Overview
The star acquisition process for a normal observation on Chandra follows the sequence:- Maneuver in normal manuever mode to target attitude
- Acquire acquisition stars
- Acquire guide stars and fid lights
- Begin Kalman filter processing
In this report we show data on the time required for each star acquisition stage as well as the total time from the end of the manuever to the start of Kalman processing. The Kalman processing start time is used in CXCDS processing as the science observation start time and marks the point from which a level-1 aspect solution is generated.
The time for the acquisition stage appears to have a narrow Gaussian normal distribution centered on 35 seconds, with no instances greater than 60 seconds. In contrast the time for the guide and fid acquisition stage has a narrow peak around 25 seconds, but then a long tail extending out to 120 seconds. This tail is reflect in the histogram for the total time from end of maneuver to start of Kalman processing. In all cases this time is less than 160 seconds.
Data
The plots below show histograms of the time required for Acquisition, Guide/Fid, and Both (Acquisition + Guide/Fid). The histograms represent science observations covering the years 2000-2005 inclusive.
Analysis directory
The code and data for this analysis are in /proj/sot/ska/analysis/aca_star_acq_time
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Last modified:12/27/13