3 ms·

The 500m telescope lacks transmitters - this is an important distinction. > Fifth, Arecibo's larger secondary platform also housed several transmitters, making

by shagie 4y ago

The 500m telescope lacks transmitters - this is an important distinction. > Fifth, Arecibo's larger secondary platform also housed several transmitters, making it one of only two instruments in the world capable of radar astronomy. ... The NASA-funded Planetary Radar System allowed Arecibo to study solid objects from Mercury to Saturn, and to perform very accurate orbit determination on near-earth objects, particularly potentially hazardous objects. China's 500m telescope wouldn't be able to capture https://www.planetary.org/space-images/radar-images-of-asteroid https://www.planetary.org/space-images/radar-images-of-aster... because it can't send a pulse. https://ui.adsabs.harvard.edu/abs/2010DPS....42.1317B/abstract https://ui.adsabs.harvard.edu/abs/2010DPS....42.1317B/abstra... > We report Arecibo (2380 MHz, 13 cm) and Goldstone (8560 MHz, 3.5 cm) delay-Doppler radar observations of binary near-Earth asteroid (NEA) 65803 Didymos (1996 GT) obtained on five dates between November 14-26, 2003 during the asteroid's approach within 0.048 AU. You'll note the Goldstone mention there and the "making it one of only two instruments in the world" from the wiki link on the 500 meter article https://en.wikipedia.org/wiki/Radar_astronomy https://en.wikipedia.org/wiki/Radar_astronomy > There is one remaining radar astronomy facility in regular use, the Goldstone Solar System Radar.

snowwrestler 4y ago
Thanks for a substantive and well-sourced comment. There is a comment lower down saying Green Bank might add radar: https://news.ycombinator.com/item?id=33233119 https://news.ycombinator.com/item?id=33233119 I’m not in a position to confirm whether that is true though.
- shagie 4y ago
  https://greenbankobservatory.org/future-of-earths-defense-is-ground-based-planetary-radar/ https://greenbankobservatory.org/future-of-earths-defense-is... > The National Science Foundation has awarded funds for the conceptual design of a higher-power radar system on the GBT – one that would be nearly 1,000 times more powerful than the proof of concept. In addition to a more powerful transmitter, NRAO and GBO, working with industry partners, will leverage new, solid-state amplifier and array receiving-system technologies to maximize the effectiveness of the new system. In parallel to this, as additional funding is allocated, the team plans to move to final design and construction activities, beginning in 2023. > The GBT’s new radar capabilities will introduce a tool that astronomy has not had before, collecting data at higher resolutions and at wavelengths not previously available. NRAO and GBO also are developing advanced data reduction and analysis tools that have not been available before. The flexibility and increased performance of this new system will fill an important need for planetary defense, and also allow astronomers to observe asteroids, comets, planets and moons. The versatility of this system will contribute to many areas of science.
  - snowwrestler 4y ago
    Does it seem like this would replace or improve upon what was lost at Arecibo?
    - shagie 4y ago
      From the page on the test - https://greenbankobservatory.org/successful-test-paves-way-for-new-planetary-radar/ https://greenbankobservatory.org/successful-test-paves-way-f... > Using the information collected with this latest test, the participants will finalize a plan to develop a 500-kilowatt, high-power radar system that can image objects in the Solar System with unprecedented detail and sensitivity. The increased performance also will allow astronomers to use radar signals as far away as the orbits of Uranus and Neptune, increasing our understanding of the Solar System. > “The planned system will be a leap forward in radar science, allowing access to never before seen features of the Solar System from right here on Earth,” said Karen O’Neil, the Green Bank Observatory site director. That use of the word "unprecedented" and looking at Uranus and Neptune suggests to me that it will go further than Arecibo did... three decades ago. https://ui.adsabs.harvard.edu/abs/2000DDA....31.0803N/abstract https://ui.adsabs.harvard.edu/abs/2000DDA....31.0803N/abstra... > In October 1999 we obtained the first radar images of Saturn's rings, using the recently-upgraded Arecibo telescope operating at a wavelength of 12.6 cm. The opening angle of the rings was 19.9o, and dual-circular polarization data were collected over a period of 5 days. The resulting delay-Doppler maps have a range resolution of 100 msec and a frequency resolution of 2 kHz, corresponding to a spatial resolution cell of 15000 x 2000 km. Previous radar observations (e.g., Ostro et al. [1982] Icarus 49, 367) demonstrated the rings' high cross section and depolarization ratio, but did not yield 2-dimensional images. The key thing with this is the radar astronomy rather than radio astronomy. The tracking is likely what's at play for the Uranus and Neptune though. https://en.wikipedia.org/wiki/Arecibo_Telescope https://en.wikipedia.org/wiki/Arecibo_Telescope > The round trip light time to objects beyond Saturn is longer than the 2.6-hour time that the telescope could track a celestial position, preventing radar observations of more distant objects. Uranus is about 2.5 light hours Neptune is about 4 light hours from us. Double that for the round trip time. The primary interesting part of this is getting the accurate ephemeris of near earth asteroids. https://www.lpi.usra.edu/meetings/acm2008/pdf/8285.pdf https://www.lpi.usra.edu/meetings/acm2008/pdf/8285.pdf > Arecibo Doppler measurements (2380-MHz, 12.6- cm) of asteroid 99942 Apophis, obtained in August 2005 and May 2006, have been combined with optical astrometry reported through August 2006 to produce a new orbit solution. https://www.sciencedirect.com/science/article/pii/S0019103521002591 https://www.sciencedirect.com/science/article/pii/S001910352... > During these encounters the Arecibo and Goldstone radar stations collected seven Doppler and 22 delay measurements of Bennu. For a general description of radar astrometry see Yeomans et al., 1987, Ostro et al., 2002. This wealth of ground-based tracking data allows an extremely accurate description of Bennu’s motion (Chesley et al., 2014). The trajectory of Bennu is deterministic until 2135, when a close encounter with Earth leads to strong scattering and makes the knowledge of its future motion statistical. --- So it looks like Green Bank will have improved transmitter and tracking. It won't have quite the sensitivity of Arecibo, but it's still one of the more impressive resources.

by shagie 4y ago

snowwrestler 4y ago

Thanks for a substantive and well-sourced comment. There is a comment lower down saying Green Bank might add radar: https://news.ycombinator.com/item?id=33233119 https://news.ycombinator.com/item?id=33233119 I’m not in a position to confirm whether that is true though.

shagie 4y ago
https://greenbankobservatory.org/future-of-earths-defense-is-ground-based-planetary-radar/ https://greenbankobservatory.org/future-of-earths-defense-is... > The National Science Foundation has awarded funds for the conceptual design of a higher-power radar system on the GBT – one that would be nearly 1,000 times more powerful than the proof of concept. In addition to a more powerful transmitter, NRAO and GBO, working with industry partners, will leverage new, solid-state amplifier and array receiving-system technologies to maximize the effectiveness of the new system. In parallel to this, as additional funding is allocated, the team plans to move to final design and construction activities, beginning in 2023. > The GBT’s new radar capabilities will introduce a tool that astronomy has not had before, collecting data at higher resolutions and at wavelengths not previously available. NRAO and GBO also are developing advanced data reduction and analysis tools that have not been available before. The flexibility and increased performance of this new system will fill an important need for planetary defense, and also allow astronomers to observe asteroids, comets, planets and moons. The versatility of this system will contribute to many areas of science.
- snowwrestler 4y ago
  Does it seem like this would replace or improve upon what was lost at Arecibo?
  - shagie 4y ago
    From the page on the test - https://greenbankobservatory.org/successful-test-paves-way-for-new-planetary-radar/ https://greenbankobservatory.org/successful-test-paves-way-f... > Using the information collected with this latest test, the participants will finalize a plan to develop a 500-kilowatt, high-power radar system that can image objects in the Solar System with unprecedented detail and sensitivity. The increased performance also will allow astronomers to use radar signals as far away as the orbits of Uranus and Neptune, increasing our understanding of the Solar System. > “The planned system will be a leap forward in radar science, allowing access to never before seen features of the Solar System from right here on Earth,” said Karen O’Neil, the Green Bank Observatory site director. That use of the word "unprecedented" and looking at Uranus and Neptune suggests to me that it will go further than Arecibo did... three decades ago. https://ui.adsabs.harvard.edu/abs/2000DDA....31.0803N/abstract https://ui.adsabs.harvard.edu/abs/2000DDA....31.0803N/abstra... > In October 1999 we obtained the first radar images of Saturn's rings, using the recently-upgraded Arecibo telescope operating at a wavelength of 12.6 cm. The opening angle of the rings was 19.9o, and dual-circular polarization data were collected over a period of 5 days. The resulting delay-Doppler maps have a range resolution of 100 msec and a frequency resolution of 2 kHz, corresponding to a spatial resolution cell of 15000 x 2000 km. Previous radar observations (e.g., Ostro et al. [1982] Icarus 49, 367) demonstrated the rings' high cross section and depolarization ratio, but did not yield 2-dimensional images. The key thing with this is the radar astronomy rather than radio astronomy. The tracking is likely what's at play for the Uranus and Neptune though. https://en.wikipedia.org/wiki/Arecibo_Telescope https://en.wikipedia.org/wiki/Arecibo_Telescope > The round trip light time to objects beyond Saturn is longer than the 2.6-hour time that the telescope could track a celestial position, preventing radar observations of more distant objects. Uranus is about 2.5 light hours Neptune is about 4 light hours from us. Double that for the round trip time. The primary interesting part of this is getting the accurate ephemeris of near earth asteroids. https://www.lpi.usra.edu/meetings/acm2008/pdf/8285.pdf https://www.lpi.usra.edu/meetings/acm2008/pdf/8285.pdf > Arecibo Doppler measurements (2380-MHz, 12.6- cm) of asteroid 99942 Apophis, obtained in August 2005 and May 2006, have been combined with optical astrometry reported through August 2006 to produce a new orbit solution. https://www.sciencedirect.com/science/article/pii/S0019103521002591 https://www.sciencedirect.com/science/article/pii/S001910352... > During these encounters the Arecibo and Goldstone radar stations collected seven Doppler and 22 delay measurements of Bennu. For a general description of radar astrometry see Yeomans et al., 1987, Ostro et al., 2002. This wealth of ground-based tracking data allows an extremely accurate description of Bennu’s motion (Chesley et al., 2014). The trajectory of Bennu is deterministic until 2135, when a close encounter with Earth leads to strong scattering and makes the knowledge of its future motion statistical. --- So it looks like Green Bank will have improved transmitter and tracking. It won't have quite the sensitivity of Arecibo, but it's still one of the more impressive resources.