Emergency Managers Weather Information Network Frequently Asked Questions (FAQ)
1. What is EMWIN?
The Emergency Managers Weather Information Network (EMWIN) is a dissemination system used to provide timely dissemination of warnings, watches, graphics, and other hydro meteorological products to emergency managers with minimal equipment cost to them. In the Continental US, EMWIN uses the GOES-East and GOES-West satellite platforms to broadcast the EMWIN data stream. Within the satellite footprint, the EMWIN data stream can be received directly from the satellite using a small receiving dish, an inexpensive receiver and down converter and a PC for data management and display.
In many communities, the received satellite broadcast is re-broadcast to local users by the NWS or other public and private agencies as an audio signal on a dedicated VHF or UHF radio frequency. Users receive this rebroadcast EMWIN data stream using an inexpensive radio receiver, a demodulator, and a personal computer. Some users parse the products into components of their interest such as state zones or county warnings and redistribute the targeted information to the relevant geographical area using pager systems, FM radio sub-carriers, and the Internet.
In the Pacific Rim area, the EMWIN data stream is rebroadcast over the Peace Sat (GOES 7) satellite. The Peace Sat EMWIN rebroadcast provides users with a very low cost and effective data systems throughout the pacific Rim including 26 island nations such as Samoa, Fiji, Cook Islands, Kiribati, Togo, Tuvalu and many others.
2. Who owns and operates the GOES satellites?
The GOES satellites are owned and operated by the National Environmental Satellite, Data, and Information Service (NESDIS). NESDIS is an element of the National Oceanic and Atmospheric Administration (NOAA) which is, in turn, an element of the U.S. Department of Commerce. The National Weather Service (NWS) provides the EMWIN data stream broadcast from the NWS Telecommunication Operations Center. The NWS is also an element of NOAA. Peace Sat (formerly known as GOES 7 when it was operated by NESDIS) now is operated by the University of Hawaii.
3. Is the EMWIN data stream used by other dissemination systems?
In addition to the EMWIN data stream broadcast via the GOES-East and GOES-West, the EMWIN data stream is rebroadcast via Peace Sat, on local radio broadcasts and is available on the Internet at iwin.nws.noaa.gov. On GOES-East and GOES-West and on Peace Sat, the EMWIN data stream is broadcast on the WEFAX channel.
4. What happened to the WEFAX channel?
The WEFAX channel was replaced by the Low Rate Information Transmission (LRIT).
5. In the next generation of GOES satellites will EMWIN change?
Yes. The next generation of GOES satellites, the N/Q series, will have a transponder dedicated to EMWIN. The current EMWIN broadcast will be replaced by "EMWIN-N". In addition, the NWS is currently participating with NESDIS to define the EMWIN service in the GOES R series now targeted for the 2014 era and beyond. We will ensure the user community is informed well in advance of all changes to EMWIN.
6. What changes will occur to the EMWIN broadcast for the GOES N/Q era?
When EMWIN transitions to the GOES N/Q satellites the EMWIN broadcast will change in several ways. The new broadcast called EMWIN-N will have the data rate doubled to 19.2 kbps, use offset quadrature phase shift keying (OQPSK) modulation, and employ error correction coding for additional gain. The EMWIN-N data stream will be an enhanced version of the current EMWIN data set. In addition, the frequency will change to 1692.7MHz.
7. Why are these changes being made?
The WEFAX replacement broadcast, LRIT, will be expanded to use all of the bandwidth available in the WEFAX channel on GOES N/Q, sufficient for the 128 Kbps LRIT data stream. As a result, the EMWIN Channel will be moved to a frequency of 1692.7 MHz. Additionally, the current EMWIN/WEFAX power level exceeds that authorized by the International Telecommunication Union (ITU), a United Nations agency, under the international agreement on satellite broadcasts. The current broadcast is permitted to operate only because it was granted an exemption from the agreement. The exemptions are granted on a case-by-case basis and there was no assurance an exemption would be granted for the new series of satellites. Under those conditions, the designers and builders of the GOES N/Q series of satellites decided it would be better to build the satellites to operate within the international agreements than to take the chance an exemption would not be granted. If the satellite was 'over designed' and an exemption were not granted, the LRIT and EMWIN Channel would not be permitted to operate. The EMWIN Channel is planned to operate at a power level (EIRP) of 44.62 dBmi.
8. What impact will these changes have on the users receiving the GOES N/Q EMWIN Channel?
The effect of a lower broadcast power must be offset by employing a more complex communication protocol. The effects on a user receive system will vary depending on the type of equipment.
9. Will existing EMWIN receivers have to be modified to receive the new GOES-N broadcast?
Yes. The EMWIN transponder on the GOES-N satellite had to be designed with a significant reduction in broadcast power (7 dB less) and on a different frequency in order to satisfy international radio agreements. The modulation scheme now planned for the EMWIN-N will provide double the data rate of the existing EMWIN system (from 9.6 kbps to 19.2 kbps) The degree of the adaptation will depend upon the manufacturers design.
10. When will the GOES N-Q series be launched?
The GOES N satellite is currently stored in orbit and was launched in May 2006. GOES-O is planned to launch in July 2007.
11. How will the current EMWIN transition to the GOES-N EMWIN Channel?
A phased transition is planned from EMWIN-I to EMWIN-N barring premature satellite failures:
12. What will need to be done to have my legacy EMWIN system work with the new specifications?
Several solutions are possible. You will need to contact your specific hardware vendor for their system solution.
13. How long will I be able to use my EMWIN (EMWIN-I) legacy system?
The latest possible date will be 2011, however full transition could occur earlier depending on the health of the presently operating GOES satellites.
14. Will a 1 meter dish still work with EMWIN-N?
Based on tests with the prototype receiver, if the antenna is working well with the existing EMWIN-I signal it will almost certainly work just as well, or better, with the EMWIN-N signal.
The EMWIN-N signal will be about 7 dB less than the EMWIN-I signal,
but the better sensitivity of the prototype EMWIN-N receiver is more
than able to compensate for that reduction. There is about 4 dB
improvement in the demodulator sensitivity by changing from DFSK
modulation to QPSK modulation and a theoretical 8 dB improvement due
to the use of forward error correction coding.
There is a potential problem if there is noticeable interference in an existing EMWIN receiver. The EMWIN-N signal will need about 3 times the bandwidth that the EMWIN-I signal needs. Therefore, it is possible for some interference to pass through the wider receive filter in the EMWIN-N receiver that would have been blocked by the narrower EMWIN-I filter. This is considered a low probability event, but it is not impossible. If such interference did occur, the best solution would likely be a larger antenna (larger than a 1 meter dish). Under any other conditions, there should be no need to change the antenna.
Will the modulation or data speed change again or is this the final modulation type, speed, and power for EMWIN-N?
There are no plans to change the signal specifications as shown on the EMWIN website.
15. Will the modulation or data speed change again or is this the final modulation type, speed, and power for EMWIN-N?
There are no plans to change the signal specifications as shown on the EMWIN website.
16. What do EMWIN users gain out of all this?
The data speed will be at twice the current speed. It will have forward error correction so that more products can be added and compressed thus improving delivery speed and content. It will also be inherently more reliable. Most important, the signal can remain on the air since the old signal is out of compliance with ITU requirements.
17. What is being done to encourage prospective manufacturers to produce a model capable of accomplishing the transition to the GOES-N satellite?
A Federal Request for Information (RFI) has been issued on the Federal Business Opportunities (FedBizOps) publication describing the system and giving prospective manufacturers an opportunity to show their interest in marketing a suitable product. Also, the NWS held an EMWIN industry day in December 2006 that was attended by several satellite receiver equipment manufacturers.
US Dept of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
1325 East-West Highway
Silver Spring, MD 20910
Page Author: EMWIN Team
Web site owner: NWS/OPS17
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