SPACE SYSTEMS USER PERSPECTIVE ON SPACE WEATHER DATA PRODUCTS

David Chenette, Lockheed Martin Space Systems Company Advanced Technology Center


Lockheed Martin and its customers rely on high-quality space weather data products from the NOAA/NWS Space Weather Prediction Center to help manage the risks of a variety of critical, high-value activities. These include go/no-go criteria in launches, planning of on-orbit operations (including radiation protection), and support of post-anomaly investigations, which are essential to our product improvement process.

Our customers accept launch delays due to poor terrestrial weather, so launch vehicles need not be designed to operate reliably through tornados or hurricanes, for example. Similarly, significant cost efficiencies are realized by not designing launch vehicles for assured performance in unusually hazardous space weather conditions. Managing the risk of the resultant vulnerability requires that launch decisions take into account the space weather conditions expected during the launch and early on-orbit operations. Because the Sun is a significant and impulsive source of high-energy radiation that can disrupt electronics, near-real-time measurements and accurate short-term predictions of solar activity are essential to maintaining the high reliability of launch systems. Predictions of an hour to several hours in advance are required, depending on the mission.

Beyond the initial launch, other on-orbit operations may be susceptible to unusual or extreme space weather conditions. For example, some communications satellites at geosynchronous orbit are more sensitive to the effects of spacecraft charging during orbit maintenance operations than during normal operations. Planning these operations to avoid this susceptibility requires predicting the level of geomagnetic activity from several days to a week in advance. Real-time monitors of geomagnetic activity and predictions for up to a day in advance are required during the actual operations.

Forecasts and knowledge of high-energy solar activity also are critical to radiation safety in manned space operations. The amount of radiation shielding provided by a space suit during extravehicular activity, for example, is significantly less than the maximum shielding that can be provided by a spacecraft. Systems in low Earth orbit are shielded from high-energy solar radiation by Earth and its magnetic field, but for high-inclination orbits, depending on the longitude of the orbit ascending node, Earth’s magnetic shielding is not effective, and systems and people can be exposed to radiation at dose rates that are thousands of times higher than average. Also, the shielding effect of Earth’s magnetic field does not extend to the Moon; and for flights to Mars humans could be susceptible to solar events on the far side of the Sun, which are not visible from Earth.

Accurate predictions of major solar events are required to protect man and space systems against the radiation risks posed by major solar flare events. Today we can identify active regions that are likely to produce large solar particle events, and we can classify events and predict expected radiation levels after they occur, but we do not have sufficient data and understanding to predict the timing of these events. Improvements are required both in understanding the precursors to major solar events and in the type and resolution of the data necessary to reveal the signatures of those precursors.

Finally, Lockheed Martin depends on comprehensive space weather data products to support post-anomaly investigations. Detailed data are required to describe the space weather conditions at the time and location of any anomaly to assess whether or not the anomaly was related to those conditions. In cases where a causal relationship can be identified, the results are used to improve the design, to modify the implementation of the design, or to modify operations to protect against future occurrences.

Comments on Data and Predictions

The data now provided from the combination of POES and GOES space weather sensors provide excellent real-time monitors of space weather conditions at low Earth orbit and at geosynchronous orbit, and together they can be used to estimate conditions at intermediate altitudes. These data also monitor solar energetic particle radiation intensity near Earth and the extent to which this radiation penetrates into the magnetosphere. They do not support predictions of space weather events, beyond extrapolations that can describe the evolution of a space weather event after it has occurred.

Real predictions depend on measurements of the Sun and the solar wind. The state of the art of these predic-



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