NASA's Heliophysics Observatories Study the Sun and Geospace
Released on December 15, 2008
Heliophysics is a term to describe the study of the Sun, its atmosphere or the heliosphere, and the planets within it as a system. As a result, it encompasses the study of planetary atmospheres and their magnetic environment, or magnetospheres. These environments are important in the study of space weather.
As a society dependent on technology, both in everyday life, and as part of our economic growth, space weather becomes increasingly important. Changes in space weather, either by solar events or geomagnetic events, can disrupt and even damage power grids and satellite communications. Space weather events can also generate x-rays and gamma-rays, as well as particle radiations, that can jeopardize the lives of astronauts living and working in space.
This visualization tours the regions of near-Earth orbit; the Earth's magnetosphere, sometimes called geospace; the region between the Earth and the Sun; and finally out beyond Pluto, where Voyager 1 and 2 are exploring the boundary between the Sun and the rest of our Milky Way galaxy. Along the way, we see these regions patrolled by a fleet of satellites that make up NASA's Heliophysics Observatory Telescopes. Many of these spacecraft do not take images in the conventional sense but record fields, particle energies and fluxes in situ. Many of these missions are operated in conjunction with international partners, such as the European Space Agency (ESA) and the Japanese Space Agency (JAXA).
The Earth and distances are to scale. Larger objects are used to represent the satellites and other planets for clarity.
Here are the spacecraft featured in this movie:
Hinode: Observes the Sun in multiple wavelengths up to x-rays. SVS page
The L1 point is a Lagrange Point between the Sun and the Earth. Spacecraft can orbit this location for continuous coverage of the Sun.
SOHO: Studies the Sun with cameras and a multitude of other instruments. SVS page
ACE: Measures the composition and characteristics of the solar wind.
Wind: Measures particle flows and fields in the solar wind.
STEREO-A and B: These two satellites observe the Sun, with imagers and particle detectors, off the Earth-Sun line, providing a 3-D view of solar activity. SVS page
Voyager 1 and 2: These spacecraft conducted the original 'Planetary Grand Tour' of the solar system in the 1970s and 1980s. They have now travelled further than any human-built spacecraft and are still returning measurements of the interplanetary medium. SVS page
As we approach the Earth, we get a wide view of the spacecraft located at L1 as well as the Earth nestled within the magnetosphere. The magnetosphere forms due to the interaction of the Earth's geomagnetic field with the plasma of the solar wind. Solar wind pressure drags the magnetosphere back from the Earth, away from the Sun, much like a 'wind sock'. For convenience, arrows remind us of the direction of the Sun (yellow) and the direction that the Earth travels along its orbit (blue).
We fly throught the boundary of the magnetosphere for a closeup view of the Earth (note that the clouds are changing, updating based on weather satellite imagery from this time). We also see the orbits of heliofleet satellites that occupy near-Earth orbit. Here, the fleet include not only Earth-observing missions like TIMED and FAST, but solar observatories as well: TRACE, RHESSI, and Hinode.
Passing back through the boundary of the magnetosphere, we can now see the satellites, Geotail and Cluster, that patrol this region measuring the particles and fields. Cluster (actually Cluster II), is a group of four identical satellites that fly in formation through this region.
As we continue our pull-out, we see the two STEREO satellites, STEREO-A and B, shortly after launch, while still in their post-launch phasing orbit which travels from the Earth to the orbit of the Moon.
The spacecraft STEREO-A and B make their first lunar flyby, using the Moon for a gravity-assist. For STEREO-A, the flyby transfers enough momentum to send the satellite into a solar orbit, slightly closer to the Sun than the Earth. From this orbit, STEREO-A becomes STEREO-Ahead as it begins to move ahead relative to the Earth in its orbit.
The Moon completes another orbit before it encounters STEREO-B for its second lunar flyby. This encounter sends STEREO-B into an orbit further from the Sun than the Earth, where STEREO-B will become STEREO-Behind as it drops behind the Earth in relative position along its orbit.
Now we take a spin around the L1 point, observing SOHO, ACE, and Wind as they execute their trajectories around this location. Because L1 is actually an unstable point, the spacecraft need occasional trim maneuvers to maintain their location. We speed up time as we orbit, also noting that the L1 point seems to execute small oscillations in the yellow Earth-Sun marker. These oscillations are due to the gravitational tug of the Moon as it orbits the Earth. After spending over a year at L1, we return to the Earth to see what is new...
Returning to the geospace around the Earth, we see a new mission has come on the scene - THEMIS, with five identical spacecraft, travel in a series of aligned elliptical orbits to sample the Earth's magnetotail at different distances.
We see the changes in the trajectories of the Voyagers as they cross the orbits of the giant planets Jupiter and Saturn. With the Saturn encounter, Voyager 1 is sent out of the plane of the Solar System, called the Ecliptic.
Voyager 2 continued in the Ecliptic, making historic flybys of the planets Uranus and Neptune, The Neptune flyby is used to direct Voyager 2 below the Ecliptic, enabling it to explore a different region than Voyager 1.
The heliopause and the bowshock are the two remaining 'surfaces' for the Voyagers to cross, the regions defined by characteristics of the solar wind's interaction with the interstellar medium. The transmitters on the Voyagers are expected to still be operating when they cross the heliopause, estimated to be around 2015.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 188.8.131.52.0