Image Jitter and Attitude

3 April 1995

GOES-8 Image Navigation and Registration (INR) requirements are tough.

GOES-8 images bounce around whenever NOAA-NESDIS commands an "attitude adjustment" (pointing correction), which come in two types:

The daily reset at 1835 UTC is approximately local noon, sub-satellite time. Consequently, users experience a substantial jump in the apparent position of the Earth in the middle of a midday animation.

A SSAA is invoked when the positions of landmarks within the routine image schedule drift too far from their nominal positions. SSAAs normally take place a few times per day, but not predictably. NESDIS currently uploads SSAAs without warning, ans is considering a regular schedule.

Consequently, large jumps in image location are due to abrupt "fixes" to the image navigation system, not to actual spacecraft motion.