J/A+A/636/A45 CEGM03 model and related gravity anomaly data (Yan+, 2020)
A degree-100 lunar gravity model from the Chang'e 5T1 mission.
Yan J.G., Liu S.H., Xiao C., Ye M., Cao J.F., Harada Y., Li F., Li X.,
Barriot J.
<Astron. Astrophys. 636, A45 (2020)>
=2020A&A...636A..45Y 2020A&A...636A..45Y (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Models ; Planets ; Magnetic fields
Keywords: Moon - gravitation - planets and satellites: detection -
methods: data analysis
Abstract:
Chinese lunar missions have grown in number over the last ten years,
with an increasing focus on radio science investigations. In previous
work, we estimated two lunar gravity field models, CEGM01 and CEGM02.
The recently lunar mission, Chang'e 5T1, which had an orbital inclination
between 18 and 68 degree, and collected orbital tracking data continually
for two years, made an improved gravity field model possible.
We aimed to estimate a new lunar gravity field model up to degree and
order 100, CEGM03, and a new tidal Love number based on the Chang'e 5T1
tracking data combined with the historical tracking data ever used in
the solution of CEGM02. The new model makes use of tracking data with
this particular inclination, which has not been used in previous gravity
field modeling.
The solution for this new model was based on our in-house software,
LUGREAS. The gravity spectrum power, postfit residuals after precision
orbit determination (POD), lunar surface gravity anomalies,
correlations between parameters, admittance/coherence with topography
model, and accuracy of POD were analyzed to validate the new CEGM03
model.
We analyzed the tracking data of the Chang'e 5T1 mission and estimated
the CEGM03 lunar gravity field model. We found that the two-way Doppler
measurement accuracy reached the 0.2 mm/s with 10 s integration time.
The error spectrum shows that the formal error for CEGM03 was at least
reduced by about 2 times below the harmonic degree of 20, when compared
to the CEGM02 model. The gravity and topography admittance/correlation
was also improved when compared to the correlations for the CEGM02 model.
The lunar potential Love number k2 was estimated to be 0.02430±0.0001
(ten times the formal error).
From the model analysis and comparison of the various models, we
identified improvements in the CEGM03 model after introducing Chang'e
5T1 tracking data. Moreover, this study illustrates how the low and
middle inclination orbits could contribute better accuracy for a low
degree of lunar gravity field.
Description:
The CEGM03 model was determined from velocity perturbations of the
Chang'e 5T1 spacecraft and the historical spacecraft (Chang'e 1, SELENE,
LO-I to LO-V, Apollo 15 and 16, Clementine, LP, and SMART-1), as measured
from the Doppler shift of the S/X-band radio tracking. Besides, related
free-air anomalies, gravity anomaly, and solenoid error data are contained.
The coordinate system for the gravity data, and the coefficients
in the CEGM03 gravity field, is selenocentric, center of mass,
longitude positive east. The location of the pole and the prime
meridian are defined by the principal axes as given by the integrated
lunar librations of DE421 (Williams et al. 2008).
The spherical harmonics coefficients provide both the coefficient
values and uncertainties.
Others Parameters:
4.90281910072908D+12 : Moon's GM value (unit: m3/s2)
0.1738000D+07 : Moon's reference radius (unit: m)
cegm03nc.dat is the Free-air anomalies data based on the CEGM03 model.
gaano30.dat and sele30.dat are transfered to ASCII for scientists who
are interested. You also can calculate these anomalies by yourself
based on the CEGM03 model.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cegm03.dat 70 10197 Spherical harmonics coefficients of CEGM03
cegm03nc.dat 29 81608 Free-air anomalies data of CEGM03
gaano30.dat 13 65341 Gravity anomaly cut off at 30 degrees
sele30.dat 13 65341 Selenoid error cut off at 30 degrees
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Byte-by-byte Description of file: cegm03.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Coeff COEFC or COEFS Coefficients mark
13- 15 I3 --- Degree Degree of C or S coefficient
16- 18 I3 --- Order Order of C or S coefficient
23- 42 E20.14 --- Value Value of C or S coefficient.
60- 70 E11.6 --- e_Value Uncertainty of C or S coefficient
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Byte-by-byte Description of file: cegm03nc.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
2- 9 F8.3 deg Lat Latitude of Moon
13- 19 F7.3 deg Long Longitude of Moon
22- 29 F8.3 --- Anomaly Free-air anomalies value, in mGal unit
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Byte-by-byte Description of file: gaano30.dat
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Bytes Format Units Label Explanations
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1- 3 I3 deg Lat Latitude of Moon
5- 7 I3 deg Long Longitude of Moon
9- 13 F5.3 --- Anomaly Gravity anomaly value, in mGal unit
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Byte-by-byte Description of file: sele30.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 deg Lat Latitude of Moon
5- 7 I3 deg Long Longitude of Moon
9- 13 F5.3 m Selenoid-error Selenoid error value
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Acknowledgements:
Yan Jianguo, jgyan(at)whu.edu.cn
(End) Yan Jianguo [WHU, China], Patricia Vannier [CDS] 07-Mar-2020