ESA Science & Technology - Venus Express Pericentre Altitude Evolution

This plot shows the planned evolution of the pericentre altitude during the pericentre lowering activities in July/August 2008. 

Over a period of about four weeks, the pericentre of the orbit is permanently lowered from the former range of 250-400 km to 185-300 km. The lowering is done in four steps at one-week intervals.

Each step includes two manoeuvres: one at pericentre to raise the apocentre altitude, and one at apocentre during the next orbit to lower the pericentre altitude. The combined effect of each pair of manoeuvres will leave the orbital period largely unchanged.

The inset shows the period around the time when the 185 km altitude will be reached. Also plotted is the expected evolution over the subsequent months, including the first quarter of 2009.