On-Board Computer

For computation and calculation processes aboard the Flying Laptop, an On-Board Computer (OBC) system is necessary. As the Flying Laptop will be exposed to the environmental conditions existing in space, it needs to be robust against radiation and a wide range of temperature. Therefore an already existing processor, that has been validated to work under the mentioned conditions, has been chosen to be the core of the OBC system. The UT699 is based on the already flown LEON3FT processor family developed by ESA/ESTEC. This processor as well as the processor-close memory parts are placed on the OBC core board. This core board is designed and delivered by Aeroflex Colorado Springs, USA.

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The OBC executes the Attitude Control System (ACS) algorithms, Thermal Control System (TCS) algorithms, controls the dedicated payload computer and is in charge of housekeeping observation and Failure Detection, Isolation and Recovery (FDIR). Housekeeping data will be collected and transmitted to the ground station if requested.

As the processor board of the OBC system has only a SpaceWire-Interface to send and receive data, an interface board, or I/O-Board, is placed between the core board and the subsystems of the Flying Laptop. This board is equipped with SpaceWire interfaces on one side and the according interfaces to the particular subsystems on the other side, for example LVDS or I²C. The I/O-Board does not include any intelligence but only transmits data when a Read or Write command is sent by the on-board software. Also on the I/O-Board there are memory chips to allow buffering of telemetry data. The I/O-Board is designed and delivered by 4Links, U.K.

For the communication to the ground station a dedicated board with a CCSDS-Chip implementation is also part of the OBC system. This chip handles the data link layer of the CCSDS satellite communication protocol. Using this protocol ensures compatibility to many ground stations, for example those from space agencies like ESA. The board is designed and delivered by 4Links and is loaded with a CCSDS-Chip-implementation by Aeroflex Gaisler, Sweden. The CCSDS-Board will also be connected to the OBC via SpaceWire interface.

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All boards are available in duplex design. This allows to switch between devices to gain redundancy and compensation of malfunctions. Except for the communication boards, all boards are used in cold redundancy.

Due to the unregulated voltage bus aboard the Flying Laptop, there are two identical power boards which produce the required small voltage levels. In total there are eight boards comprising the FLP OBC system, as shown in the above picture.

The eight boards are are conncted via an especially designed micro-harness. This can be seen in the picture at the top. Regarding the significantly small space available for this internal harness, specialists from HEMA Kabeltechnik have been doing the design and manufacturing.

On the back of every second board there are emergency heaters. These will be activated by the PCDU in case the temperature in the system drops below a certain limit. This heater system has also been installed in duplex design.