MESSENGER Exits Longest Solar Conjunction Period of Mission

On Friday, November 30, the MESSENGER team resumed daily contact with its Mercury-bound spacecraft. Engineers had suspended their contact schedule on November 13 as the Sun-Earth-Probe angle passed below 1* — entering a period known as solar conjunction, when the spacecraft’s trajectory moved it to the opposite side of the Sun from Earth and out of radio contact with NASA’s Deep Space Network for several weeks.

“Almost immediately after the start of this first tracking period, we were able to get a radio fix on and begin receiving telemetry from the spacecraft,” says MESSENGER Mission Systems Engineer Eric Finnegan. “A review of these early data indicates that the spacecraft is healthy and has operated nominally during the previous two weeks of communications outage.”

After verifying the condition of the spacecraft, the operations team at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., began sending commands to the spacecraft. “Intermittent contact with the spacecraft may still occur because of the potential for increased solar activity,” Finnegan says, “but the communication link reliability will continue to increase in the coming days.”

The spacecraft will officially exit the longest solar conjunction period of the mission on December 12 when the Sun-Earth-probe angle increases above 3*. “This positive contact with the spacecraft places one more critical event for the MESSENGER team in the past,” Mission Operations Manager Andy Calloway says. “We are now planning for a trajectory correction maneuver in late December that will keep the spacecraft on target for the first Mercury flyby of the mission and the first encounter with the planet by any spacecraft in nearly 33 years.”

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as principal investigator. The Johns Hopkins University Applied Physics Laboratory built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.