WHAT?

This tutorial explores problems in Orbit Mechanics which may easily be solved on the TI-89 or TI-92. Successful completion of this material may benefit in three ways :

1. You will learn something about orbital mechanics
2. You will learn to program your TI-89/92
3. You will learn some math and physics.

HOW?

Navigate this tutorial in several ways :

1. Randomly access any topic of interest through the sidebar on the left.
2. Progress systematically through all topics by using the TOUR --> link at the bottom of each page.
3. Download all the programs, install them on your calculator, and hope for the best.

The best method for moving back through the levels is to use the Back button on your browser.

The recommended course is to follow the tour links and, with your calculator, work through the examples at the end of each section.

DOWNLOADS

Orbit.89g  This is the entire set of orbit mechanics programs. Download this file and scroll down to INSTALLATION INSTRUCTIONS.

FONTS  The Ti92PlusPC font must be installed on your computer to view the TI-89 code in these documents. The Star Jedi font is used to see this site in its full glory.

Program Documentation  A listing of all program code in a Microsoft Word document. FONTS need to be installed to read the TI-89 program code.

You will need Adobe Acrobat 6.0 to read the .pdf files on this WebSite. It is a free download. Note: version 5.0 has a bug and will not work

WinZip is shareware.

TI Graph-Link 89 is a free download from Texas Instruments. ti89usa.exe   is the old version of the graphlink software, but if you install it the fonts will automatically be installed and you will be able to edit programs outside of your calculator.

Equation Writer is a free download. This program will become an indispensable addition to your calculator. We will use it as a subroutine for input and output.

INSTALLATION INSTRUCTIONS

Installing the Orbit.89g programs on your calculator

1. Create a new directory on your calculator and name it ORBIT.
2. Connect the calculator to your computer with the GraphLink cable and open the GraphLink program.
3. Select the "Link" drop down menu and choose "Send".
4. In the dialogue box that comes up, point to the directory on your computer where you downloaded Orbit.89g. Look for "List Files of Type" Group(*.89g).
5. Select "Orbit.89g" and send it to the ORBIT directory on your calculator. The files will be automatically ungrouped. The "Retain Folder" check-box must be unchecked, and the user must then select ORBIT from the list displayed by GraphLink.
6. Disconnect the calculator from your computer and go into the ORBIT directory. Find the file named "kbdprgm4.89p" and MOVE it to the MAIN directory.
7. Go to the home screen and press "green diamond", then "4" to activate the custom orbit program menu.
   
   
   
   
8. Immediately archive the matrices "f", "g", "up", "zzd", "zzl", and "zzt" so they will not be destroyed by data. Eventually you will want to archive all the files in the ORBIT dirctory. Don't archive them until they have been run on the calculator. The programs will run faster from the archives if they have been compiled (run at least once) before they are archived.
9. Dowload and install EQW. Place EQW and rclclip in the MAIN folder.

Installing the TrueType Fonts on Your PC

1. Copy the font ( ex: Ti92ppc.ttf, Starjhol.ttf ) files to your WINDOWS directory.
2. Open the Windows Control Panel.
3. Double click the Fonts icon to display the Fonts dialog box.
4. Click the TrueType... button, make sure you have enabled TrueType fonts, and then select "OK."
5. Select "Add." Windows displays a listing of available fonts. (If necessary, set "Drives" to your WINDOWS directory.)
6. Highlight the font name ( ex: "TI92Pluspc (TrueType)", Star Jedi Hollow (True Type) ) and select "OK." Windows adds the fonts to your font list and shows you a small sample of the symbols in the font.
7. Close the Fonts dialog box.

PROGRAMMING PHILOSOPHY

It is generally true that a TI-89/92 function is better that a program : the output is on the home screen and no global variables are created. Functions are neat and clean.

You are probably wondering why I have chosen to develop this package as programs instead of functions. Programs are better for this application precisely because of the programs ability to use and write global variables.

The complexity of the algorithms begs for them to be broken into smaller pieces and then used by each other as subroutines. This in turn demands that a large number of common variables be used in the input and output of almost every program.

There are a large number of variables common to many of the algorithms and most programs use half a dozen or more. Once a calculation is begun, several programs and subroutines will normally be required to complete it. The many parameters required to solve the problem will be passed from program to program as they are created, modified, and used by each subroutine.

The problems associated with tracking and passing numerous variables are avoided by using global variables as the most current value of a global variable is always available for every subroutine that needs it. Then when a calculation is complete, all the global variables may be deleted from memory by the cleanup program.

REFERENCES

The first three books were the main references for the material contained in this site. For further reading on the topic of Celestial Mechanics I would enthusiastically recommend any of these books.

1. Fundamentals of Astrodynamics, Bate, Mueller, White
2. Methods of Orbit Determination for the Microcomputer, Boulet
3. Astronomical Algorithms, Meeus
4. Methods of Orbit Determination, Escobal
5. Celestial Mechanics, Moulton
6. Modern Astrodynamics: fundamentals and perturbation methods, Bond, Allman
7. Adventures in Celestial Mechanics, Szebehely

TOUR -->