1H. Laakso, SERENA - HEWG meeting, Mykonos, Greece, 8-11 June 2009
1
Coordinated MMO and MPO observations
Harri LaaksoESA/ESTEC, Code SRE-OS, Noordwijk, The Netherlands
H. Laakso, SERENA - HEWG meeting, Mykonos, Greece, 8-11 June 2009
2H. Laakso, SERENA - HEWG meeting, Mykonos, Greece, 8-11 June 2009
1:4 Synchronization of the MPO-MMO orbits There is no fuel for orbit
maintenance
The orbits will evolve under the gravity field, causing a continuous phase shift between the two orbits
Currently the MMO and MPO orbital periods are 1:4 synchronized
This is not favorable to magnetospheric science because there will be close conjunctions only a few times for one short period of time (1-2 weeks) once a year
A few close encounters !
The two spacecraft are never close to each other
3H. Laakso, SERENA - HEWG meeting, Mykonos, Greece, 8-11 June 2009
Conjunctions During Synchronization
1:4 synchronization means that whenever MPO is at perigee (red square), MMO can be at four points (blue squares) that changes slowly due to orbital phase shift
When MMO moves to the perigee region, MPO has moved over the polar region
The orbital phase shift provides close encounters at the perigee only a few times within about 2 weeks
4H. Laakso, SERENA - HEWG meeting, Mykonos, Greece, 8-11 June 2009
Benefits of Non-Synchronized orbits It is highly desirable to have regularly repeated
close encounters
Science objectives: many magnetospheric objectives will have benefits from having a large variety of different types of conjunctions, e.g.,
when MMO is at perigee, MPO should be located at various positions, e.g., over the poles or in the opposite side of Mercury
both satellites should regularly approach the perigee at the same time
Question: how often certain conjunctions should be repeated? Instrument cross-calibrations: MPO and MMO carry similar in-situ instruments whose
calibrations are challenging (aging, spacecraft effects etc): The close encounters of <100 km will help the calibration activities Question: how often close (<100 km, TBC) conjunctions should be repeated?
5H. Laakso, SERENA - HEWG meeting, Mykonos, Greece, 8-11 June 2009
De-Synchronization of the MPO-MMO orbits
MMO orbital period is
4*MPO orbital period + 10 min
MMO orbital period is
4*MPO orbital period
6H. Laakso, SERENA - HEWG meeting, Mykonos, Greece, 8-11 June 2009
De-Synchronization of the MPO-MMO orbits
MMO orbital period is 4*MPO orbital period + 10 min
MMO and MPO at perigee at the same time
When MMO is at perigee MPO is at the opposite side
7H. Laakso, SERENA - HEWG meeting, Mykonos, Greece, 8-11 June 2009
Example: One MMO orbit, part 1
8H. Laakso, SERENA - HEWG meeting, Mykonos, Greece, 8-11 June 2009
Example: One MMO orbit, part 2
9H. Laakso, SERENA - HEWG meeting, Mykonos, Greece, 8-11 June 2009