Abstract
This article presents a feasibility analysis to remotely estimate the geo-location of a femto-satellite only using two station-CubeSats and the communication link between the femto-satellite and each CubeSat. The presented approach combines the Time Difference Of Arrival (TDOA) and Angle Of Arrival (AOA) methods. We present the motivation, the envisioned solution together with the constraints for reaching it, and the best potential sensitivity of the location precision for different (1) deployment scenarios of the femto-satellite, (2) precisions in the location of the CubeSats, and (3) precisions in each CubeSat’s Attitude Determination and Control Systems (ADCS). We implemented a simulation tool to evaluate the average performance for different random scenarios in space. For the evaluated cases, we found that the Cramér-Rao Bound (CRB) for Gaussian noise over the small error region of the solution is highly dependent on the deployment direction, with differences in the location precision close to three orders of magnitude between the best and worst deployment directions. For the best deployment case, we also studied the best location estimation that might be achieved with the current Global Navigation Satellite System (GNSS) and ADCS commercially available for CubeSats. We found that the mean-square error (MSE) matrix of the proposed solution under the small error condition can attain the CRB for the simulated time, achieving a precision below 30 m when the femto-satellite is separated by around 800 m from the mother-CubeSat.
Highlights
Location estimation for satellites is relevant for many reasons, such as establishing the communication with the ground station(s), operating the payload, and orbital maneuvering, among many others
We found that the Cramér-Rao Bound (CRB) for Gaussian noise over the small error region of the solution is highly dependent on the deployment direction, with differences in the location precision close to three orders of magnitude between the best and worst deployment directions
For the best deployment case, we studied the best location estimation that might be achieved with the current Global Navigation Satellite System (GNSS) and ADCS commercially available for CubeSats
Summary
Location estimation for satellites is relevant for many reasons, such as establishing the communication with the ground station(s), operating the payload (e.g., imaging over a particular region), and orbital maneuvering, among many others. The location estimation of satellites can be either passive or active. The passive solution requires no action from the satellite to estimate its location. An example of localization systems with passive methods is the use of ground- and space-based (located in other satellites) radars or telescopes. Leolabs is a company that focuses on the Low Earth Orbit (LEO) and uses phased-array radars to locate the satellites. Neither NORAD nor Leolabs requires the satellite to have special hardware to obtain its position. With this method, the satellite is unaware of its position unless it is communicated to it. The active solution requires some action from the satellite to perform the location estimation.
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