The HXT data is ``pre-stored'' in a buffer before being inserted into the telemetry. This pre-storage generally results in a 4.5 sec offset in the time saved in the index for high telemetry rate data, and 8.5 sec offset for medium telemetry data. See Figures 8 through 11 for a diagram of the timings. Unfortunately, not all programs correct for this offset when displaying the data. The user should look at the source code or send a message to the author asking for details.
HXT data are delayed by an additional 62.5 ms in the telemetry buffer in DP (see e.g. pp. 68-69 of the `Blue Book'). Suppose Tf is a time tag which is attached to a certain telemetry frame, then the corresponding time tag T0 for HXT is: T0 = Tf-62.5 ms. To be precise, labels T1 and T2 in the HXT timing Figure 8 through 11 correspond to T0, rather than Tf.
Figure 8: Timing of HXT data for Hi/Hi telemetry frames
Figure 9: Timing of HXT data for Med/Med telemetry frames
Figure 10: Timing of HXT data for Hi/Med telemetry frames
Figure 11: Timing of HXT data for Med/Hi telemetry frames
NOTE: T2 is not necessarily T2=T1+16.0 for the case of MED to HI telemetry
rate change. It is 16.0 sec only when a QUICK-HI
transition for invoking flare-mode does not take place at the boundary of
medium-bit rate major frames.
Even if T2=T1+16.0, there is a data gap between the end of MED major frame
and the beginning of HI major frame (i.e. T1+7.5 not equal to T
).