What's New in FreeFlyer?

•The International Celestial Reference Frame (ICRF) is the new default reference frame for all objects in FreeFlyer

oICRF is a fundamental reference frame defined by the International Astronomical Union (IAU)

oThe transformation between the inertial ICRF frame and earth fixed ITRF frame is computed in FreeFlyer using the Standards of Fundamental Astronomy (SOFA) Tools for Earth Attitude software library

• By default, FreeFlyer uses an interpolated version of the IAU 2006/2000A earth orientation model

oUsers can choose between IAU 2006/2000A and IAU 2006/2000B precession/nutation models through the SolarSystem.EarthOrientationModel property

•In most places data which would formerly have been interpreted as MJ2000 will now be interpreted as ICRF. Review the "MJ2000 to ICRF" section of "Migrating to FreeFlyer 7.9" below for all details including:

oReference Frame Mapping

oSolarSystem Editor Updates

oFile Updates

oMJ2000 Earth Equator Functions that are not Interpreted as ICRF

•Covariance and Process Noise now supported in all Attitude Reference Frames

oAbility to read and write covariance in all Attitude Reference Frames such as RIC

oProvides more physically-intuitive representation for Orbit Determination and Conjunction Analysis

•New Process Noise Rate Model

oAbility to set a constant process noise rate which is applied uniformly regardless of step size

oUsers can specify process noise model to use through the SpacecraftODProperties.ProcessNoiseModel property

oLegacy process noise by step model with fixed amount of process noise per step is still supported

•Added light-time velocity terms to range partial derivatives

•Added State Transition Matrix (STM) mapping to Spacecraft partial derivatives to account for light-time

•Added a SpacecraftODProperties.SmoothedEpoch property to allow users to retrieve the epoch of a smoothed state of a Spacecraft

•Earth Orientation Parameter data now uses celestrak.org data

oThe legacy UT1-UTC and UTC-TAI files are still supported, but new updates to these files will no longer be distributed with new versions of FreeFlyer

•Added support for CSV formatted Celestrak Space Weather File

•The default Development Ephemeris (DE) used in FreeFlyer for determining the precise location of solar system objects has been upgraded to DE440.dat

oCelestialObject.Mu values are now dynamically sourced from DE files

•Help File Updates

oThe help file pages for object types which cannot be created in script, but live on other objects (e.g. PlateModel, GroundAntenntaODProperties, etc.), now indicate which object(s) can be their parent objects

oAdded relevant information about members, including object types and read/write usage, to object pages

•FreeFlyer Certification Level 2 is now available

oAdvanced certification modules covering Maneuvering and Targeting & Coverage and Contact

•FreeFlyer Users Forum

oDedicated website with a discussion board for users all over the world to learn about FreeFlyer from FreeFlyer team members and each other

oFreeFlyer users can ask questions about the tool or engage in conversations with other users in the forum

•Lower system memory usage for many Optimal Control scenarios

•Added Optimizer.JacobianSparsity property to increase efficiency of the sampling phase

•Added the ability to set the orientation of a CelestialObject using quaternions through the CelestialObject.SetOrientation() method

•Added new Icons for asteroids, ground vehicles, aircraft, planetary landers, rovers, and habitats

•Corrected an issue where FreeFlyer generated CCSDS OEM Files did not follow the CCSDS Blue Book regarding the maximum number of floating point digits

•Fixed error where the ThrustScaleFactor property could not be set using the BatchLeastSquares OD object dialog

•Fixed an error where allocating list elements could cause a memory leak

•Fixed an issue where setting the Spacecraft.OD.PropagateCovariance property to true when using an Ephemeris for propagation would report NaNs for covariance

•Fixed a crash when removing TrajectoryPhase objects from the Optimizer but leaving phase links

•Fixed a crash when referencing assigning a List<List<Object>>

•Fixed a crash when using TimeSpan.RoundedToUnits() and TimeSpan.TruncatedToUnits() without an argument specified

•Millisecond timing precision mode is deprecated and will be removed in a future release. We recommend that you migrate your Mission Plans to nanosecond timing precision mode. Review the Timing Precision Modes page for assistance in upgrading from millisecond to nanosecond mode.

Because the International Astronomical Union (IAU) defined ICRF to align as closely as possible to MJ2000, we have replaced nearly all usages of MJ2000 in FreeFlyer in-place with ICRF, so that Mission Plans will now use ICRF with little or no action required by users.

Reference Frame Mapping

Properties, methods, and arguments that represented a state in MJ2000 Earth Equator are now represented in ICRF

•Example:

Properties, methods, and arguments that are an int set representing MJ2000 Earth Equator are now represented in ICRF

•Example:

Spacecraft.GetCartesianState() Int Set

7.8.1 Int Set   7.9 Int Set

Properties, methods, and arguments that are a string set representing MJ2000 Earth Equator are now represented in ICRF

•Example: Spacecraft.AttitudeRefFrame

Spacecraft.AttitudeRefFrame String Set

7.8.1 String Set   7.9 String Set

Note: For backwards compatibility, "MJ2000" is still available for string sets but will be treated the same as ICRF.

SolarSystem Editor Updates

•SolarSystem.NPUpdateInterval property deprecated and SolarSystem.CIRFEvaluationMode property added

oThis property determines whether the Celestial Intermediate Reference Frame (CIRF) transformation will be computed exactly at each epoch, or interpolated. The interpolated mode should give the best balance of performance and accuracy for most configurations.

oDefault Value: Interpolated

File Updates

•FreeFlyer Ephemeris V1/V2/V3

oFreeFlyer Ephemeris files generated in FreeFlyer 7.9 are now all written in ICRF and not MJ2000 like in previous versions of FreeFlyer. If you want to generate reports in MJ2000, you should do so manually via the Report command or FileInterface object.

oExisting Ephemerides will load data as if it is ICRF

oFFEphemProperties.WriteBackwardsCompatibleReferenceFrameLabel property added

▪When this property is set to 1, the "ReferenceFrame" field of the FreeFlyer Ephemeris file will be written as "Mean of J2000" rather than "ICRF". This will allow the resulting file to be read in FreeFlyer releases previous to 7.9. Note, no transformations on the data will be performed.

•Code 500

oCode 500 Ephemeris files generated in FreeFlyer 7.9 are now all written in ICRF and not MJ2000 like in previous versions of FreeFlyer. If you want to generate reports in MJ2000, you should do so manually via the Report command or FileInterface object.

▪Data is interpreted as True of Date (TOD) and converted to ICRF

oCode 500 Ephemeris files generated in FreeFlyer 7.9 use Greenwich Apparent Sidereal Time (GAST) for Greenwich Hour Angle (GHA) values unlike previous versions of FreeFlyer.

o'TOD' or 'J2000' can be chosen with the Put command.

▪Choosing 'TOD' will write TOD data

▪Choosing 'J2000' will write ICRF data

•AcqData

oEPV:

▪Geocentric True of Data Rotating EPV files are now all written in TIRF and not True of Date Rotating like in previous versions of FreeFlyer.

▪Geocentric mean of 2000.0 (J2000.0) EPV files are now all written in ICRF and not MJ2000 like in previous versions of FreeFlyer.

oIIRV:

▪Geocentric True of Data Rotating IIRV files are now all written in TIRF and not True of Date Rotating like in previous versions of FreeFlyer.

•Burn Report

oBurn reports generated through the Maneuver command are now all written in ICRF and not MJ2000 like in previous versions of FreeFlyer. If you want to generate reports in MJ2000, you should do so manually via the Report command or FileInterface object.

MJ2000 Earth Equator Functions that are not Interpreted as ICRF

•In most places data which would formerly have been interpreted as MJ2000 will now be interpreted as ICRF. The exceptions are:

oPositionConvert()

oPositionVelocityConvert()

oVelocityConvert()