John D. Odegard School of Aerospace Sciences

News and information from the UND John D. Odegard School of Aerospace Sciences.

Final 2016 Brown Bag seminar with Shankar Nag Ramaseri Chandra on December 1

The fall semester Brown Bag Seminar Series features graduate students providing presentations on their current research and recent internships. This series of presentations is held in the Space Studies Library at 12:30 PM.

On December 1,  Shankar Nag Ramaseri Chandra will present “Math Modeling Approaches for Asteroid Gravity Field.”

About the Presentation:  There has been great interest in the study of minor planets and asteroids due to their ability to reveal secrets of solar system formation.  Various spacecraft missions to asteroids have helped us reveal the compositions of these bodies by performing close proximity operations.  The study of asteroid compositions is also crucial since they can provide in-situ resources for deep space exploration missions.

Due to the presence of undetermined mass distributions, asteroid bodies exhibit complex gravitational fields. The Hayabusa spacecraft which visited and analyzed asteroid Itokawa experienced perturbations due to the tenuous gravity field of the body. Hence, to efficiently model spacecraft orbits around these irregular bodies, the knowledge of their gravity field is important.

Currently, a spherical harmonic gravity model of degree and order 20 is available for Itokawa modeled using the shape model derived from the Hayabusa spacecraft (Gaskell et al. (2006) and Scheeres et al. (2006)). A spherical harmonic gravity model of degree and order 16 was modeled prior to Hayabusa mission to Itokawa, using the shape model derived from ground based radar observations (Ostro et al. (2004)). The dynamics of the satellites around these gravity fields have different behavior because of the difference in the accuracy of the shape model. In this work, we compare the dynamics of satellites using the above gravity models up to degree and order 4.

In this method, the asteroid is assumed to be of homogeneous density with the shape of a tri-axial ellipsoid given by Scheeres et al. 2004. The gravity coefficients are fed into Systems Tool Kit (STK) to model scenarios involving various close orbit operations and maneuvers. The parameters, radius and eccentricity for the above simulated satellite orbits are compared with both gravity models.  We expect to find that the state vectors show higher deviation with radar based gravity model than the gravity model obtained by Hayabusa spacecraft. We ought to show that better the shape model of the asteroid, better is the characterization of the gravity field and hence the better chance of mapping the dynamics of the satellite.

About the presenter:   Shankar is from Hyderabad in the southern part of India. His bachelor’s degree is in Aeronautical Engineering from JNT University, Hyderabad. After his graduation, he worked as a Satellite Systems Engineer for two years at Defence Research Development Organization (DRDO) in India where he was responsible for studying the orbit design and payload characteristics.  He learned very interesting facts about space engineering from his two years of work at DRDO which motivated him to choose UND Space Studies for his Masters. Shankar is a Master Certified STK professional focusing on modeling scenarios involving close proximity satellite operations around asteroids. He has also been studying the techniques to model gravitational fields of asteroids. His aim is to become a satellite systems engineer for a reputable space organization.