Use of weak GNSS signals in a mission to the moon

Abstract

According to the European Space Agency (ESA) Lunar Exploration program, the use of GNSS weak-signal navigation in future lunar exploration missions has the potential to increase the robustness of the navigation during all mission phases and improve considerably its autonomy. The major objectives of the ESA Moon-GNSS project have been to determine the feasibility of using GNSS (GPS/Galileo) weak-signal technology in future lunar missions to improve the navigation performance in terms of accuracy, cost reduction and autonomy. The Moon mission scenario is very challenging for the GNSS signals processing: less visibility compared to an Earth-based receiver, low signal strength, poor satellite geometry, Earth and Moon signal occultation, and spacecraft dynamics. The identification of the Moon-GNSS navigation receiver requirements for the upcoming lunar exploration missions has been performed. The impact of the receiver requirements on the Moon-GNSS receiver module architecture and algorithms has been analyzed (weak signal processing, filtering and navigation), including an overview of the state of the art space-borne GNSS receivers. Besides, the synergies between GNSS signal/navigation processing and other navigation sensors (i.e. accelerometers, optical camera, laser altimeter) have been analyzed, using the state of the art of sensors integration for space missions. A demonstrator of the weak-signal Moon-GNSS navigation has been designed and implemented, showing the main functional and performance capabilities of the Moon-GNSS receiver. A test campaign representative of a real Moon-GNSS mission has been carried out, covering all the mission phases of the real mission conditions in terms of dynamics and signal disturbances, for different configurations: standard sensors, standard sensors plus GNSS and stand-alone GNSS navigation. Keywords 1 -GNSS weak-signals, Moon missions, navigation, Proof of Concept I. MOON-GNSS SCENARIO DESCRIPTION In order to analyze and identify, the Moon-GNSS navigation receiver requirements, the first task has been to define the Moon-GNSS scenario to be used as the reference scenario for the Moon-GNSS activity. The selected Moon-GNSS reference scenario is based on the ESA Lunar Lander mission, with landing site near Moon's South Pole. The different mission phases of the Moon-GNSS reference trajectory are listed below: 1 This work was supported by the ESA project 4000107112/12/NL/AF/fk.

Standalone GPS L1 C/A Receiver for Lunar Missions

“…These receivers are picking up the spillover of the main lobe of the GNSS transmit antenna pattern around the Earth mask and also signals from the weaker side lobes of the antenna pattern. Research presented in [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ] shows feasibility studies of GNSS as navigation system for space missions in High Earth Orbits (HEO) and beyond up to Moon altitude. Other research work, such as [ 9 , 10 , 11 , 12 ] and [ 13 ] has proposed GNSS receivers designed for such missions and the demonstration of a receiver positioning in HEO is detailed in [ 14 ].…”

GPS-based orbital filter to reach the moon

“…Promising experimental results presented in Powell et al (1999) and Balbach et al (1998) have demonstrated that by modifying the traditional signal processing techniques, GNSS can also be used in higher orbits such as medium Earth orbit (MEO) and high Earth orbit (HEO). More recent research studies have shown the interest of the scientific space community to investigate the potential use of GNSS as navigation system for lunar missions (Manzano-Jurado et al, 2014;Silva et al, 2013;Capuano et al, 2014aCapuano et al, , 2014bPalmerini et al, 2009). Being its service originally conceived for Earth applications, the GNSS transmitters point towards the Earth, making their transmitted signals very weak above the GNSS constellation.…”

“…Being its service originally conceived for Earth applications, the GNSS transmitters point towards the Earth, making their transmitted signals very weak above the GNSS constellation. However, some of these first studies (see e.g., Manzano-Jurado et al, 2014;Capuano et al, 2014a;Silva et al, 2013) have revealed that although weak, GNSS signals from the side lobes of the GNSS transmitters antennas or from the spillover of the main lobe can still be acquired and tracked successfully. Experimental demonstrations have been presented in Balbach et al (1998) for HEO, while theoretical studies have been described in Capuano et al (2014a) for higher orbits up to moon altitude.…”

Research on the Effectiveness of Different Estimation Algorithm on the Autonomous Orbit Determination of Lagrangian Navigation Constellation

“…For deep space transfer orbits and deep space target orbits, the GPS is not good enough. Several researchers investigated weak GNSS signal navigation for the deep space probes [6][7][8]. Witternigg et al introduced how GPS and Galileo could be used for orbit determination in future missions to the Moon [8].…”

“…The methods introduced in [1][2][3][4][5] can be considered as absolute navigation (or absolute autonomous orbit determination) because the estimated orbit refers to an inertial or quasi-inertial frame. Methods introduced in [6][7][8][9][10][11][12][13][14] can be classified as relative navigation. Relative navigation seeks optimal estimates for the position and velocity of one satellite relative to the other one.…”