A sneak peek at Artemis IV in LUNA
NASA has announced the two scientific instruments that astronauts will deploy and operate near the lunar South Pole during the second crewed lunar landing of the Artemis programme, Artemis IV, on December 4th, 2025. One of these instruments is the South Pole Seismic Station (SPSS), which consists of a seismometer and an active seismic experiment. A prototype of the seismic source that belongs to the active experiment, developed by Prof. Takeshi Tsuji at University Tokyo (Japan), already visited LUNA during the Polar Explorer Campaign in October 2025 and was tested in regolith simulant for the first time.
The Artemis IV crew will operate the seismic source PASS (Portable Active Seismic Source) at several locations close to the seismometer, generating seismic energy to map the shallow subsurface at the landing site. Analysing the data allows to constrain the existence of volatiles like water ice as well as the thickness and structure of the regolith, which is also considered as a construction material. The variable regolith thickness in LUNA of up to three meters in the Deep Floor Area and the buried exploration targets, some of which have similar elastic properties as water ice, allow to also test this exploration of the subsurface.
The PASS source itself generates structure-born sound and is located in the black cylinder at the lower end of the instrument. The long handle permits the astronauts to activate the source by pressing it to the ground, without having to kneel in their space suits. The design appears superficially similar to the „thumper“, a seismic source used by astronauts during Apollo 14 and 16 more than 50 years ago. In contrast to the „thumper“, PASS does not contain explosive charges, though, but generates a reproducible source signal with increasing frequencies, like used at significantly larger scales for vibroseis campaigns on Earth. The broad frequency range ensures that structures at different length scales can be resolved simultaneously, and the high reproducibility of the source allows stacking data from multiple activations to enhance small signals.
The SPSS seismometer will continue to operate once the Artemis IV crew has left the Moon and record moonquakes and meteorite impacts. These data help to improve the understanding of the interior structure of the Moon, down to the core, and its geologic history, as well as the present-day impact rate. Additionally, monitoring of moonquakes and impacts, even from micrometeorites, is important for astronaut safety, e.g. in plans for a future permanent base on the Moon, but also for possible future astrophysical observatories on the Moon with high sensitivity to shaking, e.g. gravitational wave detectors.
Now that SPSS has been selected, we expect additional campaigns in LUNA, not limited to PASS, to e.g. test instrument deployment under conditions that are as realistic as possible. SPSS is led by Jet Propulsion Laboratory (USA), with French (CNES) and Japanese (JAXA) contributions. An employee at the Microgravity User Support Center (MUSC) of DLR is SPSS co-investigator, supports tests in LUNA and was able to already garner first-hand experience with PASS in October 2025.