Coordinated observations of the Martian ionosphere and induced magnetosphere with Mars Express and MAVEN

The NASA Mars Atmosphere and Volatile Evolution (MAVEN) mission is scheduled to launch in November 2013, and arrive in Mars orbit in September 2014. Meanwhile, the ESA Mars Express (MEX) mission is expected to be conducting its 10th year of scientific operations. The presence of both spacecraft simultaneously orbiting Mars, with complementary suites of scientific instruments, affords an excellent opportunity to study the Martian plasma environment in unprecedented detail. We present an overview of the coordinated measurements that are planned to be undertaken with MEX and MAVEN. The polar orbits of MEX (86 degree inclination, 300×10,000 km altitude, 7.5 h period) and MAVEN (76 degree inclination, 150×6200 km, 4.5 h period) will provide near-continuous measurements within the solar wind, along with frequent passages through the magnetosheath and ionosphere. The differing orbital parameters will provide a range of relative orbital configurations of the two spacecraft during the one-year MAVEN prime mission. A significant overlap exists between the scientific payloads of both missions, while each spacecraft also possesses unique instruments (e.g., the MAG vector magnetometer on MAVEN, and the MARSIS radar on MEX). Near continual monitoring of the solar wind bulk parameters will provide a new opportunity to understand the response of the Martian system to variable upstream conditions. Opportunities will also be present to cross-calibrate measurements made with different instruments on both spacecraft. During fortuitous close conjunctions, use of two spacecraft measurements will resolve spatial-temporal ambiguities in the dynamics of plasma boundaries and ionospheric structures. Two-spacecraft measurements will provide higher-cadence measurements of the numerous classes of anomalous or transient structures seen already at Mars, such as a large ionospheric flux ropes, outflow plumes and plasma density structures and boundaries. Throughout multiple ';deep-dip campaigns', MAVEN will traverse the Martian ionosphere to altitudes below the photochemical peak and neutral atmosphere down to the homopause. We envisage that MEX will provide supporting scientific measurements, both during these campaigns and during periods of other interesting orbital configurations. These are likely to include measurements made with ASPERA particle detectors and ionospheric sounding with MARSIS at higher than nominal rates. Overall, these coordinated measurements should result in significantly higher science return than passive, ';default' data collection from both spacecraft.