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The evolution of MESSENGER's orbit in its second extended mission
The evolution of MESSENGER's orbit in its second extended mission This chart shows how the periapsis (closest approach point) of MESSENGER's orbit moves southward over time, and closer to Mercury. The figure also highlights the locations of hot seasons, when components of the spacecraft sheltered from direct sunlight are subjected to excessive heating from Mercury’s sunlit surface at low altitude. NASA / JHUAPL / CIW