After a long and launchless six weeks, United Launch Alliance (ULA) has moved a step nearer to sending Europe’s Solar Orbiter on its multi-year voyage to study the Sun at closer range, in greater detail and from higher heliographic latitudes than ever before. The giant Atlas V booster assigned to the mission has wrapped up a smooth fueled (or “wet”) dress rehearsal (WDR) at Space Launch Complex (SLC)-41 at Cape Canaveral Air Force Station, Fla.
“NASA requires a WDR for missions with limited launch opportunities such as those to planets and the Sun,” says NASA. “WDRs allow us to test the rocket early in an effort to mitigate issues that could result in a missed opportunity for launch.”
The Wet Dress Rehearsal (WDR) was conducted primarily on account of the criticality of Solar Orbiter’s launch window. The spacecraft—which has been on the drawing boards at the European Space Agency (ESA) for more than two decades—will fly within 0.3 Astronomical Units (AU) of the Sun, a mere 26 million miles (42 million km), deep inside the orbit of the planet Mercury. Moreover, it will gradually adjust its trajectory to achieve heliographic latitudes as high as 34 degrees, allowing its fields and particles sensors and imaging instruments to directly observe the poles of the Sun as never before and examine fast-moving solar wind ions and coronal plasmas almost from their point of origin.