7. Calculate the upper limits for the linear term and the higher order terms of the ionospheric refractive index (see lecture notes, part 11) for measurements of the LIGPS signal (f=1575.42 MHz) for 750 km above the ground. Use the following simplified distribution for the electron density (Ne): Ne(h) = 0 h 1 000 000 m Ne(h) = a ( h - 100 000 ) 100 000 m