The COSMOCUBE Lunar Mission: Probing the Dark Ages and Cosmic Dawn via 21-cm Cosmology

THE COSMOCUBE LUNAR MISSION: PROBING THE DARK AGES AND COSMIC DAWN VIA 21‐CM COSMOLOGY Authors: E. de Lera Acedo¹,², D. Bacon³, W. Grainger⁴, D. Anstey¹,², H. Bevins¹,², L. King³,⁵, K. Artuc¹,², M. Al‑Badri¹,², C. Pearson⁴, S. Balaji⁴, R. Holdaway⁶, J. Bowman⁷, D. Jacobs⁷, T. Varelidi‑Strati⁵, S. Eckersley⁸, G. Johnston⁸, J. Friend⁸, N. Bernardini⁸, A. Harvey⁸, A. Turconi⁸, A.-M. Dorobat⁸, A.M. Gretarsson⁹, Y. Liao¹⁰, X. Morice‑Atkinson³, O. Olumodimu³. Affiliations: ¹ Affiliation: Cavendish Laboratory, University of Cambridge, JJ Thomson Ave, Cambridge, CB3 0HE, Cambridgeshire, UK; [email protected]; ² Affiliation: Kavli Institute for Cosmology in Cambridge, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, Cambridgeshire, UK. ³ Affiliation: University of Portsmouth, University House, Winston Churchill Avenue, Portsmouth, PO1 2UP, Hampshire, UK; david.ba- [email protected]; ⁴ Affiliation: RAL Space, STFC, Rutherford Appleton Laboratory, Didcot, OX11 0QX, Oxfordshire, UK; [email protected]; ⁵ Affiliation: In-Space Missions, BAE Systems, 8 Oriel Court, Omega Park, Alton, GU34 2YT, Hampshire, UK; ⁶ Affiliation: Cambridge Space Associates, c/o Opus, Lindenmuth House, 37 Greenham Business Park, Newbury, RG19 6HWT, Berkshire, UK; ⁷ Affiliation: School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA; ⁸ Affiliation: Surrey Satellite Technology Limited, Tycho House, 20 Stephenson Road, Guildford, GU2 7YE, Surrey, UK; ⁹ Affiliation: Physics and Astronomy Department, Embry-Riddle Aeronautical University, Prescott, AZ 86301, USA; ¹⁰ Affiliation: Aerospace Engineering Department, Embry-Riddle Aeronautical University, Prescott, AZ 86301, USA. Introduction: The CosmoCube Lunar Mission is a pioneering approach to explore the formative epochs of the Universe—from the Dark Ages to the Cosmic Dawn—by measuring the redshifted 21‐cm line from neutral hydrogen [1]. Terrestrial observatories are hampered by ionospheric distortions, radio frequency interference, and near-field ground emissions, especially below ∼45 MHz, thereby impeding the detection of signals from epochs earlier than the formation of the first stars. In contrast, the proposed mission utilizes a cost-effective small satellite deployed in lunar orbit (see Fig. 1). Shielded from Earth’s radio noise on the Moon’s far side, the mission offers an unparalleled opportunity to directly observe the faint 21‐cm signal across redshifts spanning from ∼13 to 285 (corresponding roughly to 5–100 MHz and extendable up to 100 MHz), thus providing a continuous window into the Universe’s earliest baryonic content. Figure 1. Drawing of the CosmoCube satellite orbiting the Moon. Science goal and landscape: CosmoCube will detect the sky-averaged 21-cm absorption profile against the CMB, sensitive to baryon density, Hubble expansion, and potential dark matter interactions. Using signal emulation and Bayesian analysis, the mission targets <10 mK precision. Ground-based instruments like EDGES, SARAS, and REACH have initiated this effort, though challenged by RFI and calibration ([2]-[4]). It is worth highlighting the first potential detection was repored back in 2018 by the EDGES team, although still unconfirmed by other experiments to date. Interferometers (HERA, LOFAR, MWA) focus on spatial fluctuations, offering upper limits on the power spectrum ([5]-[7]). SKA-LOW will enable high-resolution imaging of the Cosmic Dawn and the Epoch of Re-ionization in the next decade [8]. Space-based missions eliminate Earth-induced limitations. CosmoCube in lunar orbit avoids RFI, offering continuous low-frequency coverage. Related efforts include NCLE, PRATUSH, and proposed arrays such as DSL, FARSIDE, FarView, and ALO targeting ultra-low-frequency windows ([9]-[13]). This complementary strategy between ground and space missions will refine our cosmological understanding. The experiment: Central to the mission’s design is the integration of a wideband deployable radio antenna and a state-of-the-art receiver system onboard a small satellite. The payload architecture features: • A deployable, wideband radio antenna optimized for frequencies from ∼5 to 50 MHz (with potential extension to 100 MHz) that ensures compact stowage during launch and efficient expansion in orbit. • An integrated analog block incorporating a Dicke switch calibrator and a low-noise amplifier [14], essential for mitigating gain fluctuations and achieving high signal-to-noise ratios. • A Radio Frequency System-on-Chip (RFSoC) spectrometer for high-fidelity digitization and spectral analysis [15]. This combination of components, adapted to the small satellite form factor, addresses the challenges of size, weight, power, and thermal management, ensuring robust performance in the harsh space environment. The mission: The mission leverages lunar orbit to circumvent the limitations imposed by terrestrial RFI and atmospheric disturbances. A baseline orbital height of approximately 100 km is proposed, balancing the duration of Earth occultation and the operational constraints of the small satellite platform. The design ensures that a minimum of 15 minutes of continuous, shielded observation per orbit is achieved, ultimately allowing the accumulation of roughly 1,000 hours of science data over a two-year mission. Data transmission is facilitated via a heritage X-band transponder system that supports daily downlink sessions, while navigation and thermal control are managed to maintain precise calibration and system stability throughout the mission lifetime. Conclusions: The CosmoCube Lunar Mission represents a significant advancement in our quest to unveil the Universe’s earliest phases. By capitalizing on the quiet radio environment of the lunar far side and the agility of a small satellite platform, this mission promises to overcome the longstanding obstacles of ground-based 21‐cm cosmology. The resulting high-precision measurements will not only refine our understanding of dark ages physics and cosmic dawn but also contribute to resolving critical cosmological tensions, thereby opening new avenues for exploration in astrophysics and fundamental physics. References: [1] Pritchard, J.R. and Loeb, A. (2012) “21-cm cosmology”, Rept. Prog. Phys., 75, 086901. [2] Bowman, J.D., Rogers, A.E.E., Monsalve, R.A., Mozdzen, T.J., & Mahesh, N. (2018) “An absorption profile centred at 78 megahertz in the skyaveraged spectrum,” Nature, 555, 67–70. [3] Singh, S., et al. (2021) “Astrophysical constraints from the SARAS3 non-detection of the cosmic dawn sky-averaged 21-cm signal,” Nature Astronomy. [4] Lera Acedo, E., Villiers, D.I.L., et al. (2022) “The REACH radiometer for detecting the 21-cm hydrogen signal from redshift z ∼ 7.5–28,” Nature Astronomy, 6(8), 984–998. [5] DeBoer, D.R., et al. (2017) “Hydrogen Epoch of Reionization Array (HERA),” Publications of the Astronomical Society of the Pacific, 129(974), 045001. [6] Mertens, F.G., et al. (2020) “Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z = 9.1 from LOFAR,” Monthly Notices of the Royal Astronomical Society, 493, 1662–1685. [7] Tingay, S.J., et al. (2013) “The Murchison Widefield Array: The Square Kilometre Array precursor at low radio frequencies,” Publications of the Astronomical Society of Australia, 30. [8] Dewdney, P.E., et al. (2009) “The Square Kilometre Array,” Proceedings of the IEEE, 97(8), 1482–1496. [9] Bentum, M.J., Verma, M.K., et al. (2020) “A roadmap towards a space-based radio telescope for ultra-low frequency radio astronomy,” Advances in Space Research, 65(2), 856–867. [10] Pratush. (2024) “Probing Radio Astronomy at UHF and SHF,” Raman Research Institute. Available online. [11] Chen, X., Yan, J., Deng, L., et al. (2020) “Discovering the sky at the longest wavelengths with a lunar orbit array,” Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. [12] Burns, J.O., et al. (2021) “A Lunar Farside Low Radio Frequency Array for Dark Ages 21-cm Cosmology,” proposal (see related mission concept). [13] Polidan, R.S., Burns, J.O., Ignatiev, A., et al. (2024) “FarView: An In-Situ Manufactured Lunar Far Side Radio Array Concept for 21-cm Dark Ages Cosmology,” American Astronomical Society Meeting Abstracts. [14] Zhu, J., Acedo, E.d.L., Artuc, K., Chen, X. (2025) “RFSoC receiver calibration system for 21-cm global spectrum experiments from space: The CosmoCube case”, RAS Techniques and Instruments, 4, 064. [15] Artuc, K., de Lera Acedo, E. (2024) “The spectrometer development of CosmoCube, a lunar orbiting small satellite to detect the 21-cm hydrogen signal from cosmic dark ages”, RAS Techniques and Instruments, 4, 061.