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Coordinated MMO and MPO observations Harri Laakso

Coordinated MMO and MPO observations Harri Laakso ESA/ESTEC, Code SRE-OS, Noordwijk, The Netherlands. 1. H. 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

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Coordinated MMO and MPO observations Harri Laakso

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  1. Coordinated MMO and MPO observations Harri Laakso ESA/ESTEC, Code SRE-OS, Noordwijk, The Netherlands 1 H. Laakso, SERENA - HEWG meeting, Mykonos, Greece, 8-11 June 2009

  2. 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 The two spacecraft are never close to each other A few close encounters !

  3. 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

  4. 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?

  5. 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

  6. De-Synchronization of the MPO-MMO orbits MMO orbital period is 4*MPO orbital period + 10 min When MMO is at perigee MPO is at the opposite side MMO and MPO at perigee at the same time

  7. Example: One MMO orbit, part 1

  8. Example: One MMO orbit, part 2

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