FEED: Feed characteristics

Name Format Units Measure Comments Keywords

NUM_FEED TpInt # feeds. Columns Keys

FEED_ID TpInt Feed id

ANTENNA_ID TpInt Antenna id

ARRAY_ID TpInt Array id

TIME TpDouble s EPOCH Midpoint of time for which this set of parameters is accurate

INTERVAL TpDouble s EPOCH Interval

FREQUENCY_ID TpInt Frequency id

PHASED_FEED_ID TpInt Phased feed

BEAM_ID TpInt Beam model Data description

NUM_RECEPTORS TpInt # receptors on this feed Data

POSITION TpFloat(3) m POSITION Position of feed relative to feed reference position for this antenna

BEAM_OFFSET TpFloat (2, NUM_RECEPTORS) rad Beam position offset (on sky but in antenna reference frame).

POLARIZE_TYPE TpString (NUM_RECEPTORS) Type of polarization to which a given RECEPTOR responds. Probably R, L or X, Y.

POL_RESPONSE TpComplex (NUM_RECEPTORS, NUM_RECEPTORS) D-matrix i.e. leakage between two receptors

RECEPTOR_ANGLE TpFloat rad The reference angle for polarization. Converts into Parallactic angle in the Sky domain. Flags

Notes:

FEED

A FEED is e.g. a single horn. A FEED can have one or two RECEPTORs that respond to different polarization states. Feeds are numbered from 0 on each separate antenna. Feeds for 20cm and 6cm observing would have separate FREQUENCY_IDs and thus could (should) have FEED_ID=0.