The eighth
Keplerian orbital element, specifying the deceleration, (in revolutions per day per day) experienced by
low earth orbiting satellites, due to the slowing effect of the upper atmosphere. Drag is measured at the
epoch. Expression varies from format to formats. Negative values can indicate
tidal forces on higher satellites or observational error. A high drag, (> 10
-4) indicates the need for frequent observation.
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