Dynamics of 3rd Body effects in Highly Elliptic and Critically Inclined Orbits

Satellite coverage of the Arctic region is becoming more and more important as there has been an increase in the demand for communications and Earth observation duties, which cannot be performed by geostationary satellites. Canada, in particular, has a vested interest in increasing the ability for remote settlements in the north to communicate with the rest of the world. In 2007, the Canadian Space Agency (CSA), in cooperation with the Department of National Defence (DND), Environment Canada, and Natural Resource Canada (NRCan), began looking into a satellite constellation that could supplement the communication infrastructure of northern Canada, in addition to providing meteorological coverage of Canada and promoting Canadian sovereignty in the Arctic. This became the Polar Communications and Weather program, or PCW. To optimally cover the Arctic, a pair of satellites would be used, in highly elliptical, critically inclined orbits, called Molniya orbits. This would provide the northern regions with near 24 hr communications, imagery, and meteorological coverage.

In a recent attempt by Professor Afagh and his co-workers to study the effects of atmospheric drag on satellites with highly eccentric orbits, specifically Molniya orbits for the PCW program, it was observed that the gravitational effects of the Moon and the Sun were much more significant than the forces due to drag for most Molniya orbits. It was also found that these gravitational effects, also known as 3rd body forces, were dependent on the initial orientation of the Molniya orbit with respect to an inertial frame. Depending on the orbit’s initial orientation, these 3rd body forces could extend the lifetime of the satellite to more than 20 years, or lower the orbit to the point where the satellite re-enters the atmosphere after a little over a year. A recent research project under the co-supervision of Professor Afagh is currently examining the 3rd body effects of the Moon and the Sun on all highly eccentric orbits. This investigation will result in an accurate force model that can be used on the satellite to compute optimal orbit maneuvers to compensate for the perturbations, and even aid with end-of-life disposal after the mission is complete

Lifetime of a Satellite as a function of the Initial RAAN


Variation in perigee altitude over time

Effect of the RAAN on the Altitude’s Rate of Change