Mission engineers optimistic about resuming contact with Opportunity rover

Engineers are prepared for possible "fault modes" rover entered to assure its survival.
By Laurel Kornfeld | Aug 20, 2018
With the two-month global dust storm on Mars now weakening, engineers at NASA's Jet Propulsion Laboratory (JPL) remain optimistic about resuming contact with the Opportunity rover, which was last heard from on June 10.

Opportunity put itself to sleep in response to the dust storm, which blocked its solar panels from receiving sunlight, leaving them unable to recharge its batteries.

The batteries were in good health before the dust storm began. Because it is summer in Opportunity's location, temperatures never got cold enough to freeze the rover. Furthermore, dust storms actually have a warming effect on their environments.

Through NASA's Deep Space Network (DSN), with the benefit of special antennas capable of detecting a wide range of frequencies, mission engineers attempt to contact Opportunity several times a week.

If /when the rover responds, there could be several weeks between its first and subsequent communications, as it needs time to come out of hibernation. Once regular communication with Earth is resumed, the mission team will inquire about the state of the rover's batteries and solar cells, take its temperature, and have it take pictures of itself, so they can see any accumulations of dust that need to be removed.

Mission scientists use a measurement unit known as a "tau" to determine the amount of sunlight obscured from the planet's surface, with higher tau numbers meaning more obscuration. Opportunity needs a tau below 2.0 for its solar panels to recharge its batteries.

The last tau the rover recorded was 10.8 on June 10.

From Martian orbit, NASA's Mars Reconnaissance Orbiter (MRO) will use its wide angle camera to distinguish surface features as the dust storm dissipates.

Opportunity may have entered several "fault modes," steps taken to keep it healthy under stress, when the dust storm began. Mission engineers assume it went into low-power fault, which put it in a stage of hibernation when it failed to receive enough sunlight.

Clock fault would mean its internal clock loses track of time, resulting in the rover not knowing when it is supposed to communicate with Earth. Should clock fault occur, Opportunity can try to learn the time from environmental factors, such as an increase in sunlight.

Uploss fault can occur when the rover fails to hear from Earth over a long period of time. As a warning that its communication equipment may be malfunctioning, this state leads it to attempt various methods of resuming communication.

There is a possibility that the long period of inactivity reduced the level of charge its batteries can hold. This could adversely impact its ability to function normally and potentially destroy the batteries during Martian winter, when a high level of energy is necessary to keep Opportunity properly heated.

Assuming contact is resumed, the mission team will decide on whether to attempt a complete recovery of Opportunity once they have all the necessary data.

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