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Fact Sheets

Ground-Based Electro-Optical Deep Space Surveillance



The Ground-Based Electro-Optical Deep Space Surveillance (GEODSS) System plays a vital role in tracking deep space objects. More than 2,500 objects, including geostationary communication satellites, are in deep space orbits varying in altitude from 10,000 to 45,000 kilometers from earth. 

Approximately 25,000 known man-made objects orbit the earth. These objects range from active payloads, such as weather monitoring satellites or Global Positioning System satellites, to “space junk” such as rocket bodies from previous satellite launches or debris from past satellite breakups. 

Space Delta 2 is responsible for tracking all man-made objects in orbit. Space Delta 2 receives positional tracking data, known as metric observations, from the Space Surveillance Network (SSN) which is comprised of optical and radar sensors throughout the world. This enables DEL 2 to maintain accurate data on many man-made objects currently in orbit. 

There are three DEL 2 operational GEODSS sites in the SSN located in the U.S. and U.S. Indo-Pacific Command.


GEODSS performs its mission using one-meter telescopes that are equipped with highly sensitive digital camera technology, developed under a program known as Deep STARE. Each operational GEODSS site has three telescopes that are used in conjunction with each other or separately. These telescopes are able to “see” objects 10,000 times dimmer than the human eye can detect.

The GEODSS’ camera system is able to track multiple satellites in the field of view. The telescopes take rapid electronic snapshots of satellites in the night sky, showing up on the operator’s console as tiny streaks. Computers then measure these streaks and use the data to compute the position of satellites in their orbits. Star images, which remain fixed, are used as reference or calibration points for each of the three telescopes. The resulting metric observation data is then sent instantaneously to Delta 2 for the management of the satellite catalog databases. 


The GEODSS system has been an important piece of the space situational awareness mission since the early 1980s. Over the years, the GEODSS systems have undergone several refurbishments and upgrades, the most significant being the addition of cameras. In 2005, each site began using the cameras. This upgrade provided the sites with some of the most accurate and sensitive optical telescopes in the world. The GEODSS system can track objects as small as a basketball more than 20,000 miles away and is a vital part of the U.S. Space Force’s SSN.

(Current as of Oct 2020)