The orbiting Einstein Observatory has returned to full-time scientific operation after an onboard gyro that failed last August inexplicably came back to life, according to controllers at the Goddard Space Flight Center, Greenbelt, Md. First indications of maneuvering problems in the X ray observing satellite were noted last August, limiting the observatory's scientific investigations. During the following 6 weeks, ground controllers modified radio command instructions to the spacecraft, allowing them to bypass the troubled gyro and continue operations with the two remaining gyros. Since mid-October, controllers had attempted repeatedly to reactivate the faulty gyro by sending literally thousands of radio commands to the ailing subsystem, with no effect.