Missile Tracking Satellites Explore New Missions
By Rob Zmarzlak, STSS-D Program Manager, Northrop Grumman Aerospace Systems
The Space Tracking and Surveillance System Demonstration satellites are far more capable today than when launched four years ago thanks to enhancements that fully leverage their unique sensor suitethey arent just for missile defense any longer.
Recent enhancements are taking full advantage of the twin satellites highly advanced infrared (IR) sensors, transforming them from a missile defense experiment into a nearly operational system. Both spacecraft are performing adjacent missions including space situational awareness, technical intelligence, battlefield assessment, civil disaster support and environmental monitoring.
Simultaneously, improvements in mission planning, spacecraft and payload software, ground automation and power management have allowed a 10-fold increase in STSS-Ds data collections workload, making the satellites far more capable today than when they were launched in September 2009. Their increased tasking provides mission utility beyond missile defense into other critical areas, while simultaneously adding value at a time when military budgets are the most constrained ever.
The U.S. Missile Defense Agency (MDA) notes that STSS-Ds adjunct missions include tracking
of space launches, on-orbit satellites, satellite re-entries, and collecting scientific background and scene data on space and terrestrial environments.
Make no mistaketheir paramount mission remains precision missile tracking through all phases of flight. STSS-D continues to participate in numerous Missile Defense Agency (MDA) flight tests, regularly demonstrating Holy Grail-type capabilities from Low Earth Orbit such as birth-to-death and stereo tracking.
This is a priority mission because the proliferation of ballistic missiles gives reckless regimes the ability to carry out devastating attacks against the United States, its deployed troops and its allies. A robust defense against these growing and evolving threats to U.S. national security requires tracking ballistic missiles from birth-to-death with emphasis on midcourse tracking to improve chances of intercept.
Midcourse is the longest phase, or about 80 percent of total flight time, when engines stop firing and deadly warheads are deployed. However, traditional radar and IR sensors cant always see them at this point. Without the ability to track missiles through midcourse, theres no hope of having an effective defense against them.
Thats why each space vehicle has a pair of IR sensors: (1) A short-wave IR, fixed, wide-field-of-view acquisition sensor that looks above and below the horizon to monitor, autonomously detect and track missiles through boost phase; and (2) A narrow-field-of-view, gimbaled track sensor capable of tracking missiles from post-boost, through midcourse and then to reentry or intercept, using multiple IR bands.
Northrop Grumman is the prime contractor for both spacecraft and the operational ground station at Schriever Air Force Base, in Colorado.
Enhancements Benefit All Missions
Recent enhancements that make adjunct missions possible also make missile defense capabilities all the more resilient as well. A February test of a U.S. Navy Aegis Ballistic Missile Defense launch on remote (LOR) concept is a case in point.
It proved that midcourse, space-based infrared tracking by STSS-D can alert Navy ships to launch interceptors accurately before their radars can see the incoming missilesallowing the U.S. Navy to defend larger areas with fewer Aegis assets.
To accommodate Aegis LOR, system engineers had to develop numerous data flow options for getting data to an Aegis cruiser. A new external interface was implemented and validated through early hardware-in-the-loop testing. So far, STSS-D has achieved LOR quality of service in six BMDS tests.
For another Aegis LOR test, the team arranged for the satellites to be cued remotely by another BMDS sensora function that didnt exist previously. The result: Both STSS-D space vehicles received the external cue, acquired the target and provided hundreds of seconds of valuable midcourse tracking dataincluding the first three-dimensional or stereo observations of multiple objects.
Improvements began shortly after Early On-Orbit Testing was completed. Northrop Grumman engineers knew the satellites had inherent capabilities to perform additional missions beyond the modest requirements of their pre-launch designif they could be performed efficiently.
STSS-D was built to be an on-orbit, research and development (R&D) platform to demonstrate the unique capabilities of a space-based sensor for the BMDS. It was never intended to be an operational system. Built-in limitations were appropriate for an experimental system with a mission life requirement of only two years.
This posed significant challenges as BMDS capabilities matured and MDA required the satellites participation in all system-wide tests. It meant making complex interface upgrades and operational concept changes to adapt the demonstrators for much broader missions. These were the major challenges and results after improvements.
Manual Processes & Data Collection
(Before Enhancements): Operators had to use highly complex, manual processes for conducting all tasks because of STSS-Ds role as an experimental space layer for the BMDS. Much of the planning for payload data collections was done in Southern California where the satellites were built, resulting in inefficiencies when employees / satellite operators at the Missile Defense Space Development Center (MDSDC) ground station in Colorado Springs, Colorado, needed to act in real time.
After Enhancements: The company developed test planning tools, test execution scripts and a collection parameter database organized by real-world target location and type, allowing employees at the MDSDC to plan payload data collections against real-world areas-of-interest and targets-of-opportunity in response to tip-offs from other systems or national data sources.
Planning these data collections at the ground station significantly reduced test planning and execution timelines from several days to a few hours.
Automated planning tools all but eliminated human mission planning errors. Operators currently maintain a command error rate of less than 0.0003 percent as data collections increased by a factor of 10or from one to two each day per spacecraft to 10 to 12 per spacecraft daily. This quadrupled data collections in 2012, compared with 2011.
Anomaly Safeguards (Before Enhancements): A conservative, pre-launch design assured space vehicle safety by shutting down the payload in response to any indication of an anomaly. Although the built-in defense mechanism kept both satellites safe, returning a payload to operational status could take as long as several weeks.
After Enhancements: Improvements to fault management monitoring and response processes resulted in a significantly shorter recovery to mission timeline from 12 days to two days.
On-Orbit Operating Time (Before Enhancements): At launch, satellite designers expected to operate each payload for 36 minutes per orbitan improvement from the 10 minutes per orbit specification. But each orbital period currently is 112 minutes, leaving much capacity unused.
After Enhancements: Payload per-orbit operating time increased to 75 minutes. Engineers designed and executed a series of experiments that demonstrated the safety of longer payload operating time, and verified there was sufficient power to accommodate extended operations.
Crosslink Resiliency (Before Enhancements): STSS-D demonstrators fly in tandem, separated by 3,000 miles. An RF relay establishes communications between one spacecraft that is out of view of a ground station through the other satellite, which is in range. The crosslink was intended to be used only once, during an initial on-orbit demonstration.
However, to fulfill mission requirements, systems aboard the satellite and on the ground must send data to other missile defense systems quickly enough to allow them to target and destroy incoming missiles. That requires fast data processing and communication links. They also must work under the harsh environmental conditions of space, which requires materials that can withstand radiation and cold temperatures.
After Enhancements: Modifications allowed routine use of the communications crosslink on back-to-back orbits, extending the operational utility from 20 minutes to more than 40 minutes for each crosslink operation.
Today, MDA says it plans to operate STSS-D into 2017significantly beyond the satellites two-year mission life and four-year design life. A former MDA director cited STSS as the most capable sensor currently in the MDA sensor suite.
During 2011 congressional budget testimony, he stated, Two recent flight tests demonstrated that STSS dramatically improved the precision of threat missile tracks 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 systems.
Such accomplishments are validating the need for a space layer as a practical and affordable component for fulfilling the real-world mission of MDAs Ballistic Missile Defense System (BMDS). Lessons learned from the two STSS-D satellites are guiding decisions on the development of a fiscally sustainable, continuously available, future operational constellation and ground communications/processing system.
The satellites have only improved since the end of Early On-Orbit Tests in late 2010. They are continuing to increase their value to users and taxpayers as they perform a wider range of tasks and demonstrate why space-based sensors can be a ballistic missiles worst nightmare.
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About the author
Rob Zmarzlak was named program manager for Northrop Grummans Space Tracking and Surveillance System Demonstration satellites in 2013 after managing launch preparation, launch, deployment, on-orbit test and extended operations and sustainment since 2007. Altogether, Rob has 30 years of experience in space and launch operations, systems engineering, and functional and program management of space programs including GeoLITE, NASAs Earth Observation Satellites, Future Imagery Architecture, Space Based Radar and restricted military programs. He also served 24 years active and reserve military duty in both the U.S. Navy and Army in the intelligence field, which includes several overseas deployments and NATO peacekeeping operations.