Frequently Asked Questions

Requesting Astrodynamic Standards

What is the process for requesting Astrodynamic Standards?

Government users and contractors supporting the government under a valid contract may request the Astrodynamic Standards software using the Space/Cyberspace Analysis Resource Portal (SARP), accessible on the Air Force Non-Secure Internet Protocol Router Network (NIPRNet).  

You will first have to request a SARP account and once approved, you will be able to make a request by selecting the Astrodynamic Standards menu item.   The request process uses a wizard that collects multiple Points of Contact information as well as the desired software. It is highly recommended that you review the document in the Astrodynamic Forum that describes the request wizard so that you are prepared to enter the required information according to Air Force Space Command Instruction (AFSPCI) 17-105. 

The wizard also requires you to select the specific algorithms, version, platforms (Windows 32/64 bit or Linux 32/64 bit).  The Astrodynamic Standards Forum also contains the most current list of the available software.

What if I don’t have access to the Air Force Non-Secure Internet Protocol Router Network (NIPRNet) but need to request the software?

You can make your request on Public Astrodynamic Standards Distribution Site (PAADS) website using the request wizard.  Once your request is processed, accepted and approved, you will receive a Compact Disk with the software. 

Before making the request, please see the for a list of available software and versions as well as the Requesting Astrodynamic Standards Software Guide at

What is the difference between a contractor request and a government request?

Per Air Force Space Command Instruction (AFSPCI) 17-105, a government request is one in which ONLY government personnel would be using the Astrodynamic Standards software.  Contractors or FRDC personnel must complete a contractor request.  Only Government personnel will be required to sign a Non-Disclosure Agreement (NDA) with Air Force Space Command.

A contractor request is when one or more contractors or FRDC organizations will be using the Astrodynamic Standards software regardless of whether they are using it in a government or contractor facility.  Contractors and their sub-contractors will be required to sign an Acknowledgement of Use with Air Force Space Command.

In most cases, if the contractor makes a request for the software, the government agency that they are working for should ALSO make a government request.

I’m a contractor but I have a number of sub-contractors that also need the Astrodynamic Standards software. Do I have to make a separate request for each?

The request wizard will ask you if you have any sub-contractors (you can add as many as you need to).  Please ensure that the list of software that you request covers all the required software. For example the prime contractor may need SGP4 but the sub-contractors may need SP and LAMOD, the request should include all three pieces of software.

I’m a contractor and I already requested the software on another contract. Can I use it on a different contract?

No. Per the Acknowledgement of Use each request is specifically for the use of the software for a specific government program under a specific government contract.  If you need to use the Astrodynamic Standards software on another contract, a new request must be submitted.

I’m a government agency and I already requested the software on another program but want to use the software on different program. Can I use it on the different program?

Requests are specifically for a program.  You will have to make another request.

I’ve made a request on Space/Cyberspace Analysis Resource Portal (SARP), before and my request is similar. Is there an easy way to make a new request?

Yes. You can use the copy feature (only available on SARP) to make the request.

Why does the government COR or PM need to make a request for the same software that a contractor is making under a contract that the COR/PM are managing?

Per Air Force Space Command Instruction (AFSPCI) 17-105, redistribution of the software by any entity is strictly forbidden.  If a valid contractor inserts the Astrodynamic Standards software into any software product/system in their performance of a contract with the US government and plans on providing that software product/system to the government under the terms and conditions of the contract Statement of Work or Performance Work Statement (e.g. Contract Deliverable), that software product/system cannot include the Astrodynamic Standards as this would be considered redistribution.

In order for the contractor’s software product to work, the government must request the Astrodynamic Standards software and then “plug” it in to the deliverable.

This requires the contractor to loosely couple the integration to allow for the delivery of the system/software without the Astrodynamic Standards. This is typically done by designing/architecting the software/system where all of the Astrodynamic Standards Dynamic Link Libraries or Share Objects are placed in a folder.

What does it mean the software is Export Controlled?

Export controlled means that the distribution of the software falls under the International Trade and Arms Regulations (ITAR). What that means is that the U.S. Government controls the export and distribution of the software and technology as a means to promote our national security interests and foreign policy objectives.

Which algorithms are Export Controlled?

SGP4 and the AS Utilities are not Export Controlled; all other algorithms are export controlled.  The diagram on shows which algorithms are export controlled and which are not.

I don’t know which algorithms to select. Who can help me?

A brief description of the algorithms can be found on the Astrodynamic Standards Forum on SARP,, or on the Public Astrodynamic Distribution Site (PAADS) website at

If you need additional help, please email with the subject line: Request Assistance in Selecting Astrodynamic Standards Algorithms.

The list of algorithms shows a V5.4.X and a V7.X being available. Which should I use?

You should request the latest V7.x software. Version 5.4.X is legacy software that AFSPC will stop supporting starting 1 October 2017.

I’m a current user of the Astrodynamic Standards. How do I get updates?

If you made your request for the software using Space/Cyberspace Analysis Resource Portal (SARP), and if your request was made after 1 January 2010, you should have received an email from SARP informing you of updates. Government users will be able to immediately download the software on the SARP website. Contractors with a valid contract (contract that the request was made originally on which has not expired) will also be able to download the software on the SARP website. Contractors whose contracts have expired will have to make a new request under their new contract to receive the software.

If you haven’t received an email, it is likely that your request was made prior to 1 January 2010 and was made manually (e.g. not through SARP) and therefore you are not in the system. If this is the case, you will have to submit a new request using SARP, regardless of whether you are a contractor or government agency. Reductions in staff at AFSPC no longer permit processing manual requests.

If your request was made after 1 January 2010 and you need an update but haven’t received an email, please contact the AS Manager at with your request number so the AS manager can update your information in the database.

What are some of the reasons why I may be required to obtain new approval paperwork?

When the following information changes from what is listed in the original approval paperwork:

  1. Company name change
  2. New company or organization added to project with access to software
  3. New or changed contract number
  4. Contract that request was initially made under has expired
  5. Project name change
  6. Other unusual circumstances

What are some of the reasons where I may not need new paperwork?

Contract that request was initially made has been extended. If this is the case, please contact the AS Manager at to let them know of the extension.

SAA Library General Questions

Where can I report an issue or suggest an enhancement to the algorithms in the SAA Library?

Please use the SAA Library Feedback web page on the Public Astrodynamic Distribution Site (PAADS) website,, to submit issues or enhancements. All requests will be entered into the SAA Library database and reviewed by the Standardized Astrodynamic Algorithm (SAA) Configuration Control Board (CCB) who meet monthly to discuss what features, issues, and enhancements will be integrated into the next release of the SAA Library.

If you have already submitted an issue or enhancement, please contact the SAA CCB Secretary at

How can I request help with using the algorithms in the SAA Library?

Assistance on using the Export Controlled Astrodynamic Standards algorithms are provided to government personnel and contractors supporting the government with a valid contract only. Please contact the AS Manager at with your specific questions.

How can I request help with using the SGP4 which is not Export Controlled in the SAA Library?

Requests for assistance on SGP4 can be obtained by logging onto the website.  Air Force Space Command will only provide assistance to valid users who have a Space Situation Awareness (SSA) Sharing Agreement with USSTRATCOM/J513, Space Plans and Policy. They negotiate the SSA Sharing Agreements, which establish the parameters within which data will be exchanged by both signing parties to facilitate ongoing cooperation and advance spaceflight safety. All members of the space community, including satellite operators, launching agencies, commercial service providers, and research/academic institutions, are welcome to contact for more information on the agreement process. U.S. government (USG) organizations and their contractors have implied agreements and do not need to pursue additional documentation with USSTRATCOM. 

Additional information can be obtained at

I am a current user of V5.4 of the algorithms and need assistance with migrating to V7.x. How do I request help?

Please contact the Air Force Space Command AS Manager at AFSPC will soon provide documentation to assist users in migrating to V7x. Please check the Astrodynamic Standards Forum on SARP,, or Public Astrodynamic Distribution Site (PAADS) for this document starting in 2016.

I’ve reviewed the list of software and the descriptions, but I need additional information that could help me in selecting the right algorithm. Is there some documentation I can read?

Updates to the documentation are currently being made. As they become available, the documentation will be posted on the Space/Cyberspace Analysis Resource Portal (SARP), in the Astrodynamic Standards Forum under each algorithm and the Public Astrodynamic Distribution Site (PAADS).

When do the days since 1950 (DS50) start?

It starts from 31/12/1949 00:00:00.000.

I’m still using the old versions of the algorithms, V5.4 2. Example driver programs for the different programming languages are supplied for SGP4 and SP. Why can’t I find driver examples for all of the environments for the other SAAs (e.g. LAMOD, COMBO, etc.)?

AFSPC only distributes the C driver for the other SAAs (V5.4.2) because the example drivers for SGP4 and SP provide the basis for using the other DLLs and they can be adapted easily. AFSPC resources are limited in creating more examples and must focus their efforts in the developing and maintenance of the SAA Library. We encourage users of the old algorithms to migrate to V7.x where we do provide examples for all languages.

I'm using the Java wrappers on Linux, and I get an error that says "Failed to create temporary file for jnidispatch library: Permission denied." What do I need to change?

On the Linux platform, the user running the application must have read/write permission on the /tmp/jna folder or this error will occur. To eliminate this error, either grant the user read/write permission on /tmp/jna or use the “sudo” command to run the application with elevated privileges.

I'm using the Java wrappers, and I get an UnsatisfiedLinkError when loading the SAAL DLLs.  What do I need to change?

Make sure the JVM and the SAAL DLLs are of the same platform/architecture (both have the same 32-bit or 64-bit architecture). If not, you will get an exception like:

 Exception in thread "main" java.lang.UnsatisfiedLinkError: Unable to load library 'DllMain': The specified module could not be found.

        at com.sun.jna.NativeLibrary.loadLibrary(

        at com.sun.jna.NativeLibrary.getInstance(

        at com.sun.jna.NativeLibrary.getInstance(

        at com.sun.jna.Native.register(

        at jnaDllMain.<clinit>( 

You can run the 32-bit SAAL DLLs on a 64-bit operating system, but you must be running a 32-bit version of Java.  Similarly, if you are using 64-bit Java, you must use 64-bit SAAL DLLs.

For Java 8 and newer versions of Java, run the command-line version query with these two flags:

        java -d64 -version

        java -d32 -version

One of them should report “unsupported”, which will indicate which version of Java is active. 

On older versions of java, the command "java -version" will report what version of the JVM is active.

I get an error when running the Run_Test_Cases.bat file as described in the readme: “MSVCR120.dll is missing from your computer” or "MSVCR110.dll is missing from your computer".

Your computer doesn't have the Microsoft C++ Runtime files.  This may happen on computers that don’t have development tools installed, and it may happen when using 32-bit DLLs on 64-bit systems. 

If you are missing MSVCR120.dll, it can be installed by downloading the Microsoft Visual C++ Redistributable Packages for Visual Studio 2013 from this location:

If you are missing MSVCR110.dll, it can be installed by downloading the Microsoft Visual C++ Redistributable Packages for Visual Studio 2012 from this location:

If you are running 32-bit SAAL DLLs on a 64-bit Windows operating system, make sure you install the 32-bit version of the appropriate Redistributable Packages from the links above.

What drag models does the SAAL support?

V7.8 currently supports the Jacchia 64 model, Jacchia 70 model, and the Dynamic Calibration Atmosphere (DCA) model. Support for the JBH09/HASDM2 model is planned for a future release of the SAAL.

Does the SAAL support the nine-digit satellite number?

Full implementation of the nine-digit satellite number is still under review, but V7.8 does have several functions that can take them as input:  SpVecAddSatFrFields, ExtEphAddSat, TleAddSatFrFieldsGP2, TleAddSatFrFieldsSP, ObsAddFrArray, ObsAddFrFields, ObsFieldstoB3Card, and ObsFieldstoTTYCard.

Astrodynamic Standards Utilities

Are the Astrodynamic Standards Utilities Export Controlled?

The Astrodynamic Standards Utilities were Export Controlled until May 2014 when HQ AFSPC Foreign Disclosure removed the designation. However, they are not publicly available and are still considered FOUO. Users who have access to the NIPRNet can immediately download the Astrodynamic Standards Utilities on the Space/Cyberspace Analysis Resource Portal (SARP),; no Acknowledgement of Use is required. AFSPC is currently staffing the requirement to make these algorithms publicly available in the near future.


What’s the Earth Constants (physical shape) used in SGP4?

The Earth Constants being used in SGP4 is WGS-72. Even though the EnvConst DLL allows the user to change the Earth Constants, by design SGP4 can only work with WGS-72. This is to assure the "most accurate" prediction possible the user can get from propagating JSpOC TLEs. If the user set the Earth Constants to anything other than WGS-72, SGP4 will not propagate and generate an error message.

What’s the accuracy of SGP4?

The accuracy of a propagation using SGP4 is driven by two things – the accuracy of the theory itself and the accuracy of the input element set with respect to SGP4.

The accuracy of the SGP4 theory is limited by the level of the truncation of the mathematical theory. This truncation was done during the origination of the theory in order to decrease the runtime of SGP4. Truncations in the near earth regime and the deep space circular regimes are on the order of a few kilometers, while they are greater for highly eccentric orbits.

The accuracy of element sets from the JSpOC varies based on things like amount of tracking of the object and amount of the object’s orbit that was covered by the tracking.

What’s the coordinate system used in SGP4?

SGP4 uses the ECI True Equator and Mean Equinox of Epoch system. Each ephemeris data point output in this system is in the fixed ECI frame defined at the epoch of the input TLE.

Is SGP4 Export Controlled?

SGP4 was Export Controlled until 31 December 2016. It is now publicly available and can be downloaded from the Space Track site,, or from Space/Cyberspace Analysis Resource Portal (SARP), No Acknowledgement of Use is required and it is available for immediate download once logged into either site.

What is a TLE?

A TLE is a Two Line Element (TLE), a data format that contains orbital elements of an Earth-orbiting object for a given point in time, the epoch. TLEs are used in the SGP4 propagator to predict the position and velocity of the object at any point in the past or future that can be estimated to some accuracy. The format uses two lines of 80-column ASCII text to store the data. The TLE format is a de facto standard for distribution of an Earth-orbiting object's orbital elements. TLEs can describe the trajectories only of earth orbiting objects.

A TLE set may include a title line preceding the element data, so each listing may take up three lines in the file. The title is not required, as each data line includes a unique object identifier code.

Where can I get Two Line Element (TLE) data?

Two Line Element (TLE) data can be downloaded from or

Where can I find additional information about SGP4?

The Public Astrodynamic Standards Distribution website has additional information about the SGP4 and other Export Controlled Astrodynamic Standards. See

I can’t get SGP4 to work correctly; it states that I need a license file?

The public release of SGP4 requires a license file to be present to work. The method Sgp4SetLicFilePath can be used to set the folder that the license file should be in when SGP4 is initialized. If you don’t have the license file, you will have to download SGP4 again from

Does SGP4 support 3LE’s (Three Line Elements)?

V7.8 does not currently support 3LE’s as the format is still under review. Plans to implement this functionality are scheduled to begin late 2017.