Giovanni Bignami, President of the Committee on Space Research (COSPAR), and COSPAR Bureau member, Lev Zelenyi, presented the Bremen scientist with the award during the opening event of the COSPAR space conference in Moscow on 4 August 2014.

Since 1990, the award has gone to junior researchers under 36 years of age for outstanding achievements in their particular disciplines. The medal is awarded in memory of astrophysicist Yakov B. Zeldovich. Rievers’ particular accomplishment: His investigation into the Pioneer anomaly, an observed deviation from predicted accelerations of the NASA Pioneer space probes 10 and 11.

Scientists had been puzzled by the Pioneer anomaly for a long time, and many thought it would be necessary to modify the theory of gravity because of it. Then, by means of a complex numerical investigation, Rievers was able to show that the probes’ deceleration was due to uneven thermal radiation. As result of temperature distribution and the shape of the probes, the thermal radiation emitted from the spacecraft was biased in the direction of flight, causing what is known as thermal recoil. This is what subsequently slows the spacecraft down. In the meantime, this finding has been corroborated by research teams in America and Portugal. Rievers had thus illustrated that the anomaly was indeed in keeping with the laws of physics and the established theory of gravity, putting an end to a heated controversial debate among scientists that had been going on for several years.

For further information on this topic, please contact:

University of Bremen:
Center of Applied Space Technology and Microgravity (ZARM)
ZARM Fallturm-Betriebsgesellschaft mbH
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