next up previous contents
Next: 5.1.2 Telemetry Format Up: 5.1 Ground Telemetry Processing Previous: 5.1 Ground Telemetry Processing

5.1.1 Introduction

During periods of contact between AXAF and the ground, data are telemetered to the Operations Control Center via NASA's Deep Space Network. Two distinct channels of data are sent simultaneously. One channel carries the real-time telemetry that is produced while the contact is ongoing. A second channel carries telemetry that was previously recorded onboard the satellite.

The OCC merges playback and real-time telemetry into a single, time-ordered stream which is known as Merged Telemetry. The OCC also performs operations to detect and correct (when possible) errors that were introduced by the communications channel from the satellite. The Merged Telemetry is then sent to the AXAF Science Center (ASC).

The ASC archives the telemetry and processes it to recover data from the science instruments. The ACIS science data are organized and formatted into a wide variety of data products for distribution to the scientific community and are also used in a number of calibration and operations activities within the ASC.

John Nousek