on1 - after the "first look" sees a signal worthy of followup, it is observed again.
off1 - if the signal is seen during the "on1" the beams are moved off their targets and the beams are observed again. If the signal is seen when pointed OFF, the signal is deemed RFI.
on2 - if the "off1" did not see the signal, the beams are again pointed on the objects and observed again.
off2, on3, off3, on4, off4 - the on/off activities are continues till either the signal is determined RFI or not seen again.