Enhanced timing accuracy for Cluster data

Abstract

Abstract. The standard timing accuracy for the Cluster mission is ±2 ms. However for inter-spacecraft comparisons of waveform data a much higher accuracy is needed – for example a timing error of 1 ms results in a phase error of 65° for a signal at 180 Hz. Most Cluster data are recorded on an onboard solid state recorder and time stamped using an onboard clock which is calibrated to UTC. Until recently, the error of this onboard clock was allowed to increase to the ±2 ms limit before a new calibration was applied. However, the timing error for real time data is estimated to be only ~11 μs, so these data may be used to prepare a time correction dataset which allows the standard timing accuracy to be improved considerably. This paper describes the details of the preparation and validation of this dataset. Two independent source datasets are used: telemetry to ESTRACK ground stations supporting the main operations of the Cluster spacecraft, and the real time telemetry to the NASA DSN stations supporting the Wide-Band Plasma Wave Investigation.