The Gravity Probe B experiment was carried out in collaboration between Stanford University, NASA, Lockheed Martin and KACST.
On 4 May 2011, NASA announced the long-awaited results of Gravity Probe (GP-B), and a month later the results appeared in Phys. After more than 47 years and 750 million dollars, GP-B had succeeded in measuring the general relativistic geodetic and frame-dragging effects on orbiting gyroscopes. In this focus issue, CQG publishes a set of refereed papers that provide the complete details of the experiment, from design of the spacecraft to the final data analysis, thus bringing to a close an extraordinary chapter in experimental gravitation.