Space weather effects on satellites
Space weather affects satellite missions in a variety of ways,
depending on the orbit and satellite function. Our society
increasingly depends on satellites for communication, navigation,
exploration and research. The impact of satellite system failures is
more far-reaching than ever before.
Energetic particles that originate from the sun and from the Earth's
magnetosphere continually impact the surfaces of spacecraft. Highly
energetic particles penetrate to electronic components, causing
bit-flips in a chain of electronic signals that can result in spurious
commands within the spacecraft or erroneous data from an instrument.
These spurious commands have caused major failures to satellite
systems, many of which could have been avoided had ground controllers
known in advance of impending particle hazards. Less energetic
particles contribute to a variety of spacecraft surface charging
problems, especially during periods of high geomagnetic activity. In
addition, energetic electrons responsible for deep dielectric
charging can degrade the useful lifetime of internal components.
Major geomagnetic storms result in heating and expansion of the
atmosphere, causing significant perturbations in satellite
trajectories. At times, these effects may be sufficiently severe as
to cause premature re-entry of orbiting objects, such as Skylab in
1979. It is important that satellite controllers be warned of
these changes and that accurate models are in place to realistically
account for the resulting atmospheric effects. The Space Shuttle is
also vulnerable to changes in atmospheric drag; re-entry
calculations for the orbiter are highly sensitive to atmospheric
density, and errors can threaten the safety of the vehicle and its
crew. (see NSWP)
Examples of satellite anomalies
Many satellites suffer operations anomalies and upsets:
AT&T lost contact with its Telstar 401 satellite early Saturday January 11, 1997.
Telesat lost both the C and Ku-bands on the satellite on March 26, 1996.
Intelsat 511 lost earth lock on October 7, 1995.
GOES-8, had attitude problems on February 14, 1995.
Anik E-1, Anik E-2, Intelsat, had attitude control electronics anomalies starting on January 20, 1994.