6.9.6 Vehicle operators should be aware the 19th SDS specifies an earlier timeframe for submitting the COLA request.
6.9.6.1 According to the 19th SDS, New Operators should submit their request 30 days in advance of the launch. Experienced Operators should submit their request 15 days in advance of the launch. The timelines established in § 450.169(f)(1) account for the time necessary to evaluate and process COLA data. The 19th SDS performs many functions in addition to processing COLA data. For this reason, the FAA encourages operators to meet the 19th SDS timelines to ensure COLA products are available to meet the operator’s launch dates.
6.9.6.2 The vehicle operator must receive the results of the COLA from the processing entity no later than 3 hours prior to launch to satisfy the requirements found in § 450.169(f)(2). The mission may proceed if the results meet the appropriate license criteria, which are discussed in the next subsection. For a launch delay, in accordance with § 450.169(e)(3), the vehicle operator can resubmit data at least 12 hours prior to the beginning of a new launch or reentry window.
Provide request to 19 SDS L-7 days is FAA requirement, 19 SDS requests L-15 days.
Provide request to 19 SDS L-15 days is FAA requirement, 19 SDS requests L-30 days.
Upon Receipt of Form 22 19 SDS reviews form and acknowledges receipt with Launch Operator (L/O) POCs Launch minus 1 week Launch operator provides initial trajectory files to 19 SDS. 19 SDS Launch CA SMEs complete preliminary screening check. No feedback is provided to L/O unless there are problems with files.
19 SDS Mission Planning 19 SDS determines and assigns resources to support earliest space tracking and cataloguing during launch requests.
Frequency IAW Form 22 19 SDS Launch CA SMEs complete screenings and provide results per Form 22 via Space-Track.org.
Delivery of Results 19 SDS will always screen to requirements of 450.169, in addition to requirements within AFI 91-202 and to stricter criteria if requested in the Form 22.
Launch 12 hour limit (FAA) 24 hour limit (19SPCS)
450.169 (15 days)
450.169 (7 days) New Operator Experienced Operator Update Form 22 If the launch is delayed or scrubbed, L/O submits new Form 22 with new launch date and window to 19 SDS.
Figure 1 – Timeline for the COLA process 12
7 COLLISION ANALYSIS WORKSHEET.
Pursuant to § 450.169(f), operators must prepare a collision avoidance analysis worksheet for each launch or reentry using a standardized format that contains the input data required by Appendix A to part 450.
7.1 General Submittal Process.
7.1.1 If the processing entity is 19th SDS, then the FAA collision analysis worksheet information could be used to assist in filling out the two forms that 19th SDS requires.
7.1.1.1 Both can be accessed through the 19th SDS website at https://www.spacetrack.org/documentation#/odr.
7.1.1.2 The first is Form 22 to request that 19th SDS perform a COLA analysis for the launch operator. It is accessed by choosing from the web page the item “Launch Conjunction Assessment” and then “Form 22 – Launch Collision Avoidance Request.” Following the main body of the form, the document provides detailed instruction on how to fill out the specific form entries.
7.1.1.3 The second is Form R-15/VIM which specifies vehicle information. It is accessed by choosing from the web page the item “Launch Early Orbit Determination” and then “Form R-15/VIM Report.”
7.1.2 Much of the collision analysis worksheet in part 450 Appendix A and Launch Conjunction Assessment Form 22 consists of basic information, such as what and when is the mission, what the significant flight events are, and when and how communication between the launch operator and processing entity occur. Form R-15/VIM Report consists of details of which bodies will remain in orbit after a launch. Regardless of which processing entity is involved with the COLA, the 18th SDS LCA Handbook contains valuable information on how to develop COLA products.
7.2 Normal Trajectory Specifications.
7.2.1 The worksheet requires a table of orbital parameters and events to satisfy part 450, Appendix A, paragraph (a)(6), Orbital Parameters. For the SDS forms, these items are entered using an R-15 form/VIM Report, Attachment A. These items include the sequence of events from liftoff to final injection into operational orbit, that may include separation of booster(s)/stage(s), motor ignition(s)/cutoff(s), jettison of pieces (fairings etc.), maneuvers and reorientation, deorbit and ejection(s) of packages/booms, and so forth. The events are defined by time, latitude, longitude, altitude, and speed in earth-rotating coordinates.
7.2.2 The final attained body orbits are defined in terms of Keplerian orbital parameters. The orbits follow elliptical paths and so the orbital parameters define specific elliptical path quantities. The parameters include:
• apogee altitude,
• perigee altitude,
• eccentricity,
• semi-major axis radius,
• inclination,
• true anomaly,
• argument of perigee, and
• right ascension of the ascending node (RAAN), also called the Longitude of the ascending node.
7.2.3 The vehicle operator must provide nominal trajectory files for each mission body that reaches 150 km altitude for the collision analysis worksheet found in part 450 Appendix A, section (d), Trajectory Files, for the time durations discussed in Section 7.3 of this AC. The format of these files depends on requirements of the COLA processing entity. For submitting trajectory files to 19th SDS, follow the LCA Handbook that details file format and their required content.
7.2.4 Trajectories require position and velocity to be defined in accordance with part 450, Appendix A, section (d) for all components at sufficiently frequent time points that interpolation may be used with negligible error. Paragraph 7.3 of this AC discusses the screening criteria based on the probability of a conjunction event. If this option is selected, at each stated time of the trajectory, the applicant must provide the position covariance, in accordance with part 450, Appendix A, section (d)(3). The position covariance is based on the Gaussian distribution, and corresponds to state vector uncertainty of the position state vector computed using a set of Monte Carlo generated dispersed set of trajectories that account for uncertainty in the initial lift-off condition, Guidance and Performance, drag, etc. Dispersed trajectories are discussed in AC
450.117 Normal Trajectory Analysis, and AC 450.119 Malfunction Trajectory Analysis.
In accordance with part 450, Appendix A, section (d)(2), the radial cross section of each object must be provided for each object file and is specified in the worksheet.
7.3 Screening Categories.
7.3.1 Part 450 license criteria contains several options for meeting the requirements specified by § 450.169(a). These options are defined in terms of screening categories, specified on the collision analysis worksheet of part 450, Appendix A, Section (e). Complete details and limitations on selecting the category can be found in the 19th SDS LCA Handbook. The vehicle operator may select probability of collision or separation distance approaches. The most effective analysis is the probability of collision approach, provided the operator can produce realistic covariance data. Operators are highly encouraged to develop a repeatable process to use probability of collision analysis.
7.3.2 The least conservative screening criteria, i.e., least likely to be violated, is based on the probability of collision of the conjunction event specified by part 450 Appendix A, Section (d)(3). These criterion require that the launch operator provide the position covariance at each state time. The covariance matrix should be in vehicle-centered frame, ideally the UVW coordinates. U (“radial”) is the unit vector in the radial direction, W (“cross-track”) is the unit vector normal to the launch vehicle’s inertial orbit plane, and V (“in-track”) is the unit vector which completes the right-handed coordinate system. To comply with § 450.169(a), probability of collision criteria thresholds must be either 1 × 10-6 for inhabitable objects, or 1 × 10-5 for neither inhabitable objects nor orbital debris.
7.3.3 If the vehicle operator does not provide the position covariance, a stand-off radius of either ellipsoidal or spherical criteria is employed. The size and shape of the exclusion volume, to avoid a conjunction event, is chosen by the vehicle operator and noted in the request for analysis (on the Form 22 for 19th SDS analysis). Alternatively, if the vehicle operator provides a positional covariance that is either too large or too small to use probability of collision analysis confidently, the FAA may inform an applicant that stand-off distance screening, either ellipsoidal or spherical, is appropriate instead of probability of collision screening. For instance, if an operator is burning an upper stage to exhaustion and not targeting a specific altitude, the positional covariance would be so large it would create unrealistically low probability of collision analysis.
7.3.4 The methodology used by the 19th SDS for performing the probability of collision is based on Foster’s method.1 A more detailed description of the technique is provided in pages 38-45 of the Spaceflight Safety Handbook for Satellite Operators.
1 Alfano, Salvatore, A Numerical Implementation of Spherical Object Collision Probability. The Journal of the Astronautical Sciences, Vol. 53, No. 1, January-March 2005, pp. 103-109.
7.4 Common Errors.
7.4.1 The vehicle operator should make note of the following common errors encountered with previous operators in processing their COLA analysis.
• The trajectory file contains values with the incorrect sign (plus or minus) on relevant parameters.
• The trajectory of objects before and after deployment are not continuous, i.e., pre-and post-deployment do not match.
• The trajectory files are missing some deployed objects.
• The trajectory file contains missing values or repeated values, most commonly a frozen trajectory model output is recorded.
• The trajectory file starts above 150 km, the minimum as required by the regulation.
However, the trajectory should begin before 150 km, so that the analysis can start at the prescribed value.
• The covariance is an unrealistic or impossible value, specifically it is smaller than the vehicle size or extremely and unrealistically large.
• The deployed objects have a zero velocity.
7.4.2 Incorrect data files prevent the correct launch conjunctions from being identified. To check the trajectory files, one suggestion is to use a commercially available software tool designed for launch trajectory and orbit propagation. Two such tools are Systems Tool Kit (STK) offered by AGI, an ANSYS company and FreeFlyer® Astrodynamic Software by a. i. solutions. Both platforms provide visualization of the provided trajectory files. These platforms also provide the opportunity to provide a COLA analysis when loaded with the catalog of space debris. The catalogs are available from Space Track as well as through commercial providers, including STK and CelesTrak.
While these tools are useful guides to troubleshoot files and provide analyses on COLA, they cannot be utilized in place of the process. For one, these catalogs do not have the covariance of space debris necessary to meet the requirements of § 450.169.
8 SPECIAL CONDITIONS: GROUPING OF OBJECTS AND CLUSTER DEPLOYMENTS.
8.1.1 Part 450, appendix A, paragraph (d) directs operators to prepare separate trajectory file for each jettisoned component, and payload. However, there are several instances when it simply is not practical to provide a separate file for each such object.
8.1.2 For example, if there are a large number of deployments (i.e. more than 20), then the number of files becomes difficult to manage and analyze. It is possible to obtain a waiver to this requirement. Several objects can be grouped together and assessed as one object by providing a single file. For the collection of the group of objects, an effective size and corresponding covariance is provided which represents the collection of individual objects in the group.
• Intra grouping requirement (distance between groups – representative and substantiated in waiver application).
• Inter grouping requirement (distance between objects – appropriate and substantiated in waiver application).
8.1.3 If a vehicle operator needs to request a waiver from the requirement in Appendix A to provide individual trajectory files, the operator should demonstrate that the grouping of these objects is appropriate for the specified screen period. A petition for waiver must include the reason why granting the request for relief is in the public interest and will not jeopardize the public health and safety, safety of property, and national security and foreign policy interests of the United States as specified in § 404.5(b)(3). To demonstrate that the waiver would not jeopardize the public health and safety, the launch operator should show that the launched objects remain sufficiently close to one another, such that the trajectory file is representative for all objects in the grouping, and that the objects remain in close proximity such that the effective size accurately reflects the potential dispersion of objects, through the screening timeframe.
8.1.4 For the deployment of satellites, the National Aeronautics and Space Administration (NASA), and the 19th SDS provide best practices for successful deployment to ensure early orbit tracking.2,3 Vehicle operators should avoid deploying payloads laterally, with no change in altitude. Because the satellite and launch vehicle remain at the same altitude, there is greater potential for re-contact or collision.
Variations in altitude provide for natural dispersions in object orbits. For the specification of trajectories, improperly specified deployments can result in an inadvertent re-contact.
2 NASA/SP-20205011318 Spacecraft Conjunction Assessment and Collision Avoidance Best Practices Handbook , dated December 2020, available on the Space Track website.
3 JSpOC Recommendations for Optimal CubeSat Operations, dated August 4, 2015.
8.1.5 Early planning is also important when there are multiple deployments from a non-stabilized platform. In this scenario there is no covariance because the nominal trajectory is unavailable. It may be extremely difficult to discriminate between payloads that are randomly deployed. Screening for conjunctions is also complicated and necessitates a specific “shotgun cloud” approach tailored to the launch activity specifics. A shotgun cloud approach entails clearing a swath of space along the nominal trajectory of the payload deployer or upper stage large enough to cover the deployment and subsequent spreading out, in random directions, of multiple objects.
9 SPECIAL CONDITIONS: GROUPING OF TRAJECTORY FILES.
9.1 In some cases, it is not possible to provide a single trajectory file for a launch that is valid throughout the identified launch window (this is typical of a rendezvous trajectory that is targeting a specific orbital plane). A launch vehicle that performs guidance maneuvers to target a specific destination follows a different trajectory depending on the time of launch. Because launch sites rotate as the Earth revolves under fixed orbital planes, a launch differential of 1 second can change the trajectory significantly, for the purpose of a COLA analysis. For this class of launches, it is difficult and cumbersome to develop a trajectory file for every second of the launch window, and subsequently assess each file. It is possible, and advisable, to request a waiver to the requirement by providing bounding cases that are inclusive of the dispersion of the trajectory throughout the launch window.
9.2 For example, one recommended solution could be to provide an initial, intermediate, and final trajectory file that is representative of the possible range of trajectories. The waiver would need to include an engineering analysis justification to show that these cases are indeed representative of the range of potential trajectories. Additionally, the trajectory spacing must be such that the dispersion over time does not increase beyond intended screening standoff distances. As such, the probability of collision or separation distance from objects would be effectively analyzed.
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