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| ===== (Compiled by TC) ===== | |
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| === Description === * Allows user to tailor sigmas to mission phase * Ties set of 5 identified sequential images so if one image is moved with an updated trajectory, the surrounding tied images are encouraged to move to maintain a dynamically realistic solution |
== Description == DYNAMIS augments the nominals file by appending the nominal inertial space position differences dW=W1-W0 between the current image and up to two images before and after. This information is used to 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 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: |
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| === Inputs === | ETLM= 1800, 1.D-6 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'] 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. 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. 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 == |
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| === Outputs === | == Outputs == |
dynamics
(Compiled by TC)
Description
DYNAMIS augments the nominals file by appending the nominal inertial space position differences dW=W1-W0 between the current image and up to two images before and after. This information is used to 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 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= 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']
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.
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.
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
FRAME='dxR_FRAME' SURVEY ETLM= 1800, 1.D-6 VSIG= 0.100, 0.100, 0.040 PSIG= 0.0001, 0.0001, 0.0001
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
- NOMINALSMS
Outputs
- Updated NOMINALSD