Antenna performance:Gain/SEFD
Gain Kelvins/Jansky of telescope:
- Telescope gain (K/Jy) measured using diode
temperature and a set of calibrator sources of known flux.
- The diode temperature is used to transfer the
flux of the calibrator sources to the flux of the unkown sources.
- Measure unknown source strength using the cals
to get source strength in kelvins.
- Using the gain curves computed above:
- SourceJanskies=
SourceInkelvins/(telescope gain (Kelvins/Jy))
SEFD: System equivalent flux density.
- Tsys/Gain: measures the gain of the telescope in
units of Tsys rather than degK.
- Is independent of the cal value (since cal in
Tsys and gain, they cancel)
- this is the quantity that determines the
integration time needed (Tsys/Gain).
- It is good to measure both values:
- sefd shows when cal might be changing
- Tsys can jump (bad cable, electronic element)
and gain K/Jy is still correct.
More info
gain curves:
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