NASA will suspend uploading of commands to its two Mars rovers and three Mars orbiters between July 22 and August 1, when the Red Planet will be in solar conjunction, putting it almost directly behind the Sun.
This alignment occurs every 26 months. Communications sent from Earth to Mars during these times become degraded because hot, ionized gas from Sun’s corona, which stretches quite far from the Sun’s surface, interferes with radio waves that pass through the corona.
Such interference can cause commands uploaded to rovers and orbiters to become corrupted, potentially harming the vehicles if carried out.
“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,” explained Chad Edwards, who manages the Mars Relay Network Office at NASA’s Jet Propulsion Laboratory (JPL) in California.
The potential for communications being corrupted during this time is strong in spite of the fact that Mars usually does not pass directly behind the Sun during solar conjunctions.
As a precautionary measure, the suspension of all communications to Mars rovers and orbiters will begin several days before the conjunction begins and continue for several days after it ends.
All five Mars mission teams have spent the last few weeks preparing for this phenomenon.
Rovers Opportunity and Curiosity will remain stationary during this time although they will continue to conduct observations and collect data.
Their mission teams have spent the last few weeks searching for ideal sites where they can stay parked while continuing science operations.
NASA’s three Mars orbiters–Mars Odyssey, the Mars Reconnaissance Orbiter, and the MAVEN orbiter, will continue to circle the planet, conduct science observations, and transmit data.
While no commands will be sent from Earth to Mars, data will continue to be transmitted from Mars back to Earth even though such transmission may involve some information loss.
To address possible data loss, the information will be transmitted back again once the conjunction is over.
“We will continue to receive telemetry, so we will have information every day about the status of the vehicles,” Edwards said.
“The vehicles will stay active, carrying out commands sent in advance.”
A video depicting the positions of Mars, the Sun, and the Earth can be viewed at https://mars.nasa.gov/allaboutmars/nightsky/solar-conjunction/