Nailong Wu’s HOHI Technology Doubles Radio Telescope Resolvability, Revolutionizing Sky Imaging

The High Order Harmonic Interferometer (HOHI), proposed by independent researcher Nailong Wu in 1996, is a new technology designed to enhance imaging by aperture synthesis radio telescopes. The HOHI uses a conventional base or first harmonic correlator and a second harmonic correlator to virtually increase every baseline by a factor of 2, effectively doubling the resolvability of the telescope. Computer simulations are being used to validate the theory of the HOHI and prepare it for practical use, offering a new technique to increase resolvability without the need to physically extend the maximum baseline.

What is the High Order Harmonic Interferometer (HOHI) and How Does it Improve Radio Telescope Imaging?

The High Order Harmonic Interferometer (HOHI) is a new type of interferometer proposed by independent researcher Nailong Wu in 1996. This innovative technology was designed to enhance imaging by aperture synthesis radio telescopes. The feasibility of the HOHI was initially proven through theoretical analysis, and now, computer simulation is being used as an intermediate stage before practical application.

In an aperture synthesis radio telescope (ASRT), a correlator is used for each baseline to generate a Fourier component of the radio map. This map represents the distribution of power density or brightness of the field of view (FOV) in the sky under observation. The map is then reconstructed using the Fourier transform (FT) technique. The resolvability of an ASRT primarily depends on the maximum baseline. Traditionally, the increase of resolvability is achieved by extending the maximum baseline. However, the HOHI offers a new technique to increase resolvability without extending the maximum baseline.

How Does the HOHI Work?

The HOHI operates on a simple principle. It uses a conventional base or first harmonic correlator and a second harmonic correlator. The radiations of wavelength λ from a single point source arrive at an angle with respect to the normal to the baseline. The phase difference between the two signals in the left and right branches for the baseline is then calculated. The output from the conventional interferometer and the second harmonic correlator consists of desirable second harmonics and unwanted cross terms. The latter can be eliminated by operations, resulting in the visibility output for the baseline from the HOHI of the second order. This process virtually increases every baseline by a factor of 2, effectively doubling the resolvability of the telescope.

How is Computer Simulation Used to Validate the HOHI?

Computer simulation is a crucial step in validating the theory of the HOHI and preparing it for practical use. The simulation generates 1D maps using visibilities from the conventional interferometer and the HOHI of the second order. These maps are then studied in detail to validate the theory of the HOHI. The simulation also helps to address practical issues in the implementation of the HOHI.

The simulation is carried out using the Octave language and studies a number of cases. These include scenarios where two point sources are located far apart, closely together, or so closely that they are not resolved in either the base or 2nd order maps. An extended source is also studied. The results of these simulations provide valuable insights into the performance of the HOHI under different conditions.

What are the Implications of the HOHI for Radio Telescope Imaging?

The HOHI represents a significant advancement in radio telescope imaging. By virtually increasing the baseline by a factor of 2, the HOHI effectively doubles the resolvability of the telescope. This means that the telescope can resolve smaller details in the field of view, leading to more detailed and accurate images of the sky. The HOHI also offers a new technique to increase resolvability without the need to physically extend the maximum baseline, which could have significant practical and cost benefits.

The computer simulations carried out by Wu provide important validation of the theory of the HOHI and help to prepare it for practical use. The simulations also help to address practical issues in the implementation of the HOHI, paving the way for its future application in radio telescope imaging.