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Images from two spacecraft and VAULT sounding rocket (rectangular inset) on June 14, 2002. Credit: NASA/ESA/LMSAL/NRL
Click on image for an animation
The images captured by the Very high Angular resolution ULtraviolet Telescope (VAULT for short) were about three times better than the previous-best pictures from space. A few ground-based telescopes can observe the Sun in similar increments as VAULT, but only at visible wavelengths of light. UV and X-ray wavelength observations are most directly related to the science of space weather.
Since most space weather originates as explosions of the electrified gas (plasma) in the corona, understanding the heating and magnetic activity of the coronal plasmas will lead to better predictions of space weather events. Severe events, like solar flares and coronal mass ejections, can disrupt satellites and power grids, affecting life on Earth.
Zoom shows an active area of the Sun's chromosphere taken by VAULT. Credit: NASA/NRL
Scientists have been surprised by other observations from VAULT. For example, they found that a large number of structures in the pictures change rapidly from one image to the next, only 17 seconds later. It was previously thought that these changes occurred over five minutes or more. Also spotted: features in the chromosphere that match those seen in images from the TRACE spacecraft taken at the same time. The comparison shows that these two layers have much higher correlation than previously thought and implies that similar physical processes heat both. However, theory predicts the activity in the chromosphere should be lower than what scientists observed in the VAULT emissions.
VAULT also revealed unexpected structures in quiet areas of the Sun. The plasma and magnetic field bubble up like boiling water on the Sun's visible surface (photosphere), and, like bubbles gathering and forming a ring at the edge of a pot, the field builds up in rings (network cells) in the quiet areas. VAULT captured images of smaller features and significant activity within the network cells, surprising scientists.
Zoom shows a quiet region of the Sun's chromosphere seen by VAULT. Credit: NASA/NRL
The telescope took 21 images in the Lyman-alpha wavelength of the electromagnetic spectrum during a six-minute-nine-second picture-taking window on its 15-minute flight. Offering the brightest solar emissions, the Lyman-alpha wavelength assured the best likelihood for pictures from the rocket and allowed for shorter exposure times and more pictures. An increase in Lyman-alpha radiation may indicate an increase in solar radiation reaching Earth.
The VAULT payload consists of a 30-centimeter (11.8-inch) Cassegrain telescope with a dedicated Lyman-alpha spectroheliograph focusing images onto a charge-coupled device (CCD) camera. The CCD, also employed in consumer digital cameras, has a photosensitivity 320 times greater than photographic film previously used. The Normal Incidence X-ray Telescope (NIXT) from the Harvard-Smithsonian Center for Astrophysics took the previous best-resolution pictures of the Sun from space in September 1989, also aboard a sounding rocket.
The scientists verified the payload performance with an engineering flight from White Sands Missile Range, N.M., May 7, 1999. The June 14, 2002, flight from White Sands was the first scientific flight of the payload. The NRL team led a campaign combining observations from satellites and ground-based instruments. Scientists plan a third launch in Summer 2004. The mission was conducted through NASA's Sounding Rocket Program.
Related Links
Original Story with Additional Materials
Electromagnetic Spectrum Tutorial
Electromagnetic Spectrum - Advanced
VAULT Project Web Site
NASA Sounding Rocket Program
NASA Goddard Space Flight Center