O

Octet
Synonym for byte

Online
Data that is available on demand, though not instantaneously.

Orbital period
The time to complete one orbit, 24 hours for a geostationary system.

Orbital slot
The longitude of a geostationary satellite.

Outage
An event that makes a device or system un-usable or un-acceptable degrades its performance.

Overflow
The use of a system, on demand, only when the capacity normally used is busy.