High-precision measurement of satellite range and velocity using the EISCAT radar

This paper is a continuation of an earlier work by Nygr´ en et al. (2012), where the velocity of a hard target was determined from a set of echo pulses reflected by the target flying through the radar beam. Here the method is extended to include the determination of range at a high accuracy. The method is as follows. First, the flight time of the pulse from the transmitter to the target is determined at an accuracy es- sentially better than the accuracy given by the sampling in- terval. This method makes use of the fact that the receiver fil- tering creates slopes at the phase flips of the phase modulated echo pulse. A precise flight time is found by investigating the echo amplitude within this slope. A value of velocity is calcu- lated from each echo pulse as explained in the earlier paper. Next, the ranges together with velocities from a single beam pass are combined to a measurement vector for a linear in- version problem. The solution of the inversion problem gives the time-dependent range and velocity from the time inter- val of satellite flight through the radar beam. The method is demonstrated using the EISCAT (European Incoherent Scat- ter) UHF radar and radio pulses reflected by a satellite. The achieved standard deviations of range are about 5-50 cm and those of velocity are about 3-25 mm s 1 .