Each impact observed during the post-flight analysis is measured and several parameters are stored in the database. The main parameters are described following (see figure).

Front Top: a central pit (Dp); a region of shatter immediately outside this (Ds); a conchoidal fracture zone beyond this (Dco); an outermost area of irregular damage (Dm).

Front Back: a central pit (Dp), in some cases the RTV adhesive is exposed (Drtv), regions of inner and outer spall (Dis and Dos) and a large area of variable damage (Dm).

Rear Top and Back: a central hole (Dh) and an extended burned area (Dl).

Scale: S is the spacing in mm of the silver wire grid on the cell side or the space between two meshes on the back side to be converted in SI units.

Magnification: Z is the zoom factor of the microscope obtained with dividing the scale factor by 1.25 for cell side or 0.35 for the rear side.

Engineering units: real dimensions in mm.

Cracks n°: number of clear cracks present in a given feature.

Spall n°: number of spall presents in a feature particularly on FB impacts type A or B

Angle: In the case of FT non-circular impacts it is possible to determine the impact direction, q is defined as the angle anticlockwise from the vector X parallel to the grid and the velocity vector V in the direction of impact.


  • C is the position of the pit centroid relative to the spallation diameter;
  • M is the mean impact diameter,
  • Da is the along axis of the pit (parallel to the direction of approach of impactor),
  • Db is the cross axis of the pit (generally Da>Db excepted for butterfly features),
  • S is the scale factor,
  • Z is the magnification.

It is noted that if the impact feature of any feature is elliptical, the minimum and the maximum diameters are recorded in the same Excel cell separated by "/".