Deep space navigation is essential for coordinating space satellites and future missions, including sending probes beyond the solar system. Methods like radar ranging can give accurate measurements of the radial coordinate of a spacecraft, but are uncertain on other axes. This method also becomes problematic for spacecraft that are far from earth. One solution to this limitation which has often been discussed in literature is to use pulsars as reference clocks to calculate the inertial position of the satellite on-board, removing any dependence on an Earth-origin signal. X-ray pulsars are ideal for this as high energy detectors can be more compact than radio antennas.
To test and demonstrate this principle, we propose a small payload utilizing X-ray detectors to observe a pulsars for navigation in deep space. The payload will have a small form factor (2U) and will be equipped with two Cadmium Zinc Telluride (CZT) detectors, covering an energy range of 20 – 250 keV. Data will be procured using a Xilinx FPGA, which will also undertake basic processing. In addition, we will also incorporate a Coded Aperture Mask (CAM) to measure the attitude of the payload. By tracking pulse time delays relative to the Solar System Barycentre (SSB) by analysing phase shifts, we can estimate the position of CubeSat with respect to SSB.
We have proposed a pulsar-based timing payload as a technology demonstration for use in future deep-space missions, in response to a call for Expression of Interests from INSPACe.