3 ms·

Great Observatory for Long Wavelengths (GO-LoW) funded by NASA NIAC program

24 points by 8bitsrule 4y ago

superkuh 4y ago
The most immediate test of this will be in the form of https://www.haystack.mit.edu/geospace/geospace-projects/aero-vista-cubesat-mission/ https://www.haystack.mit.edu/geospace/geospace-projects/aero... (HeRo-> AERO & VISTA) which will test the cubesat design concept in LEO for auroral low frequency radio. These are really cool radio "telescopes" even individually and not in a coherent array because each satellite fully samples the full 3 directional components of both the magnetic field and the electrical field; a "vector" antenna. By doing this you can compute the poynting vector of the electromagnetic wave and determine it's directional of travel, and so, where it's from. In this way a single vector antenna for low frequencies, even though it's much smaller than the wavelength, can still do a sort of 'imaging' or at least direction finding. A vector sensor is composed of three orthogonal dipole elements and three orthogonal loop elements. And if you look at the diagram in the "Great Observatory For Long Wavelength" page you won't see 6 antenna elements. But in these designs the magnetic loops can be operated either in loop mode or in dipole mode (or equiv monopole+ground) by switching the way current/voltage is sampled between the feed points. Since astronomical radio sources are (mostly) steady over microseconds this switching between modes to sample all the electric and magnetic field components works. Vector sensors usually are only used when you're expecting strong signals though. I'm surprised at the proposal for a large array of them for general purpose low frequency work. I would've thought that at least they'd have the full physical vector sensor with 6 antenna elements rather than relying on mode switching between loop/dipole/monopole+ground sampling between the minimal set of 3 multi-purpose elements.

3 ms·

Great Observatory for Long Wavelengths (GO-LoW) funded by NASA NIAC program

24 points by 8bitsrule 4y ago

superkuh 4y ago
The most immediate test of this will be in the form of https://www.haystack.mit.edu/geospace/geospace-projects/aero-vista-cubesat-mission/ https://www.haystack.mit.edu/geospace/geospace-projects/aero... (HeRo-> AERO & VISTA) which will test the cubesat design concept in LEO for auroral low frequency radio. These are really cool radio "telescopes" even individually and not in a coherent array because each satellite fully samples the full 3 directional components of both the magnetic field and the electrical field; a "vector" antenna. By doing this you can compute the poynting vector of the electromagnetic wave and determine it's directional of travel, and so, where it's from. In this way a single vector antenna for low frequencies, even though it's much smaller than the wavelength, can still do a sort of 'imaging' or at least direction finding. A vector sensor is composed of three orthogonal dipole elements and three orthogonal loop elements. And if you look at the diagram in the "Great Observatory For Long Wavelength" page you won't see 6 antenna elements. But in these designs the magnetic loops can be operated either in loop mode or in dipole mode (or equiv monopole+ground) by switching the way current/voltage is sampled between the feed points. Since astronomical radio sources are (mostly) steady over microseconds this switching between modes to sample all the electric and magnetic field components works. Vector sensors usually are only used when you're expecting strong signals though. I'm surprised at the proposal for a large array of them for general purpose low frequency work. I would've thought that at least they'd have the full physical vector sensor with 6 antenna elements rather than relying on mode switching between loop/dipole/monopole+ground sampling between the minimal set of 3 multi-purpose elements.