Very Low Frequency Instrument for the ILO

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Very Low Frequency Instrument for the ILO

• Maohai Huang
• National Astronomical Observatories, Chinese
  Academy of Sciences

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Electromagnetic spectrum for astronomy
? ray X-ray UV Visible IR
microwave meterwave VLF
opaque
Total Atmosphere absorption
Total Ionosphere aborption
Partial Atmosphere absorption
transparent
Wavelength
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(No Transcript)
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Gamma RayIntegral 4 tons, 5meters size
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X-rayXMM-Newton 3.8 tons 10meters
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Ultraviolet IUE, FUSE 1 ton,only 0.4m diameter
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visibleHubble, 11 ton 2.4m diameter
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Infrared James Webb 6.2 tons 6.5m diameter
Herschel 3.5m diameter
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The low end of EM spectrum ?
VLFRAE, 1973
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Very Low Frequency (30MHz0.03MHz)
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Wavelength of peak emission of different solar
activities
cm-waves up chrom. corona bottom
mm-waves Chromosphere
dm-waves low corona
Visible Photosphere
metric waves corona
Decametric (30MHz)?2R?
10 KHz ?200R?,1AU
2MHz?10R?
4-10 R? ( ? 20-2 MHz) is where the solar wind is
originated. Degree level spatial resolution is
needed to see how solar wind forms.
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What about interference from the earth that ILO
is exposed to?
90Re

• WAVES showed that at the distance of the moon
  (60Re away) interference from the earth is about
  6 dB stronger than the Galactic signal.
• Easily within linear range of measurement system
• Interference has signatures in time, direction,
  frequency which help to remove them form signal.
• Aurora Kilometeric Radiation has scientific value
  to study

90Re
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How to get resolution better than one radius?

• Avoid using interferometry with big arrays for
  ILO
• Take advantage of low signal frequency and
  measure the Poynting Vector of the signal
• Sample E field component on three orthogonal axes
• Calculate the direction of the arrival of EM
  wave
• Also can measure the polarization and spectral
  properties

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Prototype system

• Freq. range 0.0130MHz
• Spatial resolution 1 degree
• Sensitivity 10nV/sqrt(Hz)
• Comparable to STEREO, WIND/WAVES specs
• Power lt 6W
• Weight lt 3kg
• Processing system demonstrated

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Technical advantages

• Small, light, rugged against vibration and
  temperature changes (of antenna)
• For VLF on-board processing is not difficult
• If the received sky signal is used to modulate
  carrier frequency of the communication link
• no data processing is needed on board
• Measure and process the signal on ground
• Very small and simple payload
• Phase information of signal is preserved so
  interferometry is possible with ground or
  space-based antenna
• a very wide range of frequency can be observed
  with a tunable intermediate frequency generator

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objectives

• Solar wind and ejection imaging and tracking at
  degree-level angular resolution
• Galactic sources
• Pulsar emission time profile (using folding to
  pick out the sources), spectral profile
• Time variation sources
• Earth-moon interferometry experiment
• nano Rad spatial resolution at 200MHz!

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Objectives

• Measure the properties of lunar ionosphere
• Soviet measurement (Luna 19,22) of 2100cm-3
  (0.46MHz inversion freq.) in day time.
• How is it in permanent twilight zone at the S.
  Pole?
• Is it possible to use the ionosphere for
  lunar-surface communication like shortwave is
  used on the earth?
• Characterize VLF environment on the moon
• Ionosphere, regolith radio properties,
  interference
• What can the data tell about future, big-ticket
  VLF mission on the moon people talk about?

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ILO could teach NASA something about the moon

• Grey HautaluomaHeadquarters, Washington202-358-0
  668grey.hautaluoma-1_at_nasa.gov Aug. 3, 2007
• RELEASE 07-169 NASA Selects Astrophysics
  Projects for New Science on the MoonWASHINGTON
  -- NASA has selected four proposals focusing on
  astrophysics priorities in lunar science to
  facilitate the nation's exploration program. The
  proposed studies are part of a NASA effort to
  develop new opportunities to conduct important
  science investigations during the planned renewal
  of human exploration of the moon.A third
  concept study proposes to place a small radio
  telescope array on the moon to study particle
  acceleration in celestial objects such as
  supernovae, quasars and the solar corona. It also
  will serve as a pathfinder for a future possible
  radio telescope to measure the growth of
  structure in the early universe. The study is
  "Radio Observatory for Lunar Sortie Science" from
  the Naval Research Laboratory in Washington.
  Joseph Lazio is Principal Investigator.
• http//www.nasa.gov/home/hqnews/2007/aug/HQ_07169_
  Selected_Lunar_Science_Proposals.html

ILO measurement of lunar ionosphere will make
timely input to NASA mission. Maybe they can chip
in on ILO?
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thanks