Radio Technology in Space Explorations Ionosphere Vertical Echo Disturbance Disturbance Paul Song University of Massachusetts Lowell

Radio Technologies in Space Space passive radio receptions Plasma conditions Source of signals (ionospheric coupling) Space interferometry (location finding) Radio sounding (remote sensing) Ground based: ionosonder Space borne: radio plasma imager, ionospheric Ground penetration Jupiter icy moon Space high power transmission Sounding technology Transceivers, digital processing, antennas

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

IMAGE ORBIT September – October, 2003 VLF

Dynamic Spectra Measured from IMAGE/RPI Passive mode NLK-Washington 24.8 kHz

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

Signal amplitude vs. station-footprint distance Signal amplitude, dB 10dB/1000km DHO Distance, km

from ground-based transmitters VLF power in space from ground-based transmitters Peak electric field amplitude:  100 V/m Assuming whistler wave phase velocity: ~ 0.1 c Magnetic field amplitude at foot: 2×10-11 T (20 pT) Poynting Flux: 510-9 W/m2 Total flux: ~ 50 kW out of 500 kW Ionospheric coupling factor < 10%

Structured E contours, Digi field of view, ISR pencil beam

Principles of Radio Sounding Radio waves are reflected at wave cutoffs (n = 0) In a cold, magnetized plasma Ionic or ordinary (O-mode): Wave frequency = fp Extraordinary (X-mode): Wave frequency = 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

Sounding Tools ionospheric ground-based sounding RCV ARRAY XMT ANTENNA DPS 4 RCV ANTENNA

Automatic Ionogram Scaling Electron density profile

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

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.

Digisonde Skymaps

Real Time Digisonde F Region Drift

IMAGE Spacecraft 20-m dipole along z Launched 25 Mar 2000 500-m dipoles in spin plane 20-m dipole along z RPI: <10 W radiated power 3 kHz – 3 MHz 300 Hz bandwidth Launched 25 Mar 2000

RPI IMAGE Instrument Deck

Electronics Unit RPI on IMAGE

Sounding in Magnetosphere

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

Plasma Density Along Field line

One Pass of IMAGE on June 8, 2001 IMAGE trajectory

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

Plasmasphere Depleting and Refilling full depleted Lppstorm DST Storm

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

Acceleration regions

Comparison of the Jupiter moons (Icy surface of Europa)

Prometheus: Project Overview Salient Features Nuclear fission-powered electric propulsion systems will enable a new era of exploration across the solar system There will be unprecedented science data return through high power science instruments and advanced communications technology Science The Europa mission is the highest priority for a flagship mission in this decade (ref: Academy decadal report) Search for evidence of global subsurface oceans on Jupiter’s three icy Galilean moons that may harbor organic material

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

Echogram collected by the University of Kansas coherent chirp-radar operating at peak transmit power of about 100 W from aircraft at 500 m above the Greenland ice surface. Provided by S. P. Gogineni, Univ. of Kansas.

TOPAS TOPside Automated Sounder Ionospheric Topside Sounding TOPAS TOPside Automated Sounder TOPAS Vertical Echo Ionosphere Disturbance Disturbance Tx

TOPAS Topside Automated Sounder A frequency-versatile space-based Doppler radar system operating in MF – HF - VHF bands 0.1 - 40 MHz (and higher frequencies for interferometry) Global measurement of peak ionospheric electron density and peak height. In-situ density and entire profiles from ~1000 km down to F-layer peak in real time Real time data analysis using TOPIST software Direction finding techniques to locate disturbances in the ionosphere position detection of radio transmitters Inter-satellite HF measurements Accurate distance measurements Inter-satellite columnar electron content

TOPAS : Topside Plasma Radar

Topside Sounding ~200 km

Dual-Frequency Precision Ranging Swarm spacecraft configuration for precision interferometry -- 0.1 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

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

Objective and Approach 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

LORERS Mission

DSX Spacecraft

Advanced Technology at the Center for Atmospheric Research RF Technologies Analog: Front-end design (receivers/transmitters), Low/high power amplifiers, filters, Antenna design Digital: Up/down-converters, Synthesizers, Pulse code modulation (CCK & PSK), Spectral analysis using FPGA’s and DSP’s, FFTs, Filters, FPGA (Altera Stratix and Actel Radiation hardened) Mixed: AtoD, DtoA General: Circuit Board design and layout, Power Supply development, Radiation hardened circuit technology Computer Hardware Technologies Computer Systems: Embedded Computers (SPARC and Intel), Embedded microcontrollers (PIC) Enclosures and Backplanes: VME chassis, CompactPCI chassis, Ruggedized and space flight chassis Computer Software Technologies Operating Systems: Windows XP, Linux, Embedded Real time OS (RTEMS and VxWorks) Languages: C++, Java, Assembler (Intel X86, PIC embedded and DSP) Development Tools ModelSim Verilog Altera development suite (Quartus II) Gnu software development tools