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| = Dynamics = | = dynamics = ===== (Compiled by TC) ===== == Description == DYNAMICS augments the nominals file by appending the nominal inertial space position differences between the current image and up to two images before and after. This information is used to constrain the solution so that the spacecraft position solution does not deviate too much from a dynamically realistic state. DYNAMICS also allows for different mission phases to have different "sigmas" via [[DYNAMICS.TXT]]. An entry ETLIM= in the input [[DYNAMICS.TXT]] gives a maximum time difference in seconds that limits the neighboring images to be used, and an estimate of the velocity uncertainty that goes into an uncertainty estimate also is included in the added records. A typical record is: {{{ ETLM= 1800, 1.D-6 }}} A record FRAME= specifies how to interpret the sigmas in spacecraft position found in the nominals file. The choices are {{{ FRAME= ['dxR_FRAME', 'Dxr_FRAME', 'BOD_FRAME'] }}} The first one uses the radial direction (R) as prime for the third component with the second component being the cross track direction (X) and the first component, roughly in the downtrack direction completing the right-handed coordinate system. This is used in orbital operations around large bodies, where the radial component is well known from from the Doppler data. The second choice is used during approach where the downtrack velocity is best known. The "radial" (impact parameter) direction is crossed with the downtrack to give the crosstrack direction. The third option simply uses the components in the body-fixed frame, generally with equal uncertainties in each direction. A record VSIG= allows the user to change the position sigmas from those in the original nominals file. The record: {{{ VSIG= 0.100, 0.100, 0.040 }}} sets the uncertainties in the three components to 100 m, 100 m and 40 m respectively. If, during another mission phase, these sigmas change, another such record would be added to affect subsequent nominals files. A record PSIG= allows the user to change the pointing sigmas in the nominal files. The three components refer to rotations about the three camera axes. For OSIRIS_REx we expect something like: {{{ PSIG= 0.0003, 0.0003, 0.0005 }}} with a larger twist uncertainty since there is only one star tracker. == Requires == * [[DYNAMICS.TXT]] * [[NOMINALS]]/ * [[SUMFILES]]/ == Outputs == * Updated NOMINALS |
dynamics
(Compiled by TC)
Description
DYNAMICS augments the nominals file by appending the nominal inertial space position differences between the current image and up to two images before and after. This information is used to constrain the solution so that the spacecraft position solution does not deviate too much from a dynamically realistic state. DYNAMICS also allows for different mission phases to have different "sigmas" via DYNAMICS.TXT.
An entry ETLIM= in the input DYNAMICS.TXT gives a maximum time difference in seconds that limits the neighboring images to be used, and an estimate of the velocity uncertainty that goes into an uncertainty estimate also is included in the added records. A typical record is:
ETLM= 1800, 1.D-6
A record FRAME= specifies how to interpret the sigmas in spacecraft position found in the nominals file. The choices are
FRAME= ['dxR_FRAME', 'Dxr_FRAME', 'BOD_FRAME']
The first one uses the radial direction (R) as prime for the third component with the second component being the cross track direction (X) and the first component, roughly in the downtrack direction completing the right-handed coordinate system. This is used in orbital operations around large bodies, where the radial component is well known from from the Doppler data. The second choice is used during approach where the downtrack velocity is best known. The "radial" (impact parameter) direction is crossed with the downtrack to give the crosstrack direction. The third option simply uses the components in the body-fixed frame, generally with equal uncertainties in each direction.
A record VSIG= allows the user to change the position sigmas from those in the original nominals file. The record:
VSIG= 0.100, 0.100, 0.040
sets the uncertainties in the three components to 100 m, 100 m and 40 m respectively. If, during another mission phase, these sigmas change, another such record would be added to affect subsequent nominals files.
A record PSIG= allows the user to change the pointing sigmas in the nominal files. The three components refer to rotations about the three camera axes. For OSIRIS_REx we expect something like:
PSIG= 0.0003, 0.0003, 0.0005
with a larger twist uncertainty since there is only one star tracker.
Requires
Outputs
- Updated NOMINALS