4.5 Data System

 

4.5.3 Format

 

Data is collected over cycles, or intervals of 10, 20, 40 or 80 spins of the S/C, corresponding to the 1024, 512, 256, and 128 bps rates of the S/C telemetry (data) channel. The LAN experiment outputs a 2560 byte data format during four consecutive S/C formats. This data format starts immediately following the 4-format pulse. The data format is shown in Figures 4.35, 4.36, and 4.37 (below; please scroll down). Spacecraft spins start synchronously relative to the data output format.

 

The data format will be identical during each telemetry mode. The telemetry mode is specified by the mode-ID lines from the S/C. During the fastest telemetry mode, the S/C accepts a complete data format in 128 seconds, and the experiment accumulates data over 10 spin periods. In the slowest telemetry mode, the complete data format is output in 8 x 128 - 1024 seconds, and the experiment accumulates data over 80 spin periods. The definition of the mode-ID lines is appended to Figure 4.37.

 

A typical input and output timing diagram is shown in Figure 4.38.

 

Figure 4.35 Science data format

 

 

640 bytes/format
2560 bytes/data format

 

Figure 4.36 EDR summary diagram. Click here for larger view (PDF file).

 

 

 

Figure 4.37 EDR summary list

 

 

 

Figure 4.38 Data input-output timing diagram

 

 

*Since these spins started before the cycle starting gate, data collection for the next cycle does not start until the spin begins.

 

 

Next: Chapter 4.5.4: Science Data Format