The following elements have been derived from observations by Leo Barhorst, Russell Eberst, Kevin Fetter, David Hopkins, Marco Langbroek, Alberto Rango and Mike Waterman: USA 276 389 X 409 km 1 42689U 17022A 17155.10977510 .00003750 00000-0 51941-4 0 02 2 42689 50.0034 107.5651 0014909 116.4838 243.7661 15.56244436 01 Arc 20170530.95-0604.13 WRMS resid 0.045 totl 0.015 xtrk Below are updated conjunction estimates for the closest approaches on 2017 Jun 03 with range <= ~100 km. For USA 276, I used the above TLE. For ISS, I used USSTRATCOM's epoch 17154.48611204 TLE. ISS sub-satellite point USA 276 sub-sat point ------------------------- ------------------------- TCA Range Lat Lon Alt Lat Lon Alt UTC km deg deg km deg deg km Illum. 11:43:12 88.31 43.26 N 170.90 E 410.24 43.67 N 170.07 E 392.49 shadow 12:29:12 66.16 43.87 S 22.16 W 418.71 44.12 S 22.84 W 423.17 sunlight 13:15:35 27.66 43.71 N 146.41 E 410.40 43.81 N 146.21 E 392.51 shadow 14:01:48 4.39 43.87 S 45.71 W 418.70 43.87 S 45.72 W 423.06 sunlight 14:47:58 47.84 44.15 N 121.91 E 410.55 43.95 N 122.35 E 392.54 shadow 15:34:25 65.23 43.85 S 69.20 W 418.68 43.59 S 68.53 W 422.94 sunlight 16:20:19 111.23 44.64 N 97.24 E 410.73 44.14 N 98.33 E 392.58 shadow Although the conjunctions are now history, the above are not necessarily the final results. Tracking of USA 276 over the next several nights could yield elements that lead to different results. The final column denotes the state of illumination of both spacecraft. Both were either in Earth's shadow or in sunlight. The conjunctions in shadow occurred roughly one minute after entry into eclipse. At the TCA of 14:01:48 UTC, USA 276 passed 4.4 km directly above ISS. The relative angular velocity of one spacecraft seen from the other was about 6.3 deg/s (at 10 km range, approaching and departing, the angular velocity was a more sedate approx. 1.2 deg/s). The phase angle changed considerably during the period within 10 km range. At TCA, from the vantage of USA 276, the solar phase angle of ISS was 69 deg, and it was about magnitude -14; from the vantage of ISS, the phase angle of USA 276 was 111 deg, and it was about magnitude -5. The planar separation of USA 267 and ISS will remain close for some time, so a rendezvous remains technically feasible. If delta-V is a significant constraint, then the minimum energy manoeuvre would occur on Jun 24, when USA 276 and ISS would have the same RAAN, leaving only a 1.6 deg change of inclination. Ted Molczan _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Sun Jun 04 2017 - 08:51:01 UTC
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