Like to have some explanations?

GEO

A geostationary orbit, geostationary Earth orbit or geosynchronous equatorial orbit (GEO) is a circular orbit 35,786 kilometres above the Earth’s equator and following the direction of the Earth’s rotation. An object in such an orbit has an orbital period equal to the Earth’s rotational period (one sidereal day) and thus appears motionless, at a fixed position in the sky, to ground observers.

GIE

Gridded Ion Engines: see also “Gridded Ion Engine Technologies…

GIESEPP

Gridded Ion Engine Standardised Electric Propulsion Platform

Gridded Ion Engine Technologies

Gridded ion thrusters are part of the electrostatic electric propulsion thrusters. The ion thruster generate thrust in two steps. In the first step ion thrusters employ a variety of plasma generation techniques to ionize a large fraction of the propellant. In the second step the ionized fraction of the propellant is accelerated in an electrostatic field of the grid system. The ion acceleration in a grid system is the common feature of all gridded ion engines. An ion thruster consists of basically three components: the plasma generator, the accelerator grids, and the neutralizer cathode.

LEO

A Low Earth orbit (LEO) is an orbit around Earth with an altitude between 160 kilometers, and 2,000 kilometers. Objects below approximately 160 kilometers will experience very rapid orbital decay and altitude loss.

PPU

Power Processing Unit

RIT

Radio Frequency Ion Thruster

TRL

Technology readiness levels (TRL) are a method of estimating technology maturity of Critical Technology Elements (CTE) of a program during the acquisition process. They are determined during a Technology Readiness Assessment (TRA) that examines program concepts, technology requirements, and demonstrated technology capabilities. TRL are based on a scale from 1 to 9 with 9 being the most mature technology.