IMG Copyright US Space Command

In a previous post I listed some questions regarding SSN requirements for SSA/STM. After several discussions with qualified sources, I have compiled the following set of answers.

    1. What is an acceptable level of position uncertainty? Is this dependent on object size and orbit? Are the objects in the current catalog monitored according to any tracking priority?

Answer: It depends on the orbit and what active satellites share that orbit. However, there doesn’t appear to be any consensus on what an acceptable position uncertainty is, or needs to be, other than ‘better’. Currently, all objects that can be tracked are a threat. Unfortunately, many thousands of objects that are a threat are not tracked. Tracking priorities vary, but no one wants to discuss specifics publicly.


    1. Given the current catalog, how many more observations and over what period of time are required to provide this level of certainty? What percentage of high-priority objects meet this level of position uncertainty today?

Answer: It appears that few have contemplated (or willing to discuss) this total requirement. The answers vary from hundreds to thousands more per week. Only a small number of objects are adequately tracked. “We’re doing the best we can with what we have” is a common refrain.


    1. What are the criteria for adequate SSA?

Best answer so far: “When we have evidence that our decisions were well informed”. Otherwise, besides an idealized “know everything that is going on in orbit” and needing “more than we have today” there was little consensus.


    1. How many more sensors, where located, and of what type are needed today to meet this observation requirement?

Answer: Consensus appears to be at least one more Space Fence, some additional space-based sensors, several more full-monopulse tracking radars and many more telescopes geographically distributed. No one is optimistic that this will happen anytime soon.


    1. Given the expected growth of the catalog from new, more accurate sensors, what is the expected additional observations of these newly catalogued, smaller objects to maintain this level of position certainty? How many more sensors and what type will be required to meet this evolving need?

Answer: More sensors (#s TBD) to scale with catalog growth and globally-coordinated sensor tasking and data-sharing are required. The big concern is funding and acquisition timelines. The hope is that commercial SSA will cover the gap (but not supplant the government’s role).


    1. Is there a critical level of observations below which SSA is lost? How will this change over time with the anticipated launch of mega constellations?

Best answer so far: “The question presumes one can achieve adequate SSA, this may not be true.” Obviously, to some, we will never have enough data. Interestingly, however, some believe that others have better SSA, but can’t publicly claim they do. The general feeling appears to be that as long as everyone does what they have agreed to do we shouldn’t have a problem in the near term, but most agree that the more objects there are, the greater the risk. Even the most optimistic have their doubts.


I want to thank all those that provided answers.