USSTRATCOM ceased issuing 2-line elements of France's Helios and Essaim satellites after 2009 Dec 08 UTC (day 342): Helios 1A 1995-033A 23605 Helios 1B 1999-064A 25977 Helios 2A 2004-049A 28492 Essaim 1 2004-049C 28494 Essaim 2 2004-049D 28495 Essaim 3 2004-049E 28496 Essaim 4 2004-049F 28497 The embargo likely applies to the newly launched Helios 2B (2009-073A / 36124) and its upper stage, for which elements have yet to appear: Helios 2B 2009-073A 36124 Helios 2B r 2009-073B 36125 Helios Visibility Helios is a high-resolution optical imaging reconnaissance satellite. All four Helios spacecraft were launched into the same initial sun-synchronous plane. Ground tracks repeat after 395 revolutions in 27 days. Night passes occur after local midnight, so currently are in eclipse in the northern hemisphere, but are visible in the southern hemisphere. This applies to Helios 1A, 2A and 2B, which remain in the standard plane. Helios 1B was manoeuvred in late 2004 into a 40 km lower orbit, apparently due to its having reached the end of its useful life; it is no longer sun-synch, and is now well out of the standard plane. It is currently visible in evening in the northern hemisphere, and Russell Eberst reported observations on Dec 10 and 19 UTC, which I have used to produce current elements: Helios 1B 632 X 635 km 1 25977U 99064A 09353.28752709 .00000198 00000-0 27607-4 0 05 2 25977 98.3466 0.5963 0001757 66.3340 293.8054 14.77749923 07 Arc 20091210.7-1219.31 WRMS resid 0.000 totl 0.000 xtrk Based on 27 observations by Russell Eberst, the standard magnitude of Helios 1A and 1B is 6.1 (1000 km, 90 deg phase angle), with occasional flares 1 to 2 mag brighter than the mean. There are too few observations of 2A for precise analysis, but it appears to be similar in brightness to 1A and 1B. I estimate the following initial elements for Helios 2B, which was launched on 2009 Dec 18, at 16:26 UTC: Helios 2B search 1 70001U 09352.75745078 .00000000 00000-0 00000-0 0 03 2 70001 98.1000 287.2375 0002000 191.4243 168.6952 14.63850000 02 I used the operational mean motion, but its initial orbit could have been slightly lower, with mean motion ~14.69 rev/d. Essaim Visibility Prior to their launch, the four Essaim satellites were officially described as, "a demonstrator, designed to prove the feasibility of space-based detection of electromagnetic transmitters, and evaluate the performance of this type of system." They appear to fly in formation, with pairs of satellites in two planes separated by several degrees. Within a plane, leader and trailer are separated by several hundred kilometres, and the leaders of both planes cross the equator at about the same time. At mid-latitudes, this arrangement results in a roughly rectangular formation, several hundred kilometres on a side. The Essaim orbits are not sun-synchronous, and have drifted somewhat east of the standard Helios plane. They pass well after local midnight. Based on 3 observations by Russell Eberst, the standard magnitude of Essaim is roughly 7 (1000 km, 90 deg phase angle). Ted Molczan ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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