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Radiosonde Spectrum Issues

Radiosonde Spectrum Issues. Presented by David Franc U.S. National Weather Service October 8, 2002. Outline. General Technical Information (D. Franc) Definitions Interference Protection Criteria Radiosonde Technology 400.15-406 MHz (J.Nash) Discussion of operations

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Radiosonde Spectrum Issues

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  1. Radiosonde Spectrum Issues Presented by David Franc U.S. National Weather Service October 8, 2002

  2. Outline • General Technical Information (D. Franc) • Definitions • Interference Protection Criteria • Radiosonde Technology • 400.15-406 MHz (J.Nash) • Discussion of operations • Proposed changes to band • 1668.4-1700 MHz (D. Franc) • Discussion of Operations • Proposed changes to band

  3. Definitions • Radiosondes fall under the ITU radio service of meteorological aids (metaids) • Meteorological aids service: a radiocommunication service used for meteorological , including hydrological, observations and exploration • Dropsondes and rocketsondes are also part of the metaids service

  4. Metaids Frequency Bands • Two common bands are used for metaids • 400.15-406 MHz (primary allocation) • 1668.4-1700 MHz (primary allocation) • Other bands identified in ITU Radio Regulations (not covered in this workshop) • 2.025-2.045 MHz (secondary allocation, ITU Region 1) • 27.5-28 MHz (primary allocation) • 153-154 MHz (secondary allocation, ITU Region 1) • 35.2-36 GHz (primary allocation)

  5. Metaids Bands – Additional Information • The Handbook on Use of Radio Spectrum for Meteorology has additional information • Section 3.1: Discussion of bands that are allocated for metaids operations • Sections 3.6.4 – 3.6.6: Discussion of why multiple bands are required

  6. Working Party 7C • Working Party 7C is the ITU-R working Party responsible for development of metaids protection criteria and conducting studies regarding metaids systems • Working Party 7C also is responsible for passive and active remote sensing and meteorological satellite data links

  7. Metaids Interference Protection Criteria • ITU-R Recommendation SA.1263 specifies the maximum interference level that allows radiosonde systems to still meet performance objectives • Level based on margin in radio link at maximum range • Margin is excess receive power above minimum receive threshold • A small percentage of the margin is taken by interference

  8. Metaids Interference Protection Criteria (cont) • Criteria are different for the two bands, 400.15-406 MHz and 1668.4-1700 MHz • Criteria value is assumed to apply at receiver input connector • Criteria are specified as two types: • Short term: less restrictive value that can only be exceeded for a very small percentage of time • Long term: More restrictive value that can be exceeded for up to 20% of time – still allows reliable operation of system

  9. Summary of Metaids Interference Protection Criteria (SA.1263)

  10. Metaids Transmitter Characteristics • Metaids transmitters typically exhibit poor characteristics for several reasons • Expendable device - costly technology to stabilize the transmitter is avoided • Extreme operating conditions • Temperature: +50 to –90 ºC • Pressure: Surface to 36 km • Transmitter standards of normal communications systems should not be applied to radiosonde transmitters

  11. Metaids Receiver Characteristics • Metaids users should strive for the best receiver system design possible • Receivers are a long term investment where advanced technology is more applicable • Good receiver design helps reduce the potential for interference problems • Good receiver design also increases link reliability and increases data availability

  12. Metaids Receiver Characteristics (cont) • Some receiver characteristics necessary to operate with poor radiosonde transmitters result in greater interference susceptibility • Large receive bandwidth to receive signals that jump quickly in frequency • Automatic tracking loops that track strongest signal in band

  13. Metaids Equipment – Additional Information • Handbook on Use of Radio Spectrum for Meteorology: • Section 3.4.1- Ground based receiving equipment • Section 3.4.2- Ground-based signal processing systems • Section 3.4.3- Expendable sensing packages (radiosondes) • Section 3.6 – Discussion of national selection of metaids technology

  14. The Band 400.15-406 MHz

  15. The Band 1668.4 - 1700 MHz

  16. Operations in 1668.4-1700 MHz • In general, metaids systems operated in this band use radio direction finding for wind measurement • Winds calculated from balloon movement • Movement determined by change in signal azimuth and elevation, and balloon height • GPS radiosondes have also been developed for operation in this band

  17. Sharing Issues in 1668.4-1700 MHz with the Metsat Service • The band 1670-1700 MHz is currently shared with the Metsat service • Radiosondes cause interference to Metsat earth stations if they are operated in close proximity • The WMO SG-RFC recommends the band be segmented to prevent interference • Metsat operations: 1670-1675 MHz and 1683-1700 MHz • Metaids operations: 1675-1683 MHz

  18. Interference to Metsat Service MetSat MetSat Data Link (GVAR or S-VISSR) Radiosonde Link Interference Radiosonde Receiver MetSat Earth Station

  19. Sharing Issues in 1668.4-1700 MHz with the Radio Astronomy • The Radio Astronomy service has an allocation below 1670 MHz. • Metaids users should ensure transmitters do not operate below or drift in frequency to below 1668.4 MHz • Keep in mind the WMO recommends Metaids operations should be conducted within 1675-1683 MHz.

  20. Interference to Radioastronomy Signals from Stars Radiosonde Link Interference Radio Astronomy Station Radiosonde Receiver

  21. Mobile-Satellite Service Proposals for 1670-1700 MHz • WARC-92 allocated the band 1675-1710 MHz to the MSS in ITU Region 2 (N. and S. America) • Proposals were made to WRC-95, WRC-97, and WRC-2000 to extend the allocation, in at least part of the band, to worldwide • Past WRCs made no additional allocations • WRC-03 Agenda Item 1.31 calls for considering proposals for an MSS allocation in 1683-1690 MHz or some other band (if identified)

  22. Sharing Issues with MSS- Pre WRC-2000 Studies • The ITU-R concluded that metaids and MSS can not share spectrum on a co-frequency, co-location basis • Metaids typically operate in 1675-1683 MHz making that band infeasible for MSS use • Metsat operations exist in 1670-1675 and 1683-1700 MHz - metaids can not be moved

  23. MSS and MetAids Incompatibility Interference MSS Service Links Radiosonde Radiosonde Link Interference Radiosonde Receiver

  24. Sharing Issues with MSS- Pre WRC-2000 Studies (cont) • The conclusion that MSS cannot share with metaids in 1675-1683 MHz combined with the conclusion that sharing is not possible in 1690-1700 MHz due to metsat, concentrated post-WRC-2000 efforts on the band 1683-1690 MHz and an alternative band of 1670-1675 MHz

  25. Preparations for WRC-03Agenda Item 1.31 (Res 227) • WRC-03 agenda item 1.31 calls for additional studies in accordance with Resolution 227 • Resolution 227 contains a large volume of information, but the are two key points • Conduct studies for the band 1683-1690 MHz • If necessary, conduct studies on alternative bands (bands not specified)

  26. Studies: 1683-1690 MHz • WMO recommends metaids operate in 1675-1683 MHz to avoid interference to metsat stations • The ITU has concluded, with WMO concurrence, that an MSS allocation at 1683-1690 MHz will have little impact on worldwide metaids operations. • The sharing issue in 1683-1690 MHz centers on the significant sharing problems with the metsat service. (Covered in Workshop Session B - 3.1)

  27. Studies: 1670-1675 MHz • Resolution 227, referenced in WRC-03 Agenda Item 1.31 requests the ITU-R study alternative bands if the band 1683-1690 proves to be infeasible • In response, the ITU-R has conducted studies on the band 1670-1675 MHz, even though the MSS has not fully agreed 1683-1690 MHz is not feasible

  28. Studies: 1670-1675 MHz • ITU-R studies conclude that MSS operations in 1670-1675 MHz will have little impact on worldwide metaids operations • Several countries will continue to require 1670-1675 MHz into the future • MSS operations in those countries will not be feasible

  29. ITU-R Recommendation SA.1264 • Recommendation SA.1264 addresses sharing between the MSS and metaids in 1670-1700 MHz • Sharing not feasible in 1675-1683 MHz – primary sub-band for radiosonde operations • MSS operations in 1670-1675 MHz will have little impact on metaids operations except for several countries • Radiosondes can not moved elsewhere in 1683-1700 MHz due to incompatibility with metsat downlinks

  30. CPM Report Text on Agenda Item 1.31 • Section 2.8.2 addresses sharing between MSS and metaids • CPM Report Text is consistent with conclusions stated in Recommendation SA.1264. • CPM Text will be reviewed and possibly edited one last time at the CPM Meeting, November 18-29

  31. Summary of Band 1670-1700 MHz

  32. Recommended Strategy for Agenda Item 1.31 • From the metaids perspective, the CPM text is well balanced, so it should not be modified at the CPM • Text is not perfect, but also is not damaging to metaids operations • Opening text to modifications could lead to introduction of unacceptable text from the MSS • Recommend to your CPM delegation “no change” to CPM text relating to Res 227.

  33. Recommended Strategy for Agenda Item 1.31 (cont) • An allocation to the MSS in 1683-1690 MHz should be opposed, it will have a significant impact on meteorological operations • ITU Regions 2 and 3: Protection of metsat earth stations not feasible • ITU-Region 1: Limits availability of spectrum for future metsat growth

  34. Recommended Strategy for Agenda Item 1.31 (cont) • An allocation to the MSS in 1670-1675 MHz should not be opposed • Not the optimum solution since some metaids stations in several countries could be impacted • Since there is great pressure to provide the MSS some spectrum, the band 1670-1675 MHz offers a solution that the worldwide meteorological community can live with

  35. Recommended Strategy for Agenda Item 1.31 (cont) • Discussions of the sub-bands 1675-1683 or 1690-1700 MHz should be opposed - Resolution 227 considers work on them completed and MSS use infeasible • The sub-band 1675-1683 is the only available spectrum in this area of spectrum that can be used to meet metaids operations requirements

  36. Recommended Strategy for Agenda Item 1.31 (cont) • Resolution 227 should be suppressed or modified to remove any part of 1675-1700 MHz from future consideration • All studies have been completed - if WRC-03 cannot make a decision, no new work can occur to help a future WRC make a decision • Unresolved questions on protecting meteorological services in 1670-1675 MHz could be addressed in a resolution if necessary

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