> NAVSTAR 48 (USA 151) > 1 26407U 00040A 00203.00016569 .00000064 00000-0 10000-3 0 158 > 2 26407 55.0641 228.3909 0045522 273.8447 85.7199 1.99170076 175 ... > NAVSTAR 48 (USA 151) > 1 26407U 00040A 00201.47067160 .00040912 -37353-6 44785-3 0 128 > 2 26407 39.1123 221.1967 6078237 196.7985 127.6911 4.02681484 123 > So between July 19 and July 20, this satellite quickly had a change in orbit. > This is the fatest I have ever seen a gps satellite change orbit. > I thought it takes a few days to change a satellite's orbit. > So what's going on here. ALLCOLA (or COLA) can be used to find the time of a short-impulse orbit change. Then, a prediction program like TRAKSTAR, TRACK16 or HANDE can be used to find the speed in the two orbits, and the position. ALLCOLA gives the date of manouvre 2000-07-19. With the earliest elset (11) : UTC Time Range Elset Orbit separation 12:14:25.83 423.5 13 12 12:23:24.36 6.3 15 6.2 12:23:27.18 9.4 14 5.2 With elset 12: 12:14:26.99 426.9 13 12.8 12:23:25.69 7.5 15 6.2 12:23:28.51 12.5 14 5.1 If the later elsets had larger distances than the first, secondary or low-power manoeuvres could be suspected. Now, the likely reason is that elset 13 is inaccurate. Using the elsets 12/15 at time 12:23:25.69, Track16 XYZ xdot Ydot Zdot are: (-13861.32 -22020 6052.5) (1.95583 -0.52096 1.36465) before, and (-13866.013 -22013.6 6033.5) (2.28915 -0.62697 3.04609) after. Since the predictions differ, I ought to have picked two predictions closer in location, instead of the same time. The absolute speed difference is 1.42 km/s, but since there is a large change in inclination (39 to 55 degrees), and the apogee of the initial orbit was higher than the target, the speed difference vector (0.33332,-0.10601,1.68144) is larger, and not in the direction of flight. The components of the velocity change, in the direction of original motion, are 1.23 km/s forward, 1.12 km/s left, and 0.44 km/s up. Since the inclination increase (dogleg to the left) occurred at 13 deg N, an increase of the RA of Ascending Node also occurred ( 221 to 228 ) -- b_gimle@algonet.se (home) http://www.algonet.se/~b_gimle -- -- COSPAR 5919, MALMA, 59.2576 N, 18.6172 E, 23 m -- > So between July 19 and July 20, this satellite quickly had a change in orbit. This is the fatest I > have ever seen a gps satellite change orbit. I thought it takes a few days to change a satellite's > > orbit. So what's going on here. > > Thanks > > Kevin Fetter > > __________________________________________________ > Do You Yahoo!? > Get Yahoo! Mail - Free email you can access from anywhere! > http://mail.yahoo.com/ > > ----------------------------------------------------------------- > Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' > in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org > http://www2.satellite.eu.org/seesat/seesatindex.html > > ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Thu Jul 27 2000 - 01:06:15 PDT