Radio Occultation Latitude Coverage

Radio occultation experiments with MGS began in January 1998. This figure shows the distribution in latitude and season of the profiles that are currently available through this Web site. The measurement latitude is determined by the position of Earth relative to the MGS orbit plane, and the latitude varies continually due to the orbital motion of Earth and Mars about the Sun. Occultations occur at high latitudes when Earth is in or near the MGS orbit plane, but no occultations occur when the MGS orbit is nearly face-on as viewed from Earth. Measurements in the Southern Hemisphere are sporadic due to failure of a spacecraft high-gain antenna gimbal.

The horizontal axis is solar longitude (Ls), an angular measure of the position of Mars in its orbit about the Sun. By definition, Ls = 0 at the vernal equinox of the Northern Hemisphere, and one Martian year spans 360 degrees of Ls. Martian years are identified by a year number near the bottom of the figure. In this convention, Martian year 1 (MY 1) begins at Ls = 0 on 11 April 1955; MY 24 begins on 14 July 1998; MY 25 begins on 31 May 2000; MY 26 begins on 18 April 2002; and MY 27 begins on 05 March 2004.

Radio Occultation Latitude Coverage

Last updated: September 19, 2007
Joe Twicken