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The Terrascope: Challenges Going Forward

by Paul Gilster | Aug 13, 2019 | Deep Sky Astronomy & Telescopes | 23 Comments

Yesterday I renewed our acquaintance with the idea that large natural objects can stand in for technologies we have previously been engineering into existence. The progression is a natural one. The early telescope work of Hans Lippershey and Galileo Galilei began with small instruments, but both refractor and later reflector designs would grow to enormous size, so that today, even with the best adaptive optics and segmented mirrors working together, we are pushing hard on what can be done. Not to mention the fact that controversies over land use can come into play with gigantic observatory installations, as we've seen recently in Hawaii. The fascination is that there is nothing in physical law to preclude ever increasing segmented mirror instruments, but we have to question their economic realities and their practicality. I think it's a nod to the sheer ingenuity involved in linking seemingly disparate phenomena that David Kipping could turn work on the 'green flash' seen at sunrise...

Planetary Lensing: Enter the ‘Terrascope’

by Paul Gilster | Aug 12, 2019 | Deep Sky Astronomy & Telescopes | 31 Comments

I'm always fascinated with ideas that do not disrupt the known laws of physics but imply an engineering so vast that it seems to defy practical deployment. Centauri Dreams readers are well aware by now of some of Robert Forward's vast mental constructions, including lightsails in the hundreds of kilometers and enormous lenses in the outer Solar System as big as some US states. But such notions abound in the realm of interstellar thinking. Thus Clifford Singer's ideas on pellet propulsion to a receding starship, which from the mathematical analysis require an accelerator 105 kilometers long, an engineering nightmare. But then, when we reach sizes like these, we might ask ourselves whether we're not overlooking the obvious. When Cornell's Mason Peck went to work on wafer-scale spacecraft, one futuristic notion that occurred to him was to charge swarms of tiny 'sprites' through plasma interactions and use Jupiter's magnetic field as a particle accelerator, pushing the chips to thousands...

Summer Break

by Paul Gilster | Jul 29, 2019 | Administrative | 68 Comments

And boy do I need it! See you in two weeks.

TESS: Concluding First Year of Observations

by Paul Gilster | Jul 26, 2019 | Exoplanetary Science | 21 Comments

If it seemed amazing to me that 50 years had gone by since Apollo 11, it surprises me as well to realize that, on a much shorter scale, the Transiting Exoplanet Survey Satellite (TESS) has been at work for a full year. In a recent news release, NASA is calling this "the most comprehensive planet-hunting expedition ever undertaken," presumably a nod to the mission's broad sky coverage as opposed to the sharply confined field of view of the Kepler mission. Whereas Kepler took a 'long stare' at its starfield in Cygnus and Lyra, TESS keeps alternating what it sees, looking at a 24-by-96 degree section of sky for 27 days at a time. Moreover, TESS scientists are homing in on stars much closer to our Solar System. While Kepler was looking along the Orion arm of the galaxy at stars generally between 600 and 3,000 light years out (more distant stars were too faint to observe transit lightcurves), TESS puts the emphasis on stars closer than 300 light years, though with a similar method of...

VERITAS: Strengthening the Optical SETI Search

by Paul Gilster | Jul 25, 2019 | Astrobiology and SETI | 12 Comments

Breakthrough Listen has just announced a new optical SETI effort in partnership with the VERITAS Collaboration. The news took me by surprise, for VERITAS (Very Energetic Radiation Imaging Telescope Array System) generally deals in high-energy astrophysics, with a focus on gamma rays, which signal their presence through flashes of Cherenkov radiation when they strike the Earth's atmosphere. Here, the array is being used to look for technosignatures, as Andrew Siemion (UC- Berkeley SETI Research Center) explains: "Breakthrough Listen is already the most powerful, comprehensive, and intensive search yet undertaken for signs of intelligent life beyond Earth. Now, with the addition of VERITAS, we're sensitive to an important new class of signals: fast optical pulses. Optical communication has already been used by NASA to transmit high definition images to Earth from the Moon, so there's reason to believe that an advanced civilization might use a scaled-up version of this technology for...

Sail Deployment: Reflections on LightSail 2

by Paul Gilster | Jul 24, 2019 | Sail Concepts | 19 Comments

One thing that James E. Webb insisted on during his tenure as NASA administrator was that the space program was larger than an attempt to get humans to the Moon. The man who did so much to ensure that Apollo would succeed, and who will be rightfully honored in the form of the James Webb Space Telescope, was a proponent of exploration throughout the Solar System through robotic craft, and weather and communications satellites that would become part of a permanent reliance on a growing space infrastructure. Marc Millis noted some of the results in his recent essay. For while the frustration of abandoning the Moon in the 1970s lingers, we do have over 4600 spacecraft in Earth orbit, many of them doing the kind of work Webb envisioned. We've completed the initial reconnaissance of the Solar System and made our first tentative ventures into the Kuiper Belt and out past the heliopause. We're charting exoplanets and looking to explore Saturn's largest moon. So these are things to keep in...

Remembering Chris Kraft

by Paul Gilster | Jul 23, 2019 | Culture and Society | 7 Comments

As a poignant and unexpected coda to the celebrations of the Apollo 11 anniversary we learn of the death of Chris Kraft, the man who created NASA's Mission Control from scratch in the early days of the manned space program and was head of Flight Operations during that critical period. Death came at age 95 to a man who worked at ground zero in the fraught days of Mercury and Gemini, serving as flight director for all the Mercury missions and seven of the Gemini flights. Neil Armstrong would say of Kraft that he was "the 'Control' in Mission Control." Image: Christopher Kraft, flight director during Project Mercury, works at his console inside the Flight Control area at Mercury Mission Control in Houston. Kraft, the founder of NASA's Mission Control, died Monday, July 22, 2019, just two days after the 50th anniversary of the Apollo 11 moon landing. He was 95. Credit: NASA via AP. After his work with Gemini, Kraft moved up NASA management ranks and became a senior planner for the Apollo...

From the Moon to the Stars

by Paul Gilster | Jul 22, 2019 | Culture and Society | 59 Comments

I’ll close my coverage of the Apollo 11 anniversary with thoughts from Marc Millis. I was startled to discover, fifty years after watching the first landing on the Moon, that the anniversary seemed almost elegiac. So many expectations that have yet to emerge, so much energy still waiting to find an Apollo-like focus. Marc has likewise been ruminating on the Moon landings and here offers a way of placing them in context. Such an effort invariably means invoking the long view, one I found challenging to sustain because of my own freighted memories of 20 July, 1969. But I think Marc is right in looking for longer, more stable arcs of development and trends that the rush of daily activity can obscure. The former head of NASA’s Breakthrough Propulsion Physics project, Millis is also editor (with Eric Davis) of the book Frontiers of Propulsion Science (2009) and the founder of the Tau Zero Foundation. He has been developing an interstellar propulsion study from a NASA grant and recently...

Neil Armstrong: 2011 Speech in Australia

by Paul Gilster | Jul 19, 2019 | Culture and Society | 10 Comments

If a connection between accounting and astronautics seems tenuous, it's one that Neil Armstrong invoked on the 24th of August, 2011, when he spoke before CPA Australia in Sydney, doubtless motivated by his father's career as an auditor. Armstrong stopped signing autographs in 1996 and rarely spoke in public, but accepted the Sydney invitation, according to members of the audience, because of his declared 'soft spot' for accounting. While no video was allowed during the speech, author Neil McAleer has had access to an audio recording, though one of uneven quality. What follows is an excerpt from a longer project on the Moon landing that McAleer is working on, within which he adds commentary to the parts of the speech he was able to transcribe. Armstrong's words throughout are in quotes, with McAleer's additions in standard text. The first man on the Moon would die almost exactly one year after giving this speech. "I am truly delighted to be here today and I thank you for the wonderful...

Lunar Landing Backup: Apollo’s Abort Guidance System

by Paul Gilster | Jul 18, 2019 | Missions | 11 Comments

Al Jackson shares more memories of Apollo this morning in his account of a little known spacecraft component, the Abort Guidance System. A NASA historical document on computers aboard the Apollo spacecraft refers to the Abort Guidance System as "...probably the most obscure computing machine in the manned spaceflight program to date." The AGS was a backup computer system offering the capability of aborting the mission if the Lunar Module's primary guidance system failed during descent to the lunar surface, ascent or rendezvous. The very invisibility of the system is in its way a tribute to the primary guidance and navigation systems, for while the AGS could abort a landing, it was never needed for that purpose. But NASA's abort policy made its presence mandatory -- an abort would be ordered if one additional system failure could potentially cause the loss of the crew. Thus a loss of either the primary guidance and navigation control system or the AGS would have caused an abort....

How Americans See Space Exploration

by Paul Gilster | Jul 17, 2019 | Culture and Society | 38 Comments

These are unusual times for a site that usually begins its investigations no closer than the outer Solar System (asteroids are an exception). But there is no way to ignore the Apollo 11 anniversary, nor would I even consider it. Tomorrow I'll have further reminiscences from Al Jackson, who was on the scene in Houston when Apollo touched the Moon, and on Friday a piece from Neil McAleer with substantial portions of a speech Neil Armstrong gave in Australia in 2011. For today, a look at how the public views space exploration in our era and earlier, with the surprising result that there seems to be more interest in space than I had assumed. In fact, while it has often seemed as if interest peaked with the moon landings and then slackened, turning instead to space programs of the imagination via high-budget films, there is new evidence that the work we track on Centauri Dreams has a good deal of support. According to a recent survey, over 70 percent of Americans liken the exploration of...

On Apollo, Hayabusa2 & Persistence

by Paul Gilster | Jul 16, 2019 | Uncategorized | 33 Comments

Remembering how I felt 50 years ago when Apollo 11 launched, I fully understand those whose sense of let-down at the abrupt end of the moon landings has never gone away. And yes, I was one of those who assumed we would be on Mars by 1990 or earlier, with missions to the Jovian moons gearing up about now. Events in the interim have proven these expectations unrealistic, but last night as I was reminiscing I also thought about what we had done in those 50 years. 50 years ago, for example, the idea of Europa as an ocean world was still a few years out, only entering into serious speculation after Voyager 1 showed us what Jupiter’s immense tidal forces, aided by the gravitational effects of Europa and Ganymede, could do to Io. That flyby was in March of 1979, and if Io’s volcanoes told a tale, they also implicated Europa’s abundant ice. The Galileo mission, despite its problems, then showed us a Europan surface wracked by movement, with ‘chaos’ features, raft-like ice blocks evidently...

Sorting Out Circumplanetary Disks

by Paul Gilster | Jul 15, 2019 | Exoplanetary Science | 1 Comment

Some confusion has arisen about a possible circumplanetary disk in the system PDS 70, which I wrote about recently (see Exoplanet Moons in Formation?, from June 7). A team led by led by Valentin Christiaens at Monash (Australia) presented evidence for the kind of disk that may have formed the moons of Jupiter around the forming planet PDS 70b, using data from the Very Large Telescope, finding evidence for both the disk and a developing atmosphere here. The finding was admittedly tentative, which should be kept in mind as we resolve the discrepancy between this and a separate observation, what Rice University is calling in a news release 'the first observations of a circumplanetary disk of gas and dust…' What we have in the Rice document is a report on a paper from the university's Andrea Isella and colleagues, who studied millimeter wave radio signals from the Atacama Large Millimeter/submillimeter Array (ALMA) to identify a circumplanetary disk around the other forming planet...

Extending the Astrobiological ‘Red Edge’

by Paul Gilster | Jul 12, 2019 | Astrobiology and SETI | 15 Comments

A useful exercise for learning how to look for life elsewhere is to try to find it right here on Earth. Thus Carl Sagan’s observations of our planet via data taken during the 1993 flyby of the Galileo spacecraft, which was doing a gravity assist maneuver enroute to Jupiter. Sagan and team found pigments on the Earth’s surface with a sharply defined edge in the red part of the spectrum. What he was looking at was the reflection of light off vegetation. The ‘red edge’ has become well known in astrobiology circles and is considered a potential biosignature. On Earth, vegetation is the most abundant reflecting surface indicating life (vegetation covers about 60% of present-day Earth’s land surface). The increase in reflectance shows up at about 700 nm, varying in strength depending upon the species of plant. But as Jack O’Malley-James and Lisa Kaltenegger (Cornell University/Carl Sagan Institute) point out, photosynthetic structures containing chlorophyll are found not just in vegetation...

A Gravitational Wave Approach to Exoplanets

by Paul Gilster | Jul 11, 2019 | Exoplanetary Science | 13 Comments

We should always be on the lookout for new ways of finding exoplanets. Right now we're limited by our methods to stars within the neighborhood of the Sun (in galactic terms), for both radial velocity and transit detections are possible only around brighter, closer stars. The exception here is gravitational microlensing, capable of probing deep into the galaxy, but here the problem is one of numbers. We simply don't make enough detections this way to build up the kind of statistical sample that the Kepler mission has provided in terms of transiting planets. So how significant is this kind of selection bias, which thus far has been forced upon us? Without knowing the answer, we would do well to explore ideas like those put forward by Nicola Tamanini (AEI Potsdam) and colleague Camilla Danielski (CEA/Saclay, Paris). The two scientists are looking at the possibilities of gravitational wave astronomy, looking toward the launch, in the 2030s, of LISA, the Laser Interferometer Space...

Keeping Voyager Alive

by Paul Gilster | Jul 10, 2019 | Missions | 6 Comments

One of the many legacies of the Voyager spacecraft is the Interstellar Mapping and Acceleration Probe (IMAP). Scheduled for a 2024 launch, IMAP has as part of its charter the investigation of the solar wind's interactions with the heliosphere, drawing on data from an area into which only the Voyagers have thus far ventured. Let me hasten to add that IMAP will stay much closer to home, orbiting the Sun-Earth L1 Lagrange point, but like the Interstellar Boundary Explorer (IBEX), it will help us learn more about a region physically reachable only by long-duration craft. The fact that we're still talking about Voyager as an ongoing mission is the story here. Launched in 1977, the doughty probes have kept surprising us ever since. In terms of their longevity, I noted in 2017 that when Voyager 1's thrusters had begun to lose their potency (they're needed to keep the spacecraft's antenna pointed at Earth to return data), controllers were able to fire a set of backup thrusters that hadn't...

Unusual Atmosphere of a ‘Sub-Neptune’

by Paul Gilster | Jul 9, 2019 | Exoplanetary Science | 19 Comments

We refine our terminology as we go when a field as new as exoplanetology is in play. Take the case of GJ 3470b. At 12.6 Earth masses, is this a 'sub-Neptune' or a 'super Earth'? Neptune itself is 17 Earth masses, so I'd on balance give the nod to 'sub-Neptune,' though categories here get confusing. The planet is 0.031 AU out from its star, a red dwarf half the mass of our Sun. Oddly, it has a hydrogen/helium atmosphere in which heavier elements are all but absent. We know this because scientists have been able to put data from both the Hubble instrument and Spitzer to work on an analysis of the atmosphere of the planet. This is done through a technique we've examined before, transmission spectroscopy, in which astronomers study the absorption of the star's light as the planet passes across its face (a transit as seen from Earth), and then the loss of reflected planetary light as the planet moves behind the star (this is called a secondary eclipse). Image: A comparison between...

Apollo’s Lunar Module Simulator

by Paul Gilster | Jul 8, 2019 | Missions | 30 Comments

I'm staying in Apollo mode this morning because after Friday's piece about the Lunar Module Simulator, Al Jackson forwarded two further anecdotes about his work on it that mesh with the discussion. Al also reports that those interested in learning more about the LMS can go to the official Lunar Module familiarization manual, which is available here. I've also inserted some background on the LMS, with my comments in italics. by Al Jackson A couple of funny anecdotes about the Lunar Module Simulator. It took some effort to get the LMS up and running … we could do a little simulation when it was first installed, but I had a very irregular schedule. I always worked at the LMS crew training 8 am to Noon, but for most of 1967, because the crew did not train after 5 pm, I came many the night with the Singer engineers to test the LMS, sometimes 6 to midnight, sometimes midnight to 7 am, and yeah I had to stick around for the 8 am to noon shift, and then go home and sleep. There was a...

Reminiscences of Apollo

by Paul Gilster | Jul 5, 2019 | Missions | 43 Comments

While compiling materials for a book on Apollo 11, Neil McAleer accumulated a number of historical items that he passed along to me (thanks, Neil!), and I'm thinking that with the 50th anniversary of the first landing on the Moon approaching, now is the right time to publish several of these. Centauri Dreams has always focused on deep space and interstellar issues, but Apollo still carries the fire, representative of all human exploration into territories unknown. In the piece that follows, Neil talked to Al Jackson, a well known figure on this site, who as astronaut trainer on the Lunar Module Simulator (LMS) worked with Neil Armstrong and Buzz Aldrin before Apollo 11 launched, along with other Apollo crews. McAleer finalized and synthesized the text, which I'll follow with a piece Al wrote for Centauri Dreams back in 2012, as it fits with his reminiscences related to McAleer. I've also folded in some new material that Al sent me this morning. by Al Jackson and Neil McAleer In the...

Life from a Passing Star

by Paul Gilster | Jul 3, 2019 | Astrobiology and SETI | 28 Comments

Remember 'Nemesis'? The idea was that mass extinctions on Earth recur on a timescale of between 20 and 40 million years, and that this recurrence could be accounted for by the existence of a faint star in a highly elliptical orbit of the Sun. Put this object on a 26 million year orbit and it would, so the theory ran, destabilize Oort cloud comets, causing some to fall into the inner system at a rate matching the record of extinctions. Thus a cometary bombardment was to be expected on a regular basis, as were the mass extinctions that were its consequence. No one has found Nemesis, though other theories about recurring mass extinctions are in play, including recent work from Lisa Randall and Matthew Reece that explores dark matter as the trigger, with the Sun periodically passing through a disk of the stuff. Of course, finding dark matter itself continues to be a problem. Moreover, the wide range in the proposed recurrences gives rise to the possibility that these events are not...

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In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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