NASA has announced that mission planners for the various Mars probes have called for a moratorium in sending transmissions to Mars from July 22 to August 1. This coincides with Mars’ conjunction with the sun on July 27th. A conjunction occurs when an object appears to be at its closest point to the sun, as seen from Earth.
Having had to put up with Mars conjunctions before, the teams responsible for exploration missions on Mars have a good idea of what to expect in terms of their ability to communicate with distant probes during this time. Chad Edwards, manager of the Mars Relay Network Office at NASA’s Jet Propulsion Laboratory (JPL), said of the pause in transmissions, “Out of caution, we won’t talk to our Mars assets during that period because we expect significant degradation in the communication link, and we don’t want to take a chance that one of our spacecraft would act on a corrupted command.”
However, JPL will still be able to receive telemetry, although loss of signal and possible corruption is expected. When the blackout period is complete, JPL expects to have the affected telemetry retransmitted.
According to NASA officials, Mars won’t pass directly behind the sun during this conjunction. Rather, the sun’s corona will be between Earth and Mars. The corona effectively acts like the sun’s “atmosphere” and is only visible during total solar eclipses like the one that will be visible along a sixty-mile-wide stretch of North America on August 21st this year. Radio transmissions can be blocked or corrupted by the hot ionized gas in the corona, which causes concern that an expensive probe can be damaged or destroyed if it misinterprets a corrupted command.
The teams behind NASA’s currently active Mars missions will plan well in advance to direct probes and rovers like Curiosity and Opportunity in ways that will ensure their safety during the blackout. The rovers won’t drive during the conjunction, but can still carry out measurements and observations during the blackout and send the results later. When the blackout is over, normal operations for active Mars exploration missions will resume.