Space Traffic Management: Conjunction Assessment

1. Space Traffic Management: Conjunction Assessment Melissa Kemper Force

2. What I won’t be talking about …(but you should be aware of) • Defining the Problem • Rationale for Engagement with Space Traffic Management • STM Framework of Analysis: • Technical Framework • Legal and Regulatory Framework Those two dimensions are used to analyze each phase • The 12 Space Traffic Rules • European Code of Conduct (Sept. 2010) • Sharing Systems • Proposed Space Traffic Management Regime

3. What I will be talking about… 1. Overview of Space Traffic Management Rules • Conjunction Assessment/Collision Avoidance • Human Spaceflight • Sun-synchronous orbit (SSO) Zoning • Improved utility of Geosynchronous Orbit 2. Conjunction Assessment • Data Acquisition • Collision Prediction • Collision Maneuvers 3. What is currently known • US SSN • STM currently in existence

4. Overview of STM Rules:Four Targets Conjunction Assessment/Collision Avoidance • Rules provide standard data set, warnings and recommendations of avoidance maneuvers for owner-operators who don’t have tracking or analytical ability • Give owner/operator flexibility to maneuver after internal cost/benefit analysis • Provide information and tools for educated choices and satellite safety Human Spaceflight • Creates a protected zone for human traffic with minimal impact to current and future non-human rated operators Sun-Synchronous Orbit (SSO) Zoning • Room for more than an order of magnitude growth over today’s SSO population is provided and ensuring minimal collision risk Improved Utility of Geosynchronous Orbit • Rules increase efficiency of existing GEO slotting/operations

5. Conjunction AssessmentData Acquisition • Positional data collection: As an object in orbit passes over tracking sites – radars, optical telescopes, etc., metric data is obtained • Track association: This data is sent to an analysis center where it is added to observations from other tracking sites on that object • Orbit determination: An element set is produced, which can be used for predicting where an object is in orbit at a given time • Iterative process: The elsets are passed back to the tracking site, which uses newly updated data to continually track and update them • Elsets are stored in a satellite catalog that is continuously updated and corrected. Collecting this positional data is space surveillance. • When combined with other types of data on space weather, planned maneuvers, and imagery, it is called space situational awareness

6. Conjunction AssessmentCollision Prediction (Analysis) • Boxes are placed around the primary targets to indicate warning and maneuver thresholds. • Trajectories are propagated forward for a set period of time • The resulting ephemeris compares trajectories of primary objects and secondary objects to determine if any come within the box • Objects predicted to enterawarning box are reassessed • in closer intervals • using more accurate algorithms • with higher fidelity tracking data • A much smaller maneuver box is constructed • the maneuver box is large enough to provide a safety margin

7. Traffic Maneuvers Collision Avoidance Maneuvers • When an object is predicted to come within the maneuver box Other maneuvers • Station Keeping Maneuvers • Station Acquisition • Relocation Maneuvers • GEO Graveyard Orbit • De-orbiting

8. US Space Surveillance Network • 29 space surveillance sensors (radar and optical telescopes) • JSpOC detects, tracks,identifies man-made objects • Two satellite catalogs • Element sets are kept in a Two-Line Element (TLE) • High fidelity catalog with state vectors with covariance matrices • Air Force Space Surveillance System —the Space Fence • 3 high frequency radar transmission sites, 6 receiver sites in US • Next-gen will include Australia, the Kwajalein Atoll and Ascension Island

9. US SSN

10. STM Currently Exists in 2 Primitive Forms 1.Screening for close approaches (conjunction assessment) • US military's Joint Space Operations Center, and collision avoidance maneuvers • No formalized system 2. Station-keeping of satellites in the geostationary belt.  

11. Traffic Rules (1) Rule I: For all predicted conjunction assessments the STM system will calculate the probability of collision, impact velocity, and probability of the breakup creating a threat to other spacecraft. Rule II: For all predicted conjunction assessments involving at least one maneuverable spacecraft, and a collision probability over 1/10,000, the STM system will provide a suggested collision avoidance maneuver to the spacecraft owner-operator(s). Rule III: If the STM predicted conjunction has the probability higher than 1/3000 of generating space debris that could endanger other spacecraft, then the spacecraft owner-operator will be strongly urged to perform a collision avoidance maneuver, preferably the maneuver proposed by the STM system, but an alternative maneuver is acceptable if it is safe. Rule IV: If the STM predicted conjunction is only a threat to the conjunctional spacecraft and has less than a 1/3000 chance of endangering other spacecraft, then the spacecraft owner-operator(s) can choose if, when, and how to perform collision avoidance. Rule V: A new system of SSO orbital slotting is defined as follows: 1. A band of SSO orbits is formed from 12 defined altitudes between 500-1000 km which have a repeating ground track period between 50 and 100 orbits and whose separation in altitude is greater than 20km. 2. 42 bands of SSO orbits spread around the Earth separated in right ascension at the equatorial crossing. 3. Each orbit is divided into multiple slots 50 km apart, for a total of 1000 slots. 4. All future SSO satellites will be placed into one of these slots. Rule VI: All GEO spacecraft owner-operators shall, on a regular basis, provide positional data to the STM system for the purpose of conjunction assessment.

12. Traffic Rules (2) Rule VII: All GEO owner-operators shall provide notification 48 hours prior to initial station acquisition, station-keeping and relocation maneuvers to the STM system. Rule VIII: All GEO owner-operators are encouraged to grant consent for distribution of owner-operator derived positional data, via the STM system, to all neighboring GEO spacecraft owner- operators for the purpose of enhancing station-keeping planning. Rule IX: The STM system shall provide orbital data on all spacecraft that perform relocation maneuvers in GEO to all operators who may be affected. An altitude band from 41 to 200 km above and below GEO is reserved for relocation and station acquisition maneuvers. Rule X: Circular orbits with altitudes below 500 km are reserved for human-rated spacecraft; non- human rated civil or commercial space objects are not permitted in this zone unless they meet all of the following criteria: • Registered with the STM system • Will remain in orbit for less than 5years. Non-human rated spacecraft should also comply with the following: • Maneuvering capability • Satellites too small to track should have devices which allow their position to be determined. Rule XI: 48 hours before the flight of any human-rated orbital or sub-orbital vehicle, the owner-operator shall submit a flight plan to the STM system detailing the following: • Vehicle type; Number of passengers; Launch date, time, and location; Trajectory (if sub-orbital) or orbit; Length of flight (if sub-orbital) or time in orbit; Landing date, time, and location; A risk assessment and compliance with STM criteria All on-orbit maneuvers of any human-rated vehicle will, where possible, be coordinated 48 hours in advance using the same method above and providing the same information.