ICON (MIDEX 8, Explorer 96)

ICON (MIDEX 8) [Orbital ATK]

ICON (Ionospheric Connection) will explore the boundary between Earth and space – the ionosphere – to understand the physical connection between our world and the immediate space environment around us. This region, where ionized plasma and neutral gas collide and react exhibits dramatic variability that affects space-based technological systems like GPS.

Though the solar inputs are now well quantified, the drivers of ionospheric variability originating from lower atmospheric regions are not. ICON is the first space mission to simultaneously retrieve all of the properties of the system that both influence and result from the dynamical and chemical coupling of the atmosphere and ionosphere. ICON achieves this through an innovative measurement technique that combines remote optical imaging and in situ measurements of the plasma. With this approach, ICON gives us the ability to (1) separate the drivers and pinpoint the real cause of ionospheric variability (2) explain how energy and momentum from the lower atmosphere propagate into the space environment, and (3) explain how these drivers set the stage for the extreme conditions of solar-driven magnetic storms. ICON’s imaging capability combined with its in-situ measurements on the same spacecraft (Figure 1) gives a perspective of the coupled system that would otherwise require two or more orbiting observatories.

ICON targets the low-latitude ionosphere because recent global-scale observations of this region show remarkable spatial and temporal variability that contravene the conventional view of ion-neutral coupling in space, and evince strong forcing by lower atmosphere drivers. The coupling of the atmosphere to space is strongest at these latitudes because the atmospheric waves are largest and so is the density of the space plasma, produced in abundance by the sun overhead and confined by the magnetic field.

Following instruments are on boards:

• MIGHTI (Michelson Interferometer for Global High-Resolution Thermospheric Imaging): Remotely measuring the neutral wind field and temperatures – Heritage from SHIMMER flown on STPSat-1.
• EUV (Extreme Ultra-Violet): Measuring the height and density of the daytime ionosphere – Heritage from SPEAR flown on the Korean STSAT-1.
• FUV (Far Ultra-Violet): Measuring the daytime atmospheric composition and the ionosphere at night – Heritage from FUV flown on IMAGE.
• IVM (Ion Velocity Meter): Measuring the electric fields detected at the satellite – Heritage from IVM flown on C/NOFS CINDI.

Orbital was selected to provide a LEOStar-2 based bus.

ICON will launch into a low earth orbit, operating for at least two years. A Pegasus-XL launch vehicle was selected in November 2013 for a launch in 2017. The launch was delayed to 2018. In June 2018, while being transfered to Kwajalein for launch, an anomoaly on the launch vehicle was noticed and it had to be returned. Launch has now been delayed to September 2018, switching the launch site to Cape Canaveral due to limited availability of launch slots at Kwajalein at this time. The launch was again delayed due to launch vehicle issues and eventually happened in October 2019.

ICON successfully operated for its 2 year lifetime and the mission was extended. On 25 November 2022 contact with the spacecraft was lost. Attempts to restablish contact were going on as of early December 2022.