On 17 June 2013, ESA’s Herschel spacecraft burned up all of its remaining fuel. The mission ended a few minutes later, when the last command was sent to deactivate the systems forever. There was not enough time for the ground station to take measurements of the final orbit.
Astronomers from three observatories – Haleakala-Faulkes Telescope North (Hawaii), Kitt Peak (U.S.A.) and Siding Spring-Faulkes Telescope South (Australia) – observed the fading reflections from Herschel between 26 June and 1 July. Based on these observations, the flight dynamics experts at ESOC determined and predicted Herschel’s final orbit around our Sun.
In 14 years, on 13 October 2027, Herschel will pass by its home planet. It will approach the Earth at a predicted distance of 8 236 194 km. The effect of this encounter will be strong enough to change the period of Herschel’s orbit. After 2027, it will appear once every 15 years.