Change in Venus Express pericentre altitude with time from 31 March 2013 to 20 July 2013
This plot shows the change in Venus Express's pericentre altitude (Y-axis) as the mission progresses, 31 March 2013 to 20 July 2013 (medium term plan (MTP) 91 through MTP 94). The X-axis shows the orbit number; each orbit lasts 24 hours.
The pericentre altitude decreases due to predicted forces experienced by the spacecraft. The pericentre is raised by firing the main spacecraft engine. In this case, four engine firings were carried out to raise the pericentre altitude.