The spacecraft bus carries the payload. Its subsystems support the payload and helps in pointing the payload correctly. It puts the payload in the right orbit and keeps it there. It provides housekeeping functions. It also provides orbit and attitude maintenance, electric power, command, telemetry and data handling, structure and rigidity, temperature control, data storage and communication, if required. The payload and spacecraft bus may be different units or it may be a combined one. The booster adapter provides the load-carrying interface with the vehicle (payload and spacecraft bus together).