I. Introduction
The work of the present paper pertains to the task of postflight attitude determination for a suborbital sounding rocket mission: the magnetosphere-ionosphere coupling in the Alfven resonator (MICA) mission. MICA was launched from the Poker Flat Research Range in Fairbanks, Alaska, on February 19, 2012. The rocket was spin stabilized about its minor inertia axis, and it consisted of a main payload and a subpayload. The subpayload carried two MicroPulse 1273FW global positioning system (GPS) antennas, linked by about 0.6 M (2 ft) of Thermax RG-142S cable to two Zarlink/Plessey GP2015 RF front ends with a common clock. Raw GPS data from the front ends were sequentially buffered in random access memory, sent serially to the telemetry encoder, transmitted over an S-band telemetry link, received by the ground station, and recorded in digital recorders. The subpayload also carried a magnetometer and a horizon crossing indicator (HCI). The magnetometer and HCI can also be used to determine attitude [1], with accuracies demonstrated to be on the order of several degrees, and they constitute a way to verify the GPS attitude solution. Fig. 1 shows the complete rocket system.