The objective of this predevelopment activity is:
- To define the best cooled LNA thermal control design and accommodation for Alphabus,
- To identify the critical thermal control components,
- To provide to the system the impacts of the G/T improvement on the thermal control mass and heater budgets allowing then for the selection of the best compromise at system level.
Focus is given on passive thermal control devices but the active cooling means will also be investigated.
Alphabus missions include payloads with very stringent G/T requirements. Considering the antenna gain and noise temperature, one way to comply with this requirement is to minimise the input section temperature by:
- Accommodating the LNAs as close as possible to the Rx antenna feeds in order to minimise the input losses,
- Cooling the LNAs in order to decrease their Noise Figure.
The expected benefits from this study are to provide to the Alphabus programme:
- Thermal Constrol System inputs in order to assess the real benefit of cooled LNAs at system level,
- The minimum LNA temperatures achievable with simple and cost-effective passive thermal control technologies,
- An optimised and generic cooled LNA design which could afterwards be tuned to the LNA quantity baselined for each specific Alphabus mission*.
* Cooled LNAs have been identified as necessary for several Alphabus missions involving Ka-band payloads oriented towards broadband multimedia applications (coverage sampled with users spots and gateways).
The tasks performed under the project are organised as follows:
- Task 1 - Cooled LNA thermal control state-of-the-art
- Task 2 - System performance versus cooled LNA temperature
- Task 3 - Passive and active thermal control concept for cooled LNA
- Task 4 - LNA accommodation on Alphabus & justification
- Task 5 - LNA thermal control component specification
The general passive and active concepts have been established and the trade-off between them is finalised. Several concepts have been studied for the passive solution with several sun-shield shapes. The selected solution will be further studied in detail for two different payload configurations.
- Accommodation of LNA unit and associated thermal control on Alphabus platform for one conservative payload mission,
- Thermal performances to be assessed for this mission,
- Issue of component specification.