Starliner, made it safely to the ground, albeit without its crew.
Whatever unkind thoughts I have towards Boeing these days, this is good news.
Sep 072024
Jun 072024
I had a very busy day today. Or make that yesterday, since it’s almost 3 AM already.
I wanted write something about D-day. Eighty years. It’s been eighty years since Americans, Canadians, Britons and others of the Greatest Generation landed on the beaches of Normandy, opening a much-awaited second front in the global struggle against fascist totalitarianism.
The result: An imperfect, yet enduring world order, Pax Americana, which brought historically unprecedented peace, prosperity, and security to the majority of humans living on this planet.
Perfect it was not. Totalitarianism never vanished. Even after Stalin’s death, the USSR and its empire prevailed for another 36 years. Some of the worst excesses of communism were yet to come. And there were wars, big wars: I thought I’d list a few but there were too many. Even so, this was a period of global peace, a rules-based system that endured, beyond expectations I should say: When I was growing up, no sane adult existed anywhere I think who expected the world to survive beyond the year 2000 without a major nuclear war, yet here we are in 2024, and there are still no nuclear wastelands.
But eventually, all good things come to an end. This world order is crumbling. Will we survive without a civilizational catastrophe? I don’t know. I worry. Ukraine, the Middle East, Taiwan… who knows what else. The retreat of democracy and the rise authoritarianism. The storm is brewing.
Anyhow, enough about D-day. There were some good news. Boeing’s Starliner, though limping a little, made it to the International Space Station. Those astronauts were brave souls. Considering recent news from Boeing, their newfangled attitude towards quality control and safety, I expected, feared rather, a disaster. I am relieved that it has not happened, but NASA should still dump that overpriced, unsafe contraption.
Meanwhile, Musk’s SpaceX had a major success: Starship completed a full test, involving successful launch and “landing” (onto the ocean for now) of both its first stage and Starship itself. The re-entry was not without challenges, but they made it. This is a big milestone, a very big one. The promise of Starship is basically the holy grail of space travel: Fully reusable, rapidly refurnished vehicles. The fiery reentry was perhaps a bit more dramatic than planned, but the spacecraft made it, and that means that they can learn from the issues and improve both the vehicle and its landing procedure.
And I was only marginally paying attention because I am still struggling with forced upgrades: CentOS 7, the Linux version that I’ve been using since 2016, is coming up EOL (end-of-life) which means I must upgrade. But I cannot upgrade to CentOS because Red Hat turned CentOS into a bleeding edge version of Linux with a short support cycle. Joy. Anyhow, today I managed to complete another milestone of my transition plan, so I may still be able to get everything done in time.
Jan 192024
Japan’s SLIM (Smart Lander for Investigating Moon) made it to the lunar surface. Well… sort of. It accomplished its main goal of a targeted soft landing.
Unfortunately, its solar panels are non-operational. It’s unclear for now why (one speculation I read is that the lander may have tipped over after landing). Its batteries can power it only for a few hours. They’re hoping that perhaps later in the lunar day, or in a next lunar cycle, the lander will get sunlight from the right direction to be able to recharge its batteries after all.
Even so, Japan is now officially the fifth country to have landed a spacecraft on the Moon that remained (at least partially) operational on the lunar surface.
Nov 302023
I made some mistakes in the past. I never made a half-a-billion dollar mistake.
Neither did Chris Lewicki, but he came awfully close.
I just read this delightful account of how Lewicki almost fried the innards of the Spirit rover, destined for Mars, during an engineering test that took place just weeks before the rover was launched.
I can only imagine the sinking feeling in his stomach he must have felt when he thought that the rover was ruined. My mistakes never came close in value, but the sensation is uncomfortably familiar.
Fortunately, in his case, the disaster never actually materialized. In simple terms, yes, he plugged a cord into the wrong outlet, but fortunately, the other end of the cord was not plugged in.
To this day, Lewicki must feel like one of the luckiest persons on the planet.
The illustration is from his blog post, but its appearance suggests that it might have been produced by DALL-E. Or maybe Midjourney or Stable Diffusion? The style looks very reminiscent of AI-produced cartoon images.
Sep 292023
I’ve been meaning to mention this: A few days ago, the sample capsule of the OSIRIS-REx mission returned safely to the Earth, carrying inside a sample taken from the asteroid Bennu.
This is a remarkable achievement, the first* successful sample return of its type. I wonder what we will learn from the material that was obtained, but I’m sure it will reveal some intriguing secrets, especially about the history and formation of the solar system.
Love the way the capsule was sitting on the ground, upright, not even tilted. Could it be more picture perfect than this?
I am also mildly (but pleasantly) surprised that I have not heard any panicmongering about a capsule bringing back extraterrestrial microbes or whatever. OK, I wasn’t specifically looking but still. It’s a relief.
* I don’t know what possessed me when I wrote “first”; granted, OSIRIS-REx brought back a lot more material, supposedly, but the first successful such missions were the two Hayabusa missions of the Japanese Space Agency.
Aug 232023
Chandrayaan-3 landed safely on the Moon, cementing India’s position as a space superpower.
What can I say? Congratulations! Not sure who the gentleman is in this image that I saw on Twitter, but he certainly looks happy.
Aug 212023
Russia’s first probe to the Moon in nearly half a century, Luna-25, has crashed.
It would be easy to react to the news with glee, with schadenfreude. We are, after all, talking about a crash that denied a propaganda opportunity to Putin’s Evil Empire (maybe not quite as evil as Stalin’s regime but more evil, to be sure, than the USSR ever was in my lifetime).
But space exploration transcends, always transcended, national boundaries. Our petty squabbles look pretty… well, petty from the Moon. Chances are, if human beings are still around with an advanced technical civilization a millennium from now (or, if our machine descendants are still around) they’re far more likely to remember Armstrong’s first step on the Moon than Russia’s attack on Ukraine, the Cold War, or even WW2.
So this crash is sad news, Putin or no Putin. I hope India’s probe, Chandrayaan-3, is more successful. Fingers crossed. Things are looking good for now but it has yet to accomplish a tricky landing.
Apr 202023
Another paper of ours, in all its 36-page glory, was accepted by Physical Review D and I am delighted.
One of the things we do in this paper is the use of symmetric trace-free tensors (STF) that allow us, among other things, to effect a rotation of spherical harmonic coefficients. This approach likely has many uses as a bit of practical math, beyond modeling gravitational fields.
Apr 202023
I just asked GPT-4 using my freshly developed UI about Starship.
In the background, GPT-4 correctly utilized a facility to perform Google searches and make use of the resulting snippets (I’m sure I’ll find a way to prevent it from referencing those snippets, which are not visible to the user, in the actual answer). Here is the critical part of the conversation that took place in the background:
User: What happened to Starship this morning?
GPT: SEARCH(Starship event on 2023/04/20)
System: Snippet 1: 3 hours ago … The rocket got off the launchpad before exploding above the Gulf of Mexico. This segment airs on April 20, 2023. Audio will be available after …
Snippet 2: UPCOMING. April 19, 2023. STARLINK MISSION · April 20, 2023. Starship Flight Test.
Snippet 3: 6 hours ago … April 20, 2023 … SpaceX launches the inaugural test flight of the integrated Starship and Super Heavy rocket from the company’s Starbase …
Snippet 4: 5 hours ago … April 20, 2023. Elon Musk has called it the “holy grail” for space technology. Starship, a new SpaceX rocket system that launched for the …
Snippet 5: ATCSCC ADVZY 007 DCC 04/20/2023 OPERATIONS PLAN. MESSAGE: EVENT TIME: 20/0200 – AND LATER … THE SPACEX STARSHIP SUPER HEAVY LAUNCH FROM BOCA CHICA, …GPT: This morning, SpaceX launched the inaugural test flight of the integrated Starship and Super Heavy rocket from the company’s Starbase. Unfortunately, the rocket got off the launchpad but exploded above the Gulf of Mexico during the flight test (Snippet 1, Snippet 3).
In case you are wondering, yes, it knows the current date, too, thanks to the way my UI sets it up.
And yes, Starship blew up. But it blew up after the job of the first stage was nearly complete, at separation, at an altitude of some 40 km. Which means that despite the spectacular RUD (rapid unscheduled disassembly) event, this launch is still a huge success.
Now if we could only convince Elon to spend more time building rockets and less time honing his skills at corporate value destruction at Twitter, pardon me, X Corp…
Mar 222023
Students at the California State University, Northridge, are currently working on a short documentary film about our work on the Solar Gravitational Lens.
The project hopes to attract modest crowdfunding. They also produced a teaser trailer.
Of course I hope they succeed; our SGL work could use some good publicity.
Feb 272023
More than 20 years ago, I wrote a program that showed what Mars would look like if it had oceans.
I wrote it originally in C++, but then ported it to Java and turned it into a Web application.
That was a long time ago. Unfortunately, browsers no longer support Java applets for security reasons. So my beautiful applet was not working anymore.
Today, I finally spent some time reimplementing the applet in plain JavaScript. It’s working again! (Apart from some minor cosmetics.) And it has data sets for Mars, Earth, Venus and the Moon as well.
Sep 262022
Putting aside Trumpism, woke-ism, the politics of the day, populism, the whole kaboodle, here’s something to contemplate.
Tonight, Russia is continuing its efforts to subjugate the independent nation of Ukraine, not refraining from committing serious, intentional, criminal acts against the country’s civilian population to further its goals.
Also tonight, the space agency of the United States, NASA, is conducting a ground-breaking experiment, the first of its kind testing a method that might one day avert a global disaster, protecting the entire planet from an asteroid impact.
DART: View of the asteroid Dimophos 20 minutes to impact
I think it speaks volumes about the different ways in which these countries see their respective roles in the world.
I almost long for Soviet times. The regime was assuredly brutal, but at least it professed to seek noble goals. Not anymore, I guess.
Sep 132022
Oops. It’s past midnight already, so technically it was yesterday but to me it is still today, September 12.
The sixtieth anniversary of John F. Kennedy’s famous “we choose to go to the Moon” speech. How many more years before another human sets foot on the Moon?
Oh, and it was thirty years ago that Ildiko and I became married.
Yup, that’s us; 1979 vs. 2019.
Jul 162022
Doesn’t this cloud, photographed in the skies above Ottawa by my beautiful wife moments ago, look just like the USS Enterprise?
Maybe it is, doing its time-traveling thing, with a malfunctioning cloaking device.
May 232022
This morning, Google greeted me with a link in its newsstream to a Hackaday article on the Solar Gravitational Lens. The link caught my attention right away, as I recognized some of my own simulated, SGL-projected images of an exo-Earth and its reconstruction.
Reading the article I realized that it appeared in response to a brand new video by SciShow, a science-oriented YouTube channel.
Yay! I like nicely done videos presenting our work and this one is fairly good. There are a few minor inaccuracies, but nothing big enough to be even worth mentioning. And it’s very well presented.
I suppose I should offer my thanks to SciShow for choosing to feature our research with such a well-produced effort.
May 062022
A beautiful study was published the other day, and it received a lot of press coverage, so I get a lot of questions.
This study shows how, in principle, we could reconstruct the image of an exoplanet using the Solar Gravitational Lens (SGL) using just a single snapshot of the Einstein ring around the Sun.
The problem is, we cannot. As they say, the devil is in the details.
Here is a general statement about any conventional optical system that does not involve more exotic, nonlinear optics: whatever the system does, ultimately it maps light from picture elements, pixels, in the source plane, into pixels in the image plane.
Let me explain what this means in principle, through an extreme example. Suppose someone tells you that there is a distant planet in another galaxy, and you are allowed to ignore any contaminating sources of light. You are allowed to forget about the particle nature of light. You are allowed to forget the physical limitations of your cell phone’s camera, such as its CMOS sensor dynamic range or readout noise. You hold up your cell phone and take a snapshot. It doesn’t even matter if the camera is not well focused or if there is motion blur, so long as you have precise knowledge of how it is focused and how it moves. The map is still a linear map. So if your cellphone camera has 40 megapixels, a simple mathematical operation, inverting the so-called convolution matrix, lets you reconstruct the source in all its exquisite detail. All you need to know is a precise mathematical description, the so-called “point spread function” (PSF) of the camera (including any defocusing and motion blur). Beyond that, it just amounts to inverting a matrix, or equivalently, solving a linear system of equations. In other words, standard fare for anyone studying numerical computational methods, and easily solvable even at extreme high resolutions using appropriate computational resources. (A high-end GPU in your desktop computer is ideal for such calculations.)
Why can’t we do this in practice? Why do we worry about things like the diffraction limit of our camera or telescope?
The answer, ultimately, is noise. The random, unpredictable, or unmodelable element.
Noise comes from many sources. It can include so-called quantization noise because our camera sensor digitizes the light intensity using a finite number of bits. It can include systematic noises due to many reasons, such as differently calibrated sensor pixels or even approximations used in the mathematical description of the PSF. It can include unavoidable, random, “stochastic” noise that arises because light arrives as discrete packets of energy in the form of photons, not as a continuous wave.
When we invert the convolution matrix in the presence of all these noise sources, the noise gets amplified far more than the signal. In the end, the reconstructed, “deconvolved” image becomes useless unless we had an exceptionally high signal-to-noise ratio, or SNR, to begin with.
The authors of this beautiful study knew this. They even state it in their paper. They mention values such as 4,000, even 200,000 for the SNR.
And then there is reality. The Einstein ring does not appear in black, empty space. It appears on top of the bright solar corona. And even if we subtract the corona, we cannot eliminate the stochastic shot noise due to photons from the corona by any means other than collecting data for a longer time.
Let me show a plot from a paper that is work-in-progress, with the actual SNR that we can expect on pixels in a cross-sectional view of the Einstein ring that appears around the Sun:
Just look at the vertical axis. See those values there? That’s our realistic SNR, when the Einstein ring is imaged through the solar corona, using a 1-meter telescope with a 10 meter focal distance, using an image sensor pixel size of a square micron. These choices are consistent with just a tad under 5000 pixels falling within the usable area of the Einstein ring, which can be used to reconstruct, in principle, a roughly 64 by 64 pixel image of the source. As this plot shows, a typical value for the SNR would be 0.01 using 1 second of light collecting time (integration time).
What does that mean? Well, for starters it means that to collect enough light to get an SNR of 4,000, assuming everything else is absolutely, flawlessly perfect, there is no motion blur, indeed no motion at all, no sources of contamination other than the solar corona, no quantization noise, no limitations on the sensor, achieving an SNR of 4,000 would require roughly 160 billion seconds of integration time. That is roughly 5,000 years.
And that is why we are not seriously contemplating image reconstruction from a single snapshot of the Einstein ring.
Apr 122022
Our work on the Solar Gravitational Lens, complete with some diagrams created by yours truly, now made it onto TikTok.
@toknerdytome Solar Gravitational Lens #learnontiktok #tiktokpartner #science #space #astrotok #alien #nasa #physics #astronomy #technology ♬ Interstellar- Main Theme – Geek Music
How about that.
Dec 242021
Although we are not religious, we celebrate Christmas.
And I still cannot think of a better way to celebrate Christmas than with the words of the astronauts of Apollo 8, and the sense of awe they felt when they became the first human beings ever in the history of our species to be completely cut off from Mother Earth, when their spaceship disappeared behind the Moon.
Earthrise from Apollo 8
Re-emerging, they read passages from the Book of Genesis to their audience, with Frank Borman concluding with the words:
[G]ood night, good luck, a Merry Christmas – and God bless all of you, all of you on the good Earth.
To me, this is the most beautiful Christmas message ever.
Oct 242021
Thanks to streaming services, I occasionally stumble upon films and television series from foreign lands that otherwise I’d not even know about. And no, I don’t mean Squid Game, that explosively popular Korean series: I only watched the opening few minutes of the first episode so far, and I don’t yet know if it is my cup of tea. Rather, this time around it is a Russian movie that I came across on Amazon Prime: a 2017 film titled Salyut-7.
Salyut-7 was a Soviet space station. In 1985, the space station was dead, without power. The Russians launched a daring rescue mission, Soyuz-T13, which was not only able to dock with the derelict station but also able to revive and repair it.
Consistent with Soviet era secrecy, we knew very little about this mission and didn’t appreciate its significance back then.
The movie itself combined the actual story of the Soyuz-T13 mission with other events, such as the fire on board the Mir space station 12 years later or a nonsensical fictitious mission by the space shuttle Challenger to “steal” the station, for dramatic effect. In that, I think they did a disservice to the cosmonauts who pulled off this repair: perhaps less spectacular in terms of visual effects, what they accomplished was no less significant.
But otherwise, I found the movie fun to watch, very well done, with top notch special effects and (insofar as my inexpert eye can tell) excellent acting and directing. I enjoyed the movie. And its faults notwithstanding, I think it offers a worthy reminder that the USSR’s space program brought enormous value to all of humanity. It saddens me deeply when I think of how much of it went to waste in the turbulent years following the breakup of the USSR.
May 282021
I’ll be giving a virtual talk tonight, courtesy of a Texas astronomy club:
I hope it will be well received.