USSTRATCOM’s space control mission includes: surveillance of space, protection of US and friendly space systems, prevention of an adversary’s ability to use space systems and services for purposes hostile to US national security interests, and direct support to battle management, command, control, communications, and intelligence. The space control mission is conducted by USSTRATCOM’s Joint Functional Component Command for Space (JFCC SPACE).
JFCC SPACE, through its Joint Space Operations Center (JSpOC), detects, tracks, and identifies all artificial objects in Earth orbit. The JSpOC is a synergistic command and control weapon system focused on planning and executing USSTRATCOM's JFCC SPACE mission. Its purpose is to provide a focal point for the operational employment of worldwide joint space forces, and enable the Commander, JFCC SPACE (CDR JFCC SPACE) to integrate space power into global military operations.
The JSpOC is composed of six core divisions: Strategy Division (SRD), Combat Plans Division (CPD), Combat Operations Divison (COD), United Space Vault (USV), Intelligence, Surveillance and Reconnaissance Division (ISRD), and Operations Support Division (OSD).
The JSpOC maintains the catalog of all artificial Earth-orbiting objects, charts preset positions for orbital flight safety, and predicts objects reentering the Earth’s atmosphere. Since the launch of Sputnik in 1957, 39,000 man-made objects have been catalogued, many of which have since re-entered the atmosphere. Currently, the JSpOC tracks more than 16,000 objects orbiting Earth. About 5 percent of those being tracked are functioning payloads or satellites, 8 percent are rocket bodies, and about 87 percent are debris and/or inactive satellites.
JSpOC tasks the Space Surveillance Network (SSN), a worldwide network of 30 space surveillance sensors (radar and optical telescopes, both military and civilian) to observe the objects. The crews match sensor observations to the orbiting objects, catalog, and update the position and velocity of each one. These updates form the Satellite Catalog, a comprehensive listing of the numbers, types, and orbits of all trackable objects in space.
The JSpOC uses the SSN to take between 380,000 to 420,000 observations each day. The SSN sensors are categorized as dedicated (those with the primary mission of performing space surveillance), contributing, or collateral sensors (those with a primary mission other than space surveillance). SSN Sensorsuse a "predictive" technique to monitor space objects, i.e., 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). Below is a brief description of each type of sensor:
The JSpOC space protection mission consists of conducting laser clearing procedures, analyzing intentional threats, and conjunction assessment. The JSpOC compiles information on hostile events that could directly or indirectly threaten U.S. or allied space assets. This information is analyzed to determine potential impacts on assets so that timely warnings and recommendations for suitable countermeasures can be made.
On a routine basis, the JSpOC conducts conjunction analysis for all active spacecraft. During human space flight launches, the center computes possible close approaches of other orbiting objects with the flight path of the Soyuz and the International Space Station (ISS). The JSpOC constructs a theoretical box around a high interest object, (e.g. the ISS) and projects the flight path several days in advance of the launch. If any of the catalogued objects intersect this theoretical box, the JSpOC forwards the analysis to NASA. NASA makes the determination whether or not to change the flight path of the ISS. NASA offers to the general public, on its website, the opportunity to track various satellites.
The 614th Air and Space Operations Center, Detachment 1 (614 AOC/Det 1) provides the site and personnel to provide a geographically separate backup to JSpOC’s SSA Operations. The 614 AOC/Det 1 will take over SSA operations in the event the space control mission at the JSpOC could not function. This capability is routinely exercised.
Re-entry Assessment describes the operational procedures by which USSTRATCOM predicts the time and location of atmospheric reentry of decaying space objects. Current capabilities allow the ability to predict within a 30-minute, 6,000-mile window when and where a particular object will re-enter the Earth's upper atmosphere.
Objects are tracked throughout their orbital life, with the results posted in the Satellite Catalog. When an object appears to be re-entering within seven days, orbital analysts in the JSpOC will increase sensor tasking (monitoring) and begin to project a refined re-entry time and location. Messages indicating the calculated re-entry time and location are transmitted to forward users and customers at the 4, 3, 2, and 1-day points. Starting at the 24-hour point, the object is continuously refined, with processing at the 12, 6 and 2-hour points. Again, ground traces and messages are transmitted to SSN sensors and posted on public websites. The object is monitored throughout re-entry.
The Graphic above depicts the reentry of a typical satellite in a low Earth orbit. Figures may change depending on the orbital characteristics of space vehicles.
It is virtually impossible to precisely predict where and when space debris will impact due to limitations in the tracking system as well as perturbation factors that can influence reentering objects. Most of USSTRATCOM's space-tracking radars are located in the Northern Hemisphere, making continuous orbit coverage impossible. Consequently, a returning satellite could be outside sensor coverage for several hours.
Also, perturbation factors acting on an object's orbit could include variations in the gravitational field of the landmass and ocean areas, solar radiation pressure, and atmospheric drag. Objects re-entering may skip off the Earth's atmosphere, much as a stone skipped across a pond, causing it to impact much further away than originally forecast.
USSTRATCOM will verify that an object has re-entered by using a process of "No Show" sensor reports verifying the object is no longer in orbit. Once it is determined not to be in orbit, sensor tasking ends and the object is deleted from the "Active" tracking mission of the surveillance network.
The chances of someone being struck by a re-entering object are slight. The great majority of objects that re-enter disintegrate due to the intense heat created by interaction with the Earth's atmosphere. Only a small percentage of objects ever re-enter over land since water comprises 75 percent of the Earth's surface. Additionally, only about 25 percent of the Earth's landmass is actually inhabited. If the object is forecast to make landfall in North America or Hawaii, the JSpOC will notify the Federal Emergency Management Agency and/or Public Safety Canada.
USSTRATCOM maintains historical orbital data on objects even after they have re-entered the Earth's atmosphere. Unless an object is actually found and returned to NASA or any other agency, USSTRATCOM would have no knowledge of objects that have survived re-entry.
Current as of Dec 2012
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