JWST Pointing Performance

JWST's pointing performance for slewing accuracy and pointing stability, based on actual performance, is covered in this article.

On this page

See also: JWST Slew Times and Overheads

JWST's pointing accuracy, target tracking capability, and pointing stability are all the result of complex interactions between the observatory's hardware performance and flight software. Pointing performance results from the interactions between star trackers, gyroscopes, reaction wheels, fine sun sensors, the fine steering mirror, the fine guidance sensors, multiple target acquisition modes (for different science instruments), flight software (both spacecraft and science instruments), ground software, guide star selection, and observation scheduling details. In addition, the MIRI Cryocooler and High Gain Antenna movement can induce jitter. The spacecraft's attitude control system (ACS) controls the pointing and slewing of the JWST observatory. The Fine Guiding System works with the science instruments for the final location and tracking of science targets. This page summarizes the actual pointing performance. 

Please also see these related pages:

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On-orbit performance

To date, trending of the guide star acquisition success rates shows that about 0.02% of all visits fail to acquire science due to issues related to the JWST attitude control system (ACS). The causes of guide star acquisition failures range from large (>10”) ACS initial coarse pointing errors, unmasked bad pixels on the FGS detector in the vicinity of faint (FGS_Mag > 17) guide stars, GSC catalog errors, such as surprise binaries, compact galaxies, unresolved spoilers that FGS resolves. Note that most catalog errors generally will not cause loss of science if more than one guide star candidate is available for the visit (presented with a guide star acquisition failure, OSS commands an attempt on the next candidate).


References

Gardner, J. P. et al. 2006, Space Sci.Rev., 123, 485 
The James Webb Space Telescope

Hartig, G. F., & Lallo, M. 2022, JWST-STScI-008271 
JWST Line-of-Sight Jitter Measurement during Commissioning 



Notable updates
  •  
    Article underwent major reorganization. Content was updated and moved to child articles.

  •  removed warning banner about IFU astrometric offset.

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    Updated with information for on-orbit performance from commissioning and early operations.

  •  
    In "Definitions and Units," conversion between 1-σ uncertainty per axis and 1-σ radial uncertainty corrected for Rayleigh criterion.


  • Added radial uncertainties.
Originally published