| Names | Lunar Meteoroid Impact Observer |
|---|---|
| Mission type | Lunar exploration |
| Operator | ESA |
| Mission duration | 12 months (planned) |
| Spacecraft properties | |
| Spacecraft | LUMIO |
| Spacecraft type | 12U CubeSat |
| Bus | CubeSat |
| Manufacturer | Argotec |
| Launch mass | 28 kg |
| Start of mission | |
| Launch date | 2027 (planned) |
| Moon orbiter | |
| Orbits | Halo orbit |
 Lumio mission logo. | |
LUMIO (LUnarMeteoroidImpactObserver) is a plannedESAlunar exploration mission expected to launch as early as 2027.[1] The main goal of the mission is to detect, quantify, and characterize the impacts ofnear-Earth meteoroids on thelunar far side.[2] The spacecraft consists of a 12-UCubeSat that will operate in ahalo orbit around theL2 Lagrange point of the Earth-Moon system.[3] It is an autonomus mission of the European Space Agency[1] and is currently being developed by an international consortium which includesPolitecnico di Milano,Argotec,Leonardo, IMT,[4] Nautilus[5] and S&T Norway.[6][7]
The main scientific payload of LUMIO is a custom-designed opticalcamera, called LUMIO-Cam, which will observe the lunar surface inumbra to detect the flashes caused byasteroid impacts. Scientific data from the mission will be integrated with observations from the Earth to elaborate the first complete and accurate model of meteoroids flux in the lunar environment.[2][8]
Near-Earth meteoroids are fragments ofasteroids andcomets with sizes ranging from micrometers to meters.[9] These objects impact the Earth and Moon on a daily basis. It is estimated that ~33 tons[8] of these fragments get attracted intoEarth's atmosphere every day. However, due to the extreme heat of theatmospheric entry, only a few manage to reach the surface. Since the Moon has no atmosphere, lunar impacts are much more frequent and constitute a constant threat to human and robotic operations on the surface.[10]
When a meteoroid impacts the ground, most of itskinetic energy is suddenly converted into heat which partially vaporizes the impacting mass and scatters secondary debris all around the site.[8] If an impact occurs where the surface is in umbra, it appears as bright flash, which can be detected by opticaltelescopes on the Earth. The intensity of the flashes can be measured to determine the kinetic energy of the meteoroid.[11]
However, observations from Earth must be performed atnighttime and are often disturbed by atmospheric events. Moreover, only those impacts that occur on the observable face of the Moon can be detected.[2]
On the contrary, LUMIO will have a constant and unobstructed view on the lunar far side from its orbit around the L2 Earth-Moon Lagrangian point.[3] Since the observation periods (i.e., when the surface is in shadow) are opposite with respect to Earth, LUMIO will considerably increase the monitored portion of the Moon's surface. The measurements coming from thespacecraft, coupled with those from Earth, will provide a more detailed statistics about theprobability anddistribution of meteoroids impacts on the Moon.[12]
LUMIO will be a 12-U Cubesat with dimensions of 30x20x20 cm, having a maximum wet mass of 28 kg.[2] The platform will be manufactured by Argotec,[13] an Italianaerospace engineering company based inTurin. Argotec has previous experiences in deep-space CubeSats, having designedLICIACube, the companion ofNASA'sDART spacecraft,[14] andArgomoon, one of thesecondary payloads of theArtemis-1 mission.[15]
The spacecraft will be equipped with apropulsion system in order to perform the space maneuvers needed to reach the finalorbit and smallstation-keeping corrections.[13][16]
Extendablesolar arrays produced by IMT will provide enough power during all the phases of the mission.[13] IMT will also manufacture theX-bandtransponder needed for establishing communications to the Earth and performingnavigation routines.[13]
The L2 Lagrangian point is specific zone ofequilibrium in the combinedgravitational field of the Earth-Moon system. At the L2 point, thegravitational attractions of the two celestial objects are combined. Due to this, it exists a particular family of three-dimensionaltrajectories, called halo orbits, which a satellite can exploit to remain in the vicinity of the Moon without orbiting it.[3]
The LUMIO spacecraft will fly on one of these trajectories, having the possibility of constantly observing the lunar far-side from a distance ranging between 36,000 and 86,000 km.[2]
The LUMIO mission will be divided into four phases:[3]
The LUMIO-Cam is the main scientific instrument of the LUMIO mission. It will be designed and manufactured byLeonardo, in their facilities ofCampi Bisenzio (Florence). The camera will have a resolution of 1024 x 1024pixels[11] and will be able to acquire images in both thevisual andnear-infrared spectrums.[2] The refresh rate will be of 15frames per second in order to detect flashes with duration as fast as 30 ms.[11]
The camera will have afocal length of 127 mm, obtaining aField-Of-View of 6.0º. This angular size is just enough to perform full disk observations of the Moon, which has an apparent size of 5.6° at the closest point of the trajectory.[11]
When more than 50% of the Moon's surface is illuminated, the glare deriving from thealbedo is too intense for observing the flashes on the unlit portion. Due to this, the surface monitoring will be possible only 50% of the time, in 15-days time windows.[11] The spacecraft will perform station-keeping maneuvers and secondary scientific activities while waiting for the next monitoring window.
The amount of data generated by the payload during the scientific phases is close to 5TB/day.[2] Since this value is too large to be transferred back to Earth, the images will be preliminarly processed on board. Only the images with detected impact flashes will be sent to the ground-stations, effectively reducing the required data transfer to approximately 1MB/day.[2]
The secondary objective of the LUMIO mission is to demonstrate the possibility of performing navigation routines in complete autonomy, without communicating withground stations.[2][17] The images from the LUMIO-Cam will be processed by optical navigation algorithms to provide an estimate of the position of the satellite with respect to the Moon. The technique that will be used is calledfull-disk navigation and It is expected to achieve an operational accuracy of less than 100 km.[17]
With this technique each picture is processed to find the edges of the moon. Then, anellipse is fitted to reconstruct the location of fulllunar limb in the image. The fitted ellipse is the bi-dimensionalprojection of the three-dimensional Moonellipsoid onto the image plane. Since thecharacteristics of the camera and the dimensions of the Moon ellipsoid are known, the ellipse points can be used as a state measurements in aKalman filter.[17]
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