The European Space Agency (ESA) reported on October 13, 2026, that two flight-like development models of its Exploration Mass Spectrometer for LUPEX (EMS-L) had been assembled and tested successfully. The instrument is designed to study the Moon’s tenuous exosphere and volatile material associated with the LUPEX rover’s movement and drilling. ESA’s account of EMS-L

What the two models represent

The models represent different parts of the instrument’s development. ESA says the engineering test model represents EMS-L’s functions and digital interfaces. The structural thermal model represents its shape, mechanical interfaces, and thermal and structural properties. Together, they address both how the instrument is designed to operate and how its physical structure is designed to fit and perform under mission conditions.

ESA says engineers in Japan are to check the models’ mechanical, thermal, electrical and data interfaces with the LUPEX rover. The reported development-model tests are a step in EMS-L’s development; the instrument is intended to fly on the rover as part of the mission.

What EMS-L is designed to measure

EMS-L is intended to identify chemical species near the lunar surface, compare how they vary from place to place, and measure temperature. ESA also describes it as studying the extremely sparse atoms and molecules in the lunar exosphere, along with volatile material encountered as the rover travels and drills. ESA’s description of the instrument

Those observations would contribute to LUPEX’s broader investigation of lunar polar water resources. JAXA describes the mission’s aim as studying the quantity, distribution, conditions and form of those resources through observations on the Moon. Its mission outline includes excavating material, heating samples to release volatile substances, and conducting chemical, water-quantity and isotopic analyses. JAXA’s LUPEX mission overview

That wider analysis belongs to the mission’s overall program. ESA describes EMS-L’s role more specifically: investigating the exosphere and volatile material associated with rover activity. JAXA lists the rover’s intended subsurface observations to depths of up to 1.5 metres and a mission operating period of more than three months; these are rover and mission parameters, respectively, rather than EMS-L specifications. JAXA’s LUPEX mission overview

LUPEX mission and planned launch

LUPEX is a collaboration between the Japan Aerospace Exploration Agency (JAXA) and the Indian Space Research Organisation (ISRO). EMS-L is intended to ride on JAXA’s rover, which ESA says will travel to the Moon aboard ISRO’s Chandrayaan-5 lander. ESA and JAXA list an H3 rocket for the mission and a launch no earlier than 2028. ESA’s mission description · JAXA’s LUPEX mission overview