The JPL lunar gravity field to spherical harmonic degree 660 from the GRAIL Primary Mission

Abstract

[1] The lunar gravity field and topography provide a way to probe the interior structure of the Moon. Prior to the Gravity Recovery and Interior Laboratory (GRAIL) mission, knowledge of the lunar gravity was limited mostly to the nearside of the Moon, since the farside was not directly observable from missions such as Lunar Prospector. The farside gravity was directly observed for the first time with the SELENE mission, but was limited to spherical harmonic degree n ≤ 70. The GRAIL Primary Mission, for which results are presented here, dramatically improves the gravity spectrum by up to~4 orders of magnitude for the entire Moon and for more than 5 orders-of-magnitude over some spectral ranges by using interspacecraft measurements with near 0.03 μm/s accuracy. The resulting GL0660B (n = 660) solution has 98% global coherence with topography to n = 330, and has variable regional surface resolution between n = 371 (14.6 km) and n = 583 (9.3 km) because the gravity data were collected at different spacecraft altitudes. The GRAIL data also improve low-degree harmonics, and the uncertainty in the lunar Love number has been reduced bỹ 5× to k 2 = 0.02405 ± 0.00018. The reprocessing of the Lunar Prospector data indicates~3× improved orbit uncertainty for the lower altitudes to~10 m, whereas the GRAIL orbits are determined to an accuracy of 20 cm.Citation: Konopliv, A. S., et al. (2013), The JPL lunar gravity field to spherical harmonic degree 660 from the GRAIL Primary Mission,

Influence of the Choice of Lunar Gravity Model on Orbit Determination for Lunar Orbiters

“…For the degree and order effect investigation, various values were considered. The lunar gravity field can be modeled by a spherical harmonic series as follows [1,11]:…”

“…degree and order GLGM2 [7] Clementine 70 × 70 LP100K [8] Lunar Prospector 100 × 100 LP150Q [9] Lunar Prospector 150 × 150 GRAIL420A [10] GRAIL 420 × 420 GRAIL660B [11] GRAIL 660 × 660 on OD accuracy are also required. Previous studies have examined the effect of lunar gravity on the OD of actual lunar orbiter missions [2][3][4][5][6].…”

“…degree and order of 70 each; LP100K and LP150Q (derived from the Lunar Prospector mission [8,9]), having max. degree and order of 100 and 150, respectively; and GRAIL420A and GRAIL660B (derived from Gravity Recovery and Interior Laboratory mission [10,11]), having degree and order of 420 by 420 and 660 by 660, respectively. A summary of these models is presented in Table 1.…”

Evolution of the Selenopotential Model and Its Effects on the Propagation Accuracy of Orbits around the Moon

“…They differed in terms of the OD software, a priori models, data editing, and parameter estimation strategy used, among others. Later, global field models that utilized the GRAIL data, with a maximum degree and order of 420 [47], 660 [48,49], 900 [50,51], and 1200 [52], were released. Very recently, the highest resolution lunar gravity field model to date, with a maximum degree and order of 1500, was generated by analyzing the data from the primary and extended GRAIL missions, yielding a surface resolution of 3.6 km [53].…”

Geodetic VLBI with an artificial radio source on the Moon: a simulation study

“…The goal of these experiments was to obtain a better understanding of the physical properties of the Moon. Examples of recent lunar programs include LADEE (Lunar Atmosphere and Dust Environment Explorer; Elphic et al 2014), CLEP (Chinese Lunar Exploration Program; Li et al 2015) and GRAIL (Gravity Recovery and Interior Laboratory; Konopliv et al 2013). The VLBI technique was also used for the spacecraft orbit determination during the SELENE (SELenological and ENgineering Explorer) mission (Kato et al 2008) by using phase delays from same-beam differential VLBI (Kikuchi et al 2009).…”