•Gravity effects on observations
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–Due to first and second derivative of TEC
–Very dependent on geometry: maximum when line of sight is along wave fronts, small when
perpendicular to wavefronts, or //B.
–
–Typical image motion +/- 1 arcmin at 169 MHz, typical timescale: 30 mn.
• At least 10x in worst conditions
(+ some image distorsion)
•10x less at nightime.
–Focusing may occur at low frequencies, exceptionnal cases up to 50 MHz at low elevation.
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•