1. Radio Technology in Space Explorations
Paul Song
Space Science Laboratory
University of Massachusetts Lowell
Radio waves and radio technologies
Space radio wave detection:
Space radio wave transmission: flexibility, large power
Sounder/radar: Transmission and then reception.
Ionosonder
Radio plasma imager
Surface penetrating radar: mineral mine, oil field, subsurface structures (archeological sites), subsurface properties of planets and their moons
Summary

2. Radio Waves Radio Waves: 3 kHz ~ 300 GHz (=100 km ~ 1mm)
Refraction: when space medium not uniform
Reflection: when index of refraction changes sharply normally over large transverse spatial scales (compared to )
Diffraction: small (compared with ) obstacles or pathways
Multiple reflections: reflection +refraction (+ diffraction)
Directionality: better for higher frequencies (but more dead-spots)
Issues concerning frequency
Antenna length: transmission most efficient when L~/2
too small => optical: laser/source, lenses, filter, frequency scan, CCD detectors
too long => space structure stability and deployment
Digital technologies: CPU speed or “bandwidth” ~ 3 GHz ( ~10 cm)
Ionospheric reflection:
ionospheric peak reflection : 20~30 MHz
reflection vs penetration

3. Issues Concerning Space Radio Technologies
Antenna
Spatial size, mass
Stability, deployment (no gravity and no wind, but centripetal force)
Electric (straight wire, dish), magnetic (coil)
1D, arrays
Receiver: sensitivity proportional to antenna length, L
Broadband vs narrowband
Transmitter
Transmission power, for short antenna, P ~ (L/)4 (for same voltage)
Frequency control: tuner for short antenna
Complicated operations
Space issues
Radiation hardening
High voltage source on satellite: discharging
Interference with other instruments

4. Radio Technologies in Space Applications
Space passive radio receptions
In-situ plasma conditions
Distant source of signals
Space interferometry (location finding)
Radio sounding (remote sensing)
Ground-based: ionosonder
Space-borne: radio plasma imager, ionospheric
Transceiver, data processing
Ground/ice penetration
Subsurface properties: Earth, Mars, Moon, Jupiter and Saturn icy moons
Space high power transmission

5. Electronics Unit
RPI on IMAGE

6. RPI
IMAGE Instrument Deck

7. Imager for Magnetosphere-to-Aurora Global Exploration (IMAGE) Spacecraft
500-m dipoles in spin plane
20-m dipole along z
RPI:
<10 W radiated power
3 kHz – 3 MHz
300 Hz bandwidth
Launched on 25 Mar 2000

8. Sounding in Magnetosphere

9. The wave environment in space
Meredith et al [2004]
Explain scales, f, t

10. Dynamic Spectra Measured from IMAGE/RPI
Passive Mode
NLK-Washington
24.8 kHz

11. VLF to Satellite Propagation Mode
Earth – Ionosphere waveguide
Leakage out of waveguide through the ionosphere
Whistler mode to the IMAGE satellite

12. Observations of NML station, 2001/2002
La Moure, ND, L=3.26, 500 kW

13. Space Transmission Air Force DSX Spacecraft

14. Wave-Particle Interaction in Radiation Belt
Abel and Thorne, 1998
Precipitation lifetime (days)
L-shell
Objective: Mitigate threats to low-earth orbit satellites (LEO) from energetic electrons.
Energy range: 0.5~2.5 MeV
L-range: 1.7~3.5
Approach: pitch-angle scattering by whistler mode waves

15. Principles of Radio Sounding
Radio waves are reflected at wave cutoffs (n = 0)
In a cold, magnetized plasma, cutoff frequencies are
Ionic or ordinary (O-mode): fc = fp
Extraordinary (X-mode): fc =
Echo from reflections perpendicular to density contours (at reflection point)
Echo
Refracted rays
n=0
n>0
n<0
Use crossed-dipole antennas
to identify O and X waves

16. UML Digisonde ionospheric ground-based sounding
RCV ARRAY
XMT ANTENNA
DPS 4
RCV ANTENNA

17. Ionogram with Derived Density Profile
Electron density profile

18. Ne(h,t) at the Magnetic Equator
Cachimbo 16 October 2002
midnight
noon

19. Interferometric Doppler Imaging
The digisonde, operating in the skymap/drift mode, is designed to measure the drift velocity components on a routine basis. In this mode the ionosonde sounds at one or more fixed frequencies and receives and records the reflected signal from each antenna separately.
This technique depends on the presence of ionospheric structures that are embedded in the background plasma.

20. Digisonde Skymaps

21. Real Time Digisonde F Region Drift

22. Global Ionospheric Radio Observatory (UML Space Science Laboratory)

23. Sounding in Magnetosphere

24. Field-Aligned Propagation RPI Plasmagram Fig 2 of GRL paper
(Reinisch et al., GRL, 2002)

25. Plasma Density Along Field line

26. One Pass of IMAGE on June 8, 2001
IMAGE trajectory

27. Two dimensional density distribution for MLT=8.0 on June 8, 2001

28. Before Storm Partial Recovery Storm Peak
Identified plasmasphere, plasma trough, density depletion, aurora/cusp, and polar cap
The densities and the locations of these regions vary in accordance with the different solar wind/IMF conditions, not correlated with the Dst variations

29. Comparison of the Jupiter moons (Icy surface of Europa)

30. Planetary Advanced Radio Sounder (PARS)
Heritage from IMAGE Radio Plasma Imager (RPI)

31. Ice Penetrating Radar Challenges Strong surface reflections
Signal attenuation in the ice
(absorption, scattering)
Clutters
(unwanted surface reflections)
3-D Ice Bed Mapping
Gogineni, 2013

32. Under Glacier Channels/Trenches
[Gogineni et al., 2014]
~850m ice above sea level
~570m ice above sea level

33. Dual-Frequency Precision Ranging
Swarm spacecraft configuration
for precision interferometry
W transmissions from each s/c
- Each s/c transmits its own frequency
- Each s/c receives all frequencies
Swarm performs as a multi-antenna
interferometer for precision angle-of-arrival
measurements --High resolution interferometry for detection of radio transmitters

34. Magnetospheric Tomography
A 7-satellite constellation
Each satellite transmits and receives signals
Tomography methods are used to infer the plasma density distribution within the constellation

35. Summary Radio technologies can be used in space for
Detecting in situ radio waves in space (plasma conditions: plasma density, magnetic field strength, characteristic processes, wave sources)
Sounding: local plasma conditions, remote sensing plasma density profile
Monitoring ground radio sources
High power transmission in space: stimulating wave-particle interaction
(Ground/ice) Penetrating radars: Moon, Mars, Jupiter icy moons…(the technology can be used on Earth on airplanes)
Multiple transmitters/receivers: interferometer, tomography