pole

Description

This program solves for the pole right ascension, declination and rotation rate for a body in principal axis rotation. The rotation rate is calculated in degrees/day while right ascension and declination are calculated in degrees.

If you "keep the result", then pole will translate the VLM (central vector) an UX, UY, UZ (normal vectors) of the landmarks, maplets, SUMFILES and NOMINALS. It will also update the information in POLE.TXT.

Input Files

• POLE.TXT - simple text file containing nominal pole RA (deg), DEC (deg), PM (deg), OMEGA (deg/day)

• LMRKLIST.TXT

• SUMFILES

POLE.TXT and LMRKLIST.TXT must be in the working directory.

POLE.TXT is a single row file that contains the predicted pole RA (deg), DEC (deg), PM (deg), and OMEGA (deg/day). These values are given in the .tpc kernel file for the object. LMRKLIST.TXT contains a list of landmarks.

Using pole

When you run pole, it is expecting an initial value for POLE.TXT. If that file does not exist, the program will fail. To create the file, you can use the pole values from the current PCK (planetary constants kernel).

1. Input a time in UTC.

• Make sure the time is within the span supported by the kernels.

2018 NOV 16 13:09:54.824

2. Create a POLE.TXT file.

Here is a sample POLE.TXT file:

       86         -65      89.00000000    2010.48945

3. Answer whether you want the rotation rate fixed (y for yes, n for no).

4. Enter

• 0 if you want to iterate

• 1 if you want to keep the result (this updates POLE.TXT)

• 2 if you want the previous result (this is nominal if on the first iteration)

In general you will want to do several iterations to help the inversion of the matrix converge. When the pole solution ceases to change, if you think that the solution is an improvement, you can keep it. At that point, it will change most of the files in the working directory.

Here is a sample output from the POLE.TXT input:

    86.60062   -65.00002    90.42707  2009.99979311
     0.05176     0.02171                 0.00000001

• The first row gives all the new pole parameters for POLE.TXT.
• The second row shows formal uncertainty (the diagonals of the covariance). These values should be multiplied a factor of 10 or 100.

Test Results

Testing using the NTE3A data set showed that picking different Epoch times over the time span of the images used (in this case 22 days) resulted in no change of RA, DEC, or rotation rate, and the PM at J2000 only change by 0.07 deg.

(Compiled by KD)

CategoryPrograms