XMM will be in a highly elliptical orbit to keep it away from interference caused by the Sun's glare. The telescope's large size and unusual orbit explains why XMM was launched from Ariane 5, which is the largest heavy-lift vehicle currently in service. XMM consists of three advanced X-ray telescopes. They each contain 58 high-precision concentric mirrors. Each set of mirrors are designed to catch X-rays at different energy levels. The observatory is expected to remain in orbit for at least two years although a longer, extended mission is planned if fuel reserves do not become exhausted.