meetings - Space Flight Mechanics Committee

Orbit determination plays a piv-otal role in preprocessing, because preprocessed gravity
science data quality de-pends directly on ephemeris accuracy. This paper describes the role
of orbit de-termination in GRAIL preprocessing and the iterative process that has led to the
latest GRAIL lunar gravity fields.
14:30 AAS GRAIL Science Data System Orbit Determination: Approach, Strategy, and
13-271 Performance
Eugene Fahnestock, NASA / Caltech JPL; Sami Asmar, NASA / Caltech JPL; Nate
Harvey, NASA / Caltech JPL; Daniel Kahan, NASA / Caltech JPL; Alex Konopliv,
NASA / Caltech JPL; Gerhard Kruizinga, NASA / Caltech JPL; Kamal Oudrhiri,
NASA / Caltech JPL; Meegyeong Paik, NASA / Caltech JPL; Ryan Park, NASA /
Caltech JPL; Dmitry Strekalov, NASA / Caltech JPL; Dah-Ning Yuan, NASA /
Caltech JPL
This paper details orbit determination techniques and strategies employed within each stage
of the larger iterative process (ref. Kruizinga et al., this meeting) of preprocessing raw
GRAIL data into the gravity science measurements used within gravity field solutions. Each
orbit determination pass used different data, corrections to it, and estimation parameters.
We compare performance metrics among these passes, plus independent navigation team
solutions. For the primary mission, the magnitude of residuals using our orbits progressed
from ~20 to ~0.3 micron/s for inter-satellite range rate data and from ~0.7 to ~0.1 mm/s for
Doppler data.
14:50 AAS High-Resolution Lunar Gravity from the Gravity Recovery And Interior
13-272 Laboratory Mission
Ryan Park, NASA / Caltech JPL; Alex Konopliv, NASA / Caltech JPL; Dah-Ning
Yuan, NASA / Caltech JPL; Sami Asmar, NASA / Caltech JPL; Eugene Fahnestock,
NASA / Caltech JPL; Gerhard Kruizinga, NASA / Caltech JPL; Meegyeong Paik,
NASA / Caltech JPL; Michael Watkins, NASA / Caltech JPL; David Smith, NASA;
Maria Zuber, Massachusetts Institute of Technology
15:10 Break
This paper presents detailed models used to process the measurements from the Gravity
Recovery And Interior Laboratory (GRAIL) mission. The inter-satellite and ground-based
Doppler measurements during the three-month prime science phase were processed and a
420th degree and order lunar gravity field was computed. The errors in the nongravitational
forces were modeled to about $10^{-12}$ km/$s^{2}$ and the reconstruction
accuracies were 0.05 micron/s for the inter-satellite data and 0.1 mm/s for the ground-based
Doppler data.
15:35 AAS The Modeling and Precise Orbit Determination in Support of Gravity Model
13-273 Development for the GRAIL Mission
Frank Lemoine, NASA Goddard Space Flight Center; Sander Goossens, CRESST /
UMBC; Terence Sabaka, NASA Goddard Space Flight Center; Joseph Nicholas,
Emergent Space Technologies; David Rowlands, NASA Goddard Space Flight
23 rd AAS / AIAA Space Flight Mechanics Meeting Page 39