On the other hand , the MMO and MESSENGER took largely elliptical orbits .
The reason for this orbit is that the MPO will be measuring the composition of the surface and exosphere , and the close orbit will aid on data quality .
The MMO and MESSENGER took largely elliptical orbits .
The reason for this orbit is that the MPO will be measuring the composition of the surface and exosphere , and the close orbit will aid on data quality .