The objective of NADIR is to significantly advance understanding of drag forces on
satellites, including density, winds, and factors affecting the drag coefficient. We seek a level of understanding that will enable specification and
prediction at the “next level” of performance.
The specific goals are
to:
-
Understand the physical processes driving the
variability of neutral atmospheric density
-
Determine the relationship between neutral density
structure and satellite drag
-
Improve
forecasts of the drivers of the system including wave
activity from the middle and lower atmosphere,
geomagnetic/magnetospheric forcing, and solar EUV
-
Provide
the information to improve empirical models of neutral
density
-
Determine the most valuable dataset required to specify
and forecast the system state
-
Improve
estimates of drag in the re-entry regime (100-200 km)
NORAD
has the responsibility for keeping track of objects that are in orbit around the
Earth down to a certain critical size. Following major magnetic storm activity,
the atmosphere heats and expands, exerting an increased drag on satellites, and
changing their orbits. NORAD has to re-identify hundreds of objects and record
their new orbits after a large magnetic storm event. This figure shows the
number of satellites lost in connection with the March 13-14, 1989 storm. During
this event, for example, the SMM (Solar Maximum Mission) spacecraft was reported
to have "dropped as if it hit a brick wall" due to the increased atmospheric
drag. (Image courtesy of Air Force Space Command)
