Empirical Validation Of Effective Earth Radius Adjustment Factors For Earth Bulge and Diffraction Loss Parameters Computation
Eduediuyai Dan,
Constance Kalu,
Ogungbemi Emmanuel Oluropo
Issue:
Volume 2, Issue 2, March 2017
Pages:
51-56
Received:
9 January 2017
Accepted:
25 January 2017
Published:
25 March 2017
Abstract: In this paper, the effect of effective earth radius adjustment factors (k-adjustment factors) on various parameters associated with single knife edge diffraction loss is studied. The parameters considered are, the earth bulge, Fresnel-Kirchoff diffraction parameter and the number of Fresnel zones that are partially or fully blocked by obstruction in the signal path. The k-adjustment factors analytical expressions are derived and then validated using empirical elevation profile data for line-of-sight (LOS) communication link between Eket and Akwa Ibom state University. Also, k-factors considered in this paper are k1 = 0.5, k2 = 0.9 and k3= 1.333. In all, the results show that when the value of any of the three parameters is known at a given k-factor, k1, then the value of that parameter can be determined at any other k-factor, k2 by adding the k1-to-tk2 adjustment factor of that parameter to the value of the parameter at k1. The result is essential is evaluating the influence of variations in effective earth radius factor on the parameters associated with single knife edge diffraction loss.
Abstract: In this paper, the effect of effective earth radius adjustment factors (k-adjustment factors) on various parameters associated with single knife edge diffraction loss is studied. The parameters considered are, the earth bulge, Fresnel-Kirchoff diffraction parameter and the number of Fresnel zones that are partially or fully blocked by obstruction i...
Show More
Ground Based Laser Torque Effects on Both Passive and Active Control for LEO CubeSat
Thanaa E. Sharaf-Eldin,
Nabawia S. Khalifa
Issue:
Volume 2, Issue 2, March 2017
Pages:
57-63
Received:
15 March 2017
Accepted:
27 March 2017
Published:
13 April 2017
Abstract: The objective of this work is to investigate the effects of laser torque on both passive and active control for LEO CubeSat. The investigation is based on the model of the Euler equations for rotational motion. A simple case of spacecraft attitude control problem is considered, in which passive control is performed by accounting only gravity gradient torque, and then active control technique is implemented using PD control and one momentum wheel. The system simulation is conducted using the package of Matlab 7.10-(R2010a). The simulated results show the effect of applying different magnitudes of ground based laser torque on the system stability for passive and active control. Having applied the ground based laser torque on passive and active control techniques respectively; the obtained results show that the laser torque possesses negative effects on the system performance for the current study. For passive control, the ground based laser torque has a significant effect where the roll and yaw angles' responses are diverged. However, with active control, the effect of laser torque is limited by a proper PD gains tuned.
Abstract: The objective of this work is to investigate the effects of laser torque on both passive and active control for LEO CubeSat. The investigation is based on the model of the Euler equations for rotational motion. A simple case of spacecraft attitude control problem is considered, in which passive control is performed by accounting only gravity gradie...
Show More
