The solar sail of LightSail-A (15025L / 40661) may be deployed as early as 2015 Jun 02 near 15:44 UTC: http://www.planetary.org/blogs/jason-davis/2015/20150531-lightsail-possible-tuesday-deploy.html As of last night, the operators of the spacecraft believed that the following TLE provided the closest match to the received signal: 1 90727U 15150.55115000 .00017130 00000-0 45788-3 0 150 2 90727 55.0112 297.1659 0249189 205.9605 230.4519 15.12499718 1507 Observers between about 10 N and 43 N will have morning visibility of the orbit. Those south of about 38 S will have evening visibility. The good news is that I estimate that with the sail deployed, the standard visual magnitude will be about 4.4 (1000 km range, 90 deg phase angle), resulting in mag 2 to 3 on high-elevation, well illuminated passes. The bad news is that with the sail deployed, the rate of decay will be enormous, and difficult to predict with precision. I estimate final descent early on 2015 Jun 5 UTC. I have estimated post sail-deployment TLEs, based on the mass of the spacecraft (4.5 kg) and the dimensions of its sail (~5.66 x 5.66 m^2). My procedure was as follows. I propagated the above mean elements to the time of deployment, then I used TLE Analyzer 2.12 to convert the result to a state vector type compatible with GMAT. I propagated the orbit using GMAT based on the forecast space weather, and converted several of the resulting state vectors to TLEs. I computed the mean rate of decay between a pair of the TLEs and used Satevo to propagate the later of the pair using that rate of decay. I have appended the results. I consider these results preliminary, subject to possible revision. They should be useful at least for initial planning of observations. I suggest comparing against the pre-sail deployment TLE above, and taking 50% of the difference in prediction time as the uncertainty, e.g. if a 70002 TLE predicts a pass 5 min, earlier than the 90727 TLE, then allow 2.5 min. prediction time uncertainty. Ted Molczan 689 x 355 km 1 70002U 15153.77486077 .07250464 64517-2 18170+0 0 90089 2 70002 55.0090 283.2046 0241775 214.0536 144.3713 15.14697619 04 683 x 355 km 1 70002U 15153.84083312 .07381729 68047-2 18237+0 0 90087 2 70002 55.0087 282.9179 0238277 214.2147 144.2270 15.15662867 12 678 x 354 km 1 70002U 15153.90676317 .07519688 71298-2 18307+0 0 90084 2 70002 55.0084 282.6309 0234727 214.3759 144.0830 15.16645241 26 672 x 354 km 1 70002U 15153.97265022 .07664980 75422-2 18380+0 0 90088 2 70002 55.0080 282.3437 0231123 214.5372 143.9395 15.17645630 39 667 x 353 km 1 70002U 15154.03849352 .07818182 79947-2 18456+0 0 90085 2 70002 55.0076 282.0562 0227462 214.6987 143.7964 15.18665000 49 661 x 353 km 1 70002U 15154.10429228 .07980068 84187-2 18536+0 0 90083 2 70002 55.0073 281.7685 0223742 214.8604 143.6537 15.19704404 52 655 x 352 km 1 70002U 15154.17004570 .08151446 89615-2 18619+0 0 90083 2 70002 55.0069 281.4805 0219959 215.0222 143.5115 15.20764996 68 649 x 352 km 1 70002U 15154.23575288 .08333235 94734-2 18707+0 0 90083 2 70002 55.0065 281.1923 0216111 215.1841 143.3698 15.21848037 72 643 x 351 km 1 70002U 15154.30141290 .08526558 10133-1 18799+0 0 90086 2 70002 55.0061 280.9037 0212193 215.3462 143.2286 15.22954917 87 637 x 351 km 1 70002U 15154.36702478 .08732546 10871-1 18896+0 0 90086 2 70002 55.0057 280.6149 0208202 215.5085 143.0879 15.24087172 91 630 x 350 km 1 70002U 15154.43258745 .08952747 11575-1 19000+0 0 90084 2 70002 55.0053 280.3259 0204133 215.6709 142.9479 15.25246503 101 624 x 349 km 1 70002U 15154.49809978 .09198417 13208-1 19126+0 0 90081 2 70002 55.0049 280.0365 0200005 215.8335 142.8081 15.26435298 113 _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Mon Jun 01 2015 - 06:30:54 UTC
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