Paul Gilster | Centauri Dreams

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 A NASA historical document on computers aboard the Apollo spacecraft refers to the Abort Guidance System as "...probably the most obscure computing machine in the manned spaceflight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...

Study Sees ‘Oumuamua as a Natural Object

by Paul Gilster | Jul 2, 2019 | Astrobiology and SETI | 33 Comments

A paper called “The Natural History of ‘Oumuamua,” just out in Nature Astronomy, puts the emphasis on the word ‘natural.’ We know how much of a stir in the media the interstellar visitor has made given its peculiarities, and the hypothesis put forward by Harvard’s Avi Loeb that it could be a technological object. Now we have a group of 14 astronomers, European as well as American, who have assessed the available data from all angles. This is a worthwhile effort, assembling a team at the International Space Science Institute (ISSI) in Bern, Switzerland that intends to meet once again later in the year. It considers the question of whether the extraterrestrial spacecraft hypothesis is supported by examination of all the peer-reviewed work that has thus far appeared. Matthew Knight (University of Maryland), working with Alan Fitzsimmons (Queen’s University Belfast) assembled the team. Knight believes that natural phenomena can explain ‘Oumuamua: "We put together a strong team of experts...

Benchmarks for a ‘Second Venus’

by Paul Gilster | Jul 1, 2019 | Exoplanetary Science | 7 Comments

The latest find from TESS, the Transiting Exoplanet Survey Satellite, is a reminder of how interesting, and useful, a planetary system can be even if we find no Earth-like worlds there. This seems obvious, but so much of the public attention to exoplanets has to do with finding a clone of our own world that we can forget the power of a 'second Jupiter' or, in this case, a 'second Venus.' For at L 98-59 we have not one but three planets that may fit this description. One Venus, hellish as it is, would seem to be enough. But learning about planets with varying kinds of atmospheres that are in orbits that produce runaway greenhouse effects can help us place our own system's evolution in context. To be sure, we don't yet know what kind of atmospheres these planets have, or if they have atmospheres at all, but the encouraging thing is that tight orbits around relatively bright stars are what we need as we look toward future tools like the James Webb Space Telescope. Astrophysicist Joshua...

‘Dragonfly’ Chosen to Explore Titan

by Paul Gilster | Jun 28, 2019 | Outer Solar System | 56 Comments

We've looked at a number of concepts for exploring Titan over the years, from aircraft capable of staying aloft for a year or more to balloons and boats that would float on the moon's seas. Dragonfly, the work of a team based at Johns Hopkins University's Applied Physics Laboratory in Laurel, MD, is a rotorcraft with the capability of exploiting Titan's thick atmosphere to stop, sample, and move on, shaping its investigations along the way as it explores an environment rich in targets. These are the advantages of a rover, though here we're in a landscape so exotic that it enables different tools than the ones we use on Mars. And with the success of the Martian rovers in mind, what good news that NASA has chosen Dragonfly as the next mission in its New Frontiers program. We can anticipate launch in 2026 and arrival at Titan in 2034, with a craft that will sample surface organics and examine prebiotic chemistry and potential habitability. Image: This illustration shows NASA's Dragonfly...

Progress on Asteroid Discovery, Impact Mitigation

by Paul Gilster | Jun 27, 2019 | Asteroid and Comet Deflection | 9 Comments

We have two stories with good news on the asteroid impact front this morning. The first, out of the University of Hawaii’s Institute for Astronomy, is the announcement of the detection of a small asteroid prior to its entering the Earth’s atmosphere. That many not sound unusual, but this is the first time an object could be detected in time to move people away from a impact site, even though asteroid 2019 MO was only about 4 meters across and burned up in the atmosphere. The key is warning time, and here that time would have been half a day. An impactor like the 20-meter object that exploded over Chelyabinsk, Russia in 2013 could, with these same methods, be detected by the ATLAS facility at Maunaloa (Hawaii) several days before impact. ATLAS is made up of two telescopes, one on Hawai?i Island, the other 160 kilometers away at Haleakal?, Maui, providing whole-sky scans every two nights. About 100 asteroids larger than 30 meters in diameter are discovered by the facility every year....

Inside ESA’s Advanced Concept Team Interstellar Workshop

by Paul Gilster | Jun 26, 2019 | Culture and Society | 22 Comments

It's always good to have eyes and ears on the ground at events I can't get to, so I was pleased when Aleksandar Shulevski contacted me with the offer to send back notes from the European Space Agency's Advanced Concepts Team Interstellar Workshop in Noordwijk in the Netherlands. Born and raised in Bitola, Republic of Macedonia, Aleksandar is a science fiction reader and amateur astronomer who followed up electrical engineering studies in Skopje with an MSc in astronomy at Leiden University (Netherlands), dealing with calibration issues on the LOFAR radio telescope. He received a PhD from the University of Groningen, doing research on active galactic nuclei radio remnants observed with LOFAR. After working at the Netherlands Institute for Radio Astronomy (ASTRON) as junior telescope scientist, he is now a research scientist at the Anton Pannekoek Institute for Astronomy at the University of Amsterdam, specializing in low-frequency radio transients and pursuing his interest in SETI....

Titan and Astrobiology

by Paul Gilster | Jun 25, 2019 | Outer Solar System | 10 Comments

Night launches are spectacular, that's for sure, especially with a rocket as muscular as the SpaceX Falcon Heavy. Less spectacular, at least at this point in my life, is staying up until 0230, but delays are part of the rocket business, and what counts is a launch successful in everything but the return of the center booster (both side boosters landed upright at Cape Canaveral). Prox-1, the carrier vehicle for The Planetary Society's LightSail 2, was released at 720 kilometers, with deployment of the sail itself scheduled for July 2. While we wait for LightSail developments and also follow the fortunes of NASA's Deep Space Atomic Clock, launched as one of 24 satellites deployed by this bird, the 2019 Astrobiology Science Conference in Seattle draws attention this morning with new information about Saturn's tantalizing moon Titan. I'm still having to adapt to not having Cassini in Saturn space, but without its presence scientists are proceeding with laboratory studies that re-create...

Into the Uranian Rings

by Paul Gilster | Jun 24, 2019 | Outer Solar System | 2 Comments

Both DSAC (the Deep Space Atomic Clock) and LightSail 2 are on the line when a SpaceX Falcon Heavy launches on Monday evening. Both missions portend interesting developments in our push to deep space, with DSAC testing our ability to extend navigational autonomy, and LightSail 2 a solar sail that will use the power of solar photons to raise its orbit. You can follow the launch (now scheduled for 2330 Eastern (0330 UTC) on NASA Live. Also lifting off with the Falcon Heavy from the Kennedy Space Center will be almost two dozen other satellites, a nod both to the Falcon Heavy's capabilities but also to increasing spacecraft miniaturization. And speaking of interesting missions, here's something good about one whose anniversary we're about to celebrate. My friend Al Jackson, who served as astronaut trainer on the Lunar Module Simulator in the Apollo days, passed along a link to the Air-to-Ground Loop and the Flight Director's Loop from Apollo 11. Give yourself 20 minutes or so and don't...

Ring Imagery from Cassini’s Deep Dive

by Paul Gilster | Jun 21, 2019 | Outer Solar System | 5 Comments

Cassini's productivity at Saturn continues to provide fodder for scientific papers and encouragement for the builders of complex missions, who have seen enough data gathered by this one to guarantee continuing insights into the ringed planet for years to come. The June 14 issue of Science offers up four papers (citations below) that show results from four of the spacecraft's instruments, including startling views of the main rings. The data examined in the Science papers were gathered during Cassini's ring-grazing orbits from December, 2016 to April of 2017 as well as during the 'Grand Finale' between April and September of 2017, when Cassini flew closer than ever before to the giant planet's cloud tops. Consider the image below, showing an infrared view as captured by the spacecraft's Visible and Infrared Mapping Spectrometer (VIMS), with (at the left) the natural color view taken as a composite by Cassini's Imaging Science Subsystem. Imaging the rings in visible and near-infrared...

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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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