Example of a 2D cut of a velocity phase-space scan is shown. The black dots mark the central position of instrumental bins (v_{x, i, j, k}, v_{y, i, j, k}) that are scanned, with i ∈ [1, …, N_EpQ], j ∈ [1, …, N_ϕ], N_EQP as the number of energy-per-charge (EpQ) steps and N_ϕ as the number of azimuthal bins, the angle of inflow bin ϕ_j of the j^th azimuthal bin, and its corresponding bin width Δ_GSϕ_j. As an example for a solar wind instrument the calibration values of the central elevation bin k = 5 of PAS for protons are used here and in Fig. 3. Note that we explicitly differentiate between the instrumental properties (ϕ, θ), and the measured angles (φ_sw, obs and ϑ_sw, obs). All instrumental characteristics are shown in black including the utilised Frame of Reference (FoR). Dots illustrate the shells centred at the origin, i.e. in the Spacecraft Reference Frame (SRF), which are scanned by the electrostatic analyser. Each 5th electrostatic analyser step is enlarged for clarity. The shape of each instrumental bin is illustrated with a concentric grid. The instrumental resolution in velocity space becomes coarser with increasing shell radius. In red, an example of a thermalised Maxwell-Boltzmann VDF (see Eq. (6)) is depicted. Shown are the bulk-flow vector relative to the instrument v_sw, its components, v_sw, x, v_sw, y, and the thermal velocity v_th. The corresponding 1σ, 2σ, and 3σ environments of the distribution are indicated in light red. In blue, measurement quantities are shown: the absolute value of the solar wind bulk velocity |v_sw|, the y component of the thermal speed v_th, y, and the corresponding thermal angle α_y. The two relevant FoRs are depicted in the left part of the figure: the SRF in black and the Radial-Tangential-Normal Frame (RTN) frame in green. Therein, the tangential components points in the direction of the spacecraft eigenvelocity.