A method for timing for a satellite constellation, the method comprising: transmitting, by at least one first satellite, at least one crosslink ranging signal to at least one second satellite, wherein at least one of the at least one first satellite and the at least one second satellite is a timing satellite with a synchronization time; wherein when the at least one first satellite is a timing satellite, the at least one second satellite is a non-timing satellite; and when the at least one second satellite is a timing satellite, the at least one first satellite is a non-timing satellite; receiving, by the at least one second satellite, the at least one crosslink ranging signal; calculating at least one ranging measurement from the at least one first satellite to the at least one second satellite by using an amount of time elapsed from the transmitting of the at least one crosslink ranging signal to the receiving of the at least one crosslink ranging signal; and calculating an estimate of time and frequency for the at least one first satellite and the at least one second satellite relative to each other and to the synchronization time to synchronize the time and the frequency for at least one of the at least one first satellite and the at least one second satellite by using at least one of the at least one ranging measurement and the synchronization time from the at least one timing satellite; wherein the at least one timing satellite is equipped to obtain the synchronization time via at least one global positioning system (GPS) signal; and the at least one non-timing satellite is not equipped to obtain the synchronization time via at least one global positioning system (GPS) signal. transmitting, by at least one first satellite, at least one crosslink ranging signal to at least one second satellite, wherein at least one of the at least one first satellite and the at least one second satellite is a timing satellite with a synchronization time; wherein when the at least one first satellite is a timing satellite, the at least one second satellite is a non-timing satellite; and when the at least one second satellite is a timing satellite, the at least one first satellite is a non-timing satellite; when the at least one first satellite is a timing satellite, the at least one second satellite is a non-timing satellite; and when the at least one second satellite is a timing satellite, the at least one first satellite is a non-timing satellite; receiving, by the at least one second satellite, the at least one crosslink ranging signal; calculating at least one ranging measurement from the at least one first satellite to the at least one second satellite by using an amount of time elapsed from the transmitting of the at least one crosslink ranging signal to the receiving of the at least one crosslink ranging signal; and calculating an estimate of time and frequency for the at least one first satellite and the at least one second satellite relative to each other and to the synchronization time to synchronize the time and the frequency for at least one of the at least one first satellite and the at least one second satellite by using at least one of the at least one ranging measurement and the synchronization time from the at least one timing satellite; wherein the at least one timing satellite is equipped to obtain the synchronization time via at least one global positioning system (GPS) signal; and the at least one non-timing satellite is not equipped to obtain the synchronization time via at least one global positioning system (GPS) signal. <EOS>