5 ms·

> My biggest question is why they aren't putting tons of pressure on getting a telescope that can do gravitational lensing to see as far into space as possible

by shagie 4y ago

> My biggest question is why they aren't putting tons of pressure on getting a telescope that can do gravitational lensing to see as far into space as possible ASAP. But again I'm probably just speaking out of turn not being familiar with the wider industry/culture/economics. You are likely interested in the FOCAL project. https://en.wikipedia.org/wiki/FOCAL_(spacecraft) https://en.wikipedia.org/wiki/FOCAL_(spacecraft) > FOCAL (an acronym for Fast Outgoing Cyclopean Astronomical Lens) is a proposed space telescope that would use the Sun as a gravity lens. The gravitational lens effect was first derived by Albert Einstein, and the concept of a mission to the solar gravitational lens was first suggested by professor Von Eshleman, and analyzed further by Italian astronomer Claudio Maccone and others. > In order to use the Sun as a gravity lens, it would be necessary to send the telescope to a minimum distance of 550 astronomical units away from the Sun, enabling very high signal amplifications: for example, at the 203 GHz wavelength, amplification of 1.3 x 10^15. Maccone suggests that this should be enough to obtain detailed images of the surfaces of extrasolar planets. --- That 550 AU... for comparison, Voyager 1 is currently at about 159 AU and moving at 3.6 AU/year. New Horizons is "only" 55.6 AU and going at 2.9 AU/year. But its an interesting project.

Mtinie 4y ago
Was the Voyager series designed and optimized to get outside the heliosphere and into interstellar space as fast as possible? I just don’t have context to know whether covering 159 AU over ~45 years is exceptionally fast (for human-made objects) of if 550 AU could be reasonably reached in a far shorter timeframe if that was the primary goal.
- SoftTalker 4y ago
  No. The original Voyager mission was designed to explore Jupiter and Saturn. After launch, they decided to fly by Uranus and Neptune as well. There was never an expectation that the spacecraft would survive and reach, let alone still be useful in interstellar space.
- Kye 4y ago
  159 AU is about a day's travel for light (~22 light hours). Something designed to get that far quickly would be a tiny payload with a lot of fuel and a weak but efficient engine behind it to accelerate constantly for a very long time. Voyager benefited from a rare alignment of planets that let them send it on a long, wandering journey around gravity wells, so it's very slow compared to what's possible with existing technology.
  - shagie 4y ago
    If you watch DSN... https://eyes.nasa.gov/dsn/dsn.html https://eyes.nasa.gov/dsn/dsn.html (and as I type this, its got a downlink from VGR1) you can occasionally see communication links to Voyager (and others). And since its there now... SPACECRAFT NAME Voyager 1 RANGE 23.80 billion km ROUND-TRIP LIGHT TIME 1.84 days SOURCE VOYAGER 1 FREQUENCY BAND X DATA RATE 160.0 b/sec POWER RECEIVED -160 dBm (1.0 x 10-22 kW)
    - Kye 4y ago
      Was Google wrong (159 AU in light hours), or was the 159 AU I pulled from their comment off? Google answered with a conversion box, so I assumed it had a human checking the formulas and wasn't from their notoriously unreliable auto-snippets.
      - shagie 4y ago
        DSN is interested in the round trip time - they're both right. How long does it take to ACK the data that was sent? 1.84 days. How old is the data that was sent? 0.92 days (22 hours). Communication protocols at that distance are kind of interesting. Things like dropped data and delays can make it challenging. https://en.wikipedia.org/wiki/Interplanetary_Internet https://en.wikipedia.org/wiki/Interplanetary_Internet https://www.nasa.gov/directorates/heo/scan/engineering/technology/disruption_tolerant_networking_overview https://www.nasa.gov/directorates/heo/scan/engineering/techn... https://ipnsig.org/tag/deep-space-network/ https://ipnsig.org/tag/deep-space-network/ https://www.nytimes.com/1990/10/02/science/spacecraft-passes-a-critical-test.html?unlocked_article_code=hBBXhY68kw4onDAZ8jc8tjxF-ORQ3xyKQyIvfWBEmk1eUMyFXpFK26qBShUdhulioha7gfO7szqFVsg5uDOioXq8QSCCPMQB8xUCObxJiELfJziUUfrVTvzTQciT6WLP8t7bC_hL5McmXeH7tvH7Huqyj__Viv7DcO-IQljkErZrP2mhTXaUnVrlxLZOpZE0qRFxY__Eq7tCCoEdEcCRoTqwcLjDGuuv8xR2cWnNxBd-J2dpSYWsWZicLw1-1yh3aoV0bYWInS86FfmxWF1VhMbG83R_Ef5-uBDkRSe_XQOX46QTdCXpltygGm7ziGBZjvTeyP0JS0OYQtP6zseY3g5cqspn8xLOR9Xm&giftCopy=1_CurrentCopy&smid=url-share https://www.nytimes.com/1990/10/02/science/spacecraft-passes...
- shagie 4y ago
  https://ntrs.nasa.gov/api/citations/20170009181/downloads/20170009181.pdf https://ntrs.nasa.gov/api/citations/20170009181/downloads/20... > A very rare planetary alignment would occur in the late 1970’s allowing a spacecraft to visit all the outer planets (Jupiter, Saturn, Uranus, Neptune and Pluto) using gravity assists at each planet to send it on to the next. This unique alignment would not occur again for another 175 years! https://pds-ppi.igpp.ucla.edu/archive1/VGLE_1001/DOCUMENT/MISSION/MISSION.PDF https://pds-ppi.igpp.ucla.edu/archive1/VGLE_1001/DOCUMENT/MI... > During the late 1970's, alignment of the outer planets affords a variety of multi-planet launch opportunities. From the standpoint of Jupiter flyby distance, the 1977 opportunity (Bourke et al., 1972; Schurmeier, 1974) is the most favorable for reaching Saturn via a gravity-assist swingby of Jupiter. Two advanced spacecraft will be launched during a one-month launch period which opens on August 20, 1977. Each spacecraft will be launched by a Titan IIIE/Centaur D-IT from Launch Complex 41 at the Air Force Eastern Test Range. Final Earth-departure injection velocity will be delivered by a solid rocket portion of each spacecraft. After solid rocket burnout and jettison, the remainder of each spacecraft, having a mass of approximately 825 kg, begins its cruise to Jupiter. https://commons.erau.edu/cgi/viewcontent.cgi?article=2830&context=space-congress-proceedings&httpsredir=1&referer= https://commons.erau.edu/cgi/viewcontent.cgi?article=2830&co... https://solarsystem.nasa.gov/missions/voyager-2/in-depth/ https://solarsystem.nasa.gov/missions/voyager-2/in-depth/ > The two-spacecraft Voyager missions were designed to replace original plans for a “Grand Tour” of the planets that would have used four highly complex spacecraft to explore the five outer planets during the late 1970s. > In 1974, mission planners proposed a mission in which, if the first Voyager was successful, the second one could be redirected to Uranus and then Neptune using gravity assist maneuvers. > Although Voyager 2 had fulfilled its primary mission goals with the two planetary encounters, mission planners directed the veteran spacecraft to Uranus—a journey that would take about 4.5 years. > In fact, its encounter with Jupiter was optimized in part to ensure that future planetary flybys would be possible. > The Uranus encounter’s geometry was also defined by the possibility of a future encounter with Neptune: Voyager 2 had only 5.5 hours of close study during its flyby. https://www.scientificamerican.com/article/salvaging-nasas-grand-tour/ https://www.scientificamerican.com/article/salvaging-nasas-g... > When the twin spacecraft were launched, NASA was taking advantage of a rare alignment of Jupiter, Saturn, Uranus and Neptune that occurs once every 175 years to send probes on a "Grand Tour" of the solar system. The alignment allowed the spacecraft to harness the gravity of each planet and swing from one to the next using relatively minimal amounts of fuel. NASA first demonstrated the technique with its Mariner 10 mission to Venus and Mercury from 1973 to 1975. https://www.secretsofuniverse.in/voyagers-planetary-alignment/ https://www.secretsofuniverse.in/voyagers-planetary-alignmen... > ... Why did the engineers at JPL push so hard for this mission to be done? Gary Flandro was the mastermind behind all this, and what he discovered back then in 1964 was groundbreaking. It absolutely changed the game. To be fair, we have to go even further back because as important as Gary Flandro was, he was not the one to lay the foundations for this. > We’re in 1961, looking at a mathematician named Michael Minovitch. He was a 25 years-old graduate student who decided that he wanted to tackle one of the most interesting and fundamental problems in the history of physics: the three-body problem. It was something Newton himself couldn’t figure out. However, Minovitch had a powerful tool that Newton didn’t have, and that was an IBM computer. He was so excited about the new IBM computer at UCLA that he felt like giving a shot at this. http://www.gravityassist.com/IAF3-2/Ref.%203-148.pdf http://www.gravityassist.com/IAF3-2/Ref.%203-148.pdf ... and then probably the most important paper in all of this: Utilization of Energy Derived from the Gravitational Field of Jupiter for Reducing Flight Time to the Outer Solar System http://www.gravityassist.com/IAF2/Ref.%202-123.pdf http://www.gravityassist.com/IAF2/Ref.%202-123.pdf published in 1966. > 4. Conclusions > The 1975-1980 time period is characterized by an abundance of interesting multiple planet trajectories which efficiently utilize energy derived from a close approach to the planet Jupiter. The trajectories discussed here are characterized by very short flight times in comparison to those for direct flights from Earth to the corresponding target planets. Although higher launch energies are suggested for some of the multiple planet flights, the additional expense of this energy might be offset by the great savings afforded by the short flight times. This is due to the expense of providing adequate vehicle reliability for the extended flight duration characteristic of direct trajectories and to the high costs involved in maintaining tracking, orbit determination, and other flight related activities for protracted periods. --- ... And so, the Voyager probes became some very fast moving probes. Note that the Voyager probes are 825 kg... while New Horizons was 478 kg at launch time. You can go faster for getting to 550 AU... with a less massive probe. That's why New Horizons is as fast as it is. For that 3.6 AU/y rate - we haven't launched anything that will overtake them yet. That's going 1/3 the way from Earth to Saturn "direct" each year... twice as fast as Cassini took to get to Saturn. ESA just launched JUICE... it's going to to take 8 years to get to Jupiter (5.2 AU). The current speed of Voyager could do it in a year and a half... but that's with all the gravity assists that it got to where it is now.
dmix 4y ago
> Even without using the Sun as the lens, FOCAL could perform various, otherwise impossible measurements: a separate telescope could be used to measure stellar distances by parallax, which would, using the baseline of 550 AU, measure the precise position of every star in the Milky Way,: 18 enabling various further scientific discoveries.: 18–22 It could also study the interstellar medium,: 22 the heliosphere,: 27 observe gravitational waves,: 25 check for the possible variation of the gravitational constant,: 25 observe the cosmic infrared background,: 26 characterise interplanetary dust within the Solar System,: 27–28 more precisely measure the mass of the Solar System: 26 and similar. Even more reasons to be an evangelist for this sort of project. Compared to settling Mars this seems infinitely more important unless you have some hyper skeptical view of human society. Seeing the surface of extrasolar planets should be the #1 goal easily IMO
- prox 4y ago
  Wow your post got me all excited. When can we do this type of vibe!
- krisoft 4y ago
  > Seeing the surface of extrasolar planets Planet. Singular. Not plural. The nature of gravitational lensing is that you would need to build and place a new telescope for every different direction you want to look. The relevant quote from the linked wikipedia page is: “FOCAL would be able to observe only objects that are right behind the Sun from its point of view, which means that for every observed object a new telescope would have to be made.” > Compared to settling Mars this seems infinitely more important unless you have some hyper skeptical view of human society. My “hyper skeptical” view of human society is that it is fragile. There are many possible catastrophes which could wipe all of us out, then there are many other possible situations which would not kill all of us but would shunt humanity forever. Settling Mars would make us more resilient in two major ways: The settlement on Mars is a physical off-site backup to human society. And the necessary R&D to achieve a self-sustaining Mars setlement would force us to develop and test for reliability under real world circumstances tech which we could use here on Earth to better survive many of those calamities. It is literally a ticket to raise the probability of the continued existence of humankind. On the other hand a picture of an exoplanet is a picture. An interesting one sure. If we would have it now it would be probably front page news. It would be a blurry pixelated disk with smears of colour. That would be all for 99% of humanity. For the select few they would study the image and analyse it and we would have follow on studies in a few years saying things like: “We are reasonably sure this area is a shallow sea, and we think this colour fluctuation is consistent with an algea bloom.” Iff(!) we got lucky and the exoplanet we aimed the telescope at is not a dead, dry rock. So increasing the chance of our survival vs a blury picture which will pose more question than it answers. How are these two goals in any way comparable? Let alone the second being more important?

by shagie 4y ago

Mtinie 4y ago

Was the Voyager series designed and optimized to get outside the heliosphere and into interstellar space as fast as possible? I just don’t have context to know whether covering 159 AU over ~45 years is exceptionally fast (for human-made objects) of if 550 AU could be reasonably reached in a far shorter timeframe if that was the primary goal.

SoftTalker 4y ago
No. The original Voyager mission was designed to explore Jupiter and Saturn. After launch, they decided to fly by Uranus and Neptune as well. There was never an expectation that the spacecraft would survive and reach, let alone still be useful in interstellar space.
Kye 4y ago
159 AU is about a day's travel for light (~22 light hours). Something designed to get that far quickly would be a tiny payload with a lot of fuel and a weak but efficient engine behind it to accelerate constantly for a very long time. Voyager benefited from a rare alignment of planets that let them send it on a long, wandering journey around gravity wells, so it's very slow compared to what's possible with existing technology.
- shagie 4y ago
  If you watch DSN... https://eyes.nasa.gov/dsn/dsn.html https://eyes.nasa.gov/dsn/dsn.html (and as I type this, its got a downlink from VGR1) you can occasionally see communication links to Voyager (and others). And since its there now... SPACECRAFT NAME Voyager 1 RANGE 23.80 billion km ROUND-TRIP LIGHT TIME 1.84 days SOURCE VOYAGER 1 FREQUENCY BAND X DATA RATE 160.0 b/sec POWER RECEIVED -160 dBm (1.0 x 10-22 kW)
  - Kye 4y ago
    Was Google wrong (159 AU in light hours), or was the 159 AU I pulled from their comment off? Google answered with a conversion box, so I assumed it had a human checking the formulas and wasn't from their notoriously unreliable auto-snippets.
    - shagie 4y ago
      DSN is interested in the round trip time - they're both right. How long does it take to ACK the data that was sent? 1.84 days. How old is the data that was sent? 0.92 days (22 hours). Communication protocols at that distance are kind of interesting. Things like dropped data and delays can make it challenging. https://en.wikipedia.org/wiki/Interplanetary_Internet https://en.wikipedia.org/wiki/Interplanetary_Internet https://www.nasa.gov/directorates/heo/scan/engineering/technology/disruption_tolerant_networking_overview https://www.nasa.gov/directorates/heo/scan/engineering/techn... https://ipnsig.org/tag/deep-space-network/ https://ipnsig.org/tag/deep-space-network/ https://www.nytimes.com/1990/10/02/science/spacecraft-passes-a-critical-test.html?unlocked_article_code=hBBXhY68kw4onDAZ8jc8tjxF-ORQ3xyKQyIvfWBEmk1eUMyFXpFK26qBShUdhulioha7gfO7szqFVsg5uDOioXq8QSCCPMQB8xUCObxJiELfJziUUfrVTvzTQciT6WLP8t7bC_hL5McmXeH7tvH7Huqyj__Viv7DcO-IQljkErZrP2mhTXaUnVrlxLZOpZE0qRFxY__Eq7tCCoEdEcCRoTqwcLjDGuuv8xR2cWnNxBd-J2dpSYWsWZicLw1-1yh3aoV0bYWInS86FfmxWF1VhMbG83R_Ef5-uBDkRSe_XQOX46QTdCXpltygGm7ziGBZjvTeyP0JS0OYQtP6zseY3g5cqspn8xLOR9Xm&giftCopy=1_CurrentCopy&smid=url-share https://www.nytimes.com/1990/10/02/science/spacecraft-passes...
shagie 4y ago
https://ntrs.nasa.gov/api/citations/20170009181/downloads/20170009181.pdf https://ntrs.nasa.gov/api/citations/20170009181/downloads/20... > A very rare planetary alignment would occur in the late 1970’s allowing a spacecraft to visit all the outer planets (Jupiter, Saturn, Uranus, Neptune and Pluto) using gravity assists at each planet to send it on to the next. This unique alignment would not occur again for another 175 years! https://pds-ppi.igpp.ucla.edu/archive1/VGLE_1001/DOCUMENT/MISSION/MISSION.PDF https://pds-ppi.igpp.ucla.edu/archive1/VGLE_1001/DOCUMENT/MI... > During the late 1970's, alignment of the outer planets affords a variety of multi-planet launch opportunities. From the standpoint of Jupiter flyby distance, the 1977 opportunity (Bourke et al., 1972; Schurmeier, 1974) is the most favorable for reaching Saturn via a gravity-assist swingby of Jupiter. Two advanced spacecraft will be launched during a one-month launch period which opens on August 20, 1977. Each spacecraft will be launched by a Titan IIIE/Centaur D-IT from Launch Complex 41 at the Air Force Eastern Test Range. Final Earth-departure injection velocity will be delivered by a solid rocket portion of each spacecraft. After solid rocket burnout and jettison, the remainder of each spacecraft, having a mass of approximately 825 kg, begins its cruise to Jupiter. https://commons.erau.edu/cgi/viewcontent.cgi?article=2830&context=space-congress-proceedings&httpsredir=1&referer= https://commons.erau.edu/cgi/viewcontent.cgi?article=2830&co... https://solarsystem.nasa.gov/missions/voyager-2/in-depth/ https://solarsystem.nasa.gov/missions/voyager-2/in-depth/ > The two-spacecraft Voyager missions were designed to replace original plans for a “Grand Tour” of the planets that would have used four highly complex spacecraft to explore the five outer planets during the late 1970s. > In 1974, mission planners proposed a mission in which, if the first Voyager was successful, the second one could be redirected to Uranus and then Neptune using gravity assist maneuvers. > Although Voyager 2 had fulfilled its primary mission goals with the two planetary encounters, mission planners directed the veteran spacecraft to Uranus—a journey that would take about 4.5 years. > In fact, its encounter with Jupiter was optimized in part to ensure that future planetary flybys would be possible. > The Uranus encounter’s geometry was also defined by the possibility of a future encounter with Neptune: Voyager 2 had only 5.5 hours of close study during its flyby. https://www.scientificamerican.com/article/salvaging-nasas-grand-tour/ https://www.scientificamerican.com/article/salvaging-nasas-g... > When the twin spacecraft were launched, NASA was taking advantage of a rare alignment of Jupiter, Saturn, Uranus and Neptune that occurs once every 175 years to send probes on a "Grand Tour" of the solar system. The alignment allowed the spacecraft to harness the gravity of each planet and swing from one to the next using relatively minimal amounts of fuel. NASA first demonstrated the technique with its Mariner 10 mission to Venus and Mercury from 1973 to 1975. https://www.secretsofuniverse.in/voyagers-planetary-alignment/ https://www.secretsofuniverse.in/voyagers-planetary-alignmen... > ... Why did the engineers at JPL push so hard for this mission to be done? Gary Flandro was the mastermind behind all this, and what he discovered back then in 1964 was groundbreaking. It absolutely changed the game. To be fair, we have to go even further back because as important as Gary Flandro was, he was not the one to lay the foundations for this. > We’re in 1961, looking at a mathematician named Michael Minovitch. He was a 25 years-old graduate student who decided that he wanted to tackle one of the most interesting and fundamental problems in the history of physics: the three-body problem. It was something Newton himself couldn’t figure out. However, Minovitch had a powerful tool that Newton didn’t have, and that was an IBM computer. He was so excited about the new IBM computer at UCLA that he felt like giving a shot at this. http://www.gravityassist.com/IAF3-2/Ref.%203-148.pdf http://www.gravityassist.com/IAF3-2/Ref.%203-148.pdf ... and then probably the most important paper in all of this: Utilization of Energy Derived from the Gravitational Field of Jupiter for Reducing Flight Time to the Outer Solar System http://www.gravityassist.com/IAF2/Ref.%202-123.pdf http://www.gravityassist.com/IAF2/Ref.%202-123.pdf published in 1966. > 4. Conclusions > The 1975-1980 time period is characterized by an abundance of interesting multiple planet trajectories which efficiently utilize energy derived from a close approach to the planet Jupiter. The trajectories discussed here are characterized by very short flight times in comparison to those for direct flights from Earth to the corresponding target planets. Although higher launch energies are suggested for some of the multiple planet flights, the additional expense of this energy might be offset by the great savings afforded by the short flight times. This is due to the expense of providing adequate vehicle reliability for the extended flight duration characteristic of direct trajectories and to the high costs involved in maintaining tracking, orbit determination, and other flight related activities for protracted periods. --- ... And so, the Voyager probes became some very fast moving probes. Note that the Voyager probes are 825 kg... while New Horizons was 478 kg at launch time. You can go faster for getting to 550 AU... with a less massive probe. That's why New Horizons is as fast as it is. For that 3.6 AU/y rate - we haven't launched anything that will overtake them yet. That's going 1/3 the way from Earth to Saturn "direct" each year... twice as fast as Cassini took to get to Saturn. ESA just launched JUICE... it's going to to take 8 years to get to Jupiter (5.2 AU). The current speed of Voyager could do it in a year and a half... but that's with all the gravity assists that it got to where it is now.

dmix 4y ago

> Even without using the Sun as the lens, FOCAL could perform various, otherwise impossible measurements: a separate telescope could be used to measure stellar distances by parallax, which would, using the baseline of 550 AU, measure the precise position of every star in the Milky Way,: 18 enabling various further scientific discoveries.: 18–22 It could also study the interstellar medium,: 22 the heliosphere,: 27 observe gravitational waves,: 25 check for the possible variation of the gravitational constant,: 25 observe the cosmic infrared background,: 26 characterise interplanetary dust within the Solar System,: 27–28 more precisely measure the mass of the Solar System: 26 and similar. Even more reasons to be an evangelist for this sort of project. Compared to settling Mars this seems infinitely more important unless you have some hyper skeptical view of human society. Seeing the surface of extrasolar planets should be the #1 goal easily IMO

prox 4y ago
Wow your post got me all excited. When can we do this type of vibe!
krisoft 4y ago
> Seeing the surface of extrasolar planets Planet. Singular. Not plural. The nature of gravitational lensing is that you would need to build and place a new telescope for every different direction you want to look. The relevant quote from the linked wikipedia page is: “FOCAL would be able to observe only objects that are right behind the Sun from its point of view, which means that for every observed object a new telescope would have to be made.” > Compared to settling Mars this seems infinitely more important unless you have some hyper skeptical view of human society. My “hyper skeptical” view of human society is that it is fragile. There are many possible catastrophes which could wipe all of us out, then there are many other possible situations which would not kill all of us but would shunt humanity forever. Settling Mars would make us more resilient in two major ways: The settlement on Mars is a physical off-site backup to human society. And the necessary R&D to achieve a self-sustaining Mars setlement would force us to develop and test for reliability under real world circumstances tech which we could use here on Earth to better survive many of those calamities. It is literally a ticket to raise the probability of the continued existence of humankind. On the other hand a picture of an exoplanet is a picture. An interesting one sure. If we would have it now it would be probably front page news. It would be a blurry pixelated disk with smears of colour. That would be all for 99% of humanity. For the select few they would study the image and analyse it and we would have follow on studies in a few years saying things like: “We are reasonably sure this area is a shallow sea, and we think this colour fluctuation is consistent with an algea bloom.” Iff(!) we got lucky and the exoplanet we aimed the telescope at is not a dead, dry rock. So increasing the chance of our survival vs a blury picture which will pose more question than it answers. How are these two goals in any way comparable? Let alone the second being more important?