The Space Environment Monitor (SEM) consists of three instrument groups: 1) an energetic particle sensor (EPS) package, 2) two magnetometer sensors, and 3) a solar x-ray sensor (XRS). Operating at all times, the SEM provides real-time data to the Space Environment Center (SEC) in Boulder, Colorado. The SEC, as the nation’s “space weather” center, receives, monitors, and interprets a wide variety of solar terrestrial data and issues reports, alerts, warnings, and forecasts for special events such as solar flares and geomagnetic storms.

This information is important for military and civilian radio communication, satellite communication and navigation systems, electric power networks, geophysical exploration, Shuttle and Space Station astronauts, high-altitude aviators, and scientific researchers.

The EPS accurately measures the number of particles over a broad energy range, including protons, electrons, and alpha particles, and are the basis for operational alerts and warnings of hazardous conditions. Energetic particles pose a risk to satellites and to astronauts, and they can disrupt navigation and communications systems used on the ground and in aircraft.

The magnetometer sensors can operate independently and simultaneously to measure the magnitude and direction of the Earth’s geomagnetic field, detect variations in the magnetic field near the spacecraft, provide alerts of solar wind shocks or sudden impulses that impact the magnetosphere, and assess the level of geomagnetic activity. The second magnetometer sensor serves as a backup in case the first magnetometer sensor fails and provides for better calibration of the magnetometer data channel.

The XRS and The XRS is an x-ray telescope that observes and measures solar x-ray emissions in two ranges—one from 0.05 to 0.3 nanometers (nm) and the second from 0.1 to 0.8 nm. In real-time, it measures the intensity and duration of solar flares in order to provide alerts and warnings of potential geophysical responses, such as changes in ionospheric conditions, that can disrupt radio communications and Global Positioning System (GPS) signals.

The five-channel EUV telescope is new on the GOES-NO/P/Q satellites. It measures solar extreme ultraviolet energy in five wavelength bands from 10 nm to 126 nm. The EUV sensor provides a direct measure of the solar energy that heats the upper atmosphere and creates the ionosphere.