Today the Cassini spacecraft made a close approach and dive through the plume of icy spray from Enceladus, Saturn’s sixth largest moon. What surprised me was the low altitude flyby: just 48km from the moon’s surface.
OK, by aircraft standard a 48km altitude is still way up there as commercial aircraft operate at an altitude of 10km, and even the famed U2 and SR-71 spy planes designed to fly above surface or air launched missiles top out at 20 and 25km altitude respectively. But for a multi-billion dollar spacecraft this is quite low due to the high risk. Low Lunar Orbit used during the Apollo missions were at a 100km altitude, and all the hype on New Horizons Pluto flyby, it was at a distant 12,500km pass. OK ESA’s Rosetta spacecraft was maneuvered down to 29km around comet 69P, but has since moved out to a safer 300km orbit.
Looking forward to seeing what comes out of Cassini’s E-21 flyby.
Source: JPL’s Cassini E-21 Flyby Page