Characteristics and Benefits of Differential Lunar Laser Ranging

authored by: Mingyue Zhang
supervised by: Jürgen Müller
Abstract: In the future, an advanced lunar-tracking technique will be implemented at the Table Mountain Observatory (TMO) of Jet Propulsion Laboratory (JPL), called Differential Lunar Laser Ranging (DLLR). A new type of lunar observable, i.e., differential lunar ranges will be obtained by differencing successive ranges measured from one station to different lunar reflectors within a short time interval. DLLR is expected to reach a remarkably high accuracy level of ~30 μm. Research in this thesis focuses on exploring the impact of DLLR for a better understanding of the Earth-Moon system, including the investigation of the DLLR characteristics and DLLR benefits for the estimation of various Earth-Moon parameters. Simulated DLLR data with a long time span of more than 50 years (the same as real LLR data) are used for studying the DLLR characteristics. The specific parameter sensitivities are analyzed using the DLLR and LLR partial derivatives with respect to the parameters. Moreover, the accuracies of the estimated parameters from DLLR are evaluated and also compared to LLR. For some parameters, e.g., those related to the lunar orientation, rotation and interior, DLLR – by keeping the same sensitivity as LLR – is very advantageous to improve their accuracies (if it can really reach the expected extremely high observation accuracy). However, DLLR does not provide major benefit for the estimation of some other parameters, e.g., the lunar orbit elements (position and velocity of the Moon), mainly due to its less sensitivity, and the reflector coordinates for which DLLR has almost the same sensitivity but increases their correlations. DLLR will be beneficial for testing the Equivalence Principle (EP). The accuracies of the EP tests can be improved by about 2 and 3 times using DLLR. The effect of different kinds of switching time intervals and reflector baselines on parameter sensitivity are investigated. In the beginning of DLLR, only data over a short time span will be available, which is not enough to well determine the lunar orbit, also resulting in negative effects on other parameters. Thus, combining DLLR with classical LLR, which can provide an accurate lunar orbit with its long time span, is a practicable way to benefit from DLLR in the near future. Then, DLLR with a rather short time span of, e.g., 5 years is already useful for improving the parameter accuracy of the lunar orientation, rotation and interior. Also, the effects of the reflector baselines needed for DLLR, stations, time spans and “new” reflectors on the parameter estimations have been investigated. The length of the baselines and the way of their combination are relevant factors. A combination of two crossing baselines with larger length is more beneficial. Assuming the same data amount, extending the time span is more helpful for the parameter estimation than adding more stations in a shorter time span. A good position of a “new” reflector is also studied and identified for a better parameter determination.
Organisation(s): Institute of Geodesy
Type: Doctoral thesis
No. of pages: 105
Publication date: 2023
Publication status: Published
Electronic version(s): https://doi.org/10.15488/19427 (Access: Open)
: Details in the research portal "Research@Leibniz University"

BibTeX

@phdthesis{5a8059b49be146f2842f613a3b4569c9,
title = "Characteristics and Benefits of Differential Lunar Laser Ranging",
abstract = "In the future, an advanced lunar-tracking technique will be implemented at the Table Mountain Observatory (TMO) of Jet Propulsion Laboratory (JPL), called Differential Lunar Laser Ranging (DLLR). A new type of lunar observable, i.e., differential lunar ranges will be obtained by differencing successive ranges measured from one station to different lunar reflectors within a short time interval. DLLR is expected to reach a remarkably high accuracy level of ~30 μm. Research in this thesis focuses on exploring the impact of DLLR for a better understanding of the Earth-Moon system, including the investigation of the DLLR characteristics and DLLR benefits for the estimation of various Earth-Moon parameters. Simulated DLLR data with a long time span of more than 50 years (the same as real LLR data) are used for studying the DLLR characteristics. The specific parameter sensitivities are analyzed using the DLLR and LLR partial derivatives with respect to the parameters. Moreover, the accuracies of the estimated parameters from DLLR are evaluated and also compared to LLR. For some parameters, e.g., those related to the lunar orientation, rotation and interior, DLLR – by keeping the same sensitivity as LLR – is very advantageous to improve their accuracies (if it can really reach the expected extremely high observation accuracy). However, DLLR does not provide major benefit for the estimation of some other parameters, e.g., the lunar orbit elements (position and velocity of the Moon), mainly due to its less sensitivity, and the reflector coordinates for which DLLR has almost the same sensitivity but increases their correlations. DLLR will be beneficial for testing the Equivalence Principle (EP). The accuracies of the EP tests can be improved by about 2 and 3 times using DLLR. The effect of different kinds of switching time intervals and reflector baselines on parameter sensitivity are investigated. In the beginning of DLLR, only data over a short time span will be available, which is not enough to well determine the lunar orbit, also resulting in negative effects on other parameters. Thus, combining DLLR with classical LLR, which can provide an accurate lunar orbit with its long time span, is a practicable way to benefit from DLLR in the near future. Then, DLLR with a rather short time span of, e.g., 5 years is already useful for improving the parameter accuracy of the lunar orientation, rotation and interior. Also, the effects of the reflector baselines needed for DLLR, stations, time spans and “new” reflectors on the parameter estimations have been investigated. The length of the baselines and the way of their combination are relevant factors. A combination of two crossing baselines with larger length is more beneficial. Assuming the same data amount, extending the time span is more helpful for the parameter estimation than adding more stations in a shorter time span. A good position of a “new” reflector is also studied and identified for a better parameter determination.",
author = "Mingyue Zhang",
year = "2023",
doi = "10.15488/19427",
language = "English",
series = "Wissenschaftliche Arbeiten der Fachrichtung Geod{\"a}sie und Geoinformatik der Leibniz Universit{\"a}t Hannover",
number = "394",
school = "Leibniz University Hannover",
}