تلخیص
Gravity field recovery using space technology has
evolved during the last two decades. Several dedicated satellite
missions have been sent to the space to get more accurate
and up-to-date gravity field information, including, Challenging
Minisatellite Payload (CHAMP), Gravity Recovery and Climate
Experiment (GRACE) and Gravity field and Ocean Circulation
Explorer (GOCE), launched on 15 July 2000, 17 March 2002 and
17 March 2009, respectively. GRACE is the extended version of the
CHAMP. The major difference is that the CHAMP is an example of
high-low satellite-to-satellite tracking (HL-SST) while the GRACE
is an example of low-low satellite-to-satellite tracking (LL-SST)
system. We observe the inter-satellite range rates of GRACE
tandem constellation. The variation in inter-satellite range is due
to the gravity field variation underneath the satellites. There are
several methods in practice to recover the gravity field from range
rate observation such as acceleration approach, short arc approach
and energy balance approach. The most accurate and widely used
is the variational equation approach, however numerically costly
(Keller, 2014). This paper states the variational equation method
in detail and compare the performance of the its two different
implementation methods i.e. analytical and variation of constant
method. The study shows that the computation time for the
variation of constant method has reduced tremendously while
achieving the same level of accuracy.
Muhammad Athar Javaid, Wolfgang Keller. (2017) Comparison of two gravity recovery algorithms based on the variational equation approach, Journal of Space Technology , Volume 7, Issue 1.
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