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According to @StarMan's comment which links to EarthSky.org's New look at Mercury’s peaks and valleys

On May 6, 2016 NASA’s MESSENGER mission – which orbited Mercury from 2011 until 2015 – unveiled the first global digital elevation model, showing the topography, or highs and lows of natural features, across the entire innermost planet.

 

This new model reveals a variety of interesting topographic features, as shown in the animation above, including Mercury’s highest and lowest points. The highest point on Mercury is at 2.78 miles (4.48 km) above Mercury’s average elevation, located just south of the equator in some of Mercury’s oldest terrain. The lowest elevation, at 3.34 miles (5.38 km) below Mercury’s average. It’s found on the floor of Rachmaninoff basin, an intriguing double-ring impact basin suspected to host some of Mercury’s most recent volcanic deposits.

So from a topographical point of view at least a few orbits at 3 miles without colliding a surface feature.

According to @StarMan's comment which links to EarthSky.org's New look at Mercury’s peaks and valleys

On May 6, 2016 NASA’s MESSENGER mission – which orbited Mercury from 2011 until 2015 – unveiled the first global digital elevation model, showing the topography, or highs and lows of natural features, across the entire innermost planet.

This new model reveals a variety of interesting topographic features, as shown in the animation above, including Mercury’s highest and lowest points. The highest point on Mercury is at 2.78 miles (4.48 km) above Mercury’s average elevation, located just south of the equator in some of Mercury’s oldest terrain. The lowest elevation, at 3.34 miles (5.38 km) below Mercury’s average. It’s found on the floor of Rachmaninoff basin, an intriguing double-ring impact basin suspected to host some of Mercury’s most recent volcanic deposits.

So from a topographical point of view at least a few orbits at 3 miles without colliding a surface feature.

According to StarMan:

The highest point of Mercury is actually 2.78 miles (4.48 km) above Mercury's average elevation (source), so the orbiter shouldn't hit it. If it doesn't, two orbits are possible to be made around Mercury at 3 miles altitude.

According to @StarMan's comment which links to EarthSky.org's New look at Mercury’s peaks and valleys

On May 6, 2016 NASA’s MESSENGER mission – which orbited Mercury from 2011 until 2015 – unveiled the first global digital elevation model, showing the topography, or highs and lows of natural features, across the entire innermost planet.

This new model reveals a variety of interesting topographic features, as shown in the animation above, including Mercury’s highest and lowest points. The highest point on Mercury is at 2.78 miles (4.48 km) above Mercury’s average elevation, located just south of the equator in some of Mercury’s oldest terrain. The lowest elevation, at 3.34 miles (5.38 km) below Mercury’s average. It’s found on the floor of Rachmaninoff basin, an intriguing double-ring impact basin suspected to host some of Mercury’s most recent volcanic deposits.

So from a topographical point of view at least a few orbits at 3 miles without colliding a surface feature.

According to StarMan:

The highest point of Mercury is actually 2.78 miles (4.48 km) above Mercury's average elevation, so the orbiter shouldn't hit it. If it doesn't, two orbits are possible to be made around Mercury at 3 miles altitude.

According to StarMan:

The highest point of Mercury is actually 2.78 miles (4.48 km) above Mercury's average elevation (source), so the orbiter shouldn't hit it. If it doesn't, two orbits are possible to be made around Mercury at 3 miles altitude.