We have been there, on the Moon, and yet we still know very little about it. So, before returning, we will send the necessary tools to keep it “under control”.
During the Apollo missionsover 50 years ago, retroreflectors were installed on the Moon. These are – they are still physically where they were placed – passive optical devices that have until now served to reflect laser rays sent from the Earth, thus allowing the distance of the natural satellite from our planet to be measured with millimeter precision.
In practice, it is about special mirrors that reflect laser light exactly in the same direction from which they come, regardless of the angle of incidence of the received rays. To function they do not require electricity or even batteries, while to carry out the measurement the relationship between the speed of light, time and therefore space is exploited.
Thus humanity discovered that the Moon moves away from the Earth by about 38 millimeters per year. Now it’s Mpac’s turn (MoonLight Pointing Actuator), a system that will allow scientists to measure the distance from Earth to a precision of the order of millimeters.
The characteristics of the new space technology
Mpac will fly aboard Intuitive Machines’ IM-3 mission to the lunar Reiner Gamma region early next year, aiming to reveal new details about the Moon’s interior. The technique used by Mpac, always defined as laser telemetry, combines two elements: the Moonlight, a new generation angular cube retroreflector, and the actual Mpac, i.e. a precision actuator that directs the reflector towards the Earth by “aiming” the station that emits the beam.
But where the old spotlights are influenced by lunar «libration».the slight apparent wobble of the Moon as it orbits the Earth, degrading the measurement, the Moonlight uses a single large retroreflector, and this greatly reduces the spread (and degradation) of the signal, producing a sharper return beam and allowing for much more precise distance measurements.
However, the reflector necessarily has a narrow field of view and must be aimed with extreme precision towards the Earth: this is the role of Mpac, which aligns the reflector after landing and allows it to reach its maximum scientific performance, i.e. millimetric values.
Mpac’s future projects related to the Moon
The apparatus was developed byItalian National Institute of Nuclear Physics (Infin)in collaboration with the University of Maryland and thanks to funding from the European Space Agency ESA. It will then be sent to the Moon through NASA’s Commercial Lunar Payload Services program, as part of Intuitive Machines’ IM-3 mission to the lunar surface. The Italian Space Agency (ASI) will instead support Mpac through its laser telemetry observatory in Matera, together with three other ground stations located in Grasse (France), Wettzell (Germany) and in the United States.
Currently, the Mpac has completed the qualification and testing phases, and awaits integration onto Intuitive Machines’ Nova-C lander ahead of launch, scheduled for 2027 with a SpaceX Falcon 9 rocket from the Block 5 series. The IM-3 mission will be a robotic space expedition whose main objective will be to study the characteristic “lunar vortices” and the unusual magnetic field associated with them. The lander used will be the Nova-C (Trinity), which in addition to the Mpac will also carry the Lunar Vertex, an essential instrument for carrying out the scientific investigation aimed at analyzing the evolution of the lunar surface.
