PAGE CONTENTS
Objectives
The PLIU is a unit containing command and acquisition channels of standard type, like High Level Commands and Thermistor acquisition channels. It contains power switches for heater control and stepper motor drivers. The interface to a central computer consists of a dual redundant Mil-Std-1553B bus.
The challenge is to make a low-cost production series by using commercial components and a production friendly design.
The main objective of this activity is to develop and qualify a Payload Interface Unit (PLIU) which will be used on the Iridium NEXT Satellites.
Another objective is that with the development of the Iridium NEXT PLIU, RUAG Space AB will be able to take a step against a more low-cost approach in future platform and payload computers/equipments by:
- Qualifying commercial EEE part for use in space,
- Developing I/O building blocks that can be used in future equipments.
Challenges
The challenge is to make a low-cost production series by using commercial components and a production friendly design. It is clear that for Iridium NEXT PLIU Design to Cost solutions with high performances and integrated electronics components is encouraged and alternative EEE parts policy based on the experience of the suppliers are to be considered. For instance, commercial grade PED (Plastic Encapsulated semiconductor Device) has been investigated.
Plan
The development philosophy for the PLIU has been adapted to secure the design and development of the PLIU with the aim of getting a low-cost and highly suitable and producible module. The Iridium NEXT constellation requires 81 flight units, therefore a considerable effort has been made in the development phase to get a design suitable for smooth manufacturing and automated production tests.
To achieve this, several bread boards have been built before the EQM was manufactured:
- EBB
- IHBB1
- IHBB2
Current Status
A success factor in meeting the performance requirements was the development approach with several bread boards during development phase where different design solutions have been tested. Moreover, the decision having two fit-checks for the antenna motor interfaces using first a bread board motor and secondly a flight representative motor, have further decreased the risk of having a non-optimum design solution.
The use of SMD parts have been maximized, an SMD 1553 transformer has been introduced, all external connectors are designed to be directly soldered on the PCB, all chassis mounted components is soldered directly to the PCB. Only one type of ferrite core is used for the integrated magnetics, i.e. planar transformers.
The PLIU EQM test campaign has been successfully performed.
