Opportunity is on the west rim of Endeavour Crater at the 'Spirit of St. Louis' crater near the entrance of 'Marathon Valley.' The rover had been exploring the outcrops inside the Spirit of St. Louis crater.

On Sol 4018 (May 14, 2015), the project attempted to restore the rover to master sequence control after an unexplained reset on Sol 4017 (May 13, 2015).

However, an operational error prevented the use of the high-gain antenna (HGA), and the rover did not receive subsequent recovery commands.

The rover was successfully restored to normal operations on Sol 4020 (May 16, 2015).

On that sol, Opportunity executed a very small turn-in-place of only 4.6 degrees to position a surface target within reach of the robotic arm instruments. That evening, an overnight atmospheric argon measurement using the Alpha Particle X-ray Spectrometer (APXS) was made.

Another amnesia event occurred on the evening of Sol 4021 (May 17, 2015), but it was benign with no loss of data. On Sol 4023 (May 19, 2015), the Rock Abrasion Tool (RAT) was used to brush a surface target for in-situ (contact) investigation.

After the brushing, a Microscopic Imager (MI) mosaic was collected, followed by the placement of the APXS for a multi-hour integration.

As of Sol 4023 (May 19, 2015), the solar array energy production was 536 watt-hours with an atmospheric opacity (Tau) of 1.105 and a solar array dust factor of 0.727.

Total odometry is 26.28 miles (42.30 kilometers), more than a marathon.