Solar Orbiter, a probe designed to observe the Sun in unprecedented detail, will be launched in October 2018, around 15 months later than planned, the European Space Agency (ESA) said Tuesday.

Postponement was decided "to ensure that all of the spacecraft's scientific goals will be achieved, with all the system's components adequately tested," it quoted Solar Orbiter's project manager Philippe Kletzkine as saying.

Solar Orbiter is designed to carry 10 instruments to within 43 million kilometres (almost 27 million miles) of the Sun -- closer than Mercury, the innermost planet.

The seven-year mission is designed to measure solar particles, fields and waves and map the Sun's 11-year cycle of sunspots and flares.

NASA is providing one of the probe's instruments as well as the launch, which will take place at Cape Canaveral, Florida, the ESA statement said.