Airbus Defence and Space have shown that common building blocks can be considered to build the on-board Spread Spectrum System considering multi-users aspects:
1) For main operator TCR function: used for LEOP/On- station/Emergency:
- two transponders, with receivers in hot redundancy and transmitters in cold redundancy;
· - two omnidirectional antennas ensuring nearly omni coverage for LEOP and Emergency phases;
- a TM/TC TCR horn ensuring coverage of the main operator stations (alternatively, interfaces through communication antennas can be used);
·- set of couplers and switches ensuring the connection between transponders and antennas.
2) For hosted payload management: used for On-station only:
- two transceivers, with receivers and transmitters in cold redundancy;
- a hosted payload horn ensuring coverage of the HP on-ground stations;
·- set of couplers and switches ensuring the connection between transceivers and antennas.
The additional building blocks are multi-access receivers (to replace mono-access ones) for management of several hosted payloads, mono-channel Hosted Payload Interface Unit (HPIU) or multi-channel HPIUs.
These additional pieces of hardware shall be developed.
On ground, The TCR stations (LEOP and on station) shall be upgraded to support the use of spread spectrum signal and to be able to track on a spread spectrum signal. Two tracking approaches have been described in analyses (before or after dispreading the signal).
Architecture choices shall be driven by the decision tree given on the following figure:
Except in particular cases with only one hosted payload embarked on the spacecraft, with a low bit rate and no segregation need, it is recommended that hosted payloads are completely segregated from main operator TCR and data handling system: main operator will use a pair of transponders of its own and hosted payloads will use another pair of (mono or multi—channel) transponders and its own HPIU.
The following table summarized the main system requirements: