Cute-1.7 + APD II - Sub Systems

Communication Subsystem

The most important role of the Communication subsystem , which is one of the most important subsystems in the satellite , is to communicate with groud station and to transmit / receive the data . Cute1.7+APD , launched in Feb. 2006 , had been operated for about a month and its basic function showed actual performance in the orbit . It communicated by GMSK modulate system for the first time in Japanese cubesat ,and we received reception report from all arround the world. As in the case of Cute1.7 ,Cute1.7+APD II uses amateur 144MHz and amateur 1200MHz frequency for the 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. It is controlled from the operation center at Tokyo Institute of Technology "JQ1YCZ" in Tokyo, Japan. Cute-1.7 + APD II amateur missions are based on the experience of amateur satellite operation in CUTE-I and Cute1.7 , and are developed with radio amateurs all arround the world . The objectives of communication subsystem in the satellite are as follows.
1. To create a higher functioned amateur satellite using new designed methodology for micro/pico satellites
2. To share radio experiment opportunities with radio and satellite amateurs

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

missions

To create a higher functioned amateur satellite using new designed methodology for micro/pico satellites
Amateur service mission, CUTE Digipeater service

Functions

Cute-1.7 + APD II communication subsystem has following functions,

receive command from the ground station
transmit CW telemetry
transmit GMSK or FM telemetry
deploy antennas when the satellite deployed
satellite management instead of C&DH system when emergency
open digipeater services

Cute-1.7+APD II Communication System Comcept

transceivers

Cute-1.7+APD II has following transceivers

Transceivers

4 transceivers are equipped
comm link

	Frequency (MHz)	Moduration	Protocol	Transceivers	Power (mW)	Consumption (mW)
Command	144MHz	AFSK 1200bps / GMSK 9600bps, DTMF	AX.25/SRLL, DTMF	DJ-C5 (ALINCO)		??
Uplink (Digipeater)	1200MHz 1267.6MHz	GMSK 9600bps	AX.25/SRLL	TH-59 (KENWOOD)		??
Telemetry	430MHz 437.475MHz	AFSK 1200bps / GMSK 9600bps	AX.25/SRLL	DJ-C5 (ALINCO)	300	??(MAX)
Beacon	430MHz 437.275MHz	CW	CW	(INVAX)	100	??(MAX)

DJ-C5(for 144RX and 430TX), CW-TX(for 430TX), TH-59(for 1200RX))

Antennas

Four of the Cute-1.7 + APD II antennas are all monopole antennas , which showed actual performance in CUTE-I and Cute 1.7 . Amprifier is used for 1200MHz receiver to make communication stable . Antennas are made of steal tape(0.2mm thickness, 3mm width) covered by PTFE. While the satellite is in the rocket, antennas are coiled. They will be deployed after the satellite is separated from the rocket.
Controller

Communication controller handles packet assembling and disassembling. Controller has 2 micro-computers, one of them handles the data transmission, and the other handles received data. They are connected by RS-232 serial line. Because the MPU can handle only serial communication, USB-serial converter is used to communicate with PDA . And also, MPU of communication sysytem and APD unit are directly connected by serial line in order to conduct APD science mission if PDA don'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

satellite emergency control system

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

Reset other MPUs and Power management
MPU of Communication subsystem, when it receive reset command from ground the station , control the FET of electric power system and reset whole the satellite.
Memory
Communication subsystem has FeRAM to memory satellite status. If PDA don't work the memory has very important roles. Its size is 64kbits.
Monitering
MPUs monitor the satellite voltage, current, and thermal status.

digipeater

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 II provides digipeater service to all amateurs in the world.

Enabling International communication
Real time packet exchange system
Accept any messages or data less than 50 bytes
Operation schedule will be announced in the web

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 II is usually operated in Multicast mode. All registered messages will be sent sequentially. Anyone who has Cute-1.7 + APD II telemetry decodable radio transceiver can listen these messages. In Uplink mode, 1200MHz-band receiver for Cute Digipeater mission is ready to accept your message to register. When Cute-1.7 + APD II accept your message, satellite will reply acknowledgement signal imediately in 437MHz telemetry link. Anyone can listern this reply signal. Detailed information, please see amateur service section.