Cute-1.7 + APD II Project - Sub Systems > C&DH -

Small Satellite Program (SSP), Laboratory for Space Systems (LSS), Tokyo Institute of Technology

• Top
• News
• Overview
• Launch Vehicle
• Launch & Operation
• Sub Systems
• C&DH
• Communication
• EPS
• ADCS
• Structure
• Camera
• APD
• Environment
• Separation System
• Ground Station
• How to Receive
• Amateur Service
• SRLL TNC
• SatCast
• Cute-1.7 + APD Blog
• Software
• Gallery
• Acknowledgement
• Paper
• Members
• Lab Only
• Links
• Contact
• Cute-1.7 + APD I
• Japanese

TOP SUBSYSTEMS C&DH

What is C&DH？

Command and Data Handling(C&DH) system, composed of a main computer, performs two important roles in a satellite. Upon receiving an uplink from ground station or getting a calculation result in the satellite, C&DH system sends commands, information about how subsystems should process. Moreover, C&DH collects data in a satellite and distribute data to the subusystems. After collecting data such as housekeeping data and mission data, C&DH saves the data, and then, sends the data to the Comm system to downlink or uses the data to generate a command to the other subsystems. In addition to these, C&DH system also has roles to control time and detect errors in a satellites.

Introduction

C&DH system in Cute-1.7 + APD consists of PDA as the main computer, DAQ(Data AcQuisition) and USBHub expanding the interfaces PDA provides, and PDASwitch which changes working PDA. In spite of being inexpensive and having high performance, PDA provides only one USB port as the external interface, therefore, USBHub needs to be attached to the port to provide enough USB ports to the subsystems. In addition, DAQ is necessary because it is difficult to process analog data from sensor and digital data to send commands with USB interface. Being designed for terrestrial use, PDA does not cover space environment. Thus, two PDAs which PDASwitch switches on detecting errors by H8 microcomputer on communication board are used in Cute-1.7 + APD after environmental tests such as radiation, thermal, and vacuum test are conducted.

C&DH System Block Diagram

Profile of Handling Data

OBC (On Board Computer)

Specification of the PDA is shown below:

Specification of PDA
CPU		ARMV4I 400MHz
OS		Microsoft Windows CE.NET
RAM		32Mbyte
Flash Memory		SD Card 128Mbyte
Interfaces		USB,MMC/SD Card slot
Dimensions		70(W) x 100(H) x 5(D)mm
Weight		**g

PDA Board

Thermo Sensor

Dallas Semiconductor 1-wire Device DS18B20

Integrating Dosimeter

RADFET by NMRC(National Microelectronics Research Centre)

Circuit

• Constant-current Circuit (10uA)
• Measure Gate-Source Voltage by Differential Amp
• Measurement Range : ～8[krad]

Copyright ©, Tokyo Institute of Technology, All Rights Reserved.