Accuracy: the difference between a result obtained and the 'true' value.

Along track: a path along the Earth's surface (corresponding to a satellite's direction of movement).

Channel: Spectral channel (S1-S9 + F1-F2).

Detector: Pixel array at band N.

Calibration: the process of quantitatively defining the system response to known, controlled system inputs.

Field-Of-View: the angular extent of a given scene that is viewed by the instrument.

Infra-red (IR) radiation: electromagnetic radiation of wavelengths between approximately 750 nm and 1 mm. This is broken down into five wavelength regions:

• Near-IR - 0.75-1.4 μm
• Short-Wave IR - 1.4-3 μm
• Medium-Wave IR - 3-8 μm
• Long-Wave IR - 8-15 μm.

Image swath: Maximum distance on ground between the positions of two spatial samples belonging to the same row.

Image sample: image element containing radiance measurements of co-registered pixels for all bands.

Pixel: the FOV of a single detector element; the projection of that detector element onto the ground at a given instant.

Precision: the difference between one result and the mean of several results obtained by the same method, i.e. reproducibility (includes random errors only).

Visible light: electromagnetic radiation detectable by the human eye with a wavelength between approximately 400 nm and 700 nm.

Scan: defined as a complete rotation of the scan mirrors.

Scan cycle: comprises two consecutive scans during which a complete set of targets are sampled.

Scan trace, or scan locus: the trace of a single detector element on the ground. For example, in the thermal channels each detector has two elements, and so a single scan gives two scan traces, displaced by 1 km in the along track direction at the swath centre in the nadir. Adjacent scan traces represent adjacent 'rows' of the instrument grid.

Target: either the Earth view or one of the internal calibration targets (the VISCAL and the two black bodies); in the context of the telemetry data it refers to a section of the scan during which valid data is obtained, when the detectors are viewing the earth view or one of the calibration targets.