February 7, 2014
ESA’s Swarm Mission To Study Earth’s Magnetic Field
[ Watch the Video: Swarm: An Orbit with a Difference ]
redOrbit Staff & Wire Reports - Your Universe OnlineThe European Space Agency (ESA) is in the midst of maneuvering their three Swarm mission satellites into position as the probes prepare to deliver what is being called the best survey of the Earth’s magnetic field to date.
The trio of satellites launched last November, and since then, engineers have been testing the probes’ systems and instruments to make sure that everything is in proper working order before their mission begins in earnest.
“This commissioning phase is an essential part of the mission before it starts providing data to further our understanding of the complex and constantly changing magnetic field,” ESA officials said on Thursday.
“Swarm is tasked with measuring and untangling the different magnetic signals that stem from Earth’s core, mantle, crust, oceans, ionosphere and magnetosphere,” the agency added. “The satellites may be identical, but to optimize sampling in space and time their orbits are different – a key aspect of the mission.”
Upon their launch, the three satellites were released into adjacent orbits at an altitude of approximately 490 kilometers. Two of them will remain extremely close to each other (roughly just 150 km apart as they pass over the equator). They will eventually descend to the 300 kilometer level during the course of the mission.
As those satellites dipped lower, they will become more sensitive for measuring smaller magnetic features in the Earth’s crust. The third satellite, on the other hand, will remain at a higher orbit and a slightly different inclination – 87.75 degrees (compared to 87.35 for the lower two), bringing it closer to the poles.
The orbits of the three satellites will drift, causing the upper one to cross the paths of the lower two at a 90-degree angle during this third year of the mission. Thanks to these drifting orbits, the probes will be able to capture all of the magnetic signals originating from Earth, as well as those caused by the sun.
This orbital configuration “will save satellite fuel at the beginning of the mission and offer a better return for science at a later stage,” the ESA said. The slow drift of the upper satellite in relation to the path of the other two will, after three years, save enough fuel in order to slow down the relative orbital drift, they added.
“The constellation originally planned meant a continuous drift between the upper and lower satellites,” explained Swarm mission scientist Roger Haagmans. “Since we can now slow the relative drift thanks to the current state of the Sun and its even lower activity expected in the next years, we can now obtain more regular observations of the changing magnetic field over time.”
System Engineer Ralf Bock noted that the team is currently “taking the satellites to their new heights through careful thrust and aim to achieve the constellation for science operations around mid-April,” and System Manager Karim Bouridah added that they were “also continuing to fine-tune the satellite sensors, such as the new electric field instrument.”
Each satellite contains a novel instrument to measure the direction, temperature and velocity of incoming ions, the ESA said. This data will be used to calculate the electric field around it – information that serves as an important counterpart to the magnetic field when it comes to studying processes in the planet’s upper atmosphere. The agency claims that Swarm is “the first mission to make these global, multipoint measurements.”