Herschel was carried into space on 14 May 2009, at 13:12:02 UTC, by an Ariane 5 ECA launcher, from the Guiana Space Centre, Kourou, French Guiana. Herschel was launched together with ESA's Planck spacecraft, in the launch configuration as depicted on the right. The two spacecraft separated within 30 minutes after launch and proceeded independently to different orbits about the second Lagrange point of the Sun-Earth system (L2).

The upper stage of the Ariane 5 ECA launcher injected first Herschel and then Planck into their individual transfer trajectories bound for L2. Upon separation, Herschel was three-axis stabilised.

After a journey lasting about sixty days, Herschel entered its operational orbit, a large Lissajous orbit around L2, 1.5 million km away from the Earth, on Earth's night-side.  The orbit has a period of about 178 days and an average amplitude of about 700 000 km around L2.

Right: Herschel (upper) and Planck (lower, covered by the SYLDA 5 support structure) in their dual launch configuration under the Ariane 5 ECA fairing.