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We investigate the feasibility of missions in Low Mars Orbit (LMO), where atmosphere drag forces acting upon the spacecraft are compensated by an electric propulsion system. We show that a one-year mission is possible in a circular orbit at altitudes as low as 150 km. Such a mission opens opportunities for novel remote sensing approaches and new science cases. Given standard atmospheric models and assuming a medium-size spacecraft, the drag force within the Mars atmosphere acting upon the craft is approximately 100 mN at a height of 150 km, with a resulting orbit lifetime of less than two weeks. However, with typical parameters of an electric propulsion system like that on Dawn, the spacecraft would be capable to compensate this atmospheric drag by operating its ion thrusters. Remote sensing can benefit very much from operation in Low Mars Orbit. We anticipate new opportunities for next-generation spacecraft instrumentation including high-resolution imaging, radar sounding and Laser altimetry. We may (1) study seasonal and regional variations of snow-deposits in polar areas to improve models of the CO2 cycle; (2) map polar areas at high resolution to study the dynamics of ice sheets and scarps; (3) map the intricate rotation function of the planet, in particular variations in length-of-day for modeling of inertia and seasonal mass-redistributions; (4) carry out magnetic field measurements at high spatial resolution to map anomaly patterns; (5) map temporal and spatial variations in the density structure of the low Martian atmosphere. We foresee exciting prospects to advance our understanding of the geodesy and dynamics of Mars. [ABSTRACT FROM AUTHOR]

In the context of ESA's past call for medium class missions, we were investigating missions to Mars in combination with a flyby at a Mars Trojan on the way to the planet. We set up a three-impulse (Earth departure, mid-course correction and Mars orbit insertion) model to determine physically possible trajectories and flyby scenarios optimized in terms of required propellant and time (i.e., operation costs). We propose several scenarios in the time frame 2020-2050 including trajectories that involve more than one revolution about the sun. With the Earth and Mars ephemerides relatively fixed in space and time, the Trojan candidate has to be "at the right place at the right time" to minimize expensive spacecraft course adjustments. In principle, flybys are possible for any Trojan target – but we cut-off and present models having flyby delta-v < 1 km/s and transit time of < 5 years. We report on several scenarios, each including a flyby at one Trojan. Our results show that flybys of most of the Trojans are well conceivable. One good candidate for such a mission is Trojan 311999 (2007 NS2). With a launch in September 2028, the required additional delta-v will be less than 100 m/s, associated with a total transfer time (from Earth to Mars) of approximately 800 days. While a standalone mission to a Mars Trojan is currently probably far from practical due to costs, a combined mission to Mars and one of its Trojans is conceivable, and valuable science may be obtained at reasonable added resources. [ABSTRACT FROM AUTHOR]