NPOESS Transmission Frequency Issues

1. NPOESS Transmission Frequency Issues Satellite Direct Readout Conference for the Americas 11 December 02 David F. McGinnis

2. Basic Radio Frequency Management Principals • Management of radio frequencies is controlled both domestically and internationally • In U.S. the Federal Communications Commission (FCC) oversees all non-Federal Government frequency use (commercial, private, state and local governments) • The National Telecommunications and Information Administration (NTIA) is responsible for Federal Government spectrum oversight

3. Basic Radio Frequency Management Principals (cont.) • Internationally, frequency management is under the purview of the International Telecommunication Union (ITU), a United Nations agency headquartered in Geneva, Switzerland

4. Basic Radio Frequency Management Principals (cont.) • Filing of Satellite Systems -- Domestic • Through NTIA • Four stages of review – conceptual, experimental, developmental, operational • Detailed assessment of satellite system by NTIA’s System Review Branch • Need Stage 4 (operational) NTIA approval before authorization to operate system can be granted • Last step in process is to obtain necessary frequency assignments from NTIA’s Frequency Assignment Subcommittee

5. Basic Radio Frequency Management Principals (cont.) • International Filing • Geostationary satellites follow strict ITU coordination guidelines • Non-geostationary satellites are required to file with ITU, but only respond to those administrations which request coordination • NPOESS Preparatory Project (NPP) received 10 responses for coordination based on filed frequency bands by 90-day response deadline

6. Basic Radio Frequency Management Principals (cont.) • International Filing (cont.) • Exchange of information (coordination) between NOAA and interested countries to determine if any potential for interference exists • If interference potential exists, try to find way to either eliminate or minimize harmful interference so affected space systems can successfully meet mission objectives

7. Basic Radio Frequency Management Principals (cont.) • International Filing (cont.) • Coordination process between countries may last several years • Once complete, ITU is notified of the countries with whom coordination occurred, thereby ending international phase

8. Allocation Status • Radio frequencies cover part of the electromagnetic spectrum (9 kHz to 275 GHz is currently allocated by ITU) is divided into many bands and often allocated to more than one use (or service) in a given band • More than 30 different services • Two types of allocation status, viz. primary and secondary

9. Allocation Status (cont.) • Secondary service cannot cause harmful interference to a primary service allocated in same band • Secondary service must also accept interference from a primary service • When more than one primary service is allocated to the same band, onus is on new primary user to coordinate with existing primary users

10. Proposed NPOESS Use of Radio Spectrum • Preparing to file Stage 3 (Developmental) with NTIA in spring 2003 • Stage 3 will contain fewer frequencies than were filed with Stage 2, i.e. narrowing selection • Response from ITU filing of NPP will be a good reference for NPOESS, since many of frequency bands will be same for NPP and NPOESS satellites

11. Satellite Transmission Issues • Expected significant increase in data rates from proposed NPOESS sensors will require new Low Rate Data (LRD) frequency • VHF (137-138 MHz) and UHF (400.15-401 MHz) bands do not provide sufficient bandwidth to downlink useful abridged data set

12. Satellite Transmission Issues (cont.) • L-band, space to Earth, 1698-1710 MHz, proposed as new LRD spacecraft transmission frequency • Must coordinate with existing filed satellite networks – China, Russia and EUMETSAT (France/ESA) • Current NOAA polar-orbiting metsats co-exist with Chinese and Russian metsats. EUMETSAT’s METOP, expected launch in 2005, must also be considered • Must also meet power density limits reaching Earth’s surface in order to protect primary allocated terrestrial services in 1698-1710 MHz

13. Satellite Transmission Issues (cont.) • Telemetry, Space-to-Earth link at 2287.5 MHz • To be used for sending spacecraft telemetry from either NPOESS to NASA’s Tracking and Data Relay Satellites or directly from NPOESS to ground station at Svalbard • Next to Deep Space Network (DSN) space-to-Earth link at 2290-2300 MHz • Need to have very good filters to avoid interfering with DSN’s receiving very weak signals from missions millions of kilometers from Earth

14. Satellite Transmission Issues (cont.) • X-band, 7750-7850 MHz, proposed as new high rate data (HRD) spacecraft transmission frequency • Only recently (1997) allocated for use by non-geostationary metsats • METOP only metsat system to have filed for band • Intended use for transmission of stored data to few large Earth stations

15. Satellite Transmission Issues (cont.) • X-band, 7750-7850 MHz (cont.) • No restrictions placed on non-geo metsat use of band. Thus can also use band for continuous broadcast, e.g. HRD for NPOESS • Recommendation by Space Frequency Coordination Group indicates that continuous broadcasts must yield to transmission of stored mission data when co-visibility exists at same ground receiving station • EUMETSAT’s METOP would only use frequency to transmit stored data to Svalbard

16. Satellite Transmission Issues (cont.) • X-band, 7750-7850 MHz (cont.) • NPOESS intends to use band for continuous broadcast of HRD • Initial informal coordination begun with EUMETSAT on how to coexist in band • Potential for Svalbard co-visibility can be reduced by appropriate launch into orbit and continued maintenance of orbital parameters • Other administrations may wish to use band in future, thereby requiring further coordination • Must also protect co-allocated primary terrestrial users by limiting power density at Earth’s surface

17. Sensors Issues • Passive Sensors • Conical Microwave Imager Sounder • 22 different frequencies, ranging from 6.625 GHz to 183.31 GHz • Frequencies at 6.625 GHz, 10.65 GHz, 18.7 GHz, 52.24 GHz, 59.38 GHz, 59.94 GHz, 60.3712 GHz, 60.408 GHz, 60.4202 GHz, 60.435 GHz, and 60.5088 GHz are either in bands that have many existing active services or are not allocated for passive use • Frequencies above 59 GHz should be protected from active terrestrial users due to very high atmospheric absorption

18. Sensors Issues, cont. • Passive Sensors (cont.) • Conical Microwave Imager Sounder • Concern about potential interference from proposed car radars operating across exclusively passive band in 23.6-24 GHz • Advanced Technology Microwave Sounder • Only one frequency, 51.76 GHz not allocated for passive use

19. Sensors Issues, cont. • Active Sensor – Altimeter • Proposed to use 5.3 GHz and 13.575 GHz • Both frequencies allocated for active sensor use • Concern is to keep within allocated band, i.e. 5.25-5.46 GHz and 13.25-13.75 GHz • Additional concern – footnotes to both allocations restrict Earth exploration satellite (including metsat) active sensors from causing harmful interference to the Radiolocation Service (radars) and the Aeronautical Radionavigation Service

20. Summary • Process exists to coordinate use of radio spectrum through ITU • Such coordination can lead to harmonious use of same frequency band by several satellite systems • Use of frequencies on NPOESS for LRD and HRD will require international coordination with other metsat systems