Attitude Determination of small satellite using phase and code measurements of Global Navigation Satellite System: Design, simulation and comparison

Attitude Determination (AD) of a Low Earth Orbit (LEO) small satellite using the code and phase measurements of Global Navigation Satellite Systems (GNSS) is explored in this research. The proliferation of satellite based navigation system and the burgeoning application area of small satellites in the field of Earth observation has motivated this research paradigm. This contribution focuses on the design, simulation and comparison of multi-antenna, stand-alone, commercial-off-the-shelf (COTS), GPS-based attitude determination using the code and phase measurements of GPS signals. Master antenna position is obtained by Single Point positioning method using the code observations and ephemeris while differential positioning is applied to find the slave antenna positions. The problem of Ambiguity Resolution (AR) that is crucial while estimating attitude using phase measurements is done by Least-Squares AMBiguity Decorrelation Adjustment (LAMBDA) method. Finally, the attitude is determined using the direct and the least square method. It has been found that phase measurement method is more precise than the code based method and an accuracy of less than one degree in attitude parameters can be obtained using phase measurements.