What is spectrum reallocation, and what does it have to do with weather satellites?

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1 FAQ ========= SPECTRUM REALLOCATION ========= What is spectrum reallocation, and what does it have to do with weather satellites? Because of increasing demand for wireless smartphones, tablets, and Wi-Fi hotspots referred to herein collectively as broadband wireless new federal regulations are being enacted to increase portions of the available radio spectrum for sharing or reallocation for broadband wireless use. Current U.S. weather satellites now use portions of the spectrum that were previously reserved worldwide for transmission of weather data from space and are now either designated to be shared with current broadband wireless or are next to spectrum bands proposed for future broadband wireless. What are the potential problems with spectrum sharing? Satellite signals from space are much weaker than smartphone and tablet transmitters. Thus, satellite ground stations need to be very sensitive, and a result of that sensitivity, they are capable of experiencing significant interference when smartphones, PCs, tablets, and Wi-Fi zones are operating nearby. Even when the frequency bands used by broadband wireless are not the same as those used by nearby satellite ground stations, interference can still occur if the frequencies used are very close together. Such interference could potentially jeopardize access to critical data needed for weather forecasts, aviation safety, electrical power generation, and other essential functions. With adequate protection, it may be possible for satellite ground stations to share frequencies with broadband wireless devices. In order to determine if this is possible, federal agencies and end-users alike would need adequate resources to analyze situations on a per-site basis to determine whether mitigation is possible and then how to fund the fix. The staff effort and funding required for these tasks may well exceed what is currently available to some federal agencies. Could this sharing impact the availability of weather and environmental watches, warnings, guidance, forecasts, analyses and assessments? It is possible that radio frequency interference at satellite ground stations could impede the creation or distribution of weather and environmental products, as discussed below. In addition to being necessary for the protection of lives and property (e.g., from severe weather, wildfires, and hurricanes), such products are also essential to many key industries, including aviation, agriculture, electrical power 1

2 generation, satellite operation, investment activity, recreation, maritime and surface transportation, property insurance, and water resource management. Major weather events result in billions of dollars of damage on the United States each year (see and this impact could increase significantly if severe weather forecast or warning products can no longer be generated and disseminated in a timely manner. How exactly would these planned spectrum changes impact weather products? An increasingly large portion of data used in numerical weather prediction come from satellites, and the output from numerical weather prediction models, in turn, are instrumental in the creation of weather forecasts and issuance of watches, warnings, and advisories. Generally, more than 90% of all input data for large-scale weather prediction models are from satellites, with more than 80% of the total coming from polar-orbiting satellites 1. Much of the data from the current generation of satellites either uses the band about to be auctioned for sharing ( MHz) or is directly adjacent to this band ( MHz). Many non-governmental users receive environmental satellite data directly and in real-time. These data include satellite images that are quite large and typically not readily available by the Internet or NOAA s satellite broadcast system (SBN NOAAPORT see below); weather warnings to emergency managers alerting specific regions to take shelter due to hurricanes, storm surge or tornadic events; or to prepare for severe weather that can endanger life or property. These emergency warnings come directly from a satellite rebroadcast of emergency information that is received by cost-effective warning receivers used throughout the Western Hemisphere. If spectrum sharing creates interference to federal stations, the generation and issuance of products and warnings derived from the satellite data could be impacted. Are there any ways that the spectrum can be shared without posing problems? Spectrum sharing can be accommodated as long as satellite ground receiving stations are protected from interference by wireless devices. One such protective measure is a keep-away zone around the ground stations. The sizes of these zones 1 Percentage of satellite data contributions to a global data set may be computed from monthly data posted on the internet by NOAA/NCEP. 2

3 could range anywhere from 1.2 to over 60 miles 2. Ensuring that there is no interference will require thorough analysis and testing, followed by technical regulations that will protect stations. The FCC Notice of Proposed Rule Making discusses protection zones where a commercial broadband licensee can propose to locate their equipment inside these zones. Then the federal agencies would be required to validate or disprove the incursion into the protection zone under rules yet to be developed. At present, it does not appear certain that all of the relevant federal agencies will have adequate staff and funding resources to verify whether there will or will not be interference to weather satellite ground stations or to validate requests to operate within the protection zones. In addition, the initial proposed regulations do not call for any protection zones for satellite ground receiving stations that are operated by state, local, tribal or private sector entities (e.g., private weather forecasting companies or universities). The risk of interference from broadband wireless is, therefore, even greater for these entities. Final regulations will be developed by the U.S. Federal Communications Commission once they receive public comment on the proposed rulemaking. ========= WEATHER SATELLITES ========= Is there more than one kind of weather satellite? A variety of sensors and imagers aboard satellites are continuously measuring the changes constantly unfolding on our planet. These range from temperature, winds, and moisture at various levels in the atmosphere to the development of tropical storms and hurricanes, emissions from volcanic eruptions, and smoke from wildfires. The primary data used for civil weather forecasting are gathered by two types of satellites: 2 From recommendations of the (Department of) Commerce Spectrum Management Advisory Committee, Working Group One, June 18,

4 Geostationary satellites hover over the same spot on the Earth from about 22,000 miles high, giving them the ability to collect continuous data from above a given region, typically between about 80 N and 80 S latitudes. Polar-orbiting satellites, which are located at significantly lower altitudes than the geostationary satellites typically about five hundred miles high traverse the earth from pole to pole over a dozen times per day. Over a period of several hours, sensors on polar satellites can collect data from the entire planet and are denoted by the local crossing times at the equator (e.g., mid-morning, afternoon). What are the main U.S. operational weather satellites? Geostationary Operational Environmental Satellites (GOES) GOES 13, 14 and 15 are currently flying. (GOES-12 is scheduled to be decommissioned on August 16.) Polar-orbiting Operational Environmental Satellites (POES) NOAA 15, 16, 18, and 19 are currently flying. (afternoon polar orbit) Meteorological Operational (METOP) These satellites are operated under agreement with the European agency that operates Europe s weather satellites. METOP-A and METOP-B are currently flying. (mid-morning polar orbit) Suomi National Polar-orbiting Partnership (NPP) This satellite, now flying, will bridge the gap between NOAA 19 and the new JPSS satellites (see below). Two next-generation satellite series are now being planned for operations later this decade into the 2020s: Geostationary Operational Environmental Satellites, R-Series (GOES-R) Joint Polar Satellite System (JPSS) (afternoon polar orbit) NOAA s National Environmental Satellite, Data, and Information Service (NESDIS) provides more background on these and other U.S. satellites 3. What are some other satellites that support U.S. weather forecasting and environmental monitoring? 3 4

5 Defense Meteorological Satellite Program (DMSP) satellites carry out polar orbits for defense and civil-sector use. The JASON-2 satellite gathers data on sea surface height, which helps determine ocean circulation and sea level rise, for the Ocean Surface Topography Mission. NASA s Earth Observing System (EOS) satellites (Terra, Aqua and Aura) are a coordinated platform for observing the atmosphere, oceans, and land surface. The European Joint Polar System s Meteorological Operational (METOP) satellites include instruments from both the United States and Europe. ================ RECEIVING AND PROCESSING SATELLITE DATA ================ How are raw data from satellites converted into usable forms? Raw data from the satellite sensors are generally stored on the spacecraft and sent within seconds to minutes to one or more primary ground stations where the raw data is calibrated and then sent back to the satellite for rebroadcast to the myriad of receiving stations located throughout the U.S. and Possessions, and worldwide.. After calibration, the data can be used to create a variety of environmental data products which range from the fairly straightforward (such as a satellite image showing clouds that would be visible to the naked eye) to more complex diagrams that can be used to predict things like the landfall of hurricanes. Generally, the more complex a product is, the more processing is needed to create it. 5

6 Figure 1 4 : Spaghetti chart showing landfall predictions for 4 Source: Input data from satellite, terrestrial, radiosondes and dropsondes from hurricane hunter aircraft are used by supercomputers to generate hurricane landfall prediction models. Such data includes measurements from polar-orbiting satellites (using MHz), geostationary satellites (using MHz) and other satellites (Earth Observing System, Tropical Rainfall Measuring Mission, etc.). Radiosondes use MHz to send measurements collected from balloon-borne instrument packages back to receiving stations. Over 800 additional radiosonde measurements beyond the standard twice-daily U.S. launches were made in the days leading to landfall of Hurricane/Superstorm Sandy along the U.S. coast. 6

7 Hurricane/Superstorm Sandy produced by numerical models run on supercomputers several days before landfall. Two of the most common uses of processed data from weather satellites are as input to forecast models run on supercomputers, and as images that can depict current weather features and help extrapolate their behavior. How do processed data get from receiving stations to other users? Most users receive satellite data through rebroadcasting systems of various types. For example, raw images are downlinked to federal satellite ground station and then re-transmitted back to space for re-broadcast to multiple users throughout the Americas using the MHz band. A subset of the total data available is sent through the NOAAPORT Satellite Broadcast System for use by the National Weather Service Weather Forecast Offices, River Forecast Offices, NOAA centers, and domestic and international private sector, state, and local end users. The re-broadcast users and NOAAPORT recipients include companies in the U.S. weather industry; colleges and universities; and state, local and federal agencies. They capture the rebroadcast data products by using receive-only satellite stations, located in cities and towns throughout the country and throughout the world. Such receiving stations are generally not protected from potential radio frequency interference. This re-broadcast is only one method of receipt, described here in detail as an example of the critical weather systems in this spectrum which if subject to radio frequency interference could fail in their mission to communicate data. Many operational users (federal, non-federal, and private sector) who need this data in This model forecast (generated on October 25, 2012 at 8 PM Eastern Time) shows potential tracks for Sandy and predictions where the storm would make landfall. Different models are shown with each color, with the white showing the actual path. Interference to satellite ground stations could have impacted the availability of input data for these supercomputer models. 7

8 real-time and at full resolution choose to operate their own satellite ground stations, which they use to acquire and process all the data products locally, therefore bypassing the need to receive data through the internet or limited subsets of the complete data available via NOAAPORT. Many of these users are not covered by the proposed coordination zones, such as universities and the private sector (many of which provide value-added data under contract to industries, federal agencies, or the military using portions of the spectrum discussed on this website.) Which frequency bands do weather satellites use? Each instrument on a satellite platform transmits data back to Earth on a specific frequency band. One of the most common bands for meteorological satellite data transmissions and reception is megahertz. This band is used for most of the satellite data employed by U.S. government weather agencies and the American weather industry. As noted above, this band has recently been designated for sharing with broadband wireless companies through an auctioning process expected to occur over the next several years. Are other frequency bands, associated with weather satellites, under consideration for spectrum sharing? Yes, additional frequency bands are under consideration to meet the Obama administration s goals for federal spectrum sharing or repurposing. For example, a legislative action included in the FCC s fiscal year 2014 budget for the FCC, proposes that spectrum frequencies between MHz be considered for spectrum sharing 5. The new generation of GOES-R satellites will use this spectrum for Data Collection System Rebroadcast (DCPR), and other critical downlinks for space weather and rebroadcast of GOES-R and other satellite data are located close to this spectrum. Other broadband spectrum usage is near the satellite s downlink frequencies for the health and safety of the spacecraft. ============= USING SATELLITE DATA 5 Federal Communications Commission Fiscal Year 2014 Budget Estimates Submitted to Congress April 2013, page A1.pdf 8

9 ============= Can t these critical products simply be sent over the Internet? The public Internet infrastructure has no guarantee of timeliness. During times of heavy usage, internet data delays can happen unpredictably. Moreover, not all end users have adequate communications infrastructure to receive large volumes of data via a public Internet connection. Current National Weather Service data dissemination channels will not be able to handle the huge increases in data volume from the next generation of satellites, GOES-R, launching in 2015, and JPSS launching in In cases where getting weather products is time-critical, satellite re-broadcast is considered by many to be the most reliable method and often the only method to meet user requirements when lives and property are at risk. Only users with their own satellite ground station will receive the full set of rebroadcast GOES-R in realtime. The timely receipt of this data is what makes it useful for weather forecasting. During extreme weather events such as severe thunderstorms and hurricanes, the power and communications infrastructure is also affected by the same high winds, storm surge, and resultant flooding that damage private and public property. A number of examples from Hurricane Sandy (2012) include wireless cell towers that failed and problems with Internet connectivity. This is the reason that operational users cannot depend on receiving data via the Internet. Why can t this information simply be sent over the broadband network for receipt on a smartphone or tablet? Under the best of conditions, emergency information can be received via wireless networks. The Wireless Emergency Alert initiative is a partnership between the FCC and the Federal Emergency Management Agency. NOAA s National Weather Service is one of many agencies authorized to send emergency alerts to cell phones through this system. However, these are only alerts, and not the large data files or images needed by weather professionals to generate predictions, forecasts, warnings or other products. A wireless broadband network currently cannot reliably deliver such large files on a real-time guaranteed basis. As long as the meteorological satellite is operational, and correctly functioning, a ground station can receive the data and forward the information to initiate local processing. The Wireless Emergency Alert system relies on best effort networks, so delivery of alerts at a given place and time is not guaranteed. A NOAA summary states, The new alert system is not a replacement for other alert systems, and you should not 9

10 rely on it as a sole source of emergency information. 6 Broadband base stations that communicate with your WEA-capable smartphone are subject to storm damage, flooding, and power outages when severe weather events are underway. Do all users of satellite data rely on the radio spectrum in which data are sent from space to Earth? The most critical satellite ground station for receiving data from weather satellites is the NOAA Satellite Operations Facility (NSOF), located in Suitland, Maryland About two dozen other federal sites scattered around the country also receive satellite data in various bands. The locations near large cities are the ones most likely to be vulnerable to interference from broadband wireless. Many other satellite data customers use products created through data received at NSOF and other federal sites e.g., for the satellite images shown on weathercasts or the forecasts of volcanic plumes used to help route aircraft. In some cases, these users receive data directly from satellite feeds at frequencies that may be vulnerable to interference. It is possible to acquire this data several hours to days later via a NOAA data archive, but that time delay may be inadequate to provide timely warnings of critical events such as severe weather, hurricane landfall, aviation turbulence, volcanic ash that can stall jet aircraft engines, or a solar weather event which must be communicated within seconds to prevent damage to the electrical power grid or to avoid impact to aviation. What are some examples of how satellite data in and near the currently proposed reallocation bands are used? Weather forecasting: GOES data ( MHz) are received at NSOF. These data are converted to sector-based imagery that is provided through NOAAPORT to more than 100 National Weather Service forecast offices around the nation. The data are used routinely for tracking fog, snow, rain, thunderstorms, and other phenomena. (NOAAPORT itself is not on or near a band currently designated for wireless broadband use.) America s weather industry: The image sectors produced from GOES data ( MHz) received at NSOF are made available to private sector weather companies via NOAAPORT. These firms provide enhanced products to local and national media, emergency managers, utilities, and other specialized customers in the power, electrical energy, agriculture, and other sectors. Some of the larger private weather companies own satellite ground stations which operate around the clock, receiving

11 re-broadcast data at full resolution in a timely manner. The satellite images viewed by millions of Americans on thousands of U.S. weathercasts each day originate through these sector products. Hurricane monitoring: GOES data ( MHz) received at NSOF are relayed to the National Hurricane Center in Miami for use tracking tropical cyclones in the Atlantic. Such data are especially valuable for regions of incipient or distant storms that are not tracked by hurricane-hunter aircraft. POES and METOP data ( MHz) serve as primary input to supercomputer models that also are used to predict hurricane landfall. For example, polar satellite data received in Miami, Florida, is crucial to the accurate forecasting of hurricanes in the Atlantic Ocean. (The current generation of satellites, POES, are unable to store all the measurements for delayed transmission at a major federal station; therefore, if the data from POES isn t received in the geographic region of interest in near-real time, it will not be available again Tracking and forecasting volcanic plumes: GOES data ( MHz) received at Federal stations are incorporated in images and other products at selected NCEP centers for the Volcanic Ash Advisory Center (VAAC) in Washington, D.C. These products are used to identify volcanic eruptions and determine the height, speed, and direction of plume movement. The resulting data form the basis of notices issued to flight controllers by the Federal Aviation Administration and the International Civil Aviation Organization. The products are also downloaded by the VAAC in Anchorage, Alaska, to cover air routes over the Northern Pacific, again using the MHz band. Tracking harmful algal blooms and other phenomena of interest to the fishing industry: Data from POES and METOP satellites are received at Coast Watch sites (Miami, Florida; Monterey, California; Honolulu, Hawaii) where POES and METOP data is received in real time. These data are used to support fishing and maritime applications, providing wind measurements above the sea surface and sea surface temperature measurements. Coast Watch data are also used to monitor oil spills and storm runoff. Aviation hazards: GOES data ( MHz) received at the Aviation Weather Center in Kansas City is converted to imagery for use in tracking aviation hazards, including thunderstorms, high winds, and regions of potential turbulence. Data Collection System (DCS) & Data Collection System Rebroadcast (DCPR): DCPR ( MHz on current GOES) can also be affected by interference, impacting the data collection systems that carry flood, wildfire, earthquake and volcanic event monitoring data. Data Collection System information also supports the Tsunami Warning Centers. How do emergency managers use products retransmitted by satellite? One of the most useful tools for an emergency manager is NOAA s Emergency 11

12 Managers Weather Information Network (EMWIN), which operates via satellite broadcast. Many local entities drive storm warning sirens directly from an EMWIN receiver. In the next-generation GOES-R satellite, the EMWIN downlink will operate at MHz, directly adjacent to a portion of the spectrum now slated for auction ( MHz). These simple, inexpensive receivers are likely to be subjected to extreme amounts of interference, which could make them nearly useless in time of need. 12