Galileo Sat 5 and 6 launched

Discussion in 'Global Navigation Satellite Systems' started by Joop, Aug 22, 2014.

  1. Joop

    Joop Guest

    Joop, Aug 22, 2014
    #1
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  2. While we are at it, are the first four already usable, let's say
    for non-critical use? Like in a smartphone as an enhancement to
    the GPS, Glonass, Beidou, and MSAS satellites?

    Hans
     
    Hans-Georg Michna, Aug 23, 2014
    #2
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  3. Joop

    Joop Guest

    Yes, the first 4 are already operational and in fact ESA already had a
    positioning fix only using these 4 satellietes. I'm not sure if any
    gnss chipset is already actively using these birds.

    In the mean time it seems there was a "orbit injection anomaly" of
    nr. 5&6, whatever that may exactly mean.

    http://www.esa.int/Our_Activities/N...alileo/Soyuz_Galileo_launch_injection_anomaly
     
    Joop, Aug 23, 2014
    #3
  4. Joop

    Alan Browne Guest

    I wonder if the Russians are a little annoyed at European "comments"
    about the Ukrainian mess .... ?
     
    Alan Browne, Aug 23, 2014
    #4
  5. Joop

    Alan Browne Guest

    I recall seeing an article recently (a month or so ago) about a chipset
    being tested in several Android phones using Galileo and Beidou as well
    as GPS/GLONASS.

    Can't find that one offhand, but there is:
    http://gpsworld.com/quad-constellation-receiver-gps-glonass-galileo-beidou/

    A quick search also shows:
    http://hackaday.com/2014/01/17/20-gpsglonassbeidou-receiver/
    (GPS/GLONASS/Beidou - though GPS + one or the other, not all three at once).
     
    Alan Browne, Aug 23, 2014
    #5
  6. Bad news ! Those satellites ended up in the wrong orbit.
    Galileo is orbits are: 55.040 deg, 23,522 km circular
    But the two birds ended up at: 49.69 deg, 13,721-25,918 km orbits
    Back of the envelope calculations by space launch enthusiasts state that there isn't enough fuel in the birds to put them in a proper orbit (even if they were willing to sacrifice 100% of station keeping fuel).
    But the orbits are stable, so at a minimum it should be possible to perform at testing, and use those satellites in a degraded geometry anyhow.
    But they will have to be replaced much sooner in order to get a proper orbit.
     
    Marcelo Pacheco, Aug 23, 2014
    #6
  7. Bad news ! Those satellites ended up in the wrong orbit.
    Galileo is orbits are: 55.040 deg, 23,522 km circular
    But the two birds ended up at: 49.69 deg, 13,721-25,918 km orbits
    Back of the envelope calculations by space launch enthusiasts state that there isn't enough fuel in the birds to put them in a proper orbit (even if they were willing to sacrifice 100% of station keeping fuel).
    But the orbits are stable, so it should be possible to use those birds with some geometry limitations anyhow.
    But they will have to be replaced much sooner in order to get a proper constellation arrangement. Not quite like the SVN-49 debacle, but not a whole lot better.
    Speculation is the Fregat upper stage burned 30 degrees off axis.
     
    Marcelo Pacheco, Aug 23, 2014
    #7
  8. Joop

    J. J. Lodder Guest

    lileo/Soyuz_Galileo_launch_injection_anomaly

    Bureaucratese nicespeak for 'wrong orbit',

    Jan
     
    J. J. Lodder, Aug 23, 2014
    #8
  9. But they are still usable, or are they not? The main problem is
    that they are not in the best place for globally
    well-distributed coverage. In other words, they are sometimes
    visible when enough other satellites are already there, and
    sometimes they are out of view when they would be needed.

    I would guess that their elliptical orbit is not generally a
    problem, as long as the orbit is well known and communicated. I
    hope the receivers know the physics and mathematics of orbits
    well enough not to rely rely on perfectly circular orbits.

    The only possible problem could be reduced precision due to more
    atmospheric influence during the low altitude part of their
    ellipses.

    Perhaps all receivers should now be reprogrammed to give these
    satellites a lower priority, i.e. use them if you don't see
    enough better ones, but otherwise ignore them. :)-)

    Do I see things correctly?

    Hans-Georg
     
    Hans-Georg Michna, Aug 24, 2014
    #9
  10. The Samsung Galaxy S5 apparently has the best GPS chip around
    today.

    For the last two days I have a new phone (OnePlus One) that also
    receives at least GPS and Glonass.

    It is just wonderful. I got a fix within 7 seconds, 9 of 24
    satellites, in my office, not even leaning against a window.
    Typical outdoor first fix time is 3 to 4 seconds. I am very
    impressed, and this is a very big leap forward from my previous
    Google Samsung Galaxy Nexus, whis is quite a nice phone, but its
    GPS function has never been very good.

    Hans-Georg
     
    Hans-Georg Michna, Aug 24, 2014
    #10
  11. Joop

    Joop Guest

    13.700 km as lowest point is still a medium earth orbit, without any
    atmospheric drag.
    The mathematics are quite complex. Orbital math is one thing, but
    think of the relativistic clock corrections that are to be completely
    recalculated / reprogrammed. A satellite in an elliptical orbit has
    not the constant speed that the circular orbit would have had.

    What i would like to know is who to blame. How the contract with
    the Soyuz launchers exactly is described. Is it contracted to
    deliver the bird in the correct orbit?
     
    Joop, Aug 24, 2014
    #11
  12. I have a Galaxy S5 with some GPS apps. and my complaint is that it is unreadable outside in the sunlight. It is so bad, this forced me to buy a Garmin Nuvi which is much more readable outdoors.
     
    lawrence.glickman68, Aug 25, 2014
    #12
  13. I tested yesterday, using GPS Essentials to show me all the visible sats
    (20+), of these I had several 200+ numbers which should correspond to
    the Galileo sats, right?

    I know I saw 202 and 204, and possibly also 205 there (partly overlayed
    on another sat location, so hard to read), i.e. GA sat #5.

    Anyway, none of the GA signals were marked as usable, they stayed grey
    on my display.

    Terje
     
    Terje Mathisen, Aug 25, 2014
    #13
  14. I think this is an interesting question. To calculate from a
    variable speed does not require witchcraft. Still some receivers
    could conceivably use simplified maths assuming circular orbits
    for the purpose of relativistic correction, but since no orbit
    is exactly circular, why not calculate using all available data?

    Hans-Georg
     
    Hans-Georg Michna, Aug 25, 2014
    #14
  15. One would think a brand new type of Galileo satellite (first FOC birds) would undergo a few testing steps prior to L band transponder activation, and upon activation they would be operated in unhealthy mode. Plus upon L band transceiver activation, would it broadcast a data less (pilot) signal as a first step ?
    Just thinking out loud, I'm just making parallels with SBAS and what is done when a new type of GPS satellite is first launched. Step by step testing.
     
    Marcelo Pacheco, Aug 25, 2014
    #15
  16. Joop

    Alan Browne Guest

    Those always have to be calculated due to the position and velocity
    relationship between transmitter and receiver, so it's just a question
    of verifying the receiver code's ability to handle the range of data
    (limits, constraints and so on). That said, the 'gravity well' value
    might be a constant in the receiver code but could easily be calculated
    in real time. The math isn't easy, but the processing is trivial for
    today's receivers. That value could be updated 1 / minute for each
    satellite by the receiver and it would be accurate enough. (and how
    often it needs to be updated could be calculated as well...)
    Yep. So now the insurance collective will try to reduce their loss by
    "proving" the satellite is still very useful (or whatever value tending
    to 100%) and the Galileo program will try to increase its settlement by
    proving it is only slightly useful tending to 0%.

    Lawyers love bad launches.
     
    Alan Browne, Aug 27, 2014
    #16
  17. Like US govt sats, Galileo birds were also uninsured.
     
    Marcelo Pacheco, Sep 5, 2014
    #17
  18. Joop

    Alan Browne Guest

    True. I was told a few weeks ago that Galileo was insured. Samesource
    corrected himself last week. He based his original claim on the fact
    that ESA _typically_ insure satellite launches.
     
    Alan Browne, Sep 6, 2014
    #18
  19. Joop

    Joop Guest

    A minor update on the issue of the Galileo birds 5 & 6 can be found here:

    http://gpsworld.com/galileo-provides-update-on-foc-anomaly-glonass-a-no-show/

    and it points to this article

    http://www.nature.com/news/wayward-galileo-satellites-could-still-aid-scientists-1.15843

    I don't know what URL shortener to trust these days, so here's a quote:

    =============== nature.com quote ==================

    On 22 August, the European Space Agency (ESA) launched the first two
    fully operational satellites of its €6.3 billion (US$8.2 billion)
    Galileo global navigation system — but something went wrong. After a
    smooth lift-off from Kourou, French Guiana, tracking data revealed that
    the Russian Soyuz-Fregat rocket carrying the two craft had put them in
    the wrong orbit.

    Nature explains what might have gone wrong, and what it means for
    would-be users of Galileo's global navigation data.

    What is Galileo?

    Galileo is Europe’s global navigation satellite system, similar to the
    US Global Positioning System or Russia’s GLONASS. ESA plans to launch a
    constellation of 30 satellites by 2020 that constantly transmit their
    locations and times to receivers at the speed of light. Each receiver is
    able to triangulate its position on Earth by comparing the small delays
    in the arrival times of signals from multiple satellites.

    In addition to the two Galileo satellites launched on 22 August, four
    test satellites are currently in orbit.

    Where are the latest satellites now?

    A Soyuz rocket was supposed to launch the two craft into a circular
    orbit 23,222 kilometres above the Earth, and angled at 56 degrees to the
    planet’s equator. (All 30 of the Galileo satellites will eventually be
    arrayed in similar orbits to guarantee global coverage.)

    But something went wrong in the rocket’s Fregat upper stage, which
    boosts the payload to its final orbit. As a result, the satellites were
    instead placed in an elliptical orbit. The craft now swing from more
    than 2,000 kilometres too high to nearly 10,000 kilometres too low. The
    orbits are also tilted by about 5 degrees from the intended plane.

    What went wrong?

    A definitive cause has not yet been announced. The favoured explanation
    is that the Fregat upper stage of the Soyuz lost control as it was
    coasting before its final fuel burn to reach the intended orbit. The
    rocket's engine seems to have fired correctly, but it was pointing the
    wrong way.

    An investigation by an ESA and European Commission committee, appointed
    by the rocket’s European operator Arianespace, is expected to release
    initial conclusions as early as 8 September.

    Can the satellites be moved to the correct orbit?

    There are currently no options to carry out this manoeuvre. The
    satellites have some hydrazine fuel on board to help them maintain their
    orbits. But reaching the right orbit would require, by some estimates,
    two to four times more fuel than the satellites are carrying.


    An Israeli start-up, Effective Space Solutions, has said that it could,
    in theory, build a small satellite that would latch onto the two Galileo
    satellites and drag them to the intended orbit. The company's robotic
    design would use an ion thruster — rather than conventional rocket fuel
    — to slowly but efficiently manoeuvre them.

    Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center
    for Astrophysics in Cambridge, Massachusetts, says that
    back-of-the-envelope calculations suggest that the craft proposed by
    Effective Space Solutions could carry enough ion fuel to do so. But
    McDowell cautions that autonomous docking of spacecraft is a complicated
    engineering challenge for a company with no track record. “I’m very
    sceptical of this particular company doing it — even though it seems
    like they might have a good idea,” he says.

    Are the wayward Galileo satellites currently of any use?

    For most people, the answer is no. The reason is not because the
    satellites are dysfunctional — in fact, they seem to be working just
    fine. Rather, their orbit is so misshapen that its mathematical
    parameters are incompatible with Galileo’s standardized data format.

    Information about the satellites' position in orbit is transmitted as a
    series of digits, and each parameter is assigned a place in the data
    stream — a certain number of bits, and no more. For example, the value
    that represents the shape of the satellites' orbit is too big to be
    expressed within the alloted bit limit for that parameter. This means
    that would-be commercial users of the Galileo data will not be able to
    gather useful positioning data from these satellites, and will have to
    wait for ESA to launch further Galileo craft.

    But the situation is more hopeful for many scientists wanting to use
    Galileo data in their research, says Richard Langley, a GNSS expert at
    the University of New Brunswick in Fredericton, Canada. Researchers
    track such navigation probes independently with a global network of
    dozens of ground stations, and combine that information with the timing
    data transmitted by the satellites themselves.

    ESA continues to review its options and has not made a decision about
    whether to proceed with transmission of the timing data. But with the
    satellites appearing to be healthy, Langley is optimistic.

    How can scientists use the data?

    With Galileo's timing data and the independent ground-tracking
    information on the satellites' orbits, scientists should be able to
    measure changes in the position of points on the ground much smaller
    than the one-metre margin of error for standard navigation-system
    receivers. This level of precision is good enough to detect millimetres
    of movement in tectonic plates, for example.

    Bringing the satellites online and assessing their health will also
    provide a useful dry run for the Galileo team, because they are the
    first of the constellation that are built to fully functional
    specifications.

    How will this failure affect the future status of Galileo?

    Not much. ESA is planning to launch more Galileo satellites every few
    months until the end of 2020, although those plans are on hold while the
    latest launch is being investigated.

    When launches resume, ESA is expected to order two new satellites to
    replace the off-course craft.

    But Langley says that ESA may wish to reconsider which vehicles they use
    for future Galileo launches. The agency had intended to rely on the
    Soyuz-Fregat rocket for four more launches before switching to a
    beefed-up version of the Ariane 5 launcher, which can carry four Galileo
    satellites at a time. The latest launch trouble could prompt ESA to make
    the switch earlier, notes Langley.

    Nature doi:10.1038/nature.2014.15843

    ================================================================
     
    Joop, Sep 12, 2014
    #19
  20. Joop

    Alan Browne Guest

    No need to quote it all, the link was fine. Nice summary articles - the
    GPSworld one seemed more worried about the wider Doppler dhift range
    than relativistic issues - and the use of a spare flag in the messages
    to signal special Almanac contents to receivers (which will need s/w
    developed for the case...).

    The Nature art. seems too pessimistic re commercial use. TBD.

    I use tinyurl and it seems reliable. http://tinyurl.com/l26le28
     
    Alan Browne, Sep 12, 2014
    #20
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