Thank you Harro Zimmer, for your numerical analysis of the re-entry of 1976-074C / 09051. The link to Harro's ephemeris file was broken in transit via SeeSat-L. Here is the corrected link: http://satobs.org/seesat_ref/76074C/1976-074C_trajectory_H.Zimmer.txt Also, I have since received Harro's re-entry orbital elements file: http://satobs.org/seesat_ref/76074C/1976-074C_Orbital_Elements_H.Zimmer.txt I have edited the archived copy of Harro's message to include both of the above: http://satobs.org/seesat/Oct-2012/0167.html Harro's numerical method of propagating orbital elements to decay yields a more precise trajectory of the final descent than I can produce with the tools available to me. His analysis confirms my finding that 1976-074C / 09051 explains the widespread UFO sightings over Morocco, early on 1976 Sep 19 UTC. A key new finding arising from Harro's analysis is that the terminal descent, i.e. the final phase of the re-entry, where most remaining fragments begin to fall almost vertically, began near 36 N, 6 W, which places the toe of any debris field just west of the Strait of Gibraltar, as shown in this plot of the ground track: http://satobs.org/seesat_ref/76074C/76074C_track_H.Zimmer.jpg This explains the lack of any sightings from Spain and more northerly European countries. (Since I posted my original report, I have learned of possible sightings from the vicinity of Portugal, mainly by pilots of airliners. Unfortunately, the only provenance I could find in web searches traced to a tabloid style newspaper, which as a class, I regard as less than ideal sources of scientific information. That said, Harro's analysis reveals that the re-entry would have culminated about 4.6 deg above the SSE horizon of Lisbon near 01:21 UTC, travelling from S to SE, which would have been readily visible to pilots headed in that general direction. It could have been perceived to have been on a collision course crossing the path of an airliner.) Harro's analysis also reveals that the final descent occurred about 9 min earlier than I had estimated. This remains in excellent agreement with the reported UFO sighting times, most of which were between 01:00 and 01:30 UTC, according to the Moroccan Government. It is also in better agreement with the few specific times I have seen reported, typically between 01:10 and 01:20 UTC. The earlier passage of the re-entry means that its ground track was about 2.3 deg east of my estimate, which greatly increased the maximum elevation at all nine known Moroccan sighting locations. The following spreadsheet enables estimating the ephemeris (sky track) of the re-entry train from any location within range, using Harro's trajectory. Simply enter the site coordinates on the first sheet. Any portion that rises at least 3 deg above the horizon will be highlighted in red. http://satobs.org/seesat_ref/76074C/76074C_decay_ephemeris_Zimmer.xlsm The second sheet provides the ephemerides for the nine locations in Morocco from which sightings were reported. Below is a summary, listing the coordinates of each location, and the estimated elevation of the re-entry debris train at culmination: N W HASL Culm deg deg m deg Agadir 30.42 9.59 40 69 Essaouira 31.51 9.76 5 59 Marrakesh 31.63 8.00 451 36 Kalaa-Sraghna 32.06 7.40 401 30 Casablanca 33.57 7.58 5 74 Rabat 34.01 6.83 10 48 Kenitra 34.26 6.58 10 45 Meknes 33.89 5.55 480 19 Fez Region 34.04 5.00 298 15 The third sheet contains Harro's complete trajectory data, a subset of which is the basis of the first two sheets. The discrepancy between NORAD's official decay date of Sep 18 UTC and Harro's and mine of Sep 19 UTC remains unexplained. However, we know from experience that NORAD's orbital data and satellite catalogue, although of normally high precision, are by no means infallible. Our colleague Pierre Neirinck contacted me subsequent to my original report, and pointed out that in the era of the re-entry in question, NORAD errors were fairly common. As a relevant example, he cited the decay of 1975-062B / 08010, for which the official decay date of 1980 Dec 26 UTC, is at variance with the confirmed sightings of the re-entry on Dec 25 just after 21:05 UTC, from Morocco, Portugal, Spain, France and the UK. Ted Molczan _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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