JFSCC, 18th Space Control Squadron
Combined Space Operations Center (CSpOC)
Vandenberg Air Force Base, California, USA
Tel +1-805-605-3533
www.space-track.org

LAUNCH CONJUNCTIONASSESSMENT HANDBOOK
VERSION 1.0  DECEMBER 2018
18 SPCS Process for Launch Conjunction Assessment

TABLE OF CONTENTS
Contents

Revision History _________________________________________________________________________________________ 1

Important Definitions ___________________________________________________________________________________ 2

18th Space Control Squadron ____________________________________________________________________________________2
Launch Conjunction Assessment _________________________________________________________________________________2

Launch Collision Avoidance ______________________________________________________________________________________2
General Pertubations _____________________________________________________________________________________________2

Special Pertubations ______________________________________________________________________________________________2

Launch Conjunction Assessment Authorities __________________________________________________________ 3

Air Force Instruction 91-217 Space Safety And Mishap Prevention Program ________________________________3
Title 14 Code of Federal Regulations (14 CFR)__________________________________________________________________3
USSTRATCOM SSA Sharing Program _____________________________________________________________________________3

Space-Track.org____________________________________________________________________________________________________4

Launch Conjunction Assessment Process ______________________________________________________________ 5

Screening Process _________________________________________________________________________________________________5

How to Request Launch Conjunction Assessment Support ____________________________________________________6
Screening Schedule _______________________________________________________________________________________________6

Screening Timesteps ______________________________________________________________________________________________7
Screening Types ___________________________________________________________________________________________________8
Reporting Criteria _________________________________________________________________________________________________8
Results _____________________________________________________________________________________________________________8
Transition From Launch to On-Orbit Conjunction Assessment ________________________________________________9

Conjunction Assessment of Reentering Objects ________________________________________________________________9

Screening Limitations __________________________________________________________________________________ 10

General ___________________________________________________________________________________________________________ 10

Launch Windows ________________________________________________________________________________________________ 10
RCS Values _______________________________________________________________________________________________________ 10
All Sorted Results _______________________________________________________________________________________________ 10

Trajectory Formats _____________________________________________________________________________________ 12

TABLE OF CONTENTS
Overview _________________________________________________________________________________________________________ 12
System ___________________________________________________________________________________________________________ 12

Input Files - Coordinate Systems and Characteristics ________________________________________________________ 12
Caliper ___________________________________________________________________________________________________________ 13

Free-Format _____________________________________________________________________________________________________ 15

CALIPER Trajectory Covariance V2.0 __________________________________________________________________________ 15

How to Name Trajectory Files _________________________________________________________________________ 18

Overview _________________________________________________________________________________________________________ 18

File Name Examples ____________________________________________________________________________________________ 18

How to Submit Forms and Trajectory Files ___________________________________________________________ 19

Overview _________________________________________________________________________________________________________ 19

Submitting Files Through Space-Track.org ____________________________________________________________________ 20

Manual Upload of Trajectory Files and Forms ________________________________________________________________ 20
Email _____________________________________________________________________________________________________________ 21
Guidance for Requests Within 24 Hours ______________________________________________________________________ 21

How to Receive Screening Results _____________________________________________________________________ 22

Overview _________________________________________________________________________________________________________ 22

How to Subscribe for Automated Notifications _______________________________________________________________ 23

Contact Us _______________________________________________________________________________________________ 24

18 SPCS Launch Conjunction Assessment Team ______________________________________________________________ 24

18 SPCS Orbital Safety Crew ____________________________________________________________________________________ 24
18 SPCS SSA Sharing Team _____________________________________________________________________________________ 24
Space-Track.org Administration Team _________________________________________________________________________ 24

REVISION HISTORY
Revision History
Version

Page 1

Description of Changes

DateIMPORTANT DEFINITIONS
Important Definitions

18TH SPACE CONTROL SQUADRON

18th Space Control Squadron (18 SPCS) performs the space surveillance mission for the U.S. Air Force andprovides foundational space situational awareness (SSA) for the U.S. Department of Defense (DoD) and U.S.
interagency partners, as well as global space entities. This role was performed by the Joint Space
Operations Center (JSpOC) until July 2016, at which time 18 SPCS was activated and assumed all spacesurveillance functions, including detecting, tracking and identifying man-made objects in Earth orbit andmaintaining the DoD space catalog, which is make available to the public on www.space-track.org. 18 SPCS
is part of the 21st Space Wing and is currently co-located with the Combined Space Operations Center(CSpOC, previously the JSpOC) at Vandenberg Air Force Base in California.

LAUNCH CONJUNCTION ASSESSMENT

Launch conjunction assessment (CA) is the process of identifying close approaches between the planned
trajectory(s) of a launch vehicle and other man-made objects on orbit, to include active and inactive
satellites, rocket bodies, debris, and analyst objects that are not in the public catalog, as well as theInternational Space Station (ISS) and vehicles transiting to and from it. Trajectories should be provided forall objects associated with the launch vehicle, such as booster segments, payloads, jettisoned components,
and debris. Launch CA may be performed for space launches and ballistic missile launches.

LAUNCH COLLISION AVOIDANCE

Launch collision avoidance is the decision to mitigate the risk of predicted conjunctions by altering planned
launch times to avoid or resolve the close approaches. The decision is the responsibility of the launch
entity, but may be directed by agencies, such as the U.S. Air Force, who have been given the authority to do
so.

GENERAL PERTUBATIONS

Simplified General Perturbations model 4 (SGP4) is the general perturbation (GP) analytic algorithm used
for integration of equations of motion and orbit propagation of satellites in the space catalog maintained by
18 SPCS.

SPECIAL PERTUBATIONSSpecial Perturbations (SP) is the numerical method used in 18 SPCS’ mission software for integration of theequations of motion and orbit propagation of satellites in the space catalog. This technique accomplishes
direct numerical integration of the equations of motion including all necessary perturbing accelerations.

Page 2LAUNCH CONJUNCTION ASSESSMENTAUTHORITIESLaunch Conjunction Assessment Authorities

AIR FORCE INSTRUCTION 91-217 SPACE SAFETY AND MISHAP PREVENTION PROGRAM
This document provides overarching guidance on space safety for acquisition, testing, and life cycle
operations of terrestrial, launch, and orbital space systems, and includes specific direction on theacceptable risk thresholds for launches executed from Air Force launch ranges. It is applicable to all Air
Force organizations that develop, test, or operate any space system, or who provide launch/range services
for space systems, and requires that any entity launching an object to exceed 150km altitude from an Air
Force range receive launch conjunction assessment from the 18th Space Control Squadron. Launch entities
must submit their launch plans and data through the 30th Space Wing Safety Office (30 SW/SE) at
Vandenberg Air Force Base or the 45th Space Wing Safety Office (45 SW/SE) at Cape Canaveral Air Force
Station, who will be the direct interface with 18 SPCS for launch CA services.
The full instruction is available online at http://static.epublishing.af.mil/production/1/af_se/publication/afi91-217/afi91-217.pdf

As of December 27, 2018, AFI 91-217 is being revised and incorporated into AFI 91-202.

TITLE 14 CODE OF FEDERAL REGULATIONS (14 CFR)

14 CFR sets forth the procedures and requirements applicable to commercial space transportation
activities conducted in the United States or by a U.S. citizen or by a U.S.-licensed launch entity outside theU.S. In accordance with 14 CFR, the U.S. Federal Aviation Administration (FAA) requires that all launch
entities receive launch CA from the U.S. Department of Defense. The full 14 CFR is available online athttps://www.ecfr.gov/cgi-bin/textidx?gp=&SID=ccae461521090c137b5134f855ad02bc&mc=true&tpl=/ecfrbrowse/Title14/14tab_02.tpl

USSTRATCOM SSA SHARING PROGRAM

Unites States Strategic Command (USSTRATCOM), as the U.S. government entity responsible for space
situational awareness (SSA), is committed to promoting a safe, stable, sustainable and secure spaceenvironment through the sharing of SSA information. In 2009, USSTRATCOM initiated the SSA Sharing
Program to provide no-cost basic, emergency, and advanced SSA data and services that cover the full scopeof support needed through the lifetime of a satellite from pre-launch preparation to end-of-life disposal.
Services include launch conjunction assessment (CA), launch support and early orbit determination, onorbit CA and collision avoidance (COLA), anomaly support, end-of-life and disposal support, deorbit
support, and reentry assessment. The SSA Sharing Program allows any launch entity or satellite operator in
the world to request launch CA from USSTRATCOM by submitting an Orbital Data Request (ODR) andassociated forms and data to 18 SPCS. Entities who have signed SSA Sharing Agreements with
USSTRATCOM will receive expedited review of their request.

Page 3

LAUNCH CONJUNCTION ASSESSMENTAUTHORITIESUSSTRATCOM has delegated management of the SSA Sharing Program to the Joint Functional Space
Component Command (JFSCC), formerly Joint Functional Component Command for Space (JFCC SPACE).
While JFSCC oversees the SSA Sharing program, they have directed 18 SPCS to execute day-to-day SSA data
sharing and support. 18 SPCS performs the space surveillance mission for the U.S. Air Force, and provides
foundational SSA for the U.S. government, as well as global space entities through the SSA Sharing Program.
This role was performed by the Joint Space Operations Center (JSpOC) until July 2016, at which time 18
SPCS was activated and assumed all space surveillance functions. 18 SPCS is currently co-located with the
Combined Space Operations Center (CSpOC, previously the JSpOC) at Vandenberg Air Force Base, but now
has the separate and distinct mission of performing space surveillance, maintaining the space catalog, andproviding foundational SSA to U.S. and global partners.

SPACE-TRACK.ORG

Space-Track.org (www.space-track.org) is a public website owned by USSTRATCOM, managed by JFSCC,
and populated by 18 SPCS. It is the primary method of sharing SSA information with the global spacecommunity. All launch providers and satellite operators should register for a user account in order toaccess the full scope of SSA data and services available through the SSA Sharing Program.

Page 4LAUNCH CONJUNCTION ASSESSMENT PROCESS
Launch Conjunction Assessment Process
SCREENING PROCESSThe JFSCC Launch Conjunction Assessment (CA) process, executed by 18 SPCS, identifies close approaches
between launch objects which exceed 150km in altitude and other cataloged space objects. It begins withsatellite observations from the U.S. Space Surveillance Network (SSN), which includes a variety of sensors
throughout the world that detect, track, catalog and identify man-made objects orbiting Earth. SSN
observations are input into the 18 SPCS mission system, which implements GP and SP orbit propagation
theory. Orbit determination (OD) is performed automatically multiple times per day to determine theposition and velocity of every object in the catalog, which is then updated in the 18 SPCS space catalog. The
18 SPCS Orbital Safety Team screens the launch trajectories provided by launch entities against the rest of
the space catalog, which includes active and inactive satellites, rocket bodies, debris, and analyst objects
that are not in the public catalog, as well as the International Space Station (ISS) and vehicles transiting toand from it. Currently, 18 SPCS launch CA does not include screenings against other launch trajectories
occurring at the same time. Results are provided based on miss distance or probability of collision andidentify launch times that could result in a collision with an on-orbit space object.
18 SPCS will advise customers on whether GP or SP will be used for screenings. Due to customer data andmission prioritization, 18 SPCS may adjust screening requests accordingly due to mission needs.

Figure 1: Launch Conjunction Assessment Cycle

Page 5LAUNCH CONJUNCTION ASSESSMENT PROCESSHOW TO REQUEST LAUNCH CONJUNCTION ASSESSMENT SUPPORTAll entities launching from an Air Force launch range are required to receive launch CA in accordance with
AFI 91-217. All US-licensed launch providers are required by the Federal Aviation Authority (FAA) toreceive launch CA directly from 18 SPCS. All other entities may request it through the Orbital Data Request(ODR) process. (Reference Launch Conjunction Assessment Authorities for more information.) All theforms referenced below are available on Space-Track.org at: https://www.spacetrack.org/documentation#/odr
1.

2.

3.

Launch entities at Air Force ranges should consult with the 30 SW or 45 SW Safety Offices todetermine requirements, which typically include submitting the following to 18 SPCS no later than
15 days in advance of launch:a. Launch plan and orbital parameters (R-15 form)b. Launch Conjunction Assessment Request (Form 22)
c. Launch trajectories for each associated object (may be submitted within 7 days of launch)
U.S.-licensed launch entities launching from a non-Air Force range should submit the following to
18 SPCS no later than 15 days in advance of launch:a. Launch plan and orbital parameters (R-15 form)b. Launch Conjunction Assessment Request (Form 22)
c. Launch trajectories for each associated object (may be submitted within 7 days of launch)
Non-U.S. launch entities should submit the following to 18 SPCS no later than 30 days in advance of
launch:a. Orbital Data Request (submit according to instructions on the form)b. Launch plan and orbital parameters (R-15 form)c. Launch Conjunction Assessment Request (Form 22)
d. Launch trajectories for each associated object (may be submitted within 7 days of launch)

If a launch entity has never received launch CA from 18 SPCS, forms and trajectories must be
submitted 30 days in advance. All requests and associated forms should be submitted to 18 SPCS throughSpace-Track.org. Please register for a user account on Space-Track.org and contact
18SPCS.doo.launch@us.af.mil to set up a permissions-based folder (that will only be accessible by thelaunch entity and 18 SPCS), which will be used to submit files, as well as receive screening results.

SCREENING SCHEDULE

18 SPCS performs launch CA screenings according to the timing requested on the Form 22 submitted by the
Air Force launch wing or launch entity. 18 SPCS will perform at minimum a screening the day of the launchwith up to two additional screenings, as early as 7 days before mission day (e.g. L-7; L-4; and mission day),with the option of three backup days (listed as secondary launch dates within the Form 22). The initial
backup screening will be first secondary launch date provided on the Form 22. If the launch is delayed one
day, the secondary 2 date will be used as backup, with secondary 3 being used as the backup for secondary
2 if the launch continues to push. If launch delays exceed the last backup date, a new Form 22 must be

Page 6LAUNCH CONJUNCTION ASSESSMENT PROCESS
submitted to 18 SPCS. New Form 22s must be received 24 hours prior to first requested screening
delivery and include new trajectory files, if applicable.
18 SPCS will make every attempt to perform the launch CA as close as possible to the requested delivery
time but may need to complete the screenings earlier due to manning and resource constraints. Launch
mission day screenings always take precedence over screenings days prior to launch (e.g. L-4, L-7).

Suborbital launches may list a date range as discussed in the Form 22. This information can be identified in
Item 2 B) “Secondary launch date(s) & launch window(s)” and listed in Item 7 “Additional Information” on
the Form 22 for clarification. If a date range is used for a suborbital launch, delivery times must also be
noted within the Item 7. If they match the previous delivery times, just a statement in Item 7 noting thatthey match Item 3 delivery times will suffice.

SCREENING TIMESTEPS

Launch entities or Air Force launch ranges may request the frequency within the launch window the
trajectories are screened:
•
•
•
•
•

Top of every minute, +/- seconds
Every 30 Seconds
Every 10 Seconds
Every 5 Seconds
Every Second

18 SPCS will advise customers if limitations arise due to customer data or mission prioritization and may
adjust screening parameters accordingly.

Page 7

LAUNCH CONJUNCTION ASSESSMENT PROCESSSCREENING TYPES
18 SPCS provides two types of screenings: stand-off radius and probability of collision (Pc). Pc screenings
can be limited based on the data provided by the launching entity and customer, as well as mission
prioritization and screening capability. Minimum screening volumes are based on the secondary object
type according to the following table. Manned objects will only be screened using stand-off radius. In orderto receive Pc, covariance information and size (in meters) of the launch vehicle, and any other launchedobjects for which screening is desired, must be provided in the trajectory files by the launch entity. 18 SPCS
computes covariance for secondary objects. Launch entities may request larger screening volumes thanthose listed in the following table, which will be approved by 18 SPCS on a case-by-case basis. All trajectory
files will be screened to the same value per category.

TABLE 1: SCREENING VOLUMES
ObjectType

Definition

MannedManned space stations, visiting vehicles

Activesatellites
All others

Satellites performing operational mission(may or may not be maneuverable)
Debris, rocket bodies, inactive satellites

REPORTING CRITERIA

Propagation
Duration of
trajectory
Duration of
trajectory
Duration of
trajectoryStand-offRadius

Probability ofCollision

200 kmNot an option

25 km

2.5 km

1x10E-5 (0.00001)
1x10E-5 (0.00001)

Launch CA customers will receive all close approaches identified within the screening volumes in Table 1
or as requested on the Form 22 approved by 18 SPCS.

RESULTS

Results will be provided in a single text file that includes screening results for all the trajectories provided,
sorted by trajectory, referred to as the “All Sorted” file. Files known as “.res files” can be sent via SIPR in lieu
of an All Sorted file if required. Under each trajectory file name there will be list of close approaches withinformation for the following fields:
•
•
•
•
•
•
•
•
•

Page 8Year
Day of year
Launch time
Satellite catalog number of the secondary object
Common name of the secondary object
Mission elapsed time (MET) in seconds
Miss distance in km
Probability of collision (if applicable)
Screening volume

LAUNCH CONJUNCTION ASSESSMENT PROCESS
If there is no data listed under the trajectory file name it indicates that there are zero results within therequested screening volume for that file.
If .res files are required, this should be included in Item 7 of the Form 22 “Additional Details”.

TRANSITION FROM LAUNCH TO ON-ORBIT CONJUNCTION ASSESSMENT

Once a spacecraft separates from the rocket, it enters the early orbit phase of operations which lasts fromseparation until it has reached its final orbit. During this time, it is imperative that the satellite operator
provide predictive ephemeris to 18 SPCS for conjunction assessment screening to address the gap between
launch trajectories and when 18 SPCS can consistently track the separated spacecraft. Once 18 SPCS
consistently tracks the spacecraft they will be integrated into the daily on-orbit CA screening process. For
more information on early orbit and on-orbit CA, please reference the Spaceflight Safety Handbook forOperators, which is available on Space-Track.org.

CONJUNCTION ASSESSMENT OF REENTERING OBJECTS

If a trajectory is provided for a reentering rocket body or other associated launch object, 18 SPCS will
screen it and report results in accordance with launch CA parameters.

Page 9

SCREENING LIMITATIONS
Screening Limitations
GENERAL

Trajectory files that are submitted for a launch conjunction assessment screening are grouped into a
mission and screened together in a daisy-chain process. All associated trajectory files should be grouped
into missions on a Form 22 that require the same launch window, time step, and screening criteria percategory.

If a trajectory file requires a different launch window, time step, or screening criteria per category, it should
be grouped into a separate Form 22 with any other files that may require those same criteria. Essentially, a
copy of the Form 22 should be created with just the specific trajectory files listed for that different launch
window/time step/screening criteria and all the respective data should remain the same.

The additional Form 22s should add a designator of some sort to the mission name to differentiate between
the different screenings. (i.e. LAUNCH MISSION NAME-A, and the next followed by LAUNCH MISSION
NAME-B)LAUNCH WINDOWS

Trajectory files should be grouped into a mission and Form 22 based on their respective launch windowthat they will belong under. A Form 22 could be submitted with all the associated trajectory files for thesame launch window as one mission.

If there were a set of additional trajectory files that were only viable for another launch window (i.e.
trajectories that are only valid for a portion of the launch window for an interplanetary mission), theyshould then be submitted on another Form 22. Essentially, a copy of the Form 22 should be created withjust the specific trajectory files listed for that different launch window and all the respective data should
remain the same.

RCS VALUES

Only one RCS value can be used per each trajectory file. If there are multiple RCS values or another RCS
value after a certain time in the file, those trajectory files should be provided by the launch entity as
separate trajectory files for screening. If the launch entity cannot provide separate files, then the largest
RCS value listed for that file within the Form 22 will be used.

ALL SORTED RESULTS

The single text file that is used to provide results known as the “All Sorted” file limits the reported
conjunctions based on the parameters listed in the Form 22 request in Item 6 “Screening Type andCriteria”. All trajectory files within a respective mission screening will be screened to the same value percategory. For example, if a probability of collision (PoC) Criteria 1x10E-5 (0.00001) for active satellites isPage 10

SCREENING LIMITATIONS
being requested for particular screening request that criteria will be applied to all covariance trajectories
within the same mission screening for active payloads.

Page 11TRAJECTORY FORMATS
Trajectory Formats
OVERVIEWIn order to perform launch CA, 18 SPCS must receive correctly formatted launch trajectories from thelaunch entity for all objects that require screening. All launch trajectories should be listed on the Form 22
in accordance with “How to Name Trajectory Files.” Launch CA requires separate trajectory files per launch
stage or RCS value. Multiple RCS values for one trajectory file cannot be accommodated and will result in 18
SPCS using the larger RCS value indicated on the Form 22. All trajectory files must be formatted inkilometers; any other unit will compromise the accuracy of the results.
Trajectories should be provided a minimum of 7 days in advance of mission day and at least 30 days inadvance of mission day for launch entities who are receiving this service from 18 SPCS for the first time.

SYSTEM

SuperCOMBO/CALIPER is the launch CA software used by 18 SPCS. It accepts three input file formats:
CALIPER Trajectory, Free-Format Ephemeris, and CALIPER Trajectory Covariance V2.0. The CALIPER
Trajectory and Free-Format variations are used to input only ephemeris data (position and velocity),
whereas the CALIPER Trajectory Covariance V2.0 input file includes both ephemeris and position
covariance. The CALIPER Trajectory Covariance V2.0 file format is required for users who request aprobability of collision (Pc) metric in addition to a miss distance.

The following sections provide guidance on input file coordinate systems and characteristics that apply to
all formats, followed by descriptions of each specific format.

INPUT FILES - COORDINATE SYSTEMS AND CHARACTERISTICS

SuperCOMBO/CALIPER accepts launch vehicle position and velocity in rotating Earth-Fixed Greenwich(EFG) coordinates. In this system, E is along the line of intersection of the true equator of date and theGreenwich meridian, G is through the true North Pole (normal to the true equatorial plane) and F
completes the right-handed coordinate system. SuperCOMBO/CALIPER converts the EFG ephemeris to
Earth-Centered Inertial coordinates of date, a frame referred to as “ECI” in the 18 SPCS community. In theconversion from EFG to ECI, SuperCOMBO/CALIPER incorporates UT1-UTC corrections through a timing
constants file populated with values from the International Earth Rotation and Reference Systems Service(IERS) Bulletin A.

EFG differs from the crust-fixed Earth-Centered Rotating (ECR) frame in that EFG does not incorporate
polar motion. Differences between the EFG and ECR frames are small, on the order of 15 meters or less.
Note that EFG is used interchangeably with the NASA “TDR” coordinate system. ECR is terminology usedwithin 18 SPCS; it is equivalent to the Earth-Centered Earth-Fixed (ECEF) and Earth-Centered Fixed (ECF)
frames.

Page 12TRAJECTORY FORMATS
Position covariance is entered in a launch vehicle-centered frame, in either UVW or PTW coordinates. In
the UVW frame, 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 theright-handed coordinate system. (Despite the “in-track” descriptor, V is only coincident with the velocity
when the launch trajectory is circular.)In the PTW covariance frame, T is the unit vector along the launch vehicle’s velocity vector, W is again theunit vector normal to the launch vehicle’s inertial orbit plane, and P is the unit vector that completes theright-handed coordinate system. PTW is the most easily visualized covariance frame for elliptical launchvehicle trajectories because the T direction is aligned with the launch vehicle’s velocity.

The SuperCOMBO/CALIPER launch trajectory input file should have ephemeris/covariance points provided
at sufficiently frequent time points that interpolation may be used with negligible error. For boostinglaunch trajectories, an ephemeris/covariance point spacing of 10 seconds is recommended – although lessthan 10 second spacing could be needed if the trajectory contains large maneuvers. For non-boosting, nonmaneuvering phases of a launch trajectory profile, larger ephemeris/covariance point spacing can be used.
Note that SuperCOMBO/CALIPER can accept launch trajectory files with variable ephemeris/covariance
point spacing.

Because launch vehicle velocity is used for both interpolation and for identifying potential conjunctions,SuperCOMBO/CALIPER requires that the launch vehicle velocity be realistic such that the EFG velocity
represents the derivative of the EFG position. Also, the position and velocity ephemeris points should be
relatively smooth and continuous (e.g., real world delta-Vs for maneuvers are acceptable but large
deviations particularly those that are discontinuous step functions are not).

For meaningful Pc calculations, the launching entity must provide realistic launch trajectory covariance.
For responsible decision making based on Pc, the launching authority must be knowledgeable on the Pc
metric and its use/limitations.

CALIPERIn the CALIPER trajectory file, one or more launch times/trajectories can be represented in a single file. In
the previous version of CALIPER, all launch times in a launch window had to be represented in a single file.

Now, a single trajectory can be input and either run as SuperCOMBO/CALIPER or it can override the launchtime and input launch window start/stop/time steps. Since most launch profiles maintain the same earthfixed trajectory throughout the launch window, this approach is desirable as it requires less processing
time. However, if the earth-fixed trajectories do differ with each new launch time (e.g., launch azimuth
varies for interplanetary launch opportunities), then all launch times/trajectories will have to be submitted
within a single file.
Note that each trajectory file is not screened for its own window if it is grouped into a mission with one
overarching launch window (The launch window that is submitted on the Form 22 is used as an override
for all trajectory files submitted for that launch screening).

Page 13TRAJECTORY FORMATS
There are several reasons for this, but it comes to system processes and procedures and mission growth. As
launch CA has grown and launch screenings have become more system intensive, the trajectory files formissions are screened in a daisy-chain process with their screenings set up to a launch window (that would
override a window listed within the trajectory file itself).
This can become an issue with some of the deep space/interplanetary missions if the trajectory files are
only viable during a certain limited time within the launch window (i.e. a trajectory file is only valid from0450-0455 of a launch window/won’t be used after this time, but the file is six hours long and included
within the overarching launch window on the Form 22).

Trajectory files must be grouped into a mission and Form 22 based on their respective launch window thatthey will belong under. A Form 22 could be submitted with all the associated trajectory files for the samelaunch window as one mission.

If there were a set of additional trajectory files that were only viable for another launch window, they mustthen be submitted on another Form 22.

Essentially a copy of the Form 22 should be created with just the specific trajectory files listed for thatdifferent launch window and all the respective data could remain the same. The additional Form 22s
should add a designator of some sort to the mission name to differentiate between the different screenings(i.e. LAUNCH MISSION NAME-A, and the next followed by LAUNCH MISSION NAME-B)
In the example below, two launch times are represented.

LAUNCH TIME: 2019
1 1520 3.000 LAUNCH AZIMUTH:
0.000-3048.065-1597.441
5352.179
0.000000
0.000000
0.000000
0.000000000 0.000000000 0.000000000
10.000-3048.246-1597.518
5352.450-0.053000-0.018000
0.067000
0.000000000 0.000000000 0.000000000
20.000-3049.416-1597.747
5353.492-0.196000-0.026000
0.141000
0.000000000 0.000000000 0.000000000
30.000-3052.425-1598.001
5355.278-0.417000-0.023000
0.217000
0.000000000 0.000000000 0.000000000
40.000-3057.928-1598.172
5357.776-0.690000-0.009000
0.280000
0.000000000 0.000000000 0.000000000
LAUNCH TIME: 2019
1 1521 3.000 LAUNCH AZIMUTH:
0.000-3048.065-1597.441
5352.179
0.000000
0.000000
0.000000
0.000000000 0.000000000 0.000000000
10.000-3048.246-1597.518
5352.450-0.053000-0.018000
0.067000
0.000000000 0.000000000 0.000000000
20.000-3049.416-1597.747
5353.492-0.196000-0.026000
0.141000
0.000000000 0.000000000 0.000000000

Page 140.000

DISPERSION FILE:

0.000

DISPERSION FILE:TRAJECTORY FORMATS
30.000-3052.425-1598.001
5355.278-0.417000-0.023000
0.217000
0.000000000 0.000000000 0.000000000
40.000-3057.928-1598.172
5357.776-0.690000-0.009000
0.280000
0.000000000 0.000000000 0.000000000

A line with the launch time separates each EFG trajectory. Launch azimuth and the dispersion file are notused. The first line of each ephemeris point record contains time since launch in seconds followed by the
XYZ components of EFG position in km. The second line contains the XYZ components of EFG velocity in
km/s. The third line is a placeholder for acceleration of the asset, but acceleration is not currently used.

Any single CALIPER trajectory for a given launch time must contain a minimum of 5 points and a maximumof 25000 points. The maximum number of seconds since epoch is 999999.999 seconds, equivalent to11.574 days.

FREE-FORMATThe second format is a concise, space-delimited, free-format. An example is provided below.
3896.280
3900.000
3930.000
3960.000
3990.000
4020.000
4050.000
4080.000
4110.000
4140.000
4170.000
4200.000

13660.571
13669.394
13739.930
13809.394
13877.810
13945.204
14011.600
14077.022
14141.495
14205.041
14267.683
14329.444

2408.228
2427.179
2579.652
2731.493
2882.693
3033.248
3183.149
3332.393
3480.973
3628.885
3776.126
3922.691

0.000
0.000
0.003
0.006
0.009
0.012
0.015
0.018
0.021
0.024
0.027
0.030

2.374
2.369
2.333
2.298
2.263
2.230
2.197
2.165
2.134
2.103
2.073
2.044

5.095
5.093
5.072
5.051
5.029
5.008
4.986
4.964
4.942
4.919
4.897
4.874

0.020
0.020
0.030
0.030
0.030
0.040
0.040
0.040
0.050
0.050
0.050
0.050

This EFG file of positions and velocities is independent of launch time. Launch window start/stop/spansare entered within the SuperCOMBO/CALIPER program by 18 SPCS. Numbers are in standard double
precision format (not scientific/exponential format).

The first column is time since launch in seconds. The next three columns are the XYZ components of EFG
position in km. The last three columns are the XYZ components of EFG velocity in km/s.

CALIPER TRAJECTORY COVARIANCE V2.0

The elements of the CALIPER Trajectory Covariance V2.0 format are shown below:
CALIPER EPHEMERIS V2.0 COVARIANCE UVW (or PTW)LAUNCH TIME: yyyy ddd hhmm ss.sss…
TimeSinceLaunchInSeconds X Y Z Vx Vy Vz
PosCov(1,1) PosCov(2,1) PosCov(2,2)
PosCov(3,1) PosCov(3,2) PosCov(3,3)

Page 15TRAJECTORY FORMATS
A sample CALIPER Trajectory Covariance V2.0 file is shown next:
CALIPER EPHEMERIS V2.0 COVARIANCE PTW
LAUNCH TIME: 2019 20 1105 35.986inidef
0.000 -15614.190
9512.504
27201.506
0.033489-0.042779-0.000589
0.000675
258.619 -15621.660
9378.301
26541.559
0.033953-0.045187-0.000573
0.000669
510.329 -15627.212
9243.933
25878.882
0.034352-0.047596-0.000543
0.000660-0.031674
0.112008
0.005907-0.025764
0.121013
0.006007-0.018003
0.130522
0.006000-0.511889-2.511603-0.526209-2.592410-0.541701-2.673392

A CALIPER Trajectory Covariance V2.0 file begins with 2 header lines.
Header line 1:

1
2
3
4
5
6
7
8
12345678901234567890123456789012345678901234567890123456789012345678901234567890“CALIPER EPHEMERIS V2.0 COVARIANCE ccc”

ccc = covariance coordinate system in a launch vehicle-centered frame, specified as either “PTW” or “UVW”.
••

In PTW, T is along the velocity vector of the launch trajectory with W out-of plane and P
completing the triad.
In UVW, U is radial with W out-of-plane and V completing the triad.

Header line 2:

1
2
3
4
5
6
7
8
12345678901234567890123456789012345678901234567890123456789012345678901234567890“LAUNCH TIME: yyyy ddd hhmm ss.sss…”

Launch time formats are self-explanatory. Note that the decimal seconds are actually double precision freeformat and thus can contain more than 3 decimals.
Data Record Lines:

Although the ephemeris and covariance data records appear column specific and formatted, they are
actually flexible, free-format. Numbers are space delimited and are entered as standard double precisionnotation (not scientific/exponential notation). The column alignment in the example was added only to aid
readability. A data record consists of 3 lines.

The first line consists of both the timestamp and ephemeris data in EFG coordinates. EFG is an Earth-fixedrotating coordinate system related to the true equator/mean equinox of date Earth-Centered Inertial
system by a simple rotation about the Z axis (normal to the true equator of date). The second and thirdlines contain the 6 elements of the lower triangular of the position covariance matrix. Again, despite theappearance of a strict format in the example above, all numbers are free-format double precision, spacedelimited values, in standard notation (not scientific/exponential notation).

Page 16TRAJECTORY FORMATS
Data record 1:

TimeSinceLaunchInSeconds = time since launch, in seconds

X
Y
Z
Vx
Vy
Vz

= X-component of EFG position in km= Y-component of EFG position in km= Z-component of EFG position in km= X-component of EFG velocity in km/s
= Y-component of EFG velocity in km/s
= Z-component of EFG velocity in km/s

Data Record 2:

The second data record contains 3 of 6 elements of the lower triangular of the position covariance matrix.
PosCov(1,1) = position covariance element in km2
PosCov(2,1) = position covariance element in km2
PosCov(2,2) = position covariance element in km2
Data Record 3:

The third data record contains 3 of 6 elements of the lower triangular of the position covariance matrix.
PosCov(3,1) = position covariance element in km2
PosCov(3,2) = position covariance element in km2
PosCov(3,3) = position covariance element in km2

The CALIPER Trajectory Covariance Format V2.0 can be used to generate Pc and miss distance results, oronly miss distance via stand-off radius mode. In this case, SuperCOMBO/CALIPER would use only theephemeris data. This file could also be used to generate elliptical screening. In this case,SuperCOMBO/CALIPER would again ignore covariance data, using only the ephemeris data in the file.

Page 17

HOW TO NAME TRAJECTORY FILES
How to Name Trajectory FilesOVERVIEW

18 SPCS requires that launch agencies name their files following a specific format, which dictates how theephemeris file will be processed. The file name format is:<Year>_<Mission>_<LaunchObject>_<MetaData>_<FileFormat>.<FileExtension>

Table 2: Trajectory File Name Convention
Data Field

Description

Normative Value (N) or
Example (E)ObligatoryYear

The two-digit year of launch.

(E) 18 for 2019

Yes

MissionLaunchObject

MetaData

FileFormat

File Extension

Typically, the primary payload for the launch. Will
be designated by 18 SPCS.
The launch object or segment that the trajectory
represents.
Optional additional information provided at thediscretion of the launch. Often used to indicate
deployment status or additional details on thevariation of the file

Format of trajectory file. Must be one of threeformats included in “Trajectory Formats” section:
Caliper, Free-Format, or CovarianceIndicates the type of file

FILE NAME EXAMPLES•••

Page 18

19_TELSTAR-18V_PAYLOAD_COV.txt

19_CRS-16_STAGE2_UNPOWERED_CAL.txt

19_Iridium-8_STAGE2_NoBurn_FF.txt(E) 19 for 2020(E) Telstar-18V(E) Iridium-6(E) ICON(E) NROL-71(E) PAYLOAD(E) STAGE2(E) FAIRING(E) SKIRT-RING(E) Pre-Deploy(E) Post-Deploy(E) NoBurns

Yes

Yes

No

(E) Powered(N) CAL(N) FF(N) COV(N) .txt (unless otherwise
directed by 18 SPCS)

Yes

HOW TO SUBMIT FORMS AND TRAJECTORY FILES
How to Submit Forms and Trajectory FilesOVERVIEW

Launch forms (R-15s, Form-22s and trajectory files) should be submitted through the website SpaceTrack.org, or, if Space-Track access is not possible, by email to the 18 SPCS Orbital Safety Crew at
18SPCS.doo.launch@us.af.mil.

Space-Track.org is the most efficient and secure method of submitting files on a recurring basis. To set up
access, contact the 18 SPCS Launch CA Team at 18SPCS.doo.launch@us.af.mil or +1-805-605-3536. The
Launch CA Team will request the following information:

1.
2.

The title of your launch organization
The Space-Track user names of the personnel who will upload trajectories/forms and download results

The Launch CA Team will create a permissions-based launch CA (LCA) folder for your organization that will
only be accessed by 18 SPCS and the personnel you authorize. You will have upload, download, and delete
permissions to the folder, which you will access through the Files Panel:

Figure 2: Files Panel on Space-Track.org

Page 19

HOW TO SUBMIT FORMS AND TRAJECTORY FILESSUBMITTING FILES THROUGH SPACE-TRACK.ORG
Once you have an LCA folder on the Files Panel, you will also have access to the ‘Download’ and ‘Upload’
tabs. On the ‘Upload’ tab you can upload a variety of files to the folders you have permissions to. All of thesefolders will display in the ‘Destination’ dropdown menu:

Figure 3: Files Panel Upload Tab - Ephemeris

MANUAL UPLOAD OF TRAJECTORY FILES AND FORMS
1.
2.
3.
4.
5.
6.

Page 20

Log in to Space-Track.org, click on ‘Files’ at the top of the page, and then click on the ‘Upload’ tab
Click ‘Choose Files’ and select your files

2.1 Maximum number of files in a single upload is 100
2.2 Maximum total size per upload is 60 MB

Using the ‘Destination’ dropdown menu, select the ‘/LCA/’ folder for your organization
Click ‘Upload’ to upload the files
After a successful upload, the files will display in ‘My Uploads (Last 30 Days)’ Table
The 18 SPCS Orbital Safety Crew will receive a notification that you have uploaded new forms or files
for screening. However, if the screening request is within 24 hours, please phone or email the Orbital

HOW TO SUBMIT FORMS AND TRAJECTORY FILES
Safety Crew to notify them that you need an immediate response: +1-805-605-3536 or
18SPCS.doo.launch@us.af.mil.

EMAIL

If your organization does not have an LCA folder on the Files Panel, you may send your files by email to the
18 SPCS Orbital Safety Crew at 18SPCS.doo.launch@us.af.mil. Please:1.
2.

Name files in accordance with guidelines in ‘How to Name Trajectory Files’
Send only .txt files - .zip files cannot be accepted

GUIDANCE FOR REQUESTS WITHIN 24 HOURS

After you submit your trajectories and updated Form 22, please phone the 18 SPCS Orbital Safety Crew at+1-805-605-3536 to provide the following information regarding the short notice request:

1.
2.
3.
4.

Page 21

The launch mission name
The time the results are needed by
The Space-Track folder to which the updated files were uploaded
Reference your approved Orbital Data Request, if applicableHOW TO RECEIVE SCREENING RESULTS
How to Receive Screening Results
OVERVIEW

18 SPCS will post results to the launch entity’s folder on Space-Track.org as soon as they are completed andas close to the requested screening time as possible. The results will be posted to the same folder that thelaunch entity posted the Form 22 and launch trajectories to, as seen in Figure X below:

Figure 4: Download Tab - Launch CA Results

Page 22

HOW TO RECEIVE SCREENING RESULTS
HOW TO SUBSCRIBE FOR AUTOMATED NOTIFICATIONS
Launch entities should subscribe for automated notifications from Space-Track to be immediately notified
of new uploads to their respective LCA folder.

Figure 5: Folder Subscriptions

1.

2.
3.

Page 23

Login to Space-Track.org and click on your username in the top right corner. Select “My Profile” fromthe drop-down menu.
Select the “File” tabIn the “Folder Subscriptions” table select “Subscribe” for the “/LCA/YourOrganization/” folder

CONTACT US
Contact Us

18 SPCS LAUNCH CONJUNCTION ASSESSMENT TEAM
For questions on launch conjunction assessment, please contact:••

Monday – Friday, 1600 UTC – 0000 UTC:o 18SPCS.doo.launch@us.af.mil, +1-805-605-3536
Monday – Friday, 0000 UTC – 1600 UTC, and Saturday and Sunday:o 18SPCS.doo.orbitalsafety@us.af.mil, +1-805-605-3533

18 SPCS ORBITAL SAFETY CREW

For questions on on-orbit conjunction assessment and collision avoidance support, please contact the 18
SPCS Orbital Safety Crew by email at 18SPCS.doo.orbitalsafety@us.af.mil or by phone at +1-805-605-3533.
Examples of support include:•••

Questions about screening results
Screenings for high-interest events
Missing CDMs

18 SPCS SSA SHARING TEAM

For questions about specialized SSA support or data products, please contact the 18 SPCS SSA Sharing
Team by email at 18SPCS.doo.ssasharing@us.af.mil or by phone at +1-805-606-2675. Examples include:••••

Submitting an Orbital Data Request for advanced services or support
Questions about data formats
Space-Track access and permissions
Registering your satellite to receive spaceflight safety support

SPACE-TRACK.ORG ADMINISTRATION TEAM

For questions about the Space-Track.org website, please contact admin@space-track.org. Examples include:•••

Page 24

API queries
Automation
Website performance