Massive onboard data storage
Data-rate generated by scientific instruments and daughter satellites is over 3Mbyte/sec in the mother satellite. It is NOT possible to make all data down link to the ground because the high-time resolution data is huge. So data storage component is necessary to keep event data for about 10 days until that science coordinate team will select events to the ground. The requirements of MDR are as follows;
Mother satellite
over 1TB storage area (target value)
Mass is less than 20kg and Power is less than 60W
Write speed is faster than 40Mbps and Read speed is faster than 20Mbps
Daughter satellite
Over 50GB storage area
Mass is less than 3-4 kg and Power is less than 10W
Write speed is faster than 8Mbps and Read speed is faster than 1Mbps
Common
Using file systems (ex: fat32 etc) in order to delete data files not to need
Storage system have the function of search data files in the time and then the data selected by commands will be made down-link to the ground station automatically
The data handling inter face is SpaceWire (> 50Mbps)
A device for the MDR is based on the Flush-ROM because of advantage for mass and power. The concept of the MDR is shown in a following figure. It consists of two parts, one is to control data flow with CPU and the other is to control the stacked Flush-ROM memory.