Russia's Khrunichev space centre said that following an investigation the crash of the CryoSat satellite was not deemed to be attributable to the Rockot launch vehicle, which would no longer be grounded.

A statement confirmed that the cause was a failure by the command system to transmit a preliminary order for the second stage's engine to shut down.

CryoSat, designed to make very precise measurements of polar ice cap thicknesses, would have been a vital tool for environmental scientists at a time when ice at both poles seems to be shrinking.

European Space Agency official Pascal Gilles said immediately after the crash on October 8 that according to the Russians the second stage of the rocket had failed to separate.

"The second stage continued to burn after the onboard computer told it shut down. There was no separation between the second and third stages of the rocket, and the third failed to ignite. The whole thing ... fell into the Arctic Ocean," he said.

The Rockot launcher used in the mission is a converted Soviet-era SS-19 ballistic missile with an additional Breeze-KM upper stage.

All rights reserved. copyright 2018 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.