Space-walking astronauts last night successfully retrieved the malfunctioning Spartan solar-observing spacecraft, which was supposed to study the sun's outer atmosphere in tandem with another satellite. NASA managers say they might still redeploy the reusable craft--which apparently failed after being released from the Space Shuttle Columbia on 21 November--but a truncated mission will probably not resume before 1 December.
If Spartan gets a second chance on this shuttle flight, its 2-day stint would be cut to between 5 and 15 hours. But even that limited time will be welcome, says astrophysicist Madhulika Guhathakurta of the Catholic University of America in Washington, D.C. and Goddard Space Flight Center in Greenbelt, Maryland. This would be the fourth Spartan flight with a pair of instruments for observing the solar corona--the sun's active outer layers.
Both instruments create artificial eclipses in order to examine the corona. One of them, the White Light Coronagraph (WLC), makes detailed images, while the Ultraviolet Coronal Spectrometer can precisely measure part of the ultraviolet spectrum produced by hydrogen. Together, the instruments reveal the corona's temperature and density, and the velocities of electrons and protons churning within it. Solar scientists hope to learn more about the processes that heat the corona and accelerate subatomic particles toward Earth. This solar wind periodically erupts into huge coronal mass ejections, which can disrupt satellites, communications, and power grids on Earth.
Guhathakurta, a project scientist working on the WLC, notes that the sun's 11-year cycle of magnetic activity is quickly gathering strength and is already stirring up the corona. "We don't want to miss out" on this part of the cycle, she says, because the sun is likely to look quite different by the next launch opportunity, which could be a few years away.
The mission was also supposed to recalibrate similar instruments on board the Solar and Heliospheric Observatory (SOHO) spacecraft, a satellite launched almost 2 years ago. Spartan's instruments were just checked out in the lab, so mission scientists hope that their few hours might let them see "how much of the variation [previously observed between SOHO and Spartan] is due to the sun and how much is due to the instruments," says SOHO project scientist Art Poland, of Goddard. If Spartan is redeployed, the calibration would still be possible, but would not be as precise as was originally planned. Goddard's Richard Fisher, the principal investigator for the WLC, is not dwelling on the possible loss: "The wonderful thing about using a reusable spacecraft is that you get another chance."