tan2visibilities

jwst.ami.leastsqnrm.tan2visibilities(coeffs)

From the solution to the fit, calculate the fringe amplitude and phase.

Parameters:

coeffs1D float array

The coefficients providing the fit solution.

Returns:

amp, delta1D float array, 1D float array

Fringe amplitude & phase

Notes

Technically the fit measures phase AND amplitude, so to retrieve the phase we need to consider both sin and cos terms. Consider one fringe: A { cos(kx)cos(dphi) + sin(kx)sin(dphi) } = A(a cos(kx) + b sin(kx)), where a = cos(dphi) and b = sin(dphi) and A is the fringe amplitude, therefore coupling a and b. In practice we measure A*a and A*b from the coefficients, so: Ab/Aa = b/a = tan(dphi) call a’ = A*a and b’ = A*b (we actually measure a’, b’) (A*sin(dphi))^2 + (A*cos(dphi)^2) = A^2 = a’^2 + b’^2