Official TLEs of Helios and Essaim satellites no longer available

From: Ted Molczan (
Date: Mon Dec 21 2009 - 00:40:56 UTC

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    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
    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
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