3507. A Practical Method to Improve Moment of Inertia Measurement Accuracy for Formosat-3 Satellites


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HENG-CHUAN HUNG: 3507. A Practical Method to Improve Moment of Inertia Measurement Accuracy for Formosat-3 Satellites. 2010.



The ‘FORMOSAT-3 Program’ is an international collaboration project between Taiwan and the US with
joint efforts of Taiwan’s National SPace Organization (NSPO) and University Corporation for
Atmospheric Research (UCAR) of the US. The primary FORMOSAT-3 mission is to launch a
constellation of six micro-satellites into Low-Earth Orbit (LEO) in altitude range 700 ~ 800 Km to
collect atmospheric data for weather prediction, atmospheric studies, space weather monitoring and
geodetic research. The satellites integration and test were completed at NSPO I&T Facility located in
Hsinchu, Taiwan.
The objective of this paper is to present the method developed at NSPO to improve Moment Of Inertia
(MOI) measurement accuracy for FORMOSAT-3 satellites. The Mass Properties Measurement Facility
(MPMF) at NSPO is designed for three axes mass properties measurement of satellite up to 1500 Kg.
The MPMF includes a 980 Kg weight L-Fixture for horizontal axes measurement. This ‘huge’
L-Fixture greatly reduces the sensitivity of the MOI measurement for FORMOSAT-3 micro-satellites
each weighs only about 62 Kg. Redesign of a smaller L-Fixture is inevitable. However, the L-Fixture
is designed so that the test objective is well aligned with the MPMF, to manufacture a new one would be
too costly and too time consuming. Decision was made to design a smaller fixture without looking for
the alignment problem. The alignment problem is solved later when performing the measurement.
The Alignment Measurement Equipment is used to accurately identify the misalignment when the
satellite is installed in position for measurement. The misalignment data is then used to correct the
MOI data. Although the satellite installed with smaller fixture is not well aligned to the MPMF, the
misalignment is well measured. The MOI data can be accurately corrected with the alignment data.
The final results show that accuracy has been dramatically improved with this method.


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