I had some time this morning to plot Kevin's comparisons: http://iss-transit.sourceforge.net/images/comparisons.gif Lacking an actual observation, one can't say which track is the most accurate. However the moon's angular size is about 0.009 radians, so at a distance (to the ISS) of 543 miles, the transit path would be 4.9 miles wide, and any of these tracks would result in a near dead-center transit. The primary difference isn't really one of accuracy, but the fact that my track prediction- based upon the SVPOST element sets- was made several days in advance (I normally make 10 day forecasts, which are updated as NASA updates the SVPOST page). One can infer from the existence of the SVPOST page, and the apparent accuracy of predictions based upon it, that NASA has a more refined orbital model for the ISS than SGP4, and that (for the benefit of people like me), they distill that refined model down into SGP4 model 2-line element sets. A picture is worth a thousand rows of numbers... ----- Original Message ----- From: "Kevin Fetter" <kevin_fetter@hotmail.com> To: <SeeSat-L@satobs.org> Sent: Thursday, May 15, 2003 1:10 PM Subject: test of iss pass across the moon tonight > I did a test to see how close tomas fly's path was. > > Using this latest orbit. > > ISS (ZARYA) > 1 25544U 98067A 03135.48473194 .00011619 00000-0 15101-3 0 127 > 2 25544 51.6307 184.5710 0006298 116.4433 319.0011 15.59274485255903 > > For example tom gives > > 1------- 2----- 3------ 4-- 5-------- 6--------- 7 8---- 9---- > 2:55:35 23.327 168.109 543 46.6558 N, 56.4769 W n -23.7 179.4 > 2:55:36 23.288 168.193 544 46.7058 N, 56.4035 W n -23.7 179.4 > 2:55:37 23.250 168.278 544 46.7557 N, 56.3300 W n -23.6 179.4 > 2:55:38 23.212 168.362 545 46.8057 N, 56.2563 W n -23.6 179.4 > 2:55:39 23.173 168.447 545 46.8556 N, 56.1825 W n -23.5 179.4 > 2:55:40 23.135 168.532 546 46.9055 N, 56.1085 W n -23.5 179.4 > > > I got > > 16 May 2003 02:55:35.00 46.547 -56.651 > 16 May 2003 02:55:36.00 46.597 -56.578 > 16 May 2003 02:55:37.00 46.647 -56.505 > 16 May 2003 02:55:38.00 46.697 -56.431 > 16 May 2003 02:55:39.00 46.747 -56.358 > 16 May 2003 02:55:40.00 46.797 -56.284 > > > Rob's program gives > > 2003/05/16 2:55:35 46.5463 -56.6498 > 2003/05/16 2:55:36 46.5963 -56.5767 > 2003/05/16 2:55:37 46.6464 -56.5035 > 2003/05/16 2:55:38 46.6964 -56.4301 > 2003/05/16 2:55:39 46.7465 -56.3566 > 2003/05/16 2:55:40 46.7965 -56.2830 > > My results are close to rob's, but not tom's. But since he would have used a > different orbit, then he gets different results. > > Kevin > > _________________________________________________________________ > Add photos to your messages with MSN 8. Get 2 months FREE*. > http://join.msn.com/?page=features/featuredemail > > ----------------------------------------------------------------- > To unsubscribe from SeeSat-L, send a message with 'unsubscribe' > in the SUBJECT to SeeSat-L-request@satobs.org > List archived at http://www.satobs.org/seesat/seesatindex.html > ----------------------------------------------------------------- To unsubscribe from SeeSat-L, send a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@satobs.org List archived at http://www.satobs.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Sat May 17 2003 - 11:13:35 EDT
