## The header parameters

Table: CLASS header parameters used to describe the frequency/velocity axes and their translation in this document.
CLASS name | Unit | Translation | Notation
nchan | — | Number of channel | —
rchan | — | Reference channel |
restf | MHz | Tuned signal rest frequency |
image | MHz | Tuned image rest frequency |
fres | MHz | Observatory channel spacing |
vres |  | Velocity channel spacing |
voff |  | source systemic velocity |
doppler | — | Doppler factor |

Table describes the CLASS header parameters used to describe the frequency/velocity axes and their translation in this document. The signal and image frequency axis are given in the source (rest) frame by

(35)
and
(36)
with
(37)
where is the frequency channel spacing , and is the source systemic velocity in the measurement frame. The corresponding velocity axis in the measurement frame is thus given by
(38)