3.2.1 aluminium equivalent thickness
thickness of aluminium with a mass density per unit area equal to that of the material being described
NOTE The mass density is normally measured in (g cm-2).
3.2.2 auroral zone
region at a latitude between 60 and 70 degrees north or south where aurorae are formed
3.2.3 deep-dielectric charging
electrical charge deposition within the bulk of an external or internal material
pertaining to a medium in which an electric field can be maintained
NOTE Depending on their resistivity, dielectric materials can be described as insulating, antistatic, moderately conductive or conductive. The following gives a classic example of classification according to the resistivity:
• more than 109 W m: insulating
• between 102 W m and 109W m: antistatic
• between 103 W mand 106 W m: static dissipative
• between 10-2 W m and 102 W m: moderately conductive
• less than 10-2 W m: conductive
3.2.5 dose
energy absorbed locally per unit mass as a result of radiation exposure
<relating to an object at relative
motion with respect to a plasma>
on side of an object in the same direction as the plasma velocity vector
pertaining to static electricity or electricity at rest
3.2.8 electrostatic breakdown
failure of the insulation properties of a dielectric, resulting in a sudden release of charge and risk of damage to the dielectric concerned
rapid, spontaneous transfer of electrical charge induced by a high electrostatic field
3.2.10 external charging
electric charge deposition on external materials
time-integration of the flux
insulating dielectric
3.2.13 internal charging
electrical charge deposition on internal materials shielded at least by the spacecraft skin due to penetration of charged particles from the ambient medium
NOTE Materials can be conductors or dielectrics.
3.2.14 internal dielectric charging
internal charging of dielectric materials
propulsion system which operates by expelling ions at high velocities
parameter of the geomagnetic field
NOTE 1 It is also referred as L, and is used as a co-ordinate to describe positions in near-Earth space.
NOTE 2 L or L shell has a complicated derivation based on an invariant of the motion of charged particles in the terrestrial magnetic field. However, it is useful in defining plasma regimes within the magnetosphere because, for a dipole magnetic field, it is equal to the geocentric altitude in Earth-radii of the local magnetic field line where it crosses the equator.
scalar integral of the flux over all directions
NOTE This implies that no consideration is taken of the directional distribution of the particles which can be non-isotropic. The flux at a point is the number of particles crossing a sphere of unit cross-sectional surface area (i.e. of radius). An omnidirectional flux is not to be confused with an isotropic flux.
mass of molecular species evolving from a material per unit time and unit surface area
NOTE The units of outgassing rates are g cm-2 s-1. It can also be given in other units, such as in relative mass unit per time unit: (g s-1), (% s-1) or (% s-1 cm-2).
partly or wholly ionized gas whose particles exhibit collective behaviour through its electromagnetic field
3.2.20 primary discharge
initial electrostatic discharge which, by creating a temporary conductive path, can lead to a secondary arc
transfer of energy by means of a particle (including photons)
NOTE In the context of this Standard, electromagnetic radiation below the UV band is excluded. This therefore excludes visible, thermal, microwave and radio-wave radiation.
area of trapped or quasi-trapped energetic particles, contained by the Earth’s magnetic field
volume adjacent to the spacecraft and located in the same direction of the spacecraft motion where modification to the surface or plasma can occur due to the passage of the spacecraft through the medium
passage of current from an external source, such as a solar array, through a conductive path initially generated by a primary discharge
3.2.25 surface charging
electrical charge deposition on the surface of an external or internal material
flexible conductive or non-conductive cable linking two spacecraft or two parts of the same spacecraft not mechanically attached in any other way
device for altering the attitude or orbit of a spacecraft in space through reaction
NOTE E.g. rocket, cold-gas emitter, and electric propulsion.
<relating to onset of electrostatic discharge>
point where dielectric, metal and
vacuum meet
3.2.29 upstream
<relating
to an object at relative motion with respect to a plasma>
on the side of the object in the opposite direction to the plasma velocity vector
volume adjacent to a spacecraft and located in the opposite direction to the spacecraft motion where the ambient plasma is modified by the passage of the spacecraft through the medium