Telemetry data captured during operation of the ground station must often be archived for post acquisition analysis and to satisfy legal requirements that the vehicle under test was properly certified.

Typically, data is stored immediately in the ground system, as close to the received signal as possible (expensive instrumentation recorders store the PCM signal immediately after bit synchronization). Data is also archived to disk after decommutation and/or processing and is then backed up to inexpensive cartridge tape (e.g., DAT, 8mm, DLT). Selected measurands and processed parameters or the entire PCM frame can also be archived.

Current single disk technology permits storing an entire continuous 40 Mbps PCM stream for only 3 hours, and less if measurand and time tags are required. Archiving time may be extended by storing only time segments or reducing the number of measurands, i.e, data compression (see real-time processing). Conversely, if archival of EU-converted and processed data is required, storage requirements increase and archiving bandwidth may not be adequate. Bandwidth and volume size may be increased by recording to multiple disks in parallel (RAID subsystems). Single UltraSCSI disks achieve 10 MB/sec continuously over their entire 72 GB capacity, while an UltraSCSI RAID can archive rates approaching 40 MB/sec and 80 MB/sec for Fibre Channel. Archiving directly to commodity tape drives is limited to a few MB/sec and up to 15 MB/sec for expensive proprietary architectures. The system design using real-time tape must incorporate large buffers to accommodate the time required for the drive to reach operating speed.

Archiving the time of acquisition with data consume a large segment of both storage space and bandwidth. One extreme tags each measurement with either a minor time (least significant portion), only placing the entire time record periodically (once per telemetry frame). A more economic solution for synchronously acquired data is to insert time periodically; for example, at the end of each frame or block. The time associated with the acquisition of a particular measurement can be interpolated from its position in the telemetry frame. Storing aperiodic data requires time-tagging. Data playback from disk offers a challenge since measurements must be continuously metered to recreate continuous or real-time displays on workstations or strip charts.

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