The Precision Tracking Space System (PTSS) is, according to recent testimony by Missile Defense Agency (MDA) Director Lt. General Patrick O’Reilly, “the greatest potential future enhancement for both homeland and regional defense in the next ten years.”[1] PTSS is a system of satellites intended to track ballistic missiles using an infrared telescope with sufficient accuracy to be able to guide interceptors.  The PTSS program was formally initiated last year as a replacement for the Space Tracking and Surveillance System (STSS) which was the latest in a long line of proposed space-based missile tracking systems dating back to at least the late 1980s.  Two STSS “demonstration” satellites were launched in 2009, and the MDA recently noted that they had reached their 1,000th day in orbit and were still operational.[2]

PTSS Satellite (image from MDA factsheet)[3]

 At the end of April, however, the co-chairs of a National Academy of Sciences (NAS) committee sent a letter to Congress reporting on findings of a recent (still not declassified) study on missile defense:[4]  This letter stated that: “The committee finds no valid justification for pursuing PTSS and recommends terminating all effort on it.”  The letter’s authors argued that “PTSS is too far away from the threat to provide useful discrimination data, does not avoid the need for persistent infrared (OPIR) coverage and is very expensive.” Leaving aside the cost and the need for OPIR (which is already available in the form of DSP and SBIRS early warning satellites and sensors), is PTSS’s lack of discrimination capability a valid criticism?

As the NAS letter correctly notes, PTSS is much too far from potential targets to be useful for discrimination.  The satellites will be in equatorial orbits and thus at least 4,000 km from trajectories involving missiles launched from North Korea or Iran.  At  these ranges, with plausible telescope apertures (tens of centimeters), PTSS’s infrared resolution will be hundreds of meters.  That is, PTSS will not even be able to separately observe objects unless they are at least several hundreds of meters apart, much less tell which object is a warhead and which one is a decoy.

However, it appears the MDA conceded this point long ago.  As the GAO noted in 2003, “Countering more advanced and sophisticated threats will require DOD to be able to detect and track multiple objects and differentiate the threatening warheads from decoys.  Given technical challenges, DOD deferred plans to achieve this capability for STSS.”[5]  Given that PTSS is in effect an attempt to produce a simpler, less expensive tracking system than STSS, this situationalmost certainly remains unchanged.

A more recent (April 20, 2012) GAO Report reinforces the idea that discrimination is at best a secondary mission for PTSS: “PTSS is being designed strictly for BMDS [Ballistic Missile Defense System] use, so the satellite payload is geared toward the BMDS missile tracking mission, with the objective of keeping the design as simple and stable as possible.  Additionally, the acquisition strategy stipulates that PTSS will not duplicate functions found elsewhere in the BMDS, but instead will remain focused on the specific function for which it is being designed.”[6]

Despite this, it is easy to see why the NAS panel would raise the discrimination issue, since the MDA itself keeps rasing it.  Thus while the current MDA fact sheet on PTSS says only that one of the roles of PTSS is “supporting object characterization and discrimination,” MDA spokeswoman Debra Christman last year stated that “PTSS satellites will be all about midcourse missile tracking and discrimination,”[7]

How did MDA respond to the finding in the NAS letter that PTSS could not provide useful discrimination data?

General O’Reilly’s April 25 written statement argued that: “NAS did not benefit from our sensor discrimination architecture concept nor our classified programs developing PTSS’s future discrimination capability.”[8]

Translation: PTSS can’t discriminate.