= Ulysses spacecraft
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The <Ulysses spacecraft> was a joint ESA–NASA solar probe launched on 6 October 1990 to investigate the space environment above and below the Sun's poles. A <gravity assist> at Jupiter on 8 February 1992 bent its trajectory into a strongly inclined <heliocentric orbit> around the Sun. It sampled southern polar regions in 1994 and northern polar regions in 1995, extending direct measurements far beyond the solar latitudes accessible near Earth's orbit.<Ulysses Mission Overview by NASA>[Key Dates and In Depth; Jupiter flyby and first polar passes]{ref}
The payload included instruments for <solar wind> particles, <magnetic fields>, energetic particles, radio and <plasma> waves, and dust. The central experiment was to change observing location: measurements near the solar equator alone cannot determine whether the same conditions persist over the poles. During the first southern pass, the instruments found faster <solar wind> than in equatorial regions.<Ulysses Mission Overview by NASA>[Scientific Instruments and first southern polar pass]{ref}
Its observations also provided a test of the <energy cascade> in <magnetohydrodynamic turbulence>. Investigators combined <velocity> and <magnetic field> fluctuations into <Elsässer variables> and measured how mixed third-order statistics varied with separation. The 2007 analysis used selected intervals of high-speed polar wind from the first seven months of 1996. This illustrates how a mission designed for a new vantage point can later support a precise statistical experiment, with assumptions about translating measurement times into spatial separations.<Observation of inertial energy cascade in interplanetary space plasma by Luca Sorriso-Valvo and others>[analysis of Ulysses polar-wind time series and equation3]{ref}
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