Guide Star Tracking Statistics
We have compiled statistics on guide star tracking success covering
the period Jan-2001 through Dec-2005. This is an update to the
2003 report.
In this study we quickly look at the tracking success as a function of
magnitude and mission elapsed time (years).
The scatter plots below show the fraction of observation time
during which each guide star was not tracking. Each point represents a
unique star, where a random offset of +/- 1e-4 has been added for visual
clarity in the low end. The upper panel for each year shows the raw
fraction of time during an observation for which the camera reports not
tracking (Image function != 1). The lower panel shows the
fraction of time when the camera reports not tracking or when any of the
image status bits are set, indicating a condition such as ionizing
radiation or defective pixel. The lower panel corresponds to what the
OBC uses on-board to accept a star for Kalman processing.
Table of tracking results
The table below lists the fraction of stars (in percent) which were
not tracking (or having bad status) at least 5 percent of the time.
This is the treshold in the ground aspect pipeline above which a star
is declared bad.
| |
2001 |
2002 |
2003 |
2004 |
2005 |
| Tracking |
1.48
| 1.20
| 0.66
| 0.52
| 0.77
|
| Tracking or Status |
6.76
| 11.19
| 9.77
| 6.78
| 9.34
|
Interestingly, this indicator of tracking success improved between
2001 to 2003 and has been stable since then. This may be a consequence
of improved star selection via the SAUSAGE tool.
Magnitude dependence
The plot below shows the magnitude dependence of tracking success.
Analysis
The analysis scripts and data are in /proj/sot/ska/analysis/guide_success
Last modified:02/03/06
