The Space Surveillance Network has been tracking space objects since 1957 when the Soviets opened the space age with the launch of Sputnik I. Since then, the SSN has tracked more than 24,500 space objects orbiting Earth.
Of that number, the SSN currently tracks more than 8,000 orbiting objects.
The rest have re-entered Earth’s turbulent atmosphere and disintegrated, or survived re-enty and impacted the Earth. The space objects now orbiting Earth range from satellites weighting several tons to pieces of spent rocket bodies weighing only 10 pounds.
About seven percent of the space objects are operational satellites, the rest are debris. STRATCOM is primarily interested in the active satellites, but also tracks space debris. They also track space objects which are 10 centimeters in diameter (baseball size) or larger.
The SSN uses a “predictive” technique to monitor space objects; it spot checks them rather than tracking them continually. This technique is used because of the limits of the SSN (number of sensors, geographic distribution, capability, and availability).
Phased-array radars can maintain tracks on multiple satellites simultaneously and scan large areas of space in a fraction of a second. These radar’s have no moving mechanical parts to limit the speed of the radar scan – the radar energy is steered electronically.
Tracking and monitoring things like space weather and debris can help prevent issues, and can even keep our military satellites safe from storms and debris. Dr. Alex Young, Solar Physicist at the NASA Goddard Space Flight Center, explains how space weather could impact our military satellites, and how monitoring it – and developing new technology to understand it – can help the mission.
Conventional radars use immobile detection and tracking antennas. The detection antenna transmits radar energy into space in the shape of a large fan. When a satellite intersects the fan, the energy is reflected back to the antenna, triggering the tracking antenna.
The tracking antenna locks its narrow beam of energy on the target and follows it in order to establish orbital data.
The Ground-Based Electro-Optical Deep Space Surveillance System (GEODSS) consists of three telescope sensors linked to a video camera. The video cameras feed their space pictures into a nearby computer which drives a display scope. The image is transposed into electrical impulses and recorded on magnetic tape. This is the same process used by video cameras. Thus, the image can be recorded and analyzed in real-time.
Combined, these types of sensors make up to 80,000 satellite observations each day.
This enormous amount of data comes from SSN sites such as Maui, Hawaii; Eglin, Florida; Thule, Greenland; and Diego Garcia, Indian Ocean. The data is transmitted directly via satellite, ground wire, microwave and phone. Every available means of communications is used to ensure a backup is readily available if necessary.
Jessica L. Tozer is a blogger for DoDLive and Armed With Science. She is an Army veteran an avid science fiction fan, both of which contribute to her enthusiasm for technology in the military.