OMEGA

Description

This program

• Calculates the angular velocity of a body's rotation by using the position of landmarks in subsequent images

The images should be at least roughly registered (REGISTER) before starting.

• The pointing and spacecraft position is originally determined in body-fixed space from a nominal .pck file. Then they are transformed back to inertial space.

If V is the vector of a landmark at time = 0 (PICNM0) then the inertial space vector V' at time = t (PICNM1) is given by

• V' = Vcos(a) +(AxV)sin(a)/a +A(A.V)(1-cos(a))/a^2

• where A is the inertial space vector OMEGA x t and a is its magnitude with OMEGA = angular velocity.

The program solves for A, for an offset of image PICNM1 due to relative pointing errors and for the inertial space landmark positions at t=0. Many iterations (~100) are required for convergence (but it is very fast) and OMEGA is printed both as an inertial space vector and in RA, DEC,|OMEGA| in deg and deg/da.

Required Files

• POLE.TXT which has an initial guess for the RA/DEC of omega and its magnitude in deg/da.

• PICTLIST.TXT

• LMRKLIST.TXT

Inputs

• The image name of two images that have some common landmarks in them
• Option to do additional iterations

• Option to update the SCOBJ and C vectors in the SUMFILES

Outputs

• <imagename>_ROT.TXT - Log of the translation of each common landmark from inertial to body-fixed frame.

• Standard out - showing
  • Omega value
  • RA/DEC calculated for the angular momentum vector, as well as the rotate rate in degrees per day
  • the difference in time between the two image (in ET)

Using OMEGA

Here is a sample of the standard input:

$ omega
 Input PICNM0
P601293196F2
 Input PICNM1
P601293203F2

OMEGA:                  0.10196E-04    0.17130E-03   -0.36799E-03


                       ALPHA                          DP1            DL1
       -0.00020        0.00138       -0.00247       -0.05370        0.03372

  -1.3347563804838266E-004

 Iterate? (y/n)
n
        0.02842        0.01714

OMEGA:                 -0.28363E-04    0.19784E-03   -0.35343E-03
ET1 - ET0:                  7.00000
RA DEC DEG/DA:        98.15845      -60.51164     2009.99984

 Return to iteration? (y/n)
n
 Update SUMFILE? (y/n)
n

Example output file P601293196F2_ROT.TXT

 PICNM0 = P601293196F2  PICNM1 = P601293203F2

                              INERTIAL                                    BODY FIXED

EE0001        0.79740E-01   -0.24443E+00   -0.76561E-01   -0.24352E-01    0.26146E+00   -0.28265E-01
EE0002        0.76654E-01   -0.24740E+00   -0.76961E-01   -0.28215E-01    0.26180E+00   -0.28335E-01
EE0003        0.72600E-01   -0.24614E+00   -0.78760E-01   -0.31991E-01    0.26251E+00   -0.28429E-01
EE0004        0.69034E-01   -0.24720E+00   -0.79739E-01   -0.35877E-01    0.26275E+00   -0.28361E-01
EE0006        0.79252E-01   -0.24506E+00   -0.73033E-01   -0.24417E-01    0.26092E+00   -0.32141E-01
EE0007        0.75892E-01   -0.24655E+00   -0.73990E-01   -0.28216E-01    0.26158E+00   -0.32223E-01
...

OMEGA:                 -0.47507E-04    0.15800E-03   -0.37100E-03
RA DEC DEG/DA:         106.73459      -66.02445     2009.99984
ET1 - ET0:               7.00000
Rotation:                0.16285
IMAX:                        76
dP, dL, dS:            -0.91703E+00    0.51699E+00   -0.25762E-03

Body fixed frame:        87.19928      -64.78164     -115.42772

    0.2404600643D+00   -0.3024911368D+01    0.2313284431D+01   SCOBJ
    0.6384185077D+00   -0.4531136654D+00   -0.6280592064D+00   CX
    0.7669571811D+00    0.4425514816D+00    0.4690669420D+00   CY
    0.6479576942D-01   -0.7738450699D+00    0.6360038956D+00   CZ
   -0.5260644620D+00    0.8478532108D+00    0.6696761722D-01   SZ

CategoryPrograms