Session
Session II: Next on the Pad 1
Location
Utah State University, Logan, UT
Abstract
The Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) NASA mission consists of two identical spinner spacecraft built by Millennium Space Systems to investigate the effects of solar wind on the Earth's magnetosphere, particularly in the Northern "magnetic cusp" region near the magnetic North pole. The TRACERS satellites will measure AC/DC magnetic fields, electric fields, and electron/ion distributions to better characterize Earth-sun interactions and determine whether magnetic reconnection phenomena are primarily spatially or temporarily driven. This will improve our ability to understand and forecast space weather and "solar storms" which have the potential to disrupt or damage power grids and electronics devices on Earth.
To support this mission, the TRACERS vehicles must be spinning to allow for spatially averaged measurements from science instruments with disk-shaped fields of view. The vehicles must perform orbital maneuvers to maintain a desired average altitude and inter-satellite separation. The vehicles must also be capable of performing attitude reorientation maneuvers to align each spacecraft's spin axis with the local aggregate magnetic B-field (LABF) vector for science purposes. In additional to the orbital and attitude requirements levied by the science mission, the spacecraft must remain power-positive, thermally safe, and have adequate communications with the ground. This paper describes the TRACERS Guidance, Navigation, and Control (GNC) subsystem design and explains how the GNC hardware and algorithms will be utilized to enable the mission.
The TRACERS vehicles use a novel extended Kalman filter that is capable of attitude estimation using only magnetometer information. Measurements from a spinning sun sensor are also incorporated to improve spin phase knowledge and rate gyro measurements are incorporated for improved estimator stability during burns. A unique nonlinear magnetorquer controller is used for attitude re-orientation maneuvers whereby the pointing error signal is high pass filtered prior to entering the controller. This minimizes actuator efforts caused by differences between the true and estimated vehicle spin axes and ensures a pure spin about the maximum moment of inertia axis. GNC also enables mission autonomy by computing when the vehicle is within the scientific "region of interest" and sending a flag to activate the science instruments at this time.
TRACERS Mission and GNC Architecture
Utah State University, Logan, UT
The Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) NASA mission consists of two identical spinner spacecraft built by Millennium Space Systems to investigate the effects of solar wind on the Earth's magnetosphere, particularly in the Northern "magnetic cusp" region near the magnetic North pole. The TRACERS satellites will measure AC/DC magnetic fields, electric fields, and electron/ion distributions to better characterize Earth-sun interactions and determine whether magnetic reconnection phenomena are primarily spatially or temporarily driven. This will improve our ability to understand and forecast space weather and "solar storms" which have the potential to disrupt or damage power grids and electronics devices on Earth.
To support this mission, the TRACERS vehicles must be spinning to allow for spatially averaged measurements from science instruments with disk-shaped fields of view. The vehicles must perform orbital maneuvers to maintain a desired average altitude and inter-satellite separation. The vehicles must also be capable of performing attitude reorientation maneuvers to align each spacecraft's spin axis with the local aggregate magnetic B-field (LABF) vector for science purposes. In additional to the orbital and attitude requirements levied by the science mission, the spacecraft must remain power-positive, thermally safe, and have adequate communications with the ground. This paper describes the TRACERS Guidance, Navigation, and Control (GNC) subsystem design and explains how the GNC hardware and algorithms will be utilized to enable the mission.
The TRACERS vehicles use a novel extended Kalman filter that is capable of attitude estimation using only magnetometer information. Measurements from a spinning sun sensor are also incorporated to improve spin phase knowledge and rate gyro measurements are incorporated for improved estimator stability during burns. A unique nonlinear magnetorquer controller is used for attitude re-orientation maneuvers whereby the pointing error signal is high pass filtered prior to entering the controller. This minimizes actuator efforts caused by differences between the true and estimated vehicle spin axes and ensures a pure spin about the maximum moment of inertia axis. GNC also enables mission autonomy by computing when the vehicle is within the scientific "region of interest" and sending a flag to activate the science instruments at this time.
