QB50 System Requirements Document

5.9.2 Script TIME Field - @tTime-tagged command sequence scripts shall be uploaded to the CubeSat. TheCubeSat OBC shall read the script commands and execute them at the time given bythe 3-BYTE @t TIME fieldTIME is a 3-BYTE value:1 st BYTE Hours range 0-24*2 nd BYTE Mins range 0-59*3 rd BYTE Sec range 0-59*The @t TIME field is ONLY read by the OBC, but NOT sent to the SU as part of thecommand.The Science Unit shall execute commands immediately upon receipt.Time is to an accuracy of 1 sec.*Note: The SCRIPT mnemonic @NOW is encoded as time = FF:FF:FF – this shall beinterpreted by the OBC script handler to send the script command immediately.NOTE: by having TIME in a 24 hour format, it is envisaged that the same script couldbe repeated each day.5.9.3 Script Encoder Software ToolAn ASCII - user-readable “Command Sequence Script” shall be encoded into a BYTEstream using the SU_SCRIPT_ENCODER software tool provided by the SU team.As an example, the script commands:OBC_SU_ON @19:00:00SU_HK 60 @19:04:09Would be encoded into the following BYTE stream by the SU_SCRIPT_ENCODERtool:0x09, 0x04, 0x13, 0x3C, 0x13, 0x04, 0x09The SU_SCRIPT_ENCODER shall parse the script file; parameter range errors andlogical errors, such as attempting to send a SCIENCE MODE command before turningON the high voltages, will prevent a byte file being generated.5.9.4 OBC_SU_ON (0xFB)This SCRIPT command is ONLY read & interpreted by the OBC to turn ON the SU attime given by “@t”.