Abstract: The present application provides a three-mode storage method for program blocks based on check, comprising: first dividing the program to be injected into N blocks and checking each block to obtain the first checksum; then injecting the program to be injected and the first checksum twice in the program storage area, and the two injected programs are noted as the main program and the backup program, respectively; dividing the main program into N blocks, and checking each program block to obtain the second checksum during program run; dividing the backup program into N blocks and checking each block to obtain the third checksum; and comparing the checksum, second checksum and third checksum: if the three are consistent, performing no operation; updating the program or checksum and checking again, if the three are inconsistent.

Abstract: A navigation satellite time system and its autonomous recovery method are provided, including a load time system, the load time system is configured to generate and maintain the load time, and the load time system comprises an space borne atomic clock, a time-frequency processing unit and a plurality of load time backups module, the time information of the load time is obtained from the ground station time; the pulse-per-second signals of the load time are generated and maintained by the space borne atomic clock and the time-frequency processing unit; when the time-frequency processing unit fails, the first-level recovery state is triggered: the time-frequency processing unit compares the time information and the pulse-per-second signals reversely output by the multiple load time backup modules to perform load time recovery.