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Time Difference Detection of Atomic Clock-Based Reference Signal from a CubeSat in Orbit

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Satellite signal delays and errors depend on the amount of ionosphere Total Electron Content (TEC) in the signal path. The measurement of TEC has been mostly done using Global Navigation Satellite System (GNSS) signals. Signals from a satellite orbiting in lower altitude with lower frequencies than GNSS may provide more precise measurement of Total Electron Content (TEC). Space Precision Atomic Clock Timing Utility Mission (SPATIUM) is a program to do three-dimensional ionosphere mapping by a satellite constellation in Low Earth Orbit (LEO) measuring TEC with Ultra High Frequency (UHF) radio signals. The first technology demonstration satellite called SPATIUM-I, a 2U CubeSat, was deployed from the International Space Station in October 2018. The satellite emits a 467-MHz reference signal generated by a chip scale atomic clock. The signal is Spread Spectrum (SS)-modulated with 250 chips in 4 ms. This paper explains the methodologies and their results of detecting the signal time delay on the ground using a Software-Defined Radio (SDR). To improve the precision, a Global Positioning System (GPS) clock was used to put a time stamp on the satellite signal every 1 s. The time difference of two consecutive signals is the key method for deriving the TEC difference between two signal paths.
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SDR; SPATIUM-I; TEC Difference; Time Difference

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J. Arenas, E. Sardón, A. Sainz, B. Ochoa, and S. Magdaleno, Low-latitude ionospheric effects on SBAS, Radio Science (2016), 51, 603- 618.

Nugnes, M., Colombo, C., Tipaldi, M., A System-Level Engineering Approach for Preliminary Performance Analysis and Design of Global Navigation Satellite System Constellations, (2020) International Review of Aerospace Engineering (IREASE), 13 (3), pp. 80-98.

A. Noureldin et al, Fundamentals of Inertial Navigation, Satellite-based Positioning and their Integration. (Springer, Berlin, 2013).

V.V. Kumar and M. L. Parkinson, A Global Scale Picture of Ionospheric Peak Electron Density Changes During Geomagnetic Storms, Space Weather (2017), 15, 637-652.

Q. Zhang, and Q. Zhao, Global Ionosphere Mapping and Differential Code Bias Estimation during Low and High Solar Activity Periods with GIMAS Software, Remote Sensing (2018), 10, 705.

E. Musicò, C. Cesaroni, L. Spogli, J. P. Merryman Boncori, G. De Franceschi and R. Seu, The Total Electron Content from InSAR and GNSS: A Midlatitude Study, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (2018), 11(5), pp. 1725-1733.

S. Gao, M.N. Sweeting, S. Nakasuka, and S. P. Worden, Small Satellites, Proceeding of the IEEE (2018), vol. 106, 3.

Microsemi. SA.45s CSAC and RoHS CSAC Options 001 and 003 (May 7, 2018). (accessed June 5, 2019). Available at:

D. V. Buren, P. Axelrad and S. Palo, Design of a high-stability heterogeneous clock system for small satellites in LEO. GPS Solution (2021) 25, 105.

C. Cooper, C. N. Mitchell, C. J. Wright, D. R. Jackson and B. A. Witvliet, Measurement of ionospheric total electron content using single-frequency geostationary satellite observations, Radio Science (2019), 54(1), pp. 10-19.

V. Forsythe et al, Validation of Ionospheric Electron Density Measurements Derived from Spire CubeSat Constellation. Radio Science (2019), 55.

R. Rahmatillah et al, Ionosphere Irregularity Observation Using Reference Signal from CubeSat Constellation, 69th International Astronautical Congress (IAC) (2018).

S. D'Amico and J. R. Carpenter, Satellite Formation-Flying and Rendezvous, Global Positioning System: Theory and Applications, Parkinson, B. and Spilker J., eds. Ch. 50. (2018)

G. X. Gao, S. Datta-Barua, T. Walter, and P. Enge, Ionosphere effects for wideband GNSS signals, 63rd Annual Meeting of the Institute of Navigation 2007, Annual Meeting - Institute of Navigation, 147-155 (2007).

K. Aheieva et al, CubeSat Mission for Ionosphere Mapping and Weather Forecasting using Chip-Scale Atomic Clock, Progress in Electromagnetics Research Symposium (PIERS) (2017).

K. Aheieva et al, Project Overview of SPATIUM-I: A Technology Demonstration Mission Toward Global Three-Dimensional Ionosphere Mapping Via CubeSat Constellation Equipped with an Atomic Clock, Journal of Small Satellites, vol. 10, n. 2, 2021.

H. Miyashiro, M. Medrano, J. Huarcaya and J. Lezama, Software defined radio for hands-on communication theory, IEEE XXIV International Conference on Electronics, Electrical Engineering and Computing (INTERCON) (2017), 1-4.

I. Georgescu, N. Angelescu, D. C. Puchianu, G. Predusca and L. -D. Circiumarescu, Software defined radio applications - receiving and decoding images transmitted by weather satellites, 13th International Conference on Electronics, Computers and Artificial Intelligence (ECAI) (2021), 1-4.

E. G. W. Peters and C. R. Benson, A Doppler Correcting Software Defined Radio Receiver Design for Satellite Communications, IEEE Aerospace and Electronic Systems Magazine (2020), 35(2), pp. 38-48.

HackRF One. (accessed July 10, 2019).
Available at:


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