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Solar Conjunction: When The Sun Gets In The Way
By Jessica Williams

Solar Conjunction

I am a Navigation Engineer in the Mission Design and Navigation section at the Jet Propulsion Laboratory in Pasadena, California. As a Mars Reconnaissance Orbiter Navigator, my job is to determine where the spacecraft is (orbit determination) and where it is going (orbit prediction). I also keep the spacecraft on course by performing propulsive burns using the spacecraft engines.

The Earth and Mars both orbit the sun. Because Mars is farther away from the sun than is the Earth, the length of a Mars year is longer than the length of an Earth year (1 Mars year is about 1.9 Earth years). These different orbit periods cause the Earth and Mars to sometimes be on opposite sides of the solar system from one another. This event is called Solar Conjunction.

During Solar Conjunction, radio signals transmitted by the Deep Space Network to the Mars Reconnaissance spacecraft (and vice versa) must pass through the solar corona. Due to signal interference, the measurements that the Navigation team use for orbit determination become very noisy. Noisy measurements mean that the Navigation team can't figure out exactly where the spacecraft is and where it is going. Without accurate measurements (and an accurate orbit determination solution), the Mars Reconnaissance spacecraft cannot perform precise targeted science observations. The best thing for the team to do is to "wait out" Solar Conjunction until the signal noise levels go back to normal levels (when Mars re-emerges from behind the sun). For Mars Reconnaissance Orbiter, this Solar Conjunction period starts around April 4, 2013, and lasts until May 1, 2013. During this time, science observations are suspended and we won't be receiving any new images.

But not to worry! We should be back to our normal routine in May, so stay tuned!