Design of an Extended Mission for GRAIL

Sweetser, Theodore H.; Wallace, Mark; Hatch, Sara J.; Roncoli, Ralph B.

doi:10.2514/6.2012-4429

Cited by 5 publications

(10 citation statements)

References 3 publications

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“…To understand the processes that produced the subsurface structure inferred from gravity (2), we modeled the formation of Orientale using the two-dimensional version of iSALE, a multimaterial, multirheology, finite-difference shock physics code (6)(7)(8). Because iSALE is a continuum model, faults are manifest as localized regions of high strain rather than as discrete slip planes.…”

Section: Sciencemagorg Sciencementioning

confidence: 99%

“…As a consequence of its good state of preservation (1,5), with relatively few superposed large craters (6), it is often considered the standard example of a wellpreserved, multiring basin in comparative studies of large impacts on terrestrial planetary bodies (2,7). Because of the basin's importance, the GRAIL Extended Mission (see the supplementary text) featured a low-altitude mapping campaign during the mission's Endgame phase (8), in which the dual spacecraft orbited the Moon at an average altitude of 6 km and acquired observations less than 2 km above the basin's eastern rings (figs. S1 and S2).…”

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confidence: 99%

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Gravity field of the Orientale basin from the Gravity Recovery and Interior Laboratory Mission

Zuber

Smith

Neumann

et al. 2016

Science

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Section: Sciencemagorg Sciencementioning

confidence: 99%

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confidence: 99%

Gravity field of the Orientale basin from the Gravity Recovery and Interior Laboratory Mission

Zuber

Smith

Neumann

et al. 2016

Science

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“…From 17 November 2012 through the end of the mission, the periapse altitude generally ranged from 5 to 10 km while the apoapse altitude ranged from 15 to 25 km. The low altitude of the GRAIL spacecraft made the mission operations more complex, requiring sometimes as many as three maneuvers per week to maintain the desired orbit [ Sweetser et al , ; Ryne et al , ]. The end‐of‐mission operations from 4 December 2012 onward included orbits where the GRAIL spacecraft were targeted to fly within 5–10 km over part of Orientale [ Zuber et al , ].…”

Section: Extended Mission Summarymentioning

confidence: 99%

GRGM900C: A degree 900 lunar gravity model from GRAIL primary and extended mission data

Lemoine

Goossens

Sabaka

et al. 2014

Geophysical Research Letters

171

133

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We have derived a gravity field solution in spherical harmonics to degree and order 900, GRGM900C, from the tracking data of the Gravity Recovery and Interior Laboratory (GRAIL) Primary (1 March to 29 May 2012) and Extended Missions (30 August to 14 December 2012). A power law constraint of 3.6 ×10−4/ℓ2 was applied only for degree ℓ greater than 600. The model produces global correlations of gravity, and gravity predicted from lunar topography of ≥ 0.98 through degree 638. The model's degree strength varies from a minimum of 575–675 over the central nearside and farside to 900 over the polar regions. The model fits the Extended Mission Ka-Band Range Rate data through 17 November 2012 at 0.13 μm/s RMS, whereas the last month of Ka-Band Range-Rate data obtained from altitudes of 2–10 km fit at 0.98 μm/s RMS, indicating that there is still signal inherent in the tracking data beyond degree 900.

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“…A heliocentric view of the GRAIL XM is shown in Figure 9 (Sweetser et al, 2012). In late May 2012, when the PM was completed, periapsis raise maneuvers circularized the spacecraft orbits at an altitude of ~84 km for the low-activity Low Beta Angle phase.…”

Section: Extended Missionmentioning

confidence: 99%

“…Because of the low orbital altitude, operations in the Extended Mission are far more complex than in the PM (Wallace et al, 2012). Unlike the PM, which featured only one thrust maneuver to change the drift rate of the spacecraft over three months of mapping, the XM requires three maneuvers a week to maintain the mapping altitude (Sweetser et al, 2012). During extended science mapping, weekly eccentricity correction maneuvers (ECMs) on both orbiters maintain the orbits.…”

Section: Extended Missionmentioning

confidence: 99%

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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Design of an Extended Mission for GRAIL

Cited by 5 publications

References 3 publications

Gravity field of the Orientale basin from the Gravity Recovery and Interior Laboratory Mission

Gravity field of the Orientale basin from the Gravity Recovery and Interior Laboratory Mission

GRGM900C: A degree 900 lunar gravity model from GRAIL primary and extended mission data

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

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