PROCEDURE: mav_get_altitude PURPOSE: Calculates the altitude of the MAVEN spacecraft above the Martian surface (either the solid planet or the constant-pressure surface known as the 'areoid') USAGE: mav_get_altitude, elon_sc, lat_sc,r_sc, alt_sc INPUTS: elon_sc: a 1-dimensional array of values of the east longitude of the spacecraft. UNITS: Degrees! lat_sc: a 1-dimensional array of values of the latitude of the spacecraft. UNITS: Degrees! r_sc: a 1-dimensional array of values of the radial distance of the spacecraft from the planet's center of mass. UNITS: kilometers alt_sc: The output array of spacecraft altitudes. UNITS: kilometers KEYWORDS: TOPOGRAPHIC: Set this keyword to anything nonzero if the spacecraft altitude above the planet's topography is desired AREOID: Set this keyword to anything nonzero if desired is the spacecraft altitude above the constant-pressure surface known as the areoid (the equivalent of sea level). This will be the relevant altitude for most MAVEN studies and is the default if neither the topographic or areoid keywords are specified. CREATED BY: Robert J. Lillis 2013-01-22 FILE: mav_get_altitude VERSION: 1.1 Change made to enable loading of mola file