Communication satellite reliability is important for various reasons.
From a Reliability & Maintainability (R&M) perspective maintainance is expensive.
Maintenance is expensive, or indeed impossible, as the satellite is in space orbit.
In the case of a typical Geostationary Communications Satellite, it could be in an orbit, 36,000 Kilometres away from earth.
Service Life
The service life is how long the equipment should last.
The equipment in this case is the satellite.
Other types of equipment include satellite ground stations.
When a space communications satellite is in its early part of the product design lifecycle, design lifespan will be decided.
The ILS, or Integrated Logistics Support function within the design process, should occur early on.
ILS is concerned with reliability and maintainability (R&M) of satellite systems.
Systems include both space assets, such as X-Band Communications Satellites, that are orbiting in space.
It also includes ground based assets on earths surface, such as fixed location Satellite Ground Stations, and mobile systems, such as Radomes on Ships.
Satellite equipment located terrestrially, in other words on earth, needs to be considered differently, from space assets, when considering R&M.
Ground Based Systems
Reliability and Maintainability (R&M) of ground based satellite communications systems, needs to include analysis of repair levels.
Repair levels concern how and where system repair and maintenance, take place.
For example, a waveguide section of a satellite ground station can probably be replaced on-site, without removal of the whole unit, from the site.
Whereas, a gearbox that requires a rebuild, will require removal, and bringing back to a service base.
Orbiting Space Systems
Orbiting Space Systems, such as Communication Satellites, are not usually ‘field repairable’.
Therefore ILS (Integrated Logistics Support) is an important aspect of the design process.
ILS should ideally be started early in the Product Life Cycle, at the start of the design process.
For Space Communications Satellites, a number of reliability and maintainability considerations need to be made.
Redundancy
Redundancy is having backup systems, that can allow the satellite to keep functioning as intended.
For example, a geosynchronous communications satellite might have a backup communications modem.
This ensures that the satellite continues to function, if the main modem fails.
Having Redundancy built into a system, helps with the overall design reliability.
Overall system Reliability can be measured in terms of MTBF.
MTBF stands for Mean Time Between Failures, or is sometimes also called Mean Time Before Failure.
Component Analysis
To design a reliable Satellite Communications system, you need to consider component analysis.
Components are the parts which make up a satellite of ground station.
Components can be considered at a subsystem level, such as a communications receiver, or at an individual component level, such as a transistor.
By analysing the components of a satellite communications system, we can predict system lifespan.
In the case of a space based system, such as a LEO or Geostationary Satellite, the system lifespan is dependent on the quality of the components.
This is because, unlike ground based systems, they cannot have failed components replaced, either in the ‘field’, or taken back to a repair location.
Guarantees
Satellite manufacturers often offer service guarantees to their customers.
This forms part of the purchase contract, and gives the buyer confidence that the equipment will perform for the required service period.
Manufacturers need to ensure utmost reliability, and build in redundancy.
What redundancy means is that there is a backup duplicate system component, that can be used if the primary component fails in service.
This maximises communication satellite reliability.
Debris
Space debris is an increasing problem in space.
Debris hitting a satellite could cause catastrophic system failure.
The debris is travelling through space at very high speed.
Making the satellite strong enough to withstand an impact is impracticle
It is impracticle due to the additional weight that the protection would make the satellite.
Remember that the satellite has to be launched into space.
Therefore additional weight requires more powerful rockets to launch the satellite into space.
More powerful rockets cost more money.
Integrated Logistics Support
Integrated Logistics Support (ILS) is a key part of satellite reliability.