The Algonquin Radio Observatory (ARO) is the official Ground Station for the Northern Light mission. The 46 m radio telescope at ARO, operated by Thoth Technology, is the largest in Canada and one of the largest fully steerable dishes in North America. www.arocanada.com
Navigation to Mars requires range and range-rate determinations as well as differential Very Long Baseline Interferometry (VLBI) observations of the spacecraft. We will capitalize on our recent experience using ARO to track ESA?s Mars Express orbiter and the Japanese spacecraft Nozomi during Nozomi?s cruise to Mars.
Our low-cost tracking scenario uses C-band for communications and a ground-based VLBI network, also operating at C-band, for VLBI navigation. The Canadian S2 VLBI system has emerged as a world standard and is operational in more than a dozen countries around the world. Investment in Canadian VLBI capability provides a low-cost route to establishing a VLBI tracking network for the navigation of Northern Light.
Navigation of spacecraft on an interplanetary trajectory is a complex task requiring the high precision computation of a required mission trajectory, accurate determination of the actual spacecraft trajectory, and the comparison of the required trajectory and the actual trajectory followed by the determination and implementation of appropriate spacecraft maneuvers required for the correction and removal of discrepancies.
The basic tool required for spacecraft navigation is a high accuracy ephemeris of the solar system that provides the three-dimensional positions and velocities, in a barycentric frame, of the principal bodies of the solar system as a function of time. A high accuracy solar system ephemeris provides the gravitational forcing function to be used as input to a high-accuracy orbit propagator that predicts spacecraft location and rate. The first task of this navigation system is to generate a required trajectory for a Mars mission, including possible but undesirable mid-course maneuvers. Once this required trajectory is determined, it constitutes a standard against which the actual trajectory can be compared. The actual trajectory of the spacecraft is then determined by combining measurements made from ground-based tracking stations on Earth using the orbit propagator to derive an optimal stochastic estimate of spacecraft location and rate.
These measurements must be reduced from the Earth topocentric frame of reference in which they are made to a solar system barycentric frame of reference for comparison with the positions and velocities of the required trajectory for navigation purposes. We will use calibration parameters provided in near real time by the international geodetic VLBI community through the International VLBI Service (IVS), provided in part by the 46 m antenna of the Algonquin Radio Observatory (ARO).