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The Sun is intimately connected with the origins and fate of life on Earth. Without it, Earth would be a frozen, lifeless planet drifting aimlessly in space. There would be no fossil fuels, nor would plants be able to prepare photosynthesis. Sunlight is very significant in enabling and sustaining life.
Although we have a basic understanding of the Sun’s advantages, it is also important to comprehend the changing Sun and its effect on the Solar System and Earth’s atmosphere, life and society. While it enables and sustains life, the Sun’s unpredictability can produce radiations and high-energy particles that can affect life adversely. This is because of its hot and uncontrolled atmosphere called the “corona". The corona extends to Earth and beyond as the solar wind.
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Understanding “Space Weather"
It will be interesting to note that “weather" also occurs in space and the Sun’s atmosphere is responsible for it. The Sun emits a constant stream of ionized gas called the solar wind and releases billion-ton coronal mass. Every planet, asteroid and comet in the solar system is exposed to these immense clouds of materials. When it reaches Earth’s atmosphere, it can cause large magnetic storms in the magnetosphere and the upper atmosphere.
The Sun’s “weather" systems can influence the reliable technological systems on Earth and in space and can endanger human health and life. Thankfully, Earth has a thick atmosphere and global magnetic field to avoid any adverse effects. However, active artificial satellites that circle Earth can be vulnerable to space weather. Future astronauts travelling to Mars will be in direct contact with the Sun’s atmosphere leading to sporadic radiation to astronauts and potential damage to the spacecraft. Moreover, there can be interference in the navigational and GPS systems and high-altitude aircrafts can also be exposed to radiation.
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NASA Living With a Star Program: Objectives and Missions
NASA formed Living With a Star Program (LWS) in 2001 to deal with the adverse effects of the Sun’s atmosphere. Managed by the Heliophysics Division of NASA’s Science Mission Directorate, the LWS is a cross-cutting scientific program with goals and objectives significant to NASA’s Strategic Enterprises and Exploration Initiatives.
Through the LWS program NASA will launch a fleet of ‘Weather Stations’ to observe the different aspects of the sun’s atmosphere. The Living With a Star program has some significant missions in various stages of development. These missions will explore the sun and provide an in-depth view of its atmosphere. An explanation of these missions is as follows:
1. The Solar Dynamics Observatory (SDO):
It is scheduled for launch around December 2008. The SDO will be able to reveal detailed maps of the ‘invisible strings’ or magnetic fields that penetrate the Sun’s atmosphere. Its onboard camera will be able to take HDTV quality images of solar flares and sunspots. It will also probe the interior of the Sun by monitoring the Sun’s vibrating surface. This will enable them to map the flow of the Sun’s inner magnetic dynamo, the root cause of the invisible strings and other solar activity.
2. Solar Probe Mission:
The Solar Probe Mission will explore the interaction of the Earth and Sun, which affects human activity. Currently under study, the solar probe will determine the physical processes that accelerate the solar wind and heat the corona by combining remote-sensing and sampling from within the solar corona itself.
3. Radiation Belt Storm Probes (RBPS):
Earth’s radiation belts contain energetic ions and electrons which is hazardous to both astronauts and spacecraft. The Radiation Belt Storm Probes, part of the LWS Geospace program, will determine the source and transport processes governing the radiation belts. The observations derived from the radiation belts will help in the future development of physics-based and empirical models for the radiation belts.
The empirical models will allow scientists and engineers to design a spacecraft that is immune to radiation. The physics-based models will be a great help in forecasting the geomagnetic storms to alert the spacecraft and astronauts of any potential radiation hazards. The RBSP is scheduled for launch in 2011.
4. Sentinels Mission:
The initial objective of the NASA Living With a Star Solar Sentinels mission is to discover and understand the connection between the solar phenomena and disturbances in the interplanetary systems. The Solar Sentinels will provide a multi-sided view of the solar activity. The mission will consist of three advanced probes from NASA and a Solar Orbiter from the ESA. The probes will station themselves around the sun’s equator and study the solar climate and weather. The expected launch is scheduled in 2015.
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NASA Living With a Star Program will improve the understanding of terrestrial climate change and the changes in the Sun’s atmosphere. It will provide scientific data required for advance systems that can warn of any kind of energetic particle events affecting future spacecrafts, satellites and humans.