GAIN_TRACKING Antenna gain tracking information.

Name

Format

Units

Measure

Comments

Columns

Key

ANTENNA_ID

Int Antenna identifier

FEED_ID

Int Feed identifier

SPECTRAL_WINDOW_ID

Int Spectral window identifier

TIME

Double s EPOCH Time interval mid-point

INTERVAL

Double s Time interval

Data

ATTENUATOR

Float Attenuator

SAMPLING_LEVEL

Float Sampling level

DELAYOFF1

Double s Delay offset of antenna

DELAYOFF2

Double s Relative delay offsets

PHASEOFF1

Double rad Phase offset on LO

PHASEOFF2

Double rad Phase offset on LO2

RATEOFF1

Double rad s-1 Phase rate offset on LO

RATEOFF2

Double rad s-1 Phase rate offset on LO2

PHASE_REF_OFFSET

Double rad A priory phase offset applied

Notes: Time variable gain trackings. These data are indexed via the TIME key in the MAIN table, via the ANTENNA_ARRAY and FEED_LIST collections in the CONFIG_DESCRIPTION table ( ANTENNA_ID and FEED_ID) and via the DATA_DESCRIPTION table ( SPECTRAL_WINDOW_ID).
ANTENNA_ID
Antenna identifier
FEED_ID
Feed idetifier
SPECTRAL_WINDOW_ID
Spectral window identifier
TIME
Mid-point of time interval for which the feed parameters in the row are valid. The same reference used fir the TIME column in the MAIN must be used.
INTERVAL
Time interval.
ATTENUATOR
Attenuator (TBD)
SAMPLING_LEVEL
Sampling level of the digitizer
DELAYOFF1
  Delay offset. It changes when the antenna is moved. Note that the offsets are applied in addition to the geometrical values.
DELAYOFF2
  Relative delay offsets in basebands; note that this should not change when the antenna is moved.
PHASEOFF1
  Phase offset applied in addition to the geometrical values on LO1, in addition of normal phase tracking
PHASEOFF2
  Phase offset applied in addition to the geometrical values on LO2, in addition of normal phase tracking
RATEOFF1
  Phase rate offset applied in addition to the geometrical values on LO1, in addition of geometrical tracking..
RATEOFF2
  Phase rate offset in addition of geometrical tracking. It is physically the same thing as a frequency offset; it adds up to the nominal LO frequencies as specified in the spectral windows for each baseband.
PHASE_REF_OFFSET
A priori phase offset correction applied when using phase referencing (Fast-Switching observing mode) This phase offset is determined from the last observations on a FIELD_ID which is an associated FIELD of the current FIELD 

Remarks:

  1. These delay and phase offsets being applied, in hardware, per baseband, SPECTRAL_WINDOW_ID corresponds to CHANNEL-ZERO associated spectral windows. (Would, between antennas, uncorrelated phase and delay offsets with a spectral dependency be present through the baseband, this information would be stored refering to associated spectral windows with the proper spectral resolution. In that case the dimension Nf needs to be added.)
  2. Phase tracking due to the geometry, e.g. in the On-The-Fly with cross-correlation observing mode, is set in the FIELD table. Other effects for phase-tracking are considered here in this GAIN_TRACKING table. This includes atmospheric on-line phase referencing (Fast-Switching phase referencing observing mode).