Sample Implementation
These FORTRAN IV routines have been implemented on a Honeywell-6000 series computer. This machine has a processing speed in the 1MIPS range and a 36 bit floating point word providing 8 significant figures of accuracy in single precision. The information in the following table is provided to allow a comparison of the relative size and speed of the different models.1
| Model | Core Used (words) | CPU Time per Call — Initialize (ms) | CPU Time per Call — Continue (ms) |
|---|---|---|---|
| SGP | 541 | 0.8 | 2.7 |
| SGP4 | 1,041 | 1.9 | 2.5 |
| SDP4 | 3,095 | 5.1 | 3.6 |
| SGP8 | 1,601 | 1.8 | 2.2 |
| SDP8 | 3,149 | 5.4 | 3.2 |
Footnotes
Section titled “Footnotes”-
The timing results are for the test cases in Section Thirteen with a one day prediction. Times may vary slightly with orbital characteristics and, for deep-space satellites, with prediction interval. ↩