Radio amateur leads study of meteorolgy spectrum conflict with Starlink

Discussion in 'Amateur Radio News' started by W0PV, Jan 24, 2023.

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  1. W0PV

    W0PV Ham Member QRZ Page

    Radio amateurs & astronomers are not the only weak-signal spectrum users concerned with growing threats from rising background electromagnetic interference radiated or reflected by new and under-regulated terrestrial or space-based commercial systems.

    Many professionals who are also part of the ARS have through that acquired unique skills and valuable awareness to be a vanguard in helping try to manage these situations.

    73, John, WØPV

    Satellite constellations could interfere with meteorological spectrum

    Debra Werner — January 23, 2023

    [​IMG]

    Hurricane Sandy turned west in 2012 before making landfall in New Jersey. Without microwave sensor data, forecasters would have called for the storm to make landfall 24 hours later than it did and to strike Maine. Credit: National Weather Service

    SAN FRANCISCO – Satellite megaconstellations could pose a threat to the spectrum that meteorologists are eager to protect from radio frequency interference.

    At the American Meteorological Society annual meeting in Denver, meteorologists and spectrum experts expressed concern about proposals for SpaceX’s second-generation Starlink broadband constellations and acknowledged that other proposed megaconstellations could create interference as well.

    SpaceX has asked the U.S. Federal Communications Commission for a license to transmit signals from gateway stations to nearly 30,000 Starlink second-generation satellites in the 81 to 86 gigahertz band.

    “The sheer number of potential gateway uplink stations around the world could contribute to adjacent band contamination and further due diligence would be needed,” said David Lubar, WB3JEY, Aerospace Corp. senior project leader, said at the AMS meeting. “We do not know if their out-of-band emissions will be an area of concern.”

    Meteorologists pick up faint signals indicating humidity over land in the 86 to 92 gigahertz band, adjacent to the bands Starlink has proposed for uplinks.

    It’s not yet clear whether the Starlink uplinks would pose any danger to the meteorological observations, but weather forecasts rely on passive radiometers to pick up faint signals to identify water vapor, precipitation and atmospheric temperature in various spectral bands.

    “These bands are established by the fundamental laws of physics,” Tony McNally, principal scientist in the European Centre for Medium-Range Weather Forecasts Research Department, said at the AMS meeting. (see video below)

    Complicating the matter is the fact that “the signals that we are looking for with our passive satellites are much smaller than the interference patterns created by some of the other uses of the spectrum,” McNally added. “I would liken it to trying to gaze up at the stars at night when someone puts an incredibly bright flashlight in your eyes.”

    Meteorologists sought protection for unwanted emissions in the 81-86 gigahertz band at the 2019 World Radiocommunications Conference in Egypt. At the time, the International Telecommunications Union body of delegates declined to take up the matter.

    As a result, the FCC has no current regulations that would limit SpaceX’s use of the band.

    “Any new international rules are unlikely to be enacted until after 2027,” Lubar said.

    This is just one example of the whack-a-mole predicament meteorologists face in trying to safeguard atmospheric measurements and weather-data relays from RF interference.

    Another potential problem relates to the passive measurements meteorologists make from 50.2 to 50.4 gigahertz. Careful observation of that band reveals temperatures at various levels of the atmosphere. That data, paired with humidity measurements in the 180 to 184 gigahertz band, are key elements of weather forecasts.

    Existing regulations protect the 50.2 to 50.4 gigahertz band from interference, but the signals are so weak they could be drowned out by noise emitted in adjacent bands.

    “These systems in space are measuring extremely sensitive bits of energy,” said Beau Backus, Johns Hopkins Applied Physics Laboratory senior spectrum manager. “That makes it essential that this be in protected areas.”

    Tens of thousands of satellites are expected to launch in the next decade. Many satellite operators are proposing transmitting data to spacecraft in bands immediately above and below the 50.2 to 50.4 gigahertz band.

    “The industry is moving faster than our scientific development,” Michael Farrar, director of the National Centers for Environmental Prediction at National Weather Service, said at the AMS meeting. “This problem is going to accelerate. We should build a process that can rapidly respond to these scenarios.”

    The American Meteorological Society’s RF Allocation Committee also is concerned about potential interference in the 23 to 24 gigahertz band, where the Advanced Technology Microwave Sounder on the National Oceanic and Atmospheric Administration’s Joint Polar Satellite System collects passive measurements of atmospheric water vapor. Those observations combined with data from other active and passive sensors on U.S. and international satellites help meteorologists predict storm tracks and rainfall levels.

    “Our systems are making very good use of combinations of channels,” McNally said. “The problem with it is that if you then have a losing battle [to protect] one channel, you can effectively wipe out the value of channels which are not contaminated because you don’t have this corroborating piece of evidence from the channel that you’ve lost. The quality of forecasts that we enjoy in our society are a result of this very sophisticated multichannel usage in data simulation systems.”

     
    Last edited: Jan 24, 2023
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  2. KL7KN

    KL7KN Ham Member QRZ Page

    "It’s not yet clear whether the Starlink uplinks would pose any danger to the meteorological observations, but weather forecasts rely on passive radiometers to pick up faint signals to identify water vapor, precipitation and atmospheric temperature in various spectral bands."

    There are currently several methods for directly and indirectly measuring the total amount of water vapor in the atmosphere. The more traditional methods of measurement include radiosondes (Guan et al., 2019; Li et al., 2003), ground-based Global Positioning System signal delay analysis (Means and Cayan, 2013; Bevis et al., 1994), solar photometry (Raj et al., 2004; Thome et al., 1992; Thomason, 1985), and microwave radiometry (Liljegren, 1994; Hogg et al., 1983). Though each method has proven successful, the radiosonde remains the most widely used instrument to obtain atmospheric data. Some of the limitations of using radiosondes to study the atmosphere include the cost of balloons and sensors, availability of personnel and launch sites, and the frequency of launches.
    (Source - amt-15-1563-2022.pdf (copernicus.org))

    Seems like passive radiometers are part of the total picture and have their own set of problems.
    "Although PWV can be obtained from infrared measurements on satellite platforms such as GOES-R (Schmit et al., 2018, 2017), potentially large observation angles can result in degraded spatial resolution and may not provide adequate information for numerical weather prediction models to take into account local variations in PWV."
    This ^^^ from the paper linked above.

    To me this seems like an opportunity. Just as "bistatic RADARS" were developed to use existing cell phone transmitters to provide a known location signal source - I would think the ground stations could provide a signal source for PWV measurements in lieu of the radiosonde balloons....

    Don't work for the NWS, so have no real idea if this is possible. This would also require the federal bureaucrats walking to the edge of the box and looking outside of said box to see what is possible....
     
    N5XMV likes this.
  3. K6CLS

    K6CLS Ham Member QRZ Page

    Yep... This one is under attack by the egregious 5G land rush. Phew!
     
  4. W1YW

    W1YW Ham Member QRZ Page

    I would be VERY CAREFUL in assuming that Starlink is neither interested nor capable of working this problem.

    The facts, with respect to ASTRONOMY, show that SpaceX/Starlink has been more than reasonable . and continues to be so.

    INDEPENDENT of SPACE X, there are tangible and valuable efforts to view (pun intended) the satellite corruption ('trails') issue you allude to in the OP as an optimization problem for-- avoidance-- of trails in the field of view, while maximizing observing time and mimimizing slew time. One such approach is disclosed in a pending patent:

    Method and Apparatus for Mitigation of Image Corruption by Satellites

    Said solution is invented by a ham (which seems to be the point of the OP), in this case, me: W1YW.

    Radiometric measurements detect noise, I presume in this case thermal noise, or collisonally broadened spectral lines from the atmosphere. So-called interference--which may not actually indicate true transmission out of band, is deterministic. That means it is --determinstically-- removed, or removable.

    I am disappointed that we see no discussion of this from the Starlink end. We should assume they are very smart and very savvy on how to work with other users of the bowl of night. They are not the 'bad guys'.

    Work the problem....

    73
    Chip W1YW
     
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  5. K4PIH

    K4PIH Ham Member QRZ Page

    I just put Jiffy Pop on the stove.
     
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  6. W1YW

    W1YW Ham Member QRZ Page

    None of the sats are designed to transmit in that specific 50 GHz band. Let's say that again: they do not transmit in that band. If the radiometers (RX) are poor at rejection, then nonlinear products at the RX port can produce intermod-like transient spikes, that will bias the wideband radiometric measurements.

    The sats on TX do not generate 50 GHz 'noise from adjacent bands'. The sats neither transmit in that band, nor generate 'noise'. They TX coded SIGNALS that are in-band, and in-band only.

    THE RX is the problem.

    So either they can produce radiometers that are better at rejection, or take advantage of the fact that the transients are CODED and thus easily separated from (thermal) sky noise. The meteoroligists are measuring NOISE as a wideband , single value.
     
  7. K2HRO

    K2HRO Ham Member QRZ Page

  8. K6CLS

    K6CLS Ham Member QRZ Page

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  9. PA0MHS

    PA0MHS Ham Member QRZ Page

    The sats don't transmit in that band but the user stations will. See:
    https://www.researchgate.net/figure...llocation-and-Modulation-Type_tbl10_330244593
    One of the projected uplink bands is 47.2 - 52.5 GHz.

    And I think precisely that is the problem. The weather satellites look down onto the atmosphere while ground stations beam right up, into the weather satellites.

    73, Meindert
     
  10. W1YW

    W1YW Ham Member QRZ Page

    Not likely.
    Beams are beams. Projections are not realities.
     
  11. W1YW

    W1YW Ham Member QRZ Page

    Unfortunately your post not applicable to the OP...

    To wit:

    "SpaceX has asked the U.S. Federal Communications Commission for a license to transmit signals from gateway stations to nearly 30,000 Starlink second-generation satellites in the 81 to 86 gigahertz band.

    “The sheer number of potential gateway uplink stations around the world could contribute to adjacent band contamination and further due diligence would be needed,” said David Lubar, WB3JEY, Aerospace Corp. senior project leader, said at the AMS meeting. “We do not know if their out-of-band emissions will be an area of concern.”
     
  12. K3XR

    K3XR Ham Member QRZ Page

    I'm not disappointed I see it for what it is. More to do with taking a shot at Musk and little to do with Starlink. Your opinion may vary.
     
  13. W0PV

    W0PV Ham Member QRZ Page

    Using the word Starlink in the OP title became unintentionally provocative.

    IMO, unfortunately for SpaceX the Starlink trademark, aided by their massive media promotional effort, has become genericized, like Xerox, or Kleenex.

    Substituting for the word Starlink the more obvious generic term "satellite constellations" from the title of the OP article may have been more appropriate. But when the general public thinks internet by satellite constellation today, they think Starlink.

    However, as pointed out, Starlink, as the dominant of many potential satellite ISP's at this time, certainly appears to be taking a cooperative or preemptive stance on this issue as seen in other recent news.

    SpaceX signs agreement with US National Science Foundation to prevent Starlink’s interference with astronomy

    "SpaceX is addressing the concerns of radio astronomers as well as optical. The company has agreed to a number of coordination efforts since Starlink satellites use a radio band very close to that used for radio astronomy. In addition, the company has agreed to study the impact of Starlink terminals located near the Very Large Array in New Mexico and the Green Bank Observatory in West Virginia."

    "SpaceX and the NSF also agreed to work together more closely going forward to address the concerns of the astronomical community as new issues arise as Starlink's satellite constellation grows even larger."

    "We are setting the stage for a successful partnership between commercial and public endeavors that allows important science research to flourish alongside satellite communication," NSF Director Sethuraman Panchanathan said in the statement."


    However the body text of OP article points out a larger concern - obtaining similar cooperation / regulation of others seeking in the future to create competitive satellite constellations, many outside the authority of the FCC. In that regard the reply by @PA0MHS seems relevent.

    OP - Another potential problem relates to the passive measurements meteorologists make from 50.2 to 50.4 gigahertz. Careful observation of that band reveals temperatures at various levels of the atmosphere. That data, paired with humidity measurements in the 180 to 184 gigahertz band, are key elements of weather forecasts.

    PA0MHS - The sats don't transmit in that band but the user stations will. See:https://www.researchgate.net/figure...llocation-and-Modulation-Type_tbl10_330244593 One of the projected uplink bands is 47.2 - 52.5 GHz.

    Despite the probable tight beam widths being employed mitigating QRM, I am wondering about any scattering effects or other potentially disruptive phenomena (absorption) from pumping so much cumulative RF energy in or near the natural spectrum being observed by the weathermen.

    73, John, WØPV

    PS - @W1YW heard with BIG SIGNAL in FL working CW DX low end of 10m twice this weekend. 73 Chip. :)
     
    Last edited: Jan 30, 2023 at 1:46 AM
  14. W1YW

    W1YW Ham Member QRZ Page

    The kind of scattering you are referring to is called 'Langmuir scattering' and is an effect typically 100+ dB down.

    Heterodyne products are a different mechanism;-)

    The meteorlogical thermal continuum measurements are time averaged. They are just ticked because their systems were not designed with any forethought. IMO.

    Space X is not the issue here. Its the thousand of new sats NOT regulated or 'guidanced' by the USA that are the issue.

    They are coming. India, fo example, sees then as a huge cash cow opportunity. Space.com often showcases the launches of the various rocket-players. These small sats, both fab and launch, are a huge and growing industry, many NOT U.S. based.

    And yes, there are hams in this industry. I will let you guess --why-- they haven't jumped in here....my back looks likean overused dart board, to give you a clue...

    Don't be surprised if North Korea gets in on the action --to sell to non-US affiliated countries. They have the rockets, apparently.

    BTW I am now back on the air;-)
     
    Last edited: Jan 30, 2023 at 2:26 AM
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