1. Earth Exploration-Satellite Service: Passive and Active Sensing
Steven C. Reising*
Associate Professor and Director
Microwave Systems Laboratory
Colorado State University
*With extensive contributions from other members of the U.S. National Research Council’s Committee on Radio Frequencies (CORF) and Spectrum Study Committee
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

2. Types of Sensors optical cameras and scanners
thermal
emission
reflection
optical cameras and scanners
infared and microwave radiometers
backscatter
radar and lidar
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

3. JAXA’s AMSR-E Microwave Radiometer on NASA’s Aqua Satellite (EOS)
Observes Earth at 6.9, 10.7, 18.7, 23.8, 36.5 and 89.0 GHz
Launched in 2002
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

4. Motivation – Scientific Impacts
Radio-frequency measurements of natural phenomena provide essential information with broad scientific and economic impacts.
Examples:
Atmospheric humidity and temperature
Clouds and precipitation
Sea surface temperature
Soil moisture
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

5. Motivation – Economic Impacts
Excerpted from National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

6. One View from Space: Hurricane Katrina (2005)
Warm ocean waters fuel hurricanes, and there was plenty of warm water for Katrina to build up strength once she crossed over Florida and moved into the Gulf of Mexico. This image depicts a 3-day average of actual sea surface temperatures (SSTs) for the Caribbean Sea and the Atlantic Ocean, from August 25-27, Every area in yellow, orange or red represents 82 °F° or warmer, necessary to strengthen a hurricane. The data came from JAXA’s Advanced Microwave Scanning Radiometer (AMSR-E) instrument on NASA's Aqua satellite. Credit: NASA/SVS
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

7. Another View of Hurricanes from Space: Bonnie and Danielle (1998)
From Wentz et al., “Satellite Measurements of Sea Surface Temperature Through Clouds,” Science, vol. 288, pp , May 2000.
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

8. IUCAF Summer School on Spectrum Management, Tokyo, Japan
Impact of Passive Remote Sensing of Soil Moisture on Climate Forecasting
Excerpted from National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

9. IUCAF Summer School on Spectrum Management, Tokyo, Japan
Impact of Passive Remote Sensing of Soil Moisture on Weather Forecasting
Excerpted from National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

10. Motivation – Sensitivity
Receive-only (“passive”) measurements of weak natural signals in a broad range of frequencies must be made with extreme sensitivity.
Example:
Equivalent temperature (proportional to received power) of 100 K in 100 MHz bandwidth → 0.1 pW
Sensitivity to 0.1-K fluctuations → 0.1 fW
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

11. Motivation – Stewardship
The extreme sensitivity required makes it essential:
to maintain protected allocations and
to properly manage use of the spectrum near the protected allocations.
Examples
WRC-07 mandatory emission limits
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

12. Motivation – Requirements
Dedicated passive allocations exist only in a limited number of bands.
There is need for protection of bands essential to scientific and societal interests that are not now protected.
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

13. Motivation – Opportunity and Challenge
The receive-only services can sometimes take advantage of uncongested spectra not allocated to them.
Increasing congestion is increasingly precluding this capability as radar and communications technologies advance.
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

14. IUCAF Summer School on Spectrum Management, Tokyo, Japan
Science Services
Excerpted from National Research Council, Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses, The National Academies Press, Washington, D.C., 2007.
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

15. IUCAF Summer School on Spectrum Management, Tokyo, Japan
EESS Organizations
Excerpted from National Research Council, Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses, The National Academies Press, Washington, D.C., 2007.
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

16. U.S. Passive Microwave Sensing Milestones (one from USSR) – 1
1968: USSR Cosmos 243
1972: NASA Nimbus-5 (NEMS and ESMR)
First long-lived satellites for all-weather imaging
1973: NASA Skylab (S-194)
1975: NASA Nimbus-6 (SCAMS)
1978: NASA Nimbus-7 (SMMR)
1978: NOAA TIROS-N (MSU & SSU)
First operational weather using temperature sounding
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

17. U.S./Japan Passive Microwave Sensing Milestones – 2
1987: USAF DMSP F8 (SSM/I)
First operational surface and atmospheric H2O
1991: NASA UARS (MLS)
First passive satellite measuring above 90 GHz
1997: NASA / JAXA TRMM (TMI)
Added 10.7 GHz to SSM/I to increase sensitivity to SST to improve precipitation measurements
1998: NOAA-15 (AMSU)
2002: NASA EOS Aqua (JAXA’s AMSR-E)
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

18. U.S. / Japan / Europe Passive Sensor Milestones – 3
2003: NRL Coriolis (WindSat)
First polarimetric radiometry from space
2009: ESA SMOS (MIRAS)
-- First synthetic aperture radiometry from space
Anticipated Jan. 2011: NASA Aquarius and SAC-D (CONAE)
-- Combined passive ( MHz) and active ( MHz) observations
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

19. IUCAF Summer School on Spectrum Management, Tokyo, Japan
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

20. ESA’s Soil Moisture and Ocean Salinity (SMOS) Mission: Nov. 2009
Observes in the HI band reserved for RAS + EESS passive services
Needs approx. 0.1 K sensitivity for ocean salinity
Has recorded Enormous RFI, hundreds of K.
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

21. IUCAF Summer School on Spectrum Management, Tokyo, Japan
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

22. Radars below 1400 MHz
Biggest threat to passive sensing operations in MHz is from OOB emissions from terrestrial radars operating in MHz
Such radars are used for air-route surveillance by aeronautical community and many others for defense purposes
Radars are high-power emitters
Due to pulsed and/or frequency-hopping nature of operations, emissions spread well beyond allocated spectrum
From Zuzek, J., NASA Headquarters, MicroRad 2010, Washington, DC, presented March 4, 2010.

23. U.S. Radars in MHz
180 known radar systems and associated latitude and longitude positions were identified in the 1215 – 1400 MHz band for studies leading up to WRC-07 in the U.S.
65 additional radars identified as tactical shipboard radars (no specific locations)
~200 other tactical radars assigned to U.S. military (no specific locations)
From Zuzek, J., NASA Headquarters, MicroRad 2010, Washington, DC, presented March 4, 2010.

24. U.S. Radar Locations Satellite Location Dots are radar locations
From Zuzek, J., NASA Headquarters, MicroRad 2010, Washington, DC, presented March 4, 2010.

25. Physical Basis: Electromagnetic Radiation
All matter absorbs and emits electromagnetic radiation
In addition to electronic transitions in their constituent atoms, molecules rotate and atoms vibrate at temperatures above absolute zero.
The absorption of electromagnetic radiation is dependent on the type of state transition, i.e., rotational, vibrational or electronic.
The specific state transition determines the absorption frequency.
rotation
vibration e-
electronic
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

26. Planck’s Law of Blackbody Radiation
The radiobrightness, spectral brightness or simply “brightness” of a radiating object is given by Planck´s Radiation Law:
where
h = 6.63 x J·sec,
f = frequency in Hz,
k = 1.38 x J/K,
c = 3.0 x 108 m/s,
T = absolute temperature in K.
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

27. Rayleigh-Jeans Radiation Law
For objects at familiar temperatures, microwave and lower millimeter-wave frequencies (~1-100 GHz), hf << kT,
This approximation is valid within 1% up to the following frequencies for the following blackbody temperatures:
T BB
f 1%
2.7 K
100 K
300 K
1 GHz
39 GHz
117 GHz
The Rayleigh-Jeans Radiation Law is
where  = wavelength in m
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

28. Natural sources of microwave radiation
(7)
(2)
(3)
(1)
(6)
(4)
(5)
Atmosphere (4) Land (7) 2.7 K cosmic
(2) Precipitation (5) Oceans microwave
(3) Clouds (6) Scattering background

29. Land Surface Remote Sensing
Excerpted from National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

30. Ocean Surface Remote Sensing
Excerpted from National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

31. Atmospheric Absorption to 1 THz
The opacity of Earth’s atmosphere in the radio range of frequencies from 1 to 1000 GHz for six scenarios. Courtesy of A.J. Gasiewski, University of Colorado. Excerpted from National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

32. Satellite Passive Sensing Frequency Bands
1 – 2 GHz (L band)
4 – 12 GHz (C and X bands)
12 – 26 GHz (Ku and K bands)
26 – 40 GHz (Ka band)
50 – 60 GHz (V band)
75 – 110 GHz (W band)
110 GHz – 3 THz (near-mm and sub-mm waves to THz)
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

33. IUCAF Summer School on Spectrum Management, Tokyo, Japan
1 – 2 GHz (L band)
Soil Moisture (through vegetation)
Ocean Salinity
Aquarius/SAC-D
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

34. IUCAF Summer School on Spectrum Management, Tokyo, Japan
4 – 12 GHz (C and X bands)
Soil Moisture (light vegetation)
Sea Surface Temperature
Wentz, FJ, CL Gentemann, DK Smith and others, 2000, Satellite measurements of sea surface temperature through clouds, Science, 288,
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

35. IUCAF Summer School on Spectrum Management, Tokyo, Japan
12 – 26 GHz (Ku and K bands)
Snow, sea ice, precipitation, clouds
Ocean winds  Water vapor
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

36. IUCAF Summer School on Spectrum Management, Tokyo, Japan
26 – 40 GHz (Ka band)
Snow, sea ice, precipitation, and clouds
Ocean winds
September 2005 broke the record for low summer sea ice extent, the measure of area containing at least 15 percent ice. The ice extent is shown by the edge of the colored region. The long-term average minimum extent contour (1979 to 2000) is in magenta. The grey circle indicates the area where the satellite does not take data. Data are from the Special Sensor Microwave/Imager (SSM/I). (Courtesy NSIDC)
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

37. 50 – 60 GHz (V band) Atmospheric temperature
Color coded map of decadal trends in lower troposphere temperature using MSU/AMSU channel TLT:
Degrees Centigrade per Decade: (29 Years)
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

38. IUCAF Summer School on Spectrum Management, Tokyo, Japan
75 – 110 GHz (W band)
Snow, sea ice, precipitation, clouds
Atmospheric temperature
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

39. 110 GHz – 3 THz (near-mm and sub-mm waves to THz)
Precipitation and clouds
Water vapor
Atmospheric chemistry (trace gases)
Data from NASA's Earth-observing Aura satellite show that the ozone hole peaked in size on Sept. 13, reaching a maximum area extent of 9.7 million square miles – just larger than the size of North America. That's "pretty average," says Paul Newman, an atmospheric scientist at NASA Goddard Space Fight Center, when compared to the area of ozone holes measured over the last 15 years. Still, the extent this year was "very big," he says, compared to 1970s when the hole did not yet exist.
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

40. IUCAF Summer School on Spectrum Management, Tokyo, Japan
Technical Aspects – 1
EESS and RAS (my comments as a outsider to RAS)
Shared bands of interest
Atmospheric windows
Gaseous emission spectral lines
Fundamental difference
RAS generally requires local protection
EESS generally requires global protection
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

41. IUCAF Summer School on Spectrum Management, Tokyo, Japan
Technical Aspects – 2
Modulation and Filtering
Use modulation schemes minimize to out-of- band emissions (e.g. GMSK)
Filters in EESS sensors are required but not always effective
Filters in transmitters are effective but challenging
Interference Mitigation in EESS sensors
Frequency sub-banding
Time-domain pulse excision
Kurtosis technique for low-level RFI detection
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

42. Additional Protection – 1
Unwanted Emissions
Progress made at WRC-07
Mandatory limits
Challenge of shared allocations
Assumption FSS (S-E) and EESS can be shared
Recent EESS practice shows difficulties
Call for updated standards (limiting and controlling spurious, OOB, and harmonic emissions)
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

43. Additional Protection – 2
Bandwidth at C-band and higher
Need 1-2% allocation at a minimum
Desire 5% for current and emerging applications
New Frequencies
C-band is essential for EESS operational systems: Future secondary allocation?
Update of ITU footnote for 275 GHz to GHz in the works for WRC-12 (AI 1.6)
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

44. RFI in 1400-MHz Protected Band Observed in 1997
Excerpted from National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

45. RFI Observed at 10.7 GHz by JAXA’s AMSR-E on NASA’s Aqua Satellite
Excerpted from National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

46. Evolution of C- and X-band Global RFI
6.6 GHz
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

47. Evolution of C- and X-band Global RFI
6.6 GHz
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

48. Evolution of C- and X-band Global RFI
6.9 GHz
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

49. IUCAF Summer School on Spectrum Management, Tokyo, Japan
Additional Resources
Committee on Radio Frequencies (CORF) of the National Research Council: sites.nationalacademies.org/BPA/BPA_048819
International Telecommunication Union:
Scientific Committee on Frequency Allocations for Radio Astronomy and Space Science (IUCAF) of the International Council for Science:
U.S. Federal Communications Commission:
U.S. National Telecommunications and Information Administration:
U.S. National Radio Astronomy Observatory Spectrum Management:
Institute of Electrical and Electronics Engineers (IEEE) Geoscience and Remote Sensing Society (GRSS) Frequency Allocations in Remote Sensing (FARS) Committee: committees/frequency-allocations-in-remote-sensing/
Committee on Radio Astronomy Frequencies (CRAF) of the European Science Foundation:
U.S. National Science Foundation Electromagnetic Spectrum Management (ESM):
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan

50. IUCAF Summer School on Spectrum Management, Tokyo, Japan
Many thanks to NAOJ, Mitaka, Tokyo for hosting the Third IUCAF Summer School on Spectrum Management and to the entire Scientific Organizing Committee!
May 31, 2010
IUCAF Summer School on Spectrum Management, Tokyo, Japan