Architecture

The software aboard ION is as critical to the mission as any piece of hardware. The design of all the software required to make all of the satellite hardware work is a very large task; therefore, it must be broken down into small, manageable pieces. Only through a very modular design, with well-defined interfaces between parts does such a large task with so many developers become manageable. The modularity of the hardware is reflected in the design of the software.

Operating System

All ION software is custom developed and runs on a SID (Small Integrated Datalogger), a small prototype computer designed for space-based applications. It features:

7 MHz Hitachi SH2 Processor
1 MB External SDRAM
256KB EEPROM
8 MB Flash
3 Real-time Clocks
1 Temperature Sensor
Number I/O ports, A/D Converter, and watchdog timers.

The system provides the ability to schedule all activity on the satellite via commands sent from the ground and retrieve any data files generated onboard the satellite.

Applications

All activity on the satellite is performed by applications, which are controlled from the ground. Applications perform mission critical activities, data gathering, and the day-to-day maintenance of the satellite. The applications onboard the satellite are:

Communications Application
Responsible for establishing and maintaining contact with the ground station and providing the ability to upload and download files

Housekeeping Application
Performs system maintenance, such as clock synchronization, file system synchronization, and rebooting.

PMT Application
Responsible for gathering data from the PMT

CMOS Application
Responsible for taking pictures with the camera

Torque Application
Responsible for controlling satellite attitude via the torque coils

PPU Application
Responsible for controlling the thrusters onboard the satellite.

Power Application
Responsible for monitoring power usage aboard the satellite and charging the batteries.