A few hours ago the ICON (Interface Region Imaging Spectrograph) satellite was launched using a Pegasus XL rocket by Northrop Grumman brought to an altitude of about 11,900 meters by an L-1011 airplane, also by Northrop Grumman, modified for this purpose. After a little more than 11 minutes, ICON was brought into a low Earth orbit at an altitude of about 575 kilometers, where the solar panels regularly deployed and sent the first signals.
The ionosphere is a part of the atmosphere where solar radiation but also in small part cosmic rays ionize atmospheric gases. It has a remarkable extension since it ranges from 60 to 1000 kilometers of altitude, so some of its layers are also part of other layers of the atmosphere defined according to other parameters.
The low Earth orbit is inside the ionosphere so the satellites that orbit there and the International Space Station can be influenced by the ionization of the gases, even if at those altitudes they’re very rarefied. The ionosphere can also influence radio communications between ground and satellites, including those at higher altitudes such as navigation, therefore GPS and similar systems, with the possibility of distortions and sometimes interruption of the connections.
The ICON satellite is equipped with four scientific instruments to collect measurements of the plasma, even if very rarefied, and of the light emission called nocturnal luminescence or, in jargon, airglow. This will give much more accurate and complete information on the density, composition and structure of the ionosphere. In the two years of mission, ICON will improve the understanding of the ionosphere to predict the possible phenomena that disturb communications and to design satellites that take them into account.
Originally, the launch was supposed to take place from the Kwajalein Atoll in the Marshall Islands, but some problems found in the Pegasus XL rocket not only delayed it but also forced to bring it back to California for the tests needed to solve them. ICON is a small satellite weighing about 288 kg so the Pegasus XL rocket can put it into orbit also from a location near the coast of Florida, farther from the equator than the Marshall Islands.
The ICON satellite was supposed to be launched in November 2018 but abnormal readings from the Pegasus XL rocket rudder had led to abort the procedure both in the launch attempt from the Kwajalein Atoll and in the one from Florida. At that point, a more thorough investigation was required, and led to a considerable delay.
At last the ICON satellite has been launched and can begin its mission. The data it will collect will partly complete the ones detected by the Global-scale Observations of the Limb and Disk (GOLD) instrument of the SES-14 satellite, launched on January 25, 2018.