Both ICUs (main and redundant) are located in a single box and work in cold redundancy. Each ICU shall implement the following common functions (non-exhaustive list):
- Handle communications with spacecraft.
- Receive and process telecommands.
- Format and transmit cyclic and sporadic HK telemetry and scientific payload telemetry packets.
- Manage the SpaceWire network: the ICU is a remote network manager (router configuration, router monitoring, router status reporting…).
- Receive the on-board time (Central Time Reference) from the S/C, handle the time stamping of the data transmitted in HK TM and forward the CTR to the DPUs.
- Receive a SpaceWire time code from the S/C and forward it to the DPUs.
- Produce state and diagnosis information (cyclic status, progress event).
- Schedule the DPU tasks (by the way of commands sent to the DPUs).
- Manage the data flow (especially in configuration mode) and the mode transitions.
- Manage the maintenance of the ICU, N-DPU and F-DPU software and parameters.
- Manage the star catalogue.
- Compress the data using a lossless compression algorithm. A compression factor of at least 2.0 is required.
- Acquire and transmit to the S/C its own voltage and current consumptions.
Every 2.5 s, the active ICU receives the data (e.g. imagettes, HKs and FGS data) sent by the F-DPUs. The imagettes are compressed before being transmitted to the SVM.
Every 25 s, the active ICU receives the data (e.g. flux, centroids, imagettes, HKs) sent by the N-DPUs.
The incoming data are stacked before compression and transmission to the SVM.
In configuration mode, the main functions of ICU are to transmit the star catalogues and all other configuration parameters to the DPUs, to compress full-frame images sent by the DPUs, to pack and transfer to SVM all the data from DPUs necessary for subsequent validation of on-ground operations.
The expected data volume including compression is 435 Gb/day.
The ICU team
The ICU is under responsibility of Italy, with a contribution from Austria.
More information on the ICU team.