The Orbital Perturbation Environment for the COBRA and COBRA Teardrop Elliptical Constellations

2005 ◽  
Vol 53 (2) ◽  
pp. 111-129 ◽  
Author(s):  
Paul Cefola ◽  
John E. Draim ◽  
Richard Inciardi ◽  
Ronald J. Proulx ◽  
David W. Carter
Keyword(s):  
Orbital Perturbation

ORBITAL PERTURBATION DIFFERENTIAL EQUATIONS WITH NON-LINEAR CORRECTIONS FOR CHAMP-LIKE SATELLITE

2017 ◽  
Vol 60 (3) ◽  
pp. 286-299
Author(s):  
YU Jin-Hai ◽  
ZHU Yong-Chao ◽  
MENG Xiang-Chao
Keyword(s):  
Differential Equations ◽  
Orbital Perturbation ◽  
Non Linear

Orbital perturbation due to orbit-attitude coupling near asteroids

2018 ◽  
Vol 90 (1) ◽  
pp. 104-113
Author(s):  
Yue Wang ◽  
Rui Zhong ◽  
Shijie Xu
Keyword(s):  
Center Of Mass ◽  
Solar Radiation Pressure ◽  
Satellite System ◽  
Orbital Dynamics ◽  
Extended Body ◽  
Content Type ◽  
Orbital Perturbation ◽  
Close Proximity ◽  
Small Asteroid

Purpose The purpose of this paper is to assess the orbital perturbation caused by the gravitational orbit–attitude coupling of spacecraft in the proximity of asteroids. Design/methodology/approach The gravitational orbit–attitude coupling perturbation (GOACP), which has been neglected before in the close-proximity orbital dynamics about asteroids, is investigated and compared with other orbital perturbations. The GOACP has its origin in the fact that the gravity acting on a non-spherical extended body is actually different from that acting on a point mass located at the body’s center of mass, which is the approximated model in the orbital dynamics. Besides, a case study of a tethered satellite system is given by numerical simulations. Findings It is found that the ratio of GOACP to the asteroid’s non-spherical gravity is the order of ρ/ae, where ρ is the spacecraft’s characteristic dimension and ae is the asteroid’s mean radius. It can also be seen that as ρ increases, GOACP will also increase but the solar radiation pressure (SRP) will decrease due to the decreasing area-to-mass ratio. The GOACP will be more significant than SRP at small orbital radii for a large-sized spacecraft. Based on the results by analyses and simulations, it can be concluded that GOACP needs to be considered in the orbital dynamics for a large-sized spacecraft in the proximity of a small asteroid. Practical implications This study is of great importance for the future asteroids missions for scientific explorations and near-Earth objects mitigation. Originality/value The GOACP, which has been neglected before, is revealed and studied.

Effect of eye position within the orbit on electrically elicited saccadic eye movements: a comparison of the macaque monkey's frontal and supplementary eye fields

1993 ◽  
Vol 69 (3) ◽  
pp. 800-818 ◽  
Author(s):  
G. S. Russo ◽  
C. J. Bruce
Keyword(s):  
Eye Movements ◽  
Saccadic Eye Movements ◽  
Frontal Eye Field ◽  
Eye Position ◽  
Constant Vector ◽  
Rectangular Array ◽  
Supplementary Eye Field ◽  
Orbital Perturbation ◽  
Eye Field ◽  
The Mean

1. We quantitatively compared the effects of eye position within the orbit on saccadic eye movements electrically elicited from two oculomotor areas of the macaque monkey's frontal lobe cortex: the frontal eye field (FEF) and the supplementary eye field (SEF). 2. The effect of eye position on electrically elicited saccades was studied by delivering 70-ms trains of intracortical microstimulation while the monkeys fixated a spot of light. Tests of different fixation points located across a rectangular array were randomly intermixed. Complete experiments were carried out on 38 sites in three FEFs of two monkeys and 59 sites from three SEFs of the same two monkeys. Stimulation currents for the array experiments were usually 10–20 microA above the site threshold; the average current used was 36 microA for FEF and 49 microA for SEF. 3. The magnitude of effect of the initial eye position on the elicited saccade's dimensions was quantified at each site by computing the linear regression of saccadic eye movement displacement on the eye position within the orbit when stimulation was applied. This computation was done separately for the horizontal and vertical axes. We call the resulting pair of regression coefficients “orbital perturbation indexes.” Indexes of 0.0 represent elicited saccades that do not change their trajectory with different initial eye positions (constant-vector saccades), whereas indexes of -1.0 represent elicited saccades that end at the same orbital position regardless of initial eye position (goal-directed saccades). 4. The effect of eye position varied across sites. In both FEF and SEF, the orbital perturbation indexes were distributed between approximately 0.0 and -0.5, with the horizontal and vertical indexes highly correlated across sites. 5. The average orbital perturbation indexes were small for both eye fields and were not significantly different. The mean horizontal indexes were -0.13 and -0.16 for SEF and FEF, respectively. The mean vertical indexes were -0.16 and -0.13. Neither SEF versus FEF difference was statistically significant. 6. In both SEF and FEF, sites yielding larger-amplitude saccades generally had larger orbital effects than sites yielding smaller saccades. This relationship accounted for the majority of the variability of the orbital perturbation indexes across sites in both SEF and FEF. 7. These results indicate that SEF and FEF are not distinguished from each other by the orbital dependence of their electrically elicited saccades. Thus they do not confirm the previously hypothesized dichotomy that FEF codes constant-vector saccades and SEF codes goal-directed saccades.(ABSTRACT TRUNCATED AT 400 WORDS)

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