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Technical facts

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The table below provides an overview of the spacecraft platform and the ground segment.

Subsystem	Description
Attitude Determination and Control System (ADCS)	3-axis stabilized: 2 star trackers, 4 sun sensors, 2 inertial measurement units, 4 reaction wheels, 4 cold gas thrusters
On-board data handling	2 ESA LEON2 processors (dual redundant) running data handling software (command timeline and simple FDIR) and ADCS software; 32 MB Serial Flash for payload data storage; CANbus data interfaces
Communications	Low Gain Antennas for omni-directional coverage; S-band transponder with PSK-PM modulation and range & range rate capability for radio-navigation; 8 kbps downlink / 4 kbps uplink between Moon and Earth stations
Power	2 body-mounted 3J GaAs solar panels for 170 W beginning of life power & 122 W end of life power; 24-29 V unregulated bus; 15 Ah capacity Li-ion batteries
Propulsion	4 liquid MON/MMH bipropellant thrusters: 22 N thrust each, 285 s specific impulse (modulated by AOCS software during burns for reaction control); Delta-V of 1150 m/s
Structure	Al honeycomb central thrust tube with load bearing struts for launch adapter mating
Thermal control	Passive: MLI & surface coatings; active: local heaters for eclipse (e.g. propellant tanks)
Ground segment	Ground stations: 15m S-band dish in Villafranca for TT&C; 30m S-band dish in Raisting for payload downlink; Perth/Kourou for launch and early orbit phase and manoeuvres

Lunar transfer

The spacecraft of approximately 265 kg mass (incl. 93 kg propellant) and a size of 120 x 110 x 100 cm was designed to be launched as a secondary or auxiliary payload into geostationary transfer orbit.

From there, the spacecraft would use its on-board propulsion to travel to lunar orbit via a weak stability boundary transfer. This travel via the Sun-Earth L1 Lagrange point takes three months, but it requires much less propellant than a direct transfer.

Lunar orbit

The present mission design inserts the spacecraft into an initial lunar operational orbit of:

periapsis altitude: 280 km
apoapsis altitude: 16400 km
inclination: 56°

Payloads

Payloads being studied are:

Narrow Angle Camera (outreach payload): to take images of the lunar surface. High school students will be able to propose a lunar site to be imaged.
LunaNet (technology demonstration payload): internet-like network at the Moon for communication between future spacecraft in lunar orbit, landers, rovers and ground stations on the Earth. The LunaNet experiment will test the associated communication protocols for the Lunar Internet.
Radiation Monitor (scientific payload): a compact and low power radiation monitor which can provide inputs for Space environment models.
Radar (scientific payload): to provide radar observations of the Moon. (radar observations from Earth are limited to the Earth-facing side of the Moon).
Microwave Radiometric Sounder (scientific payload): a passive microwave radiometer to measure thermal and dielectric properties of the lunar regolith.