3 ms·

It is not about collecting area, but about synchetic aperture [1] alike very-long baseline interferometry (e.g. used by Event Horizon Telescope [2], which is a

by nuccy 5y ago

It is not about collecting area, but about synchetic aperture [1] alike very-long baseline interferometry (e.g. used by Event Horizon Telescope [2], which is a combination of many radio telescopes to observe the accretion disk around the supermassive black hole in M87 galaxy [3]). For that you need as long as possible distance between antenas, good time synchronisation, and as many as possible pairs of antenas (i.e. baselines) [3]. Though unfortunately advances in radio don't compensate losses in optical and survey quality due to strays. Different sources emit at different wavelengths differently and usually one needs the whole picture (spectral energy distribution) from radio, ir, visible light, uv, x-rays up to gamma-rays to explain the properties of a source. 1. https://caseyhandmer.wordpress.com/2021/11/17/science-upside-for-starship/ https://caseyhandmer.wordpress.com/2021/11/17/science-upside... 2. https://en.m.wikipedia.org/wiki/Very-long-baseline_interferometry https://en.m.wikipedia.org/wiki/Very-long-baseline_interfero... 3. https://skyandtelescope.org/astronomy-blogs/black-hole-files/how-does-very-long-baseline-interferometry-work/ https://skyandtelescope.org/astronomy-blogs/black-hole-files...

welterde 5y ago
Depends on what you are after. You need long baselines if you want high resolution. However if you want high sensitivity there is no way around having a large collecting area. And since we are not looking to detect the sun in super high resolution, but very far away objects that will be extremely faint we need very high sensitivity. There is a reason the VLA (and other arrays such as ALMA) move their antennas into different configurations. A more compact configuration achieves better sensitivity at the cost of lower resolution and a more spread out configuration gives the inverse. Your hypothetical Starlink telescope would always have extremely high resolution but virtually no sensitivity to detect anything at all (maybe the sun). Certainly not any NEO objects - those were the prime targets for large single-dish radio telescope like Arecibo. The closest radio telescope to the concept you have in mind is LOFAR, but even for that one each station has many times the collecting area of many dozens of Starlink satellites (total collecting area of all stations together is up to ~1km^2).
- shagie 5y ago
  Re: VLA - you might also be interested the HSA - High Sensitivity Array https://science.nrao.edu/facilities/vlba/HSA https://science.nrao.edu/facilities/vlba/HSA In this, they take the VLA and add a few more big ones. > By adding the GBT, phased VLA, and/or Effelsberg to a VLBA experiment the sensitivity can be increased by an order of magnitude. This capability opens up new avenues for scientific discovery. The aim of the High Sensitivity Array initiative is to facilitate the planning, scheduling, and calibration of observations making use of this array. There's also The Impact of Arecibo's Sensitivity on VLBA Observations https://ui.adsabs.harvard.edu/abs/2005AAS...207.2907D/abstract https://ui.adsabs.harvard.edu/abs/2005AAS...207.2907D/abstra... > A growing number of observers are using large single-dish telescopes as elements in VLBI arrays for increased sensitivity. Recently, the High Sensitivity Array (HSA) has been formed by adding the phased Very Large Array, the Green Bank Telescope, the Effelsberg Telescope, and the 305m Arecibo Radio Telescope, to the Very Long Baseline Array (VLBA), to deliver very sensitive VLBI observations. Arecibo is the element that contributes most to the sensitivity of the HSA, but it has limited sky coverage. The study reported here has used the 305m Arecibo Radio Telescope with the VLBA to observe the compact radio source J0837+2454, and carry out a systematic analysis of the impact of including Arecibo. In these observations, Arecibo participated for about 25% of the total observing time. ...

by nuccy 5y ago

welterde 5y ago

Depends on what you are after. You need long baselines if you want high resolution. However if you want high sensitivity there is no way around having a large collecting area. And since we are not looking to detect the sun in super high resolution, but very far away objects that will be extremely faint we need very high sensitivity. There is a reason the VLA (and other arrays such as ALMA) move their antennas into different configurations. A more compact configuration achieves better sensitivity at the cost of lower resolution and a more spread out configuration gives the inverse. Your hypothetical Starlink telescope would always have extremely high resolution but virtually no sensitivity to detect anything at all (maybe the sun). Certainly not any NEO objects - those were the prime targets for large single-dish radio telescope like Arecibo. The closest radio telescope to the concept you have in mind is LOFAR, but even for that one each station has many times the collecting area of many dozens of Starlink satellites (total collecting area of all stations together is up to ~1km^2).

shagie 5y ago
Re: VLA - you might also be interested the HSA - High Sensitivity Array https://science.nrao.edu/facilities/vlba/HSA https://science.nrao.edu/facilities/vlba/HSA In this, they take the VLA and add a few more big ones. > By adding the GBT, phased VLA, and/or Effelsberg to a VLBA experiment the sensitivity can be increased by an order of magnitude. This capability opens up new avenues for scientific discovery. The aim of the High Sensitivity Array initiative is to facilitate the planning, scheduling, and calibration of observations making use of this array. There's also The Impact of Arecibo's Sensitivity on VLBA Observations https://ui.adsabs.harvard.edu/abs/2005AAS...207.2907D/abstract https://ui.adsabs.harvard.edu/abs/2005AAS...207.2907D/abstra... > A growing number of observers are using large single-dish telescopes as elements in VLBI arrays for increased sensitivity. Recently, the High Sensitivity Array (HSA) has been formed by adding the phased Very Large Array, the Green Bank Telescope, the Effelsberg Telescope, and the 305m Arecibo Radio Telescope, to the Very Long Baseline Array (VLBA), to deliver very sensitive VLBI observations. Arecibo is the element that contributes most to the sensitivity of the HSA, but it has limited sky coverage. The study reported here has used the 305m Arecibo Radio Telescope with the VLBA to observe the compact radio source J0837+2454, and carry out a systematic analysis of the impact of including Arecibo. In these observations, Arecibo participated for about 25% of the total observing time. ...