EE Seminar: Lior Maor

~~Speaker: Lior Maor
M.Sc. student under the supervision of Prof. Anthony J. Weiss

Wednesday, February 11th, 2015  at  15:30
Room 011, Kitot Bldg., Faculty of Engineering

Orbit Determination of a micro Satellite Flying to the Moon
Abstract
 Satellite Orbit Determination (OD) is a method of determining the position and velocity (i.e., the state vector or state) of an orbiting object such as an interplanetary spacecraft or an earth orbiting satellite.
OD methodologies have evolved over the past 50 years through research by astrodynamics specialists from industry, university and government organizations. On top of this, the evolution of the Global Navigation Satellite System (GNSS) encouraged us to examine the past OD methods used for navigation to the Moon a few decades ago and explore some new, improved methods with emphasis on simplicity and low cost.
This work was motivated by the Google Lunar XPRIZE, which is a $30 million competition for private teams (with no more than 10% government funding) to land a robot on the Moon. In the framework of this competition, the Israeli team (SpaceIL) required a deep analysis for OD performance of an unmanned spacecraft (micro satellite) navigating to the Moon using low cost sensors such as Radio Frequency (RF) ranging and Global Positioning System (GPS).
The main requirements were: developing an appropriate mathematical model for the described OD problem, calculating the Cramér-Rao Lower Bound (CRLB), finding the best estimation method using the criteria of accuracy and complexity (run time) and verifying that the current sensor specifications are good enough to meet the accuracy requirement.
In this paper, we develop a detailed mathematical model for this specific problem. We also develop and calculate, using recursively applied numerical methods, the accurate CRLB. We develop and compare several estimation methods and show their convergence to the CRLB in all the examined scenarios and rank them by their complexity. We show that the GPS sensor can be used near the Moon (especially if we use a multi-constellation GNSS sensor) and quantify its accuracy degradation relative to operating near the earth. Furthermore, we suggest possible improvements for reducing the estimation root-mean-squared-error (RMSE) in order to meet the final accuracy requirement. Those improvements were done by suggesting which sensor parameters need to be improved (and find the improvement factors) and by means of sensor fusion (we developed an estimator using measurements from both sensors simultaneously). We show that by using the GNSS sensor together with the RF ranging sensor, we achieve better performance compared to the RF ranging sensor alone (as was used for Apollo Mission ground tracking approximately 50 years ago).

11 בפברואר 2015, 15:30 
חדר 011, בניין כיתות-חשמל 
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