Signal of opportunity time difference of arrival estimation using adaptive filtering techniques

EXACT and SOCRATES are a pair of CubeSats being developed to advance the TRL of a dual-use sensor. It can function either as x-ray detector used for characterization of high energy photons or as a sensor for measuring relative ranges between users in deep space operations. The ranging function of the sensor is described in this paper. After describing the measurements generated by the sensor, the algorithms that make use of this information to generate a position solution are presented. As a validation case study, data from the Japanese spacecraft Suzaku's observation of the Crab Nebula Pulsar is used to estimate the spacecraft's change in position along the line-of-sight to the pulsar, using this estimation scheme. Suzaku's observations are suitable for this application because the spacecrafts Hard X-Ray Detector (HXD) is similar in effective surface area to the prototype X-Ray/gamma-ray detector currently under development for use onboard EXACTand SOCRATES. Thus, validation of this technique using data from Suzaku serves to verify the feasibility of this navigation technique onboard other spacecraft with detectors of similar size.