def standoff(sin_rec, pdyn, a0, a1, a2):
    """Returns standoff position (s/w) given IMF sine rectifier and dynamic pressure. a0/1/2 are tuning parameters (s0/1/2, w0/1/2)"""
    d = (a0 + a1 * sin_rec) * (pdyn ** (-1 / a2))
    return d