Spin rate estimation of sounding rockets using GPS wind-up

Abstract

Carrier phase wind-up is a well known effect that appears with the relative rotation between a transmitting and receiving antennas. In GPS measurements at L1 frequency, this effect translates into an error of ca. 20cm per full relative rotation of antennas. Since this effect is independent of the satellite elevation for pure rotation about the antenna boresight axis, it is usually absorbed by the clock estimation in navigation algorithms. Therefore the impact of wind-up is usually neglected for applications that do not require accuracies to the centimeter level like RTK. However, in receiving platforms with high rotation rate, the accumulated wind-up value can be important and actually be larger than receiver noise or even ionospheric variations. Therefore, in such scenarios, the wind-up contribution can be isolated and used as a source of information to compute the spin rate of such platforms using an appropriate combination of GPS observables. This work shows some results of a coarse, yet simple, approach to monitor the rotation angle and spin-rate of spin stabilized sounding rockets flown by DLR.