Primary Binary Table Column Format

The bulk of scan position data are contained in binary tables. The extension format is dependent upon the optical configuration. Three extension names are possible: ANTPOSPF, for prime focus observations, ANTPOSGR for Gregorian observations, and ANTPOSST (not a true observing mode).

In prime focus mode, the EXTNAME is 'ANTPOSPF', and the columns are shown in table 1. In Gregorian optics configurations, the EXTNAME is 'ANTPOSGR', and the column format is shown in table 2. Although not intended for general use, a third option with no secondary information is possible in stow optics mode. The EXTNAME in this mode is 'ANTPOSST'. The column format for this mode is shown in table 3.

All tables share the following fields:

• The columns labelled 'RAJ2000' and 'DECJ2000' are the indicated position of the beam on the sky in J2000 coordinates.

• The columns labelled 'MNT_AZ' and 'MNT_EL' represent a time series of encoder samples at 10 Hz. These readings indicate the relative angle between a point on the track and the main reflector, (i.e. the position of the structure) as opposed to the position of the beam on the sky. (Normally these are synonomous, but many receivers have feeds which are not aligned with the boresight of the antenna.)

• The columns labelled 'OBSC_AZ' and 'OBSC_EL' are the refracted topocentric commanded position of the beam on the sky.

  The semantics of OBSC_AZ and OBSC_EL are mode dependent. If the offset coordinate mode Parameter is set to CABLEWRAP (i.e Encoder), then columns represent the observed command of the tracking center. Commanded offsets do not appear in the command data in this mode. If any other offset coordinate mode is selected the columns represent the observed command of the combined primary and offset position commands.

• The column labelled 'REFRACT' is a time series of the refraction correction in elevation.

• The columns labelled 'MAJOR' and 'MINOR' are the indicated position of the beam on the sky in the same reference frame as the commands were specified in. (See the primary header keyword INDICSYS.)

The tables below describe the format for each of these data table extensions.

Table 1: Column format in prime focus mode

Name	Type	Units
DMJD	1D	days
RAJ2000	1D	degrees
DECJ2000	1D	degrees
MNT_AZ	1D	degrees
MNT_EL	1D	degrees
REFRACT	1D	degrees
MAJOR	1D	degrees
MINOR	1D	degrees
OBSC_AZ	1D	degrees
OBSC_EL	1D	degrees
PF_FOCUS	1D	millimeters
PF_ROTATION	1D	degrees
PF_X	1D	millimeters

Table 2: Column format in Gregorian optics mode

Name	Type	Units
DMJD	1D	days
RAJ2000	1D	degrees
DECJ2000	1D	degrees
MNT_AZ	1D	degrees
MNT_EL	1D	degrees
REFRACT	1D	degrees
MAJOR	1D	degrees
MINOR	1D	degrees
OBSC_AZ	1D	degrees
OBSC_EL	1D	degrees
SR_XP	1D	millimeters
SR_YP	1D	millimeters
SR_ZP	1D	millimeters
SR_XT	1D	degrees
SR_YT	1D	degrees
SR_ZT	1D	degrees

Table 3: Column format in stow optics mode

Name	Type	Units
DMJD	1D	days
RAJ2000	1D	degrees
DECJ2000	1D	degrees
MNT_AZ	1D	degrees
MNT_EL	1D	degrees
REFRACT	1D	degrees
MAJOR	1D	degrees
MINOR	1D	degrees
OBSC_AZ	1D	degrees
OBSC_EL	1D	degrees