What COTS Needs for Viable Onboard Data Handling?
In recent years’ space missions have come under increasing cost pressures. This is in part due to the rise of private and commercially driven space vehicle development companies and a growth of space programs in other countries such as China, India and Japan. One method of cutting costs is to is to use Commercial-Off-The-Shelf (COTS) equipment. However, such equipment often has not been specifically designed for space applications and certain criteria need to be met before this strategy is viable.
The criteria fall into two broad categories: operational and environmental concerns. These concerns arise because of the extreme conditions experienced by launching a vehicle into space and some unique ways that launchers operate compared to other aircraft. The environmental shock and vibration experienced by equipment during launch and the journey into orbit tends to be much more extreme than that experienced by equipment during terrestrial flight. The best way to ensure COTS equipment can cope with this is extensive environmental testing.
The operational concerns, and potential resolutions, include:
- The environment during take-off prevents reliable telemetering, so if data must be retrieved from non-reusable launchers, this must happen during the flight path. This can be resolved using a delayed telemetry stream to transmit launch data after a certain delay.
- Radical changes to the instrumentation topology during the mission, as sections of the vehicle detach possibly carrying sub-sections of the data handling instrumentation network with them. A master slave system with a transducer to tell the system a separation has occurred. Another is to use an Ethernet node topology that will simply no longer collect data from the missing DAUs.
- Large vehicles may require data to be transferred over distance as high as 100 m at high speeds. Several strategies may work but a good solution is Ethernet as it can easily operate at high speed over 100 m.
- Instrumentation on orbiting vehicles may be “out of sight” of ground receiving stations for long periods of time. When instructed, a recorder can start transmitting all data recorded during a specified time frame without interfering with data acquisition that is taking place concurrently.