Timing and Record Subsystem

The Record/Timing Sub-System is responsible for recording all data that is received and processed by the other sub-systems on the Advanced Range Instrumentation Aircraft. These signals consist of Pre-D and Post-D Data as well as multiplexed signal strength, voice, and IRIG time codes. These signals are recorded on two Racal Storehorse Double-Density recorders.

The Racal Storehorse DD-4 is a 14-track analog recorder that is capable of recording up to a 4 Mhz data rate. The recorder is also self-calibrating and is remotely controlled by a 90 Mhz Pentium computer via a General Purpose Interface Bus. Two of these recorders are used simultaneously for orbital ops for redundancy reasons and sequentially during longer cruise missile ops.

Slow changing data such as voice, timing, and signal strength data is multiplexed in two 24 channel data multiplexers. These multiplexers act as "mixers" not unlike mixers in a typical recording studio. These 24 signals are recorded on a single track of the Storehorse DD-4 recorder.

The Record/Timing sub-system also generates all of the timing that is used throughout the aircraft. These timing signals are recorded on the Storehorse recorders along with the data to "time tag" the data that the aircraft is receiving. These signals are also real-time transmitted to ground stations on cruise-missile ops for range timing synchronization. All of the other sub-systems in the aircraft also use the timing signals to drive their individual time displays that supply both GMT as well as countdown-time.

Timing is received through two GPS satellite receivers in the T/R section. These receivers are capable of tracking six satellites at a time and using four of the satellites for both positioning and timing information. The GPS satellites are spaced so that there is a minimum of five satellites in view at any one time anywhere in the world. During flight, these timing signals are accurate to within 1.5 microseconds in relation to Greenwich Mean Time which is the accepted timing standard of the world.

The Record/Timing shop is responsible for the maintenance and operational checkout of all the equipment in the Record/Timing Subsystem. Maintenance is carried out down to component level with no outside support of any sub-contracted maintenance facility.

The shop is also responsible for maintaining the ARIA Central Timing Station that consists of three cesium atomic clocks, four rubidium atomic clocks, and a GPS receiver. The shops timing station is fully autonomous and independent of any outside calibration due to the highly accurate cesium atomic clocks. These clocks have a drift rate of less than .000000000001 seconds in a year.

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