considering redundancy and considering reducing of the design requirements of the satellite.
          The lid is being fixed by Hold Release Mechanism (HRM) and the HRM is held by the string.
          Cutting the string with thermal cutting by sending current through the nichrome wire. Then, the lid will be released. We designed the system which the SPROUT will be separated from the separation system within 5 seconds after receiving the signal for separating.