|Mission type||Tracking and Surveillance|
|Operator||U.S. Missile Defense Agency|
|COSPAR ID||2009-052A / 2009-052B |
|SATCAT no.||35937 / 35938|
|Mission duration||2 years (planned)|
|Spacecraft type||STSS demonstrator satellite|
|Manufacturer||Northrop Grumman Space Technology|
|Start of mission|
|Launch date||25 September 2009,|
|Rocket||Delta II 7920-10C|
|Launch site||Cape Canaveral, LC-17B|
|Contractor||United Launch Alliance|
|Entered service||Late January 2010|
|Reference system||Geocentric orbit|
|Regime||Low Earth orbit|
|Altitude||1,350 km (840 mi)|
The United States Missile Defense Agency (MDA) has developed a Space Tracking and Surveillance System (STSS) (formerly SBIRS-Low) which was used to research the space-based detection and tracking of ballistic missiles. Data from STSS satellites could allow interceptors to engage incoming missiles earlier in flight than would be possible with other missile detection systems. The STSS program began in 2001, when the "SBIRS Low" program was transferred to MDA from the United States Air Force. In December 2002, SBIRS Low Research & Development (SBIRS Low R&D) was renamed Space Tracking and Surveillance System (STSS).
Two demonstration satellites were launched together on a single Delta II launch vehicle. Launch took place 25 September 2009, from Cape Canaveral Space Launch Complex 17 (LC-17B). STSS constellation consists of two satellites orbiting at 1350 km, 58.0° inclination, with 120 minute period.
The perceived advantage of STSS is that its satellites, by operating at a lower altitude and by using long- and short-wave infrared sensors, will be able to acquire and track missiles in midcourse and during the boost phase.
STSS is designed to be the low Earth orbiter (LEO) within the layered Ballistic Missile Defense System. It complements the geosynchronous Defense Support Program, the Space-Based Infrared System, and other overhead non-imaging infrared (ONIR) systems  and provides tracking cues to systems on the surface. The STSS program is developed in phases, the first of which is the launch of two demonstrator satellites. The demonstrators will perform experiments and prove out systems and processes to establish a knowledge base for future operational designs. The demonstration satellites, built by Northrop Grumman Space Technology (spacecraft) and Raytheon Technologies (sensors) detected and tracked a two-stage Ground-Based Interceptor (GBI) during a U.S. Missile Defense Agency flight test on 6 June 2010.
According to Congressional testimony, military officials believe that STSS has the potential to bolster the nation's missile defense system. "Two recent flight tests demonstrated that STSS dramatically improved the precision of threat missile attacks and provided more accurate fire control quality data to the Aegis ships several minutes earlier than less accurate data provided by organic radars in the Aegis or THAAD (Theater High Altitude Area Defense) systems", U.S. Army Lt. General Patrick J. O'Reilly, Director of the U.S. Missile Defense Agency, told the U.S. Senate Appropriations Committee's Defense subcommittee in prepared testimony on 25 May 2011.
First STSS Object Sighting Messages (OSM) of a missile
First on-board missile track formed.
ICBM Minuteman III test launched from Vandenberg Air Force Base
Pre-determined target launched of Ronald Reagan Ballistic Missile Defense Test Site at Kwajalein Atoll, Marshall Islands
Data transmitted at Missile Defense Integration and Operations Center (MDIOC) at Schriever Air Force Base, Colorado.
First dual satellite collect of target, and
First target acquisition from a target launched beyond the horizon.
First OSMs sent to Enterprise Sensors Laboratory at Schriever Air Force Base, Colorado, for data fusion with other sensors in real time
First track of a dim theater missile.
First track of a resident space object.
Tracked a NOAA weather satellite on 19 July 2010 for several minutes (externally queued)
First autonomous acquisition sensor to track sensor handover of a target.
First track of an aircraft
Precision track sensor operation below the horizon during daylight
First autonomous acquisition sensor to track sensor handover of an aircraft
Airborne Laser Test Bed Exercise
First autonomous acquisition sensor to track sensor handover of a boosted target
ICBM Minuteman III test launched from Vandenberg Air Force Base to Island of Guam (8500 km).
First post boost track continuation of a target with track sensor
First demonstration of track sensor generating multiple tracks for separating objects.
Aegis Launch on Remote Campaign
First Track sensor stereo track of a dim boosted target
First stereo post boost tracking of midcourse target.
Second Aegis Readiness Assessment Vehicle Targeting
STSS satellites acquired and tracked its target until re-entry
Second full-course tracking during U.S. Missile Defense Agency's (MDA) Aegis launch
Successful production of "stereo" 3-D tracking software to follow the target missile's flight path to predict its impact point.
Sea-based missile defense test
STSS satellites target and help to intercept an intermediate-range ballistic missile (IRBM); destruction of the IRBM on impact.
STSS test on short-range air-launched target (SRALT)
This test proved the STSS's ability to track dim objects that have extremely short flight timelines.