user: Question: specific orbital energy of −0.5 MJ/kg is what altitude above the earth's surface?
Columns: ['orbit', 'center-to-center distance', "altitude above the Earth's surface", 'Orbital period', 'specific orbital energy']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ["Earth's surface (for comparison)", '6,400 km', '0 km', '85 minutes', '−62.6 MJ/kg']
SQL:

assistant: SELECT "altitude above the Earth's surface" FROM "Table" WHERE "specific orbital energy" = '−0.5 MJ/kg';