ICON probe air-launched on Pegasus

The oft-delayed Ionospheric Connection Explorer (ICON) is finally flying! On 11 October 2019 at 0159 UT, Northrop Grumman’s Lockheed L1011 TriStar, named Stargazer, loosed the rocket into the air, which promptly lit and hurled the 300-kg payload into a 27-degree, 600 km circular orbit.

It was the second try on the second day of its 2019 launch campaign. Just the day before, rain had scrubbed the launch. A previous attempt to fly the payload from Kwajalein Atoll in 2017, had been called off due to payload issues. Another two attempts were made in 2018, even shifting to Cape Canaveral, but these were also called off.

Even so, an abort on Pegasus doesn’t necessarily end the launch day; the initial abort being called just moments after other controllers deemed the lost radio channel non-essential. The plane, however, does need to be at a very specific speed, heading, and attitude, so the L1011 lumbered back around into the predetermined flight pattern, or “racetrack”, for a second pass. The flight made it back into the launch zone, or “box”, just before 10pm local time, and sent the probe to the top of the ionosphere.

The mission will now collect data for two years using its plasma sensor from the University of Texas-Dallas, a Michelson interferometer from the US Naval Research Laboratory, and two ultraviolet imagers from the University of California-Berkeley, which also hosts mission control.

The Pegasus strategy of using an airplane as a first stage will soon be matched by Virgin Orbit’s Cosmic Girl 747 and LauncherOne rocket, due to complete its first mission in the next few months.