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| ===== (Compiled by TC) ===== | |
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| DYNAMIS augments the nominals file by appending the nominal inertial space position differences dW=W1-W0 between the current image and up |
This program augments the nominals file by appending the nominal inertial space position differences between the current image and up |
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| constrain the solution in the subroutine IPL2SOBJPTG so that the s/c position solution does not deviate too much from a dynamically realistic state. An entry ETLIM= in the input DYNAMIS.TXT gives |
constrain the solution so that the spacecraft position solution does not deviate too much from a dynamically realistic state. This program also allows for different mission phases to have different "sigmas" via [[DYNAMICS.TXT]]. === Required Files === * [[DYNAMICS.TXT]] * [[NOMINALS]]/ * [[SUMFILES]]/ === Output Files === * Updated NOMINALS file ----- == Using dynamics == ??Insert a sample dynamics.txt file here to show and then explain below it?? A typical ETLIM= record is: {{{ ETLM= 1800, 1.D-6 }}} ETLIM= gives |
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| 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: |
images to be used. This is followed by an estimate of the velocity uncertainty that goes into an uncertainty estimate included in the added records. |
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| ETLM= 1800, 1.D-6 | FRAME= has these three choices: |
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| A record FRAME= tells IPL2SOBJPTG how to interpret the sigmas in spacecrafe position found in the nominals file. The choices are |
{{{ FRAME= ['dxR_FRAME', 'Dxr_FRAME', 'BOD_FRAME'] }}} |
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| FRAME= ['dxR_FRAME', 'Dxr_FRAME', 'BOD_FRAME'] | FRAME= specifies how to interpret the sigmas in spacecraft position found in the nominals file. |
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| The first one uses tha 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. |
* '''dxR_FRAME''' 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 the Doppler data. |
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| A record VSIG= allows the user to change the position sigmas from those in the original nominals file. The record: |
* '''Dxr_FRAME''' 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. |
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| * '''BOD_FRAME''' simply uses the components in the body-fixed frame, generally with equal uncertainties in each direction. The VSIG= record has three components: {{{ |
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| }}} | |
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| sets the uncertainties in the three components to 100 m, 100 m and | VSIG= allows the user to change the position sigmas from those in the original nominals file. The record in the sample, sets the uncertainties in the three components to 100 m, 100 m and |
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| change, another such record would be added to affect subsequent | change, another VSIG= record would be added to affect subsequent |
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| A record PSIG= allows the user to change the pointing sigmas in the | The PSIG= record has three components: {{{ PSIG= 0.0003, 0.0003, 0.0005 }}} PSIG= allows the user to change the pointing sigmas in the |
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| three camera axes. For OSIRIS_REx we expect something like: | three camera axes. The sample shows the approximate values expected for OSIRIS_REx with a larger twist uncertainty since there is only one star tracker. |
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| PSIG= 0.0003, 0.0003, 0.0005 with a larger twist uncertainty since there is only one star tracker. The DYNAMIS.TXT file looks just like the PITLIST.TXT file in that there is a space in the first column. Excerpts from such a file for DAWN at Vesta are: FRAME='BOD_FRAME' APPROAH ETLM= 1800, 1.D-6 VSIG= 0.200, 0.200, 0.200 PSIG= 0.0001, 0.0001, 0.0001 F11A0001225 F11A0001241 ... F21A0003895 F21A0003910 FRAME='dxR_FRAME' SURVEY ETLM= 1800, 1.D-6 VSIG= 0.100, 0.100, 0.040 PSIG= 0.0001, 0.0001, 0.0001 F21A0003931 F21A0003932 ... F21A0032347 F21A0032348 END There were a number of parameter changes as the mission progressed from Approach to Survey to HAMO to LAMO to HAMO2 to Departure, with transitions between phases requiring parameters of their own. == Inputs == * [[DYNAMICS.TXT]] * NOMINALSMS == Outputs == * Updated NOMINALSD |
----- ''(Compiled by TC) '' |
dynamics
Description
This program 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. This program also allows for different mission phases to have different "sigmas" via DYNAMICS.TXT.
Required Files
Output Files
- Updated NOMINALS file
Using dynamics
??Insert a sample dynamics.txt file here to show and then explain below it??
A typical ETLIM= record is:
ETLM= 1800, 1.D-6
ETLIM= gives a maximum time difference in seconds that limits the neighboring images to be used. This is followed by an estimate of the velocity uncertainty that goes into an uncertainty estimate included in the added records.
FRAME= has these three choices:
FRAME= ['dxR_FRAME', 'Dxr_FRAME', 'BOD_FRAME']
FRAME= specifies how to interpret the sigmas in spacecraft position found in the nominals file.
dxR_FRAME 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 the Doppler data.
Dxr_FRAME 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.
BOD_FRAME simply uses the components in the body-fixed frame, generally with equal uncertainties in each direction.
The VSIG= record has three components:
VSIG= 0.100, 0.100, 0.040
VSIG= allows the user to change the position sigmas from those in the original nominals file. The record in the sample, 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 VSIG= record would be added to affect subsequent nominals files.
The PSIG= record has three components:
PSIG= 0.0003, 0.0003, 0.0005
PSIG= allows the user to change the pointing sigmas in the nominal files. The three components refer to rotations about the three camera axes. The sample shows the approximate values expected for OSIRIS_REx with a larger twist uncertainty since there is only one star tracker.
(Compiled by TC)