The Topical Team for the Astrophysical Lunar Observatory (or ALO TT for short) was formed late in 2020, in response to a call by the European Space Agency. The team got the assignment to investigate the possibilities for performing astrophysical observations from the lunar surface in the context of European Moon exploration efforts. Since then, we have identified the top science cases that can be pursued using Moon-based facilities, and we have organised several lines of research into relevant technology development and the specific nature of possible scientific measurements to be performed from the Moon.
Low‑Frequency radio astronomy as a key priority for lunar science
The far side of the Moon offers the quietest radio environment in the inner Solar System, making it uniquely suited for exploring the early Universe. Earth’s ionosphere blocks and distorts ultra‑long‑wavelength radio signals, and human‑made radio interference continues to grow. In contrast, the lunar far side provides complete shielding from terrestrial emissions and is free from ionospheric disturbances, creating an unparalleled window into the lowest radio frequencies.
Within this protected environment, we can finally detect the faint redshifted hydrogen signals from the Cosmic Dark Ages and Cosmic Dawn—periods inaccessible to any ground‑based observatory. These signals offer the only direct method to probe the formation of the first stars, galaxies, and black holes, as well as to test theories of cosmic structure formation and dark matter.
For these reasons, the Astronomical Lunar Observatory (ALO) Topical Team identified low‑frequency cosmology as the top scientific priority for a future lunar‑based observatory. It offers both transformational scientific return and is uniquely enabled by the conditions on the Moon’s far side.
Science Objectives of the Astronomical Lunar Observatory (ALO)
ALO is designed to unlock transformative science in low‑frequency radio astronomy, placing the Dark Ages EXplorer (DEX) at its core. Together, these efforts pursue several high‑impact scientific objectives:
Primary Science Objective: 21‑cm Cosmology
- Measure the Global 21‑cm Signal
Detect the sky‑averaged hydrogen absorption and emission features from the Dark Ages and Cosmic Dawn to determine when the first luminous sources formed, how early heating occurred and how radiation fields evolved.
- Map the Angular Power Spectrum
Use interferometry to study spatial fluctuations in hydrogen density and temperature, revealing how cosmic structures grew and offering a sensitive probe of dark matter physics.
- Prepare for Future 3D Tomography
Lay the groundwork for eventually imaging redshift‑slice “snapshots” of the early Universe, providing a dynamic picture of the evolving intergalactic medium.
Secondary Science Drivers
ALO will also support lunar‑based investigations of:
- Solar and heliospheric radio bursts
- Planetary magnetospheric emissions
- Exoplanetary radio signatures
- Fast Radio Bursts (FRBs) at low frequencies
- Other galactic and extragalactic objects of interest
Active collaboration
To maximise the scientific return, the ALO TT also collaborates closely with research groups working on other concepts for lunar astronomical observatories in order to enable strong alignment with broader European roadmap strategies for lunar science and complementarity with existing and future facilities.
The current ALO TT consists of approximately 60 researchers, engineers, and commercial partners representing various universities, institutes and companies from Europe and beyond. We actively pursue opportunities for international collaboration with members from other scientific initiatives that focus on doing radio astronomy from the Moon.
This website is still in making. If you would like to contact the Team, please send an email to c.brinkerink@astro.ru.nl .