Cute-1.7 + APD Laboratory for Space Systems

Cute-1.7 + APD Project - Sub Systems > COMM -

Small Satellite Project (SSP)

Laboratory for Space Systems (LSS), Tokyo Institute of Technology

TOP arrow image SubSystem arrow image Communication

Communication Subsystem

The most important role of the Communication subsystem is to communicate with groud station, which is one the most important subsystem in the satellite. Cute-1.7 + APD uses amateur 144MHz and amateur 1200MHz frequency for thr ground to the satellite link, and uses 430MHz band for the satellite to the ground link. The satellite is an amateur satellite whose frequency was coordinated by International Amateur Radio Union (IARU), and was licensed by the Ministry of Internal Affairs and Communications in Japan. The Callsign is "JQ1YPC" and controled from the operation center at Tokyo Institute of Technology "JQ1YCZ" in Tokyo, Japan. Cute-1.7 + APD amateur missions are based on the acknoledgement of CUTE-I and are developed with Japanese radio amateurs. The objectives of communication subsystem in the satellite are as follows.
1. To create a higher functioned amateur satellite using micro/pico satellite with new design methodology
2. To share radio experiment opportunities with radio and satellite amateurs

To receive the telemetry and use digital repeater, please see Cute-1.7 Amateur services.


  1. To create a higher functioned amateur satellite using micro/pico satellite with new design methodology

  2. Amateur service mission, CUTE Digipeater service


Cute-1.7 + APD communication subsystem has following functions,

Cute-1.7+APD Open Rev


Cute-1.7+APD has following transceivers

  1. Transceivers

    4 transceivers are equiped
    comm link

    Moduration Protocol Transceivers Power
    Command 144MHz AFSK 1200bps / GMSK 9600bps, DTMF AX.25/SRLL, DTMF DJ-C5
    GMSK 9600bps AX.25/SRLL TH-59
    Telemetry 430MHz
    AFSK 1200bps / GMSK 9600bps AX.25/SRLL DJ-C5
    300 ??(MAX)
    Beacon 430MHz
    CW CW
    100 ??(MAX)
    DJ-5C CW-TX TH-59
    DJ-C5(for 144RX and 430TX), CW-TX(for 430TX), TH-59(for 1200RX))
    Transceiver box Transceiver box
    Transceiver Box
  2. Antennas

    Cute-1.7 + APD antennas are the same as of CUTE-I. Amprifier is used for 1200MHz receiver to make stable communication. Antennas are made of steal tape(0.2mm thickness, 3mm wide) covered by PTFE. While the satellite in the rocket, antennas are coiled. They are deployed after the satellite is separated from the rocket. The movie file is about deployment of antennas.
    Antenna deployment (quicktime, 20.8MB)
    antenna antenna
    4 mono-poles

  3. Controller

    Communication controller handles packet assembling and disassembling. Controller has 2 micro-computers, one of which handle the transmit data, and the other handles receive data. They are connected by RS-232 serial line. Because the MPU can handle only serial communication, to communicate with PDA, USB-serial converter. And also, MPU and APD unit directly connected by serial line in order to conduct APD science mission even if PDA didn't work. Micro-computer is H8S/2328 FlashROM type, which has 128kB ROM and 8kB RAM, and was tested by Gamma-ray radiation.

block diagram

block diagram

satellite emergency control system

If PDA didn't work in the orbit, micro-computers in the Communication subsystems would control the whole satellite.


The development team has considered what service using amateur radio would be fun and interesting for both amateurs and universities. The team has discussed with Japanese radio amateurs from its early stage of development. Cute-1.7 + APD provides digipeater service to all amateurs in the world.

  1. Enabling International communication
  2. Real time packet exchange system
  3. Accept any messages or data less than 50 bytes
  4. Operation schedule will be announced in the web
cute digipeater

This is the image of Cute Digipeater operation. The satellite has 2 modes, which are "Multi-cast mode" and "Uplink mode". Cute-1.7 + APD usually operates in Multicast mode. All registered messages will be sent sequentially. Anyone who has Cute-1.7 + APD telemetry decodable radio transceiver can listen these messages. In Uplink mode, 1200MHz receiver for Cute Digipeater mission is ready for accept your message to register. When Cute-1.7 + APD accept your message, satellite will reply acknowledge signal imediately in 437.505MHz telemetry link. Anyone can listern this reply signal. detailed information, please see amateur service section.


Here, the past model can be seen.

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