June 1, 1994 ============ New versions for some subroutines and programs ---------------------------------------------- The changes do not affect the core models but rather the implementation logic. The following subroutine/programs were updated: 1. Subroutine yaw_control: Allows a new input argument that can force a restart. This is needed when processing several satellites in the same program. You have to indicate a restart for every satellite after the first one. 2. Subroutine yaw_control_crude: Allows a new input argument that can force a restart. This is needed when processing several satellites in the same program. You have to indicate a restart for every satellite after the first one. Also, the startup logic has been simplified and zero step size is now tolerated. 3. Subroutine initial_yaw_angle.f: Allow for the new "restart" parameter in the calling sequence to the yaw models. 4. Subroutine attitude_info: Fixed a bug that didn't allow reading of unmerged attitude files. 5. Subroutine read_gps_attitude: Fixed a bug that didn't allow reading of unmerged attitude files. Allow for a sattelite not to be on the attitude file. Signals the absence of a satellite on the attitude file via a new output parameter. 6. Subroutine get_gps_attitude: Pass on the absence of satellite signal to the calling subroutine. 7. Subroutine gps_coordinates: Allows a new input argument that can force a restart. This is needed when processing several satellites in the same program. You have to indicate a restart for every satellite after the first one. 8. Subroutine phaser_center: Will compute the satellite attitude with the nominal model if the satellite is not on the attitude file. 9. Program gps_precise_attitude: Updates the list of satellite yaw moment of inertia. Add the "restart" argument to the calling sequence of the yaw models. Added a logic to decide which satellite has a yaw bias. By default only attitude files for eclipsing satellites are generated. This default can be overriden via a command line argument. Allow the input of moment of inertia value through a text file. Timing of setting the yaw bias ------------------------------ The yaw bias will be commanded on all GPS satellites except GPS 14,18 and 20 on June 6 around 0 Greenwich time. Recommended values for nominal yaw_rates ---------------------------------------- For block I satellites: 0.199 degrees/second For block II satellites: 0.113 degrees/second For block IIa: 0.119 degrees/second For GPS 14,18 and 20 (noon turn rates): 0.087 degrees/second The uncertainty of these values is 20%. June 2, 1994 ============ A bug was fixed in the version of program "gps_precise_attitude" that was installed yesterday. The program is now corrected. June 3, 1994 ============ New versions of program "dump_attitude" and its companion script. Added an option to get info only and made the script nicer. June 8, 1994 ============ New version of program "gps_precise_attitude". Better handling of unbiased sateliites. Also, added an option to read the yaw rates from a special text file. The text file has the format: PRN SVN TIME YAW-RATE(deg/sec) 19 19 1994 5 21 21 0 0 0.0 0.11119 19 19 1994 5 22 2 0 0 0.0 0.11304 19 19 1994 5 22 8 6 40 0.0 0.11293 19 19 1994 5 22 13 56 40 0.0 0.09456 19 19 1994 5 22 20 3 20 0.0 0.11295 19 19 1994 5 23 1 53 20 0.0 0.11300 25 25 1994 5 21 21 0 0 0.0 0.11900 25 25 1994 5 21 21 50 0 0.0 0.11906 25 25 1994 5 22 3 56 40 0.0 0.11900 25 25 1994 5 22 9 46 40 0.0 0.11684 25 25 1994 5 22 15 53 20 0.0 0.11900 25 25 1994 5 22 22 0 0 0.0 0.11900 27 27 1994 5 21 21 0 0 0.0 0.11888 27 27 1994 5 22 2 50 0 0.0 0.11900 27 27 1994 5 22 8 56 40 0.0 0.11899 27 27 1994 5 22 14 46 40 0.0 0.09183 27 27 1994 5 22 20 53 20 0.0 0.11899 9 39 1994 5 21 21 0 0 0.0 0.11900 9 39 1994 5 22 0 20 0 0.0 0.11900 9 39 1994 5 22 6 26 40 0.0 0.11900 9 39 1994 5 22 12 16 40 0.0 0.11899 9 39 1994 5 22 18 23 20 0.0 0.11901 9 39 1994 5 23 0 13 20 0.0 0.11900 This file will be generated routinely as part of the Flinn process. June 10, 1994 ============= New version of subroutine gps_coordinates is available. A bug in the definition of the sign of the beta angle was fixed. New versions of subroutines get_gps_attitude and phase_centera are available that have better treatment of small variation in input time and time reversals. June 16, 1994 ============= Add GPS10 to the list of satellites without yaw bias. (Altogether 4 satellites.) June 23, 1994 ============= A bug was fixed that affected satellites just entering eclipse season and caused a bad attitude. The fix was done in subroutine gps_coordiantes. A new version for subroutine yaw_control is also available where the logic to zero the attitude partials was made more robust. August 19, 1994 =============== A bug was eliminated from subroutine yaw_control that occasionally caused the yaw rate partials to zero out upon shadow exit. This would happen sometimes for satellites that reversed their yaw direction upon shadow exit. The script for running the program dump_attitude was improved. January 26, 1995 ================ Program gps_precise_attitude and subroutines gps_coordinates and initial_yaw_angle were modified to reflect the following changes: 1. GPS 16 is no longer biased since January 9, 1995. 2. GPS 29 will maintain a positive yaw bias regardless of the sign of the beta angle, until further notice. This is due to malfunctions on board the spacecraft. January 31, 1995 ================ Program gps_precise_attitude was modified to reflect the yaw biasing today of GPS 14, 16, 18 and 20. Their maximal yaw rate should be 0.087 deg/sec nominally. March 3, 1995 ============ A bug was fixed in the computation of partials of the wind-up model (Subroutine phase_wind_up.f). The bug was in a part of the code that is currently never accessed and so it did not cause any errors. Thanks to Young S. Nam, a graduate student at UT-CSR, who found the bug. April 4, 1995 ============= placed a yaw_bias_table depicting the exact history of the yaw bias for every satellite. The file can be found in this directory. A reader of that file was placed in the "software/subroutines" directory under the name "get_bias.f" April 25, 1995 ============= Placed a nominal_yaw_rates table depicting the exact history of the nominal yaw rate for every satellite. The file can be found in this directory. The reader of that file was placed in the "software/subroutines" directory under the name "read_nominal_yaw_rate.f." April 6, 1996 ============= GPS 33 added to the "nominal_yaw_rates" and "yaw_bias_table" files.