Aj. Butterfield et Se. Woodard, MEASURED SPACECRAFT INSTRUMENT AND STRUCTURAL INTERACTIONS, Journal of spacecraft and rockets, 33(4), 1996, pp. 556-562
Evaluation of Eight data from the Upper Atmosphere Research Satellite
shows that the solar-disk tracking subsystem within the Halogen Occult
ation Experiment responds to and completely accommodates cyclic distur
bances from the spacecraft solar-array vibration and continuous scanni
ng motions by the High-Resolution Doppler Imager instrument. A fine su
n sensor within the Halogen Occultation Experiment senses the top egde
of the solar disk as the primary tracking control input, Data streams
from such sensing show a characteristic frequency, which is principal
ly determined by the apparent solar motion. Power-spectral-density ren
derings of sun sensor data streams show the disturbing frequencies as
sideband peaks around a central peak at the characteristic frequency.
The sidebands are analogous to frequency modulation of a carrier frequ
ency. A mathematical model developed for this analysis demonstrates th
e factors that influence the frequency-modulated measurements. Modelin
g analyses verified the frequency content and allowed estimates of loc
al relative amplitudes of the principal disturbances imparted to the s
pacecraft. The model can predict mutual interactions between instrumen
ts as well as the influence of structural excitations upon instruments
. This analysis offers a means toward evaluating potentials for advers
e interactions in cases where a spacecraft carries closed-loop instrum
ents that track fixed solar or stellar targets; such interactions can
become crucial if tracking requirements have small margins of error.