The Lunar Gravity Ranging System for the Gravity Recovery and Interior Laboratory (GRAIL) Mission

Klipstein, William; Arnold, Bradford W.; Enzer, Daphna G.; Ruiz, Alberto A.; Tien, Jeffrey Y.; Wang, Rabi T.; Dunn, Charles

doi:10.1007/s11214-013-9973-x

Cited by 23 publications

(16 citation statements)

References 4 publications

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“…where k M , k C and k O are the coefficients of time difference measurement error, clock compensation error, and oscillator drifting error respectively, which can be obtained by substituting (16), (17), (18), (24) and (25) into (26).…”

Section: Theoretical Time Sync Accuracy and Its Optimizationmentioning

confidence: 99%

“…However, the clock errors for a typical satellite are on the order of 0.8 m (2.6 ns) [22]. The latter has been adopted by GRACE [23] and gravity recovery and interior laboratory (GRAIL) [24,25] to accomplish microlevel inter-satellite measurement links, and the measurement accuracy of time difference between two satellites is about 150 ps [26]. By exchanging K and Ka carrier signals, measuring the time difference between two orbiting clocks, and downloading measurement information, GRACE and GRAIL have been achieving a quantum leap in the knowledge of the Earth's and the moon's gravitational field, respectively [26].…”

Section: Introductionmentioning

confidence: 99%

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Approach to inter-satellite time synchronization for micro-satellite cluster

2018

Journal of Systems Engineering and Electronics

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Micro-satellite cluster enables a whole new class of missions for communications, remote sensing, and scientific research for both civilian and military purposes. Synchronizing the time of the satellites in a cluster is important for both cluster sensing capabilities and its autonomous operating. However, the existing time synchronization methods are not suitable for microsatellite cluster, because it requires too many human interventions and occupies too much ground control resource. Although, data post-process may realize the equivalent time synchronization, it requires processing time and powerful computing ability on the ground, which cannot be implemented by cluster itself. In order to autonomously establish and maintain the time benchmark in a cluster, we propose a compact time difference compensation system (TDCS), which is a kind of time control loop that dynamically adjusts the satellite reference frequency according to the time difference. Consequently, the time synchronization in the cluster can be autonomously achieved on-orbit by synchronizing the clock of other satellites to a chosen one's. The experimental result shows that the standard deviation of time synchronization is about 102 ps when the carrier to noise ratio (CNR) is 95 dBHz, and the standard deviation of corresponding frequency difference is approximately 0.36 Hz.

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Section: Theoretical Time Sync Accuracy and Its Optimizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Approach to inter-satellite time synchronization for micro-satellite cluster

2018

Journal of Systems Engineering and Electronics

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“…Ranging System (LGRS) (Klipstein et al, 2012) and the Education/Public Outreach (E/PO) payload is Moon Knowledge Acquired by Middle-School Students (MoonKAM). GRAIL is unique in that the science for the mission is achieved with a single instrument.…”

Section: Spac9952_sourcementioning

confidence: 99%

“…GRAIL is unique in that the science for the mission is achieved with a single instrument. Each of the payloads is briefly described herein, and detailed discussion of the LGRS is given by (Klipstein et al, 2012).…”

Section: Spac9952_sourcementioning

confidence: 99%

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Gravity Recovery and Interior Laboratory (GRAIL): Mapping the Lunar Interior from Crust to Core

et al. 2013

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The Gravity Recovery and Interior Laboratory (GRAIL) is a spacecraft-to-spacecraft tracking mission that was developed to map the structure of the lunar interior by producing a detailed map of the gravity field. The resulting model of the interior will be used to address outstanding questions regarding the Moon's thermal evolution, and will be applicable more generally to the evolution of all terrestrial planets. Each GRAIL orbiter contains a Lunar Gravity Ranging System instrument that conducts dual-one-way ranging measurements to measure precisely the relative motion between them, which in turn are used to develop the lunar gravity field map. Each orbiter also carries an Education/Public Outreach payload, Moon Knowledge Acquired by Middle-School Students (MoonKAM), in which middle school students target images of the Moon for subsequent classroom analysis. Subsequent to a successful launch on September 10, 2011, the twin GRAIL orbiters embarked on independent trajectories on a 3.5month-long cruise to the Moon via the EL-1 Lagrange point. The spacecraft were inserted into polar orbits on December 31, 2011 and January 1, 2012. After a succession of 19 maneuvers the two orbiters settled into precision formation to begin science operations in March 1, 2012 with an average altitude of 55 km. The Primary Mission, which consisted of three 27.3-day mapping cycles, was successfully completed in June 2012. The extended mission will permit a second three-month mapping phase at an average altitude of 23 km. This paper provides an overview of the mission: science objectives and measurements, spacecraft and instruments, mission development and design, and data flow and data products.

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High‐resolution lunar gravity fields from the GRAIL Primary and Extended Missions

Konopliv

Park

Yuan

et al. 2014

Geophysical Research Letters

110

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The resolution and accuracy of the lunar spherical harmonic gravity field have been dramatically improved as a result of the Gravity Recovery and Interior Laboratory (GRAIL) mission. From the Primary Mission, previous harmonic gravity fields resulted in an average n = 420 surface resolution and a Bouguer spectrum to n = 330. The GRAIL Extended Mission improves the resolution due to a lower average 23 km altitude orbit. As a result, new harmonic degree 900 gravity fields (GL0900C and GL0900D) show nearly a factor of 2 improvement with an average surface resolution n = 870 and the Bouguer spectrum extended to n = 550. Since the minimum spacecraft altitude varies spatially between 3 km and 23 km, the surface resolution is variable from near n = 680 for the central farside to near n = 900 for the polar regions. These gravity fields with 0.8 million parameters are by far the highest-degree fields of any planet ever estimated with a fully dynamic least squares technique using spacecraft tracking data.

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The Lunar Gravity Ranging System for the Gravity Recovery and Interior Laboratory (GRAIL) Mission

Cited by 23 publications

References 4 publications

Approach to inter-satellite time synchronization for micro-satellite cluster

Approach to inter-satellite time synchronization for micro-satellite cluster

Gravity Recovery and Interior Laboratory (GRAIL): Mapping the Lunar Interior from Crust to Core

High‐resolution lunar gravity fields from the GRAIL Primary and Extended Missions

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