Global Navigation Satellite System (GNSS) can be used for earth-moon navigation by spacecrafts.
Null Hypothesis (Ha): GNSS can not be used for earth-moon navigation by spacecrafts.
TABLE OF CONTENT
Objective
The objective of the research is to determine if Global Navigation Satellite System (GNSS) can be used for earth-moon navigation by spacecraft.
Null Hypothesis (H0): GNSS can not be used for earth-moon navigation by spacecraft.
Alternative Hypothesis (Ha): Ha: GNSS can be used for earth-moon navigation by spacecraft.
Methodology
An unstructured literature search centred around the terms “use of GNSS for lunar navigation” (structured literature review for gnss use in lunar missions). Lunar can be replaced by moon, earth moon or any synonym with similar meaning. The objective is not an exhaustive structured literature review. The objective is to gather evidence from published research that will refute or support the Null Hypothesis (H0) as quickly as possible and serve as the foundation for further investigation.
Since this is not a structured literature review, only the abstracts where reviewed, with exceptions made incase further understanding was required, and paraphrased in the Literature section. below. No attempt was made to scrutinise the publications with the only objective to refute or support the Null Hypothesis (H0) based on the claims made by the publications.
Only papers published from 2015 to 2024 (last 10 years) where considered, with a focus on 2020 to 2024 (last five years).
Result: Null Hypothesis (H0) is refuted
The evidence or literature presented below will show that the Null Hypothesis (H0) is refuted. GNSS can be used for earth-moon navigation for spacecraft. Sufficient theoretical evidence was acquired to state that it is plausible to use GNSS for earth-moon navigation.
Literature
[2024] Navigation performance analysis of Earth–Moon spacecraft using GNSS, INS, and star tracker by Wang et al.
Global Navigation Satellite System (GNSS) can provide an approach for spacecraft autonomous navigation in earth–moon space to make up for the insufficiency of earth-based tracking, telemetry, and control systems. However, GNSS are weak powered with poor observation geometry near the moon. The paper proposed considered the need for autonomous navigation for future spacecraft, and explored the navigation performance of GNSS in earth–moon space. It also investigated an autonomous navigation system based on the GNSS receiver, IMU, and star tracker integrated system with orbit filtering. Additionally, it proposed the Measurement Noise-Based Adaptive Estimation (MBAE) and Innovation-Based Adaptive Estimation (IBAE) algorithms, which was used in the case of GNSS ranging accuracy attenuation in earth–moon space.
The paper used an adaptive Kalman filter based on Carrier-to-Noise ratio (C/N0) and innovation vector to weaken the influence of GNSS accuracy attenuation as much as possible during Phasing Orbit (PHO) and Lunar Transfer Orbit (LTO). The experimental results show that the spacecraft position and velocity accuracy are better than 10 m and 0.1 m/s near the Earth, and better than 50 m and approximately 0.2 m/s near the moon use GNSS with the proposed adaptive algorithms. The accuracies of PHO in the X, Y, and Z directions using GNSS and orbital filter solving are 1.89, 6.27, and 5.09 m, respectively. Accuracy improved by 16.0% with the MBAE algorithm and further improved by 28.3% with the IBAE algorithm. A similar conclusion also be obtained for LTO, where the accuracies are 35.15, 20.92, and 30.21 m in the three directions when the spacecraft distance from the center of the Earth is greater than 40 Re, which proves that GNSS can provide navigation services in near-lunar space.
The paper also considered spacecraft maneuvers, for which position accuracy was substantially reduced to around 500 m when determined using GNSS alone with the orbit filter. The use of accelerometers to compensate for the dynamic model, and improve the position and velocity accuracy during orbital maneuvers was used in compbination with GNSS and integrated star trackers. With the integration of a gyroscope and star tracker, an attitude accuracy of better than 10 arcseconds can be obtained.
Key takeaways
More BDS satellites can be observed than GPS most likely due to stronger power of the BDS sidelobe signal, and the higher orbital altitude of the BDS GEO and IGSO.
With the integration of a gyroscope and star tracker, an attitude accuracy of better than 10 arcseconds can be obtained.
GNSS alone with appropriate Kalman filters can produce position accuracies of less than 10 meters and velocity of less than 0.2 m/s.
[2023] A Case Study Analysis for Designing a Lunar Navigation Satellite System with Time Transfer from the Earth GPS by Bhamidipati et al.
Research formulates twenty case studies with five different grades of onboard clocks and four lunar orbit types to analyse the trade-offs in designing a SmallSat-based Lunar Navigation Satellite System (LNSS) with time transfer from the Earth GPS. The five different grades of onboard clocks are low-SWaP onboard clocks such as Microchip CSAC, Microchip MAC and SRS PRS10 with the high-SWaP clocks the Excelitas’s RAFS or NASA’s DSAC. The four lunar orbits LLO, PCO, ELFO and NRHO. For each case study, the accuracy of ranging signals is assessed via the lunar user equivalent range error (UERE).
Even with lower-grade clocks, the lunar UERE exhibits performance comparable to that of the Earth GPS. The shortest maximum Earth-GPS continual outage period (ECOP) of only 420 s was observed for a Near-rectilinear halo orbit (NRHO). A low lunar UERE of < 30 m was demonstrated for low-SWaP onboard clocks (e.g., Microchip CSAC, SRS PRS10) even for reduced Earth-GPS measurement update rates with sampling periods of up to 30 min.
Through a case study analysis of time transfer from the Earth GPS, lower-SWaP onboard clocks and easier-to-maintain lunar orbit types were shown to still achieve the desired lunar UERE across the entire LNSS constellation. In this context, the easier-to-maintain lunar orbit types are those with higher orbital stability and longer lifespans, such as the LLO, PCO, or ELFO, in contrast to the more complex NRHO, which requires constant station-keeping maneuvers.
Key takeaways
Low-SWaP onboard clocks such as Microchip CSAC, Microchip MAC and SRS PRS10 are sufficient to provide a UERE of < 30 m with 30 min of sampling at Lunar orbits.
[2022] The Lunar GNSS Receiver Experiment (LuGRE) by Parker et al.
The Lunar GNSS Receiver Experiment (LuGRE) payload will demonstrate GNSS-based positioning, navigation, and timing (PNT) in transit to the Moon and on the lunar surface. LuGRE will fly on the Firefly Blue Ghost Mission 1 flight no earlier than mid-January 2025 (originally late 2023).
LuGRE consists of a Qascom-developed lunar GNSS receiver based on the:
QN400-Space heritage,
will receive GPS L1 C/A and L5 and Galileo E1 and E5a open signals down to 23 dB-Hz C/N0,
a high-gain L-band antenna and
a low-noise amplifier.
The payload will acquire and track GNSS signals during at least 15 hr of operations during the Earth-Moon transit phase and in lunar orbit, then nearly continuously for 12 Earth days on the lunar surface.
Preliminary analysis of the LuGRE operations indicates a high degree of signal visibility throughout the mission, with an average of 4 signals GNSS in view even on the lunar surface. Analysis of the transit phase shows the ability of an extended Kalman filter to process pseudorange measurements and converge within the available time throughout the transit operations periods.
All LuGRE data will be released publicly to the greatest extent possible, for the benefit of the GNSS space user community.
Key takeaways
Planned launch mid January 2025.
Will receive GPS L1 C/A and L5 and Galileo E1 and E5a open signals down to 23 dB-Hz C/N0.
First known Moon based GPS/Galileo receiver for GNSS practical data gathering and testing.
[2022] Navigation in GEO, HEO, and Lunar Trajectory Using Multi-GNSS Sidelobe Signals by Guan
In 2020, China finished the construction of the third generation of BeiDou navigation satellite system (BDS-3); this global coverage system will contribute better sidelobe signal visibility for spacecraft. Instead of using signal-in-space ranging errors, the paper simulate pseudorange observations with measurement noises varying with received signal powers. Results showed that, owing to GEO and inclined geosynchronous orbit (IGSO) satellites, all three types (GEO, HEO, and lunar trajectory) of spacecraft received more signals from BDS-3 than from other navigation systems.
Single point positioning (SPP) accuracy of the GEO and HEO spacecraft was 17.7 and 23.1 m, respectively, with BDS-3 data alone. Combining GPS with BDS-3, the positioning accuracy increased by 18.6% and 6.1%. Including the other systems, i.e., GPS, Galileo, and GLONASS, improved the SPP accuracy by 36.2% and 19.9% for GEO and HEO, respectively. For the lunar probe, signal geometry was less optimistic. All the combinations cannot provide a continuous navigation solution with a receiver threshold of 20 dB-Hz. The best signal geometry was provided by the GPS, GLONASS, Galileo and BeiDou (GREC) combination, which produced a max GDOP of 3392 when receiver sensitivity was 15 dB-Hz.
Navigation performance of the lunar probe was significantly improved when receiver sensitivity increased from 20 dB-Hz to 15 dB-Hz. Only dual- (BDS-3/GPS) or multi-GNSS (BDS-3, GPS, Galileo, GLONASS) could provide continuous navigation solutions with a receiver threshold of 15 dB-Hz.
For lunar missions, the SPP accuracy delivered by GREC combination was rather poor, even with 15 dB-Hz receiver thresholds. Significant improvements on SPP accuracy are hard to realize due to the high GDOP; therefore, a software receiver with an orbital filter or GNSS/INS/Star tracker integration may be necessary for lunar missions.
Key takeaways
In 2020, China completed construction of the third generation of BeiDou navigation satellite system (BDS-3) in 2020.
BDS-3 has better sidelobe signal visibility for spacecraft.
BDS-3 only can ensure a continuous navigation solution for GEO and HEO.
To ensure a continuous navigation solution for a lunar probe, it was necessary to combine BDS-3 with GPS or other GNSS systems, with a receiver threshold of 15 dB-Hz.
Galileo provided more visible satellites than GLONASS due to the smaller Earth block angle.
SPP accuracy delivered by GREC for lunar missions was rather poor, even with 15 dB-Hz receiver thresholds.
[2020] Use of GNSS for lunar missions and plans for Lunar In-Orbit Development by Delépaut et al.
The paper presents results of numerical simulations for a Single-Frequency (SF) receiver in the Deep Space Gateway (DSG) orbit, which is an Earth-Moon L2 Halo orbit, using both Galileo and GPS, for which detailed 3D antenna patterns were used. It shows that a high number of satellites are visible at Moon altitude using a receiver with a 14dBi antenna and a 15 dB-Hz Carrier-to-Noise-density ratio acquisition and tracking threshold.
It demonstrates the importance of considering the azimuthal asymmetry of the GNSS antenna patterns and the necessity of using an interoperable Galileo-GPS receiver at such altitudes. A comparative analysis between the frequency bands E1/L1 and E5a/L5 is performed to select the one providing the best results. The E5a/L5 band shows a clear improvement of the navigation performances at Moon altitude when compared to E1/L1, with an Ephemeris-based visibility average over the DSG orbital revolution period of six satellites vs. three in the E1/L1 band. It also presents ESA plans for In-Orbit Demonstration (IOD) of the use of GNSS at Moon altitude, covering both CubeSat missions and the DSG.
Key takeaways
A high number of satellites are visible at Moon altitude using a receiver with a 14dBi antenna and a 15 dB-Hz Carrier-to-Noise-density ratio acquisition.
Interoperable Galileo-GPS receiver at Moon altitudes are required to maximise GNSS visibility.
E5a/L5 frequency band presents the best results for visibility when compared to E1/L1.
[2019] A System Study for Cislunar Radio Navigation Leveraging the Use of Realistic Galileo and GPS Signals by Delépaut et al.
National Aeronautics and Space Administration (NASA), in collaboration with other international space agencies, is developing a platform called the Deep Space Gateway (DSG) or Lunar Orbital Platform-Gateway (LOP-G). This gateway, orbiting the Moon in the Near Rectilinear Halo Orbit (NRHO), seeks to facilitate the transfer of space modules to the lunar surface.
The paper investigates the most optimal way to provide communication and navigation services for the South Pole region of the Moon. Potential solutions for a Moon Navigation Satellite System (MNSS) is investigated to meet the requirements of:
spacecraft in Earth-Moon Transfer Orbit (MTO),
spacecraft Moon orbit,
spacecraft Moon landing,
spacecraft Moon launcher and
Moon surface user.
This research assesses the feasibility of a MNSS using the resources already or soon available namely Earth GNSS signals up to Moon altitudes and satellites already planned to orbit the Moon in the upcoming years, including the DSG and those considered in the Lunar Comms constellation. Different missions are considered with satellites in NRHO, ELFO and in an EM L2 Halo Orbit. Four different constellation scenarios with a varying number of satellites are compared with respect to the visibility and PDOP at three points of interest on the Moon’s surface. The results show that with a number of five satellites in the selected missions, the navigation performance in terms of PDOP values are not satisfying, as at the South Pole, for 42% of the time, no PDOP value is computable due to a too low number of satellites.
Challenges that this research identified are:
On the use of GNSS towards the Moon:
No data was available regarding the attitude control of the various Moon missions.
This has impact on the GNSS satellite visibility, and ultimately on the performances of the position solution.
The use of radiation patterns not defined on the complete elevation range (from 0 to 90 deg) degrades significantly the navigation performances at Moon altitudes.
On Moon Navigation Satellite System (MNSS):
Further analysis to assess the performances of time transfer from Earth to Moon is required.
Need for a more accurate definition of a reference frame for the Moon and its gravitational models are required.
Orbits considered for the Moon is very different when compared to the usual orbit geometries considered for Earth navigation satellites (mostly circular).
Key takeaways
NASA and ESA are planning platform deployments are future moon missions.
Current and future resources do not provide sufficient coverage for polar communication and navigation.
The results shows that a high number of satellites is visible even in L2 orbit.
[2019] GPS based autonomous navigation study for the Lunar Gateway by Winternitz et al.
This paper describes and predicts the performance of a conceptual autonomous GPS based navigation system for NASA’s planned Lunar Gateway. The system is based on the flight-proven Magnetospheric Multiscale (MMS) GPS navigation system augmented with an Earth-pointed high-gain antenna and, optionally, an atomic clock. High-fidelity simulations, calibrated against MMS flight data and making use of GPS transmitter patterns from the GPS Antenna Characterization Experiment project, are developed to predict performance of the system in the Gateway Near-Rectilinear Halo Orbit. The results indicate that GPS can provide an autonomous, realtime navigation capability with comparable, or superior, performance to a ground-based Deep Space Network approach using eight hours of tracking data per day.
Key takeaways
GPS can provide an autonomous, realtime navigation capability with comparable, or superior, performance to a ground-based Deep Space Network.
[2016] GNSS-Based Navigation for Lunar Missions by Capuano
Three research objectives and achievements are presented:
feasibility study of GNSS as an autonomous navigation system to reach the Moon, and the determination of the requirements for the design of a code-based GNSS receiver for such a mission,
the design and implementation of a GNSS receiver proof-of-concept capable of providing GNSS observations onboard a space vehicle orbiting up to Moon altitude and
the design and implementation of a GNSS-based orbital filter (OF) determination unit, which uses an extended Kalman filter (EKF), an adaptive tuning of the covariance matrix of the measurements and a flexible orbital forces model function of the space vehicle altitude, able to significantly improve the navigation performance achievable using GNSS observations.
The first (1) research objective and achievement presents the most efficient combinations of signals transmitted by the GPS, Galileo, and combined GPS-Galileo constellations by analysing the theoretical achievable signal acquisition and tracking sensitivities, the resultant constellation availability, the pseudorange error factors, and the geometry error factor. The results clearly demonstrate that GNSS signals can be tracked up to Moon altitude, but not with the current GNSS receiver technology that has been developed for terrestrial use.
The second (2) research objective and achievement describes the hardware architecture, the high-sensitivity acquisition and tracking modules and the standalone single-epoch navigation performance of the developed GPS L1 C/A hardware receiver, named the “WeakHEO” receiver. The higher the altitude the receiver is above the GNSS constellations, the poorer and the weaker are the relative geometry and the received signal powers, with a consequent significant reduction of the navigation accuracy. GNSS observations at Moon altitude, if not filtered, but simply used to compute a single-epoch least-squares solution, lead to a very coarse navigation accuracy, on the order of 1 to 10 km, depending on the number and type of signals successfully processed.
The third (3) research objective and achievement presents simulation results of the OF performance in a defined MTO are reported and discussed for different input configurations and different combinations of modelled GNSS observations (from GPS and GPS-Galileo combined). These results are then validated by filtering the real GPS L1 C/A observations provided by the WeakHEO receiver at Moon altitude, when connected in a hardware in the loop configuration to a full constellation GNSS radio frequency signal simulator, and reaching a positioning accuracy at Moon altitude of a few hundred meters.
Key takeaways
GNSS (Galileo and GPS) signals can theoretically be acquired at Moon altitude.
Current GNSS receiver technology is not sufficient for signal acquisition.
The higher the altitude the receiver is above the GNSS constellations, the poorer and weaker are the relative geometry and the received signal powers.
Raw use of GNSS observations at Moon altitude, if not filtered, lead to a very coarse navigation accuracy, on the order of 1 to 10 km.
The use of an orbital filter (OF) with hardware in the loop configurations improves the real GPS L1 C/A observations accuracy at Moon altitude to a few hundred meters.
[2015] Feasibility Study Of GNSS As Navigation System To Reach The Moon by Capuano et al.
The purpose of the present work is to determine the potential achievable accuracy of a code-based GNSS receiver solution, during the whole trajectory to reach the Moon. GPS, Galileo, and GPS-Galileo combined (dual constellation) solutions are estimated, by considering constellations availability, pseudorange error factors and geometry factors. Unlike previous investigations, the study is making use of the very accurate multi-GNSS constellation simulator “Spirent GSS8000“, which supports simultaneously the GPS and Galileo systems with L1, L5, E1, and E5 frequency bands. The study clearly demonstrates that GNSS signals can be tracked up to the Moon's surface, but not with the current GNSS receiver's technology for terrestrial use.
Key takeaways
GNSS signals can be tracked up to the Moon's surface.
GNSS signal tracking to the surface of the Moon can not be done with current GNSS receiver's technology for terrestrial use.
Takeaways
GNSS signals can be tracked up to the Moon's surface.
BDS satellites deliver higher power sidelobe signals.
Sensor fusion with GNSS, accelerometer, gyroscope and star tracker improves navigation accuracy.
The use of algorithms (Kalman filters and other data processing) for Earth-Moon GNSS navigation is encouraged as it will significantly increase accuracy.
Low-SWaP onboard clocks are sufficient to provide acceptable navigation accuracy of UERE of < 30 m.
Interoperable Galileo-GPS receiver at Moon altitudes are required to maximise GNSS visibility.
E5a/L5 frequency band presents the best results for visibility when compared to E1/L1.
Current and future resources do not provide sufficient coverage for polar communication and navigation.
Next research phase
With the Null Hypothesis (H0) refuted, the next step is to investigate the design requirements for an autonomous Earth-Moon spacecraft mission. Examples of Earth-Moon missions are the Artemis program and the Blue Ghost missions. These missions will be used as a starting point to determine the design considerations for an autonomous lunar mission.
Suggested research steps:
Determine the mission phases and operational requirements
Determine the mission trajectory and navigation requirements
Determine the mission algorithmic and filter requirements
Determine the mission hardware requirements