Specifics of GPS Code lengths CIA code is 1023 bits long P-code is 37 weeks long(2X1014 bits in code Only one P-code, satellites use different weeks from same code(P-code repeats each week) As far as we know Y-code never repeats(again classified) Data message: Implemented by changing sign of code at rate of 50 bits/second(low data rate) 02/27/02 12.540Lec0702/27/02 12.540 Lec 07 4 Specifics of GPS • Code lengths: – C/A code is 1023 bits long – P-code is 37 weeks long (2x1014 bits in code) – Only one P-code, satellites use different weeks from same code (P-code repeats each week) – As far as we know Y-code never repeats (again classified) • Data message: Implemented by changing sign of code at rate of 50 bits/second (low data rate)