Bare Earth Elements: Mars-Observing Fleet Set to Face Silent Treatment

by Timothy Oleson
Wednesday, April 3, 2013

Outbound communications from NASA to its group of Mars-observing orbiters and rovers will be curtailed starting April 4. And as of April 9, no commands will be sent in the Red Planet’s direction. Lest anyone worry that this radio silence has to do with sequester-related budgetary constraints affecting the space agency, don’t fret, it’s only temporary and it has more to do with orbital, rather than fiscal, dynamics.

The planned break in communication is a result of an impending planetary configuration, known as a solar conjunction, that will put the sun directly between Earth and Mars. In a March press release, NASA explained that the sun can disrupt interplanetary radio transmissions. So rather than risk sending commands to its fleet that might become corrupted en route, potentially endangering or damaging the orbiters and rovers, mission controllers will remain mum until Mars comes out of hiding again.

As of tomorrow, NASA’s signals to Curiosity and the Mars Reconnaissance Orbiter will be first to go, and communications to them will remain silent until May 1. Commands to the agency’s other orbiter, Mars Odyssey, and the Mars Exploration Rover Opportunity will cease from April 9 through April 26, although transmissions to those two will also be limited for several days on either side of that window, NASA said. The European Space Agency has not commented on whether it will halt communication with its orbiter, Mars Express.

Solar conjunctions between Earth and Mars occur about every 26 months. The last was in early 2011, and the next will be in mid-2015. During the current conjunction, the alignment of the two planets with the sun will be at its most linear on April 17. According to NASA’s statement, interferences in communications can vary from one conjunction to the next depending on exactly how concealed Mars is by the sun and how active the sun’s surface is at the time. The sun is currently in the upswing in its 11-year cycle of solar activity, although so far it has been relatively quiet compared to previous cycles.

Unlike Curiosity, which will be experiencing its first conjunction, each of NASA’s other spacecraft have been through multiple episodes. For the Mars Reconnaissance Orbiter, Opportunity and Odyssey, this will be the fourth, fifth and sixth conjunctions, respectively.

Although the Mars observers will not be receiving any new commands during the conjunction, they will continue to record data and make observations based on pre-programmed directions already sent. The rovers' activities will not involve any movements, so they’re stuck in place for a few weeks — Curiosity in Yellowknife Bay and Opportunity near the rim of Endeavour Crater — while the orbiters will continue to receive data from the rovers. And despite anticipated “data dropouts,” which can be recovered later, Odyssey will continue transmissions back to Earth. So whereas mission scientists will probably receive the occasional word from the Red Planet, for now, they’ll be saying “sayonara” to their robotic reporters, at least for a little while.

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