JG
J.K. Geijsberts
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Caves on the Moon provide safe shelter for humans against high temperatures, radiation and micrometeorites. They could also provide useful knowledge about the layers and composition of the Moon. Lava tubes, a type of cave, are expected to occur on the Moon, and tentative collapsed examples have already been found. Finding these lava tubes is a great priority in the exploration of the Moon. One method of searching for these lava tubes is by measuring small variations in gravitational attraction caused by the lack of mass due to these caves.
This thesis investigates whether lava tubes can be detected using current sensors and lunar DTMs. For this, a comparison of accuracy is investigated between the SPECFEM and GBOX software, which can calculate the gravity anomaly of 3D models using the spectral element method and direct integral method, respectively. 3D lunar lava tube and DTM models are created and meshed for simulation with SPECFEM. Different sensitivity analyses are performed on the mesh resolution, depth, shape, density, and scale of the lava tube, as well as on the DTM mesh resolution and DTM height. The models are from two different regions: A small lava tube that could potentially exist in the Marius Hills region, and a large lava tube that could potentially exist in the Gruithuisen K region.
SPECFEM was found to be more accurate than GBOX for the same mesh size. In terms of compute time, GBOX is found to have a quicker compute time per computation; however, for areas or volumes, many computations are necessary, and the compute time for GBOX explodes in these cases. SPECFEM is the only viable method of the two for high-resolution solutions across a volume. To understand detectability, a sensor error of 0.3 mGal , as well as a calculated total error of 5.9 mGal , which includes uncertainty in DTM height of ±4 m RMS and density of ±80 kg m−3 RMS, were used as reference. The DTM height uncertainty contributed approximately 0.6 mGal error RMS to the total error, while the DTM density uncertainty contributed most of the error, at approximately 5.275 mGal.
From the results, it was found that a mesh size of 0.0125 km (8% of the minimum diameter of the lava tube) sufficed in giving accurate results to within 0.3 mGal for all seven shapes considered for the Marius Hills lava tube. The Marius Hills lava tube model was found to be detectable up to a depth of 3.4 km using the sensor error, and 0.28 km using the total error. The Gruithuisen K lava tube was detectable at least to a depth of 6.5 km using the sensor error, although no exact bound was found, while only detectable to 0.59 km using the total error for a narrow part of the lava tube. In a part with a wider cavity, the detectability increased to a depth of 2.95 km. The shape of the lava tube was found to be distinguishable at depths lower than 25 m using the sensor error, but a simulation at 200 m depth showed that this distinguishability stops somewhere between 25 and 200 m depth. Inverted keyhole and triangular-shaped cross-sections were found to have sharper V-shaped gravity signals across the lava tube, while rectangular, keyhole, and elongated shapes had U-shaped gravity signals. Using the total error as the detection threshold, the cross-sectional shapes become indistinguishable for the Marius
Hills model. For the DTM, a resolution of 59 m was required at the surface to stay within the sensor error.
Overall, these results provide a quantitative basis for designing future lunar gravimetric surveys targeting the detection and characterisation of such lava tubes in their depth, shape, and scale. This directly supports survey designers in finding lava tubes that can help provide shelter for future lunar explorers. ...
This thesis investigates whether lava tubes can be detected using current sensors and lunar DTMs. For this, a comparison of accuracy is investigated between the SPECFEM and GBOX software, which can calculate the gravity anomaly of 3D models using the spectral element method and direct integral method, respectively. 3D lunar lava tube and DTM models are created and meshed for simulation with SPECFEM. Different sensitivity analyses are performed on the mesh resolution, depth, shape, density, and scale of the lava tube, as well as on the DTM mesh resolution and DTM height. The models are from two different regions: A small lava tube that could potentially exist in the Marius Hills region, and a large lava tube that could potentially exist in the Gruithuisen K region.
SPECFEM was found to be more accurate than GBOX for the same mesh size. In terms of compute time, GBOX is found to have a quicker compute time per computation; however, for areas or volumes, many computations are necessary, and the compute time for GBOX explodes in these cases. SPECFEM is the only viable method of the two for high-resolution solutions across a volume. To understand detectability, a sensor error of 0.3 mGal , as well as a calculated total error of 5.9 mGal , which includes uncertainty in DTM height of ±4 m RMS and density of ±80 kg m−3 RMS, were used as reference. The DTM height uncertainty contributed approximately 0.6 mGal error RMS to the total error, while the DTM density uncertainty contributed most of the error, at approximately 5.275 mGal.
From the results, it was found that a mesh size of 0.0125 km (8% of the minimum diameter of the lava tube) sufficed in giving accurate results to within 0.3 mGal for all seven shapes considered for the Marius Hills lava tube. The Marius Hills lava tube model was found to be detectable up to a depth of 3.4 km using the sensor error, and 0.28 km using the total error. The Gruithuisen K lava tube was detectable at least to a depth of 6.5 km using the sensor error, although no exact bound was found, while only detectable to 0.59 km using the total error for a narrow part of the lava tube. In a part with a wider cavity, the detectability increased to a depth of 2.95 km. The shape of the lava tube was found to be distinguishable at depths lower than 25 m using the sensor error, but a simulation at 200 m depth showed that this distinguishability stops somewhere between 25 and 200 m depth. Inverted keyhole and triangular-shaped cross-sections were found to have sharper V-shaped gravity signals across the lava tube, while rectangular, keyhole, and elongated shapes had U-shaped gravity signals. Using the total error as the detection threshold, the cross-sectional shapes become indistinguishable for the Marius
Hills model. For the DTM, a resolution of 59 m was required at the surface to stay within the sensor error.
Overall, these results provide a quantitative basis for designing future lunar gravimetric surveys targeting the detection and characterisation of such lava tubes in their depth, shape, and scale. This directly supports survey designers in finding lava tubes that can help provide shelter for future lunar explorers. ...
Caves on the Moon provide safe shelter for humans against high temperatures, radiation and micrometeorites. They could also provide useful knowledge about the layers and composition of the Moon. Lava tubes, a type of cave, are expected to occur on the Moon, and tentative collapsed examples have already been found. Finding these lava tubes is a great priority in the exploration of the Moon. One method of searching for these lava tubes is by measuring small variations in gravitational attraction caused by the lack of mass due to these caves.
This thesis investigates whether lava tubes can be detected using current sensors and lunar DTMs. For this, a comparison of accuracy is investigated between the SPECFEM and GBOX software, which can calculate the gravity anomaly of 3D models using the spectral element method and direct integral method, respectively. 3D lunar lava tube and DTM models are created and meshed for simulation with SPECFEM. Different sensitivity analyses are performed on the mesh resolution, depth, shape, density, and scale of the lava tube, as well as on the DTM mesh resolution and DTM height. The models are from two different regions: A small lava tube that could potentially exist in the Marius Hills region, and a large lava tube that could potentially exist in the Gruithuisen K region.
SPECFEM was found to be more accurate than GBOX for the same mesh size. In terms of compute time, GBOX is found to have a quicker compute time per computation; however, for areas or volumes, many computations are necessary, and the compute time for GBOX explodes in these cases. SPECFEM is the only viable method of the two for high-resolution solutions across a volume. To understand detectability, a sensor error of 0.3 mGal , as well as a calculated total error of 5.9 mGal , which includes uncertainty in DTM height of ±4 m RMS and density of ±80 kg m−3 RMS, were used as reference. The DTM height uncertainty contributed approximately 0.6 mGal error RMS to the total error, while the DTM density uncertainty contributed most of the error, at approximately 5.275 mGal.
From the results, it was found that a mesh size of 0.0125 km (8% of the minimum diameter of the lava tube) sufficed in giving accurate results to within 0.3 mGal for all seven shapes considered for the Marius Hills lava tube. The Marius Hills lava tube model was found to be detectable up to a depth of 3.4 km using the sensor error, and 0.28 km using the total error. The Gruithuisen K lava tube was detectable at least to a depth of 6.5 km using the sensor error, although no exact bound was found, while only detectable to 0.59 km using the total error for a narrow part of the lava tube. In a part with a wider cavity, the detectability increased to a depth of 2.95 km. The shape of the lava tube was found to be distinguishable at depths lower than 25 m using the sensor error, but a simulation at 200 m depth showed that this distinguishability stops somewhere between 25 and 200 m depth. Inverted keyhole and triangular-shaped cross-sections were found to have sharper V-shaped gravity signals across the lava tube, while rectangular, keyhole, and elongated shapes had U-shaped gravity signals. Using the total error as the detection threshold, the cross-sectional shapes become indistinguishable for the Marius
Hills model. For the DTM, a resolution of 59 m was required at the surface to stay within the sensor error.
Overall, these results provide a quantitative basis for designing future lunar gravimetric surveys targeting the detection and characterisation of such lava tubes in their depth, shape, and scale. This directly supports survey designers in finding lava tubes that can help provide shelter for future lunar explorers.
This thesis investigates whether lava tubes can be detected using current sensors and lunar DTMs. For this, a comparison of accuracy is investigated between the SPECFEM and GBOX software, which can calculate the gravity anomaly of 3D models using the spectral element method and direct integral method, respectively. 3D lunar lava tube and DTM models are created and meshed for simulation with SPECFEM. Different sensitivity analyses are performed on the mesh resolution, depth, shape, density, and scale of the lava tube, as well as on the DTM mesh resolution and DTM height. The models are from two different regions: A small lava tube that could potentially exist in the Marius Hills region, and a large lava tube that could potentially exist in the Gruithuisen K region.
SPECFEM was found to be more accurate than GBOX for the same mesh size. In terms of compute time, GBOX is found to have a quicker compute time per computation; however, for areas or volumes, many computations are necessary, and the compute time for GBOX explodes in these cases. SPECFEM is the only viable method of the two for high-resolution solutions across a volume. To understand detectability, a sensor error of 0.3 mGal , as well as a calculated total error of 5.9 mGal , which includes uncertainty in DTM height of ±4 m RMS and density of ±80 kg m−3 RMS, were used as reference. The DTM height uncertainty contributed approximately 0.6 mGal error RMS to the total error, while the DTM density uncertainty contributed most of the error, at approximately 5.275 mGal.
From the results, it was found that a mesh size of 0.0125 km (8% of the minimum diameter of the lava tube) sufficed in giving accurate results to within 0.3 mGal for all seven shapes considered for the Marius Hills lava tube. The Marius Hills lava tube model was found to be detectable up to a depth of 3.4 km using the sensor error, and 0.28 km using the total error. The Gruithuisen K lava tube was detectable at least to a depth of 6.5 km using the sensor error, although no exact bound was found, while only detectable to 0.59 km using the total error for a narrow part of the lava tube. In a part with a wider cavity, the detectability increased to a depth of 2.95 km. The shape of the lava tube was found to be distinguishable at depths lower than 25 m using the sensor error, but a simulation at 200 m depth showed that this distinguishability stops somewhere between 25 and 200 m depth. Inverted keyhole and triangular-shaped cross-sections were found to have sharper V-shaped gravity signals across the lava tube, while rectangular, keyhole, and elongated shapes had U-shaped gravity signals. Using the total error as the detection threshold, the cross-sectional shapes become indistinguishable for the Marius
Hills model. For the DTM, a resolution of 59 m was required at the surface to stay within the sensor error.
Overall, these results provide a quantitative basis for designing future lunar gravimetric surveys targeting the detection and characterisation of such lava tubes in their depth, shape, and scale. This directly supports survey designers in finding lava tubes that can help provide shelter for future lunar explorers.
Bachelor thesis
(2023)
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M.G. Dinescu, J.K. Geijsberts, I. Maes, S. Nedelcu, A. Van Parys, L.D. van der Peet, N.O. Ricker Chong, K.A. Scherpenzeel, C.A.G.C. Spichal, M.N. Vereycken, W. van der Wal, G. Ermis, J. Zhao
In the last few decades, a large increase in interest in space and particularly the Moon has taken place. The Moon is seen as a gateway to the rest of the Solar System. Missions to the Moon will inevitably lead to technological and scientific advancements. These would help in humanity’s mission to explore and develop habitats in the Solar System. Companies see economic opportunities in these places for activities such as the acquisition of rare Earth materials, as well as commercialising space travel. Furthermore, countries see these accomplishments
as a sort of international competition while also collaborating with other nations. The mission design presented here aims to facilitate these objectives by providing the necessary navigation support to any future mission on or around the Moon... ...
as a sort of international competition while also collaborating with other nations. The mission design presented here aims to facilitate these objectives by providing the necessary navigation support to any future mission on or around the Moon... ...
In the last few decades, a large increase in interest in space and particularly the Moon has taken place. The Moon is seen as a gateway to the rest of the Solar System. Missions to the Moon will inevitably lead to technological and scientific advancements. These would help in humanity’s mission to explore and develop habitats in the Solar System. Companies see economic opportunities in these places for activities such as the acquisition of rare Earth materials, as well as commercialising space travel. Furthermore, countries see these accomplishments
as a sort of international competition while also collaborating with other nations. The mission design presented here aims to facilitate these objectives by providing the necessary navigation support to any future mission on or around the Moon...
as a sort of international competition while also collaborating with other nations. The mission design presented here aims to facilitate these objectives by providing the necessary navigation support to any future mission on or around the Moon...