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Space Surveillance and Tracking Services

The Space Age has generated a huge number of man-made hazards to complement the naturally occurring ones. Space Weather can and does directly affect these objects, thus compounding the risks they pose and making them less predictable and harder to follow. Orbiting hardware can take a long time to decay and if present launch rates persist then certain orbital regimes will soon start to become highly congested further increasing the risk of collision.

 ▶  Atmospheric estimates for drag calculations Estimates of atmospheric density in the past years and predicted in near real-time.
 ▶  Archive of geomagnetic and solar indices for drag calculation Database of past values of solar and geomagnetic indices relevant to drag calculation
 ▶  Forecast of geomagnetic and solar indices for drag calculation Provides forecast of geomagnetic and solar induces for drag calculation.
 ▶  Nowcast of ionospheric group delay Under development.

Space Surveillance and Tracking Background

Geospace is populated by millions of man-made objects in Earth orbit of which more than 13,000 with size >10 cm are regularly tracked. The majority comprises launcher bodies and other mission-related objects and fragments, and only about 10% are active satellites. Earth-orbiting objects constitute a possible threat, in space (collisions, adverse actions on space systems) and on ground (uncontrolled and high-risk re-entry).

Tracking involves detection of objects in space and determination of orbit state and covariance (uncertainty). An important operational issue concerns forecasting of the trajectories of decaying objects that eventually enter the lower and denser atmospheric layers. The object trajectory change depends on the thermosphere density at its precise location, i.e. on altitude, latitude, and longitude, all of which appear rapidly changing during the re-entry process. Consequently, the requirement to take risk reduction measures to avoid re-entry over populated areas requires accurate 3-D modelling of the thermosphere and 3-D forecasting of the object trajectory in the geographic sector concerned.

Modelling thermospheric density for the purpose of drag calculation is an important part of the SST domain. This requires reliable space weather real-time and archive data. Space Weather nowcast and forecast of key parameters include the solar EUV radiation deposition and the level of Joule heating by ionospheric currents.

Artist's impression of the debris objects in orbit around Earth. (© ESA - P. Carril)

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