SAN FRANCISCO — NASA’s Solar Dynamics Observatory (SDO), an $848 million mission designed to offer an unprecedented level of data and imagery to scientists grappling to understand the sun and its magnetic field, is slated for launch Feb. 9 on a United Launch Alliance Atlas 5 rocket.
“SDO is the cornerstone, the foundation mission for the next decade of solar research,” Richard Fisher, Heliophysics Division director at NASA headquarters in Washington, said during a Jan. 21 briefing.
In addition to helping researchers investigate the complex processes inside the sun, the SDO mission holds the promise of economic benefit because it will lead to better prediction of solar activity that interferes with satellite operations, high-frequency radio transmissions, GPS navigation and power grids, said MadhulikaGuhathakurta, NASA headquarters program scientist for SDO and Living with a Star, the agency’s overarching campaign to understand the sun and its impact on the near-Earth space environment. SDO is the flagship mission in the Living with a Star program.
“The sun affects our life more and more as we come to depend more and more on technology,” said Dean Pesnell, SDO project scientist from NASA’s Goddard Space Flight Center in Greenbelt, Md. “Most of the effects come from the ever-changing magnetic field of the sun. SDO is designed to study that magnetic field from its creation to its destruction and how it then can affect the Earth.”
While many international missions have aided scientists studying the sun, SDO is unique because of the depth and breadth of information it will obtain, Guhathakurta said. During its scheduled five-year mission, SDO is expected to capture images of the sun continuously, sending approximately 1.5 terabytes of data to Earth every day. “SDO will observe the sun in greater detail than any previous observation, breaking barriers of time, scale and clarity that have long blocked progress in solar physics,” she added.
SDO will employ three suites of instruments to monitor solar activity: the Atmospheric Imaging Assembly (AIA) built by Lockheed Martin Solar and Astrophysics Laboratory in Palo Alto, Calif.; the Helioseismic and Magnetic Imager from Stanford University in Palo Alto, Calif.; and the Extreme Ultraviolet Variability Experiment built by the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder.
AIA is a telescope designed to obtain imagery of the sun’s atmosphere at a much higher resolution than current space-based instruments. In contrast to the Solar and Heliophysics Observatory, a cooperative NASA-European Space Agency mission launched in 1995 that relies on a detector with an array of 1,000 by 1,000 pixels, AIA will offer imagery of 4,000 by 4,000 pixels. That increase will allow scientists to see much smaller features in every image, Pesnell said. In addition, AIA will offer more imagery, taking pictures every 1.25 seconds compared with NASA’s Solar Terrestrial Relations Observatory, launched in 2006, which takes pictures every three minutes.
“The most significant change is that we will be sending down so many more images of the sun,” Pesnell said. “AIA was designed to offer high-resolution imagery of the entire sun, allowing us to zoom in on any part without forcing us to sacrifice our ability to look at all parts of the sun.”
The Helioseismic and Magnetic Imager will help scientists track the movement of materials inside the sun by measuring sound waves. It also will provide information on the strength and direction of the sun’s magnetic field, whereas previous space-based instruments measured only the field’s strength, Pesnell said. “Scientists feel that knowing the direction of the field will help us make better predictions of when flares and coronal mass ejections will occur,” he added.
The Extreme Ultraviolet Variability Experiment will provide detailed data on the sun’s energetic particles that warm the Earth’s upper atmosphere and create its ionosphere. The sensor will make measurements at 10-second intervals, in contrast to a comparable sensor aboard NASA’s Thermosphere Ionosphere Mesosphere Energetics and Dynamics mission that takes daily measurements of the extreme ultraviolet irradiance, Pesnell said. “We learned that we need a higher time cadence,” he said.
After launch, the SDO spacecraft will spend approximately three to four weeks moving into an inclined geosynchronous orbit that will enable the 3,000-kilogram spacecraft to focus on the sun continuously while maintaining contact with a dedicated ground station, said Elizabeth Citrin, SDO project manager at Goddard, the NASA center overseeing the mission. After that, NASA officials plan to spend roughly four weeks testing SDO’s instruments to ensure they are functioning well in space. “About 60 days after launch we expect to be able to release science data,” Pesnell said.
SDO, which originally was scheduled to launch in August 2008, encountered minor delays due to difficulty manufacturing spacecraft subcomponents, which moved the launch date to December 2008. That launch was then delayed for more than a year as NASA struggled to find a slot on the U.S. Air Force’s Evolved Expendable Launch Vehicle manifest.
