Category: Space

Recent arXiv:astro-ph Picks: December 2024

Here are some recent submissions on astro-ph that I found to be especially interesting. Text excerpts below are quoted directly from the articles. My comments are in italics.

Short-Term Evolution and Risks of Debris Cloud Stemming from Collisions in Geostationary Orbit
https://arxiv.org/abs/2412.13586

The geostationary orbit is a popular orbit for communication, meteorological, and navigation satellites due to its apparent motionless. Nearly all geostationary satellites are positioned in a circular orbit with a radius of 42,164 km, making this region particularly vulnerable to space traffic accidents due to the high concentration of objects and the absence of natural debris-clearing mechanisms. The growing population in geostationary region raises concerns about the potential risks posed by fragments stemming from explosions and collisions, particularly following the breakup of Intelsat-33e, which remained operational in geostationary orbit until October 19, 2024.

A breakup event generates a large number of fragments of varying sizes. In the geostationary region, only fragments larger than 1 meter are routinely tracked by the Space Surveillance Network, as the sensitivity of ground-based sensors decreases significantly with distance. However, small, non-trackable fragments can still cause catastrophic damage to spacecraft. The collision velocity of spacecraft in geostationary orbit can reach up to 4 km/s, while micro-meteoroids may hit at speeds of up to 72 km/s.

The impact of a debris cloud is inherently global as it disperses around the entire Earth.

By 2024, over 1,000 objects have been observed near the geostationary orbit (GEO). Nearly all objects exhibit inclinations of less than 15 degrees, with the majority having inclinations of less than 1 degree. Once a fragmentation event occurs, the GEO objects will be exposed to considerable risks, as they are densely clustered along a single ring above the Equator.

More about Intelsat 33e and its breakup:
https://en.wikipedia.org/wiki/Intelsat_33e

Sun-like stars produce superflares roughly once per century
https://arxiv.org/abs/2412.12265

Stellar superflares are energetic outbursts of electromagnetic radiation, similar to solar flares but releasing more energy, up to 1036 erg on main sequence stars. It is unknown whether the Sun can generate superflares, and if so, how often they might occur. We used photometry from the Kepler space observatory to investigate superflares on other stars with Sun-like fundamental parameters. We identified 2889 superflares on 2527 Sun-like stars, out of 56450 observed. This detection rate indicates that superflares with energies >1034 erg occur roughly once per century on stars with Sun-like temperature and variability. The resulting stellar superflare frequency-energy distribution is consistent with an extrapolation of the Sun’s flare distribution to higher energies, so we suggest that both are generated by the same physical mechanism.

Solar flares are sudden local bursts of bright electromagnetic emission from the Sun, which release a large amount of energy within a short interval of time. The increase in short-wavelength solar radiation during flares influences the Earth’s upper atmosphere and ionosphere, sometimes causing radio blackouts and ionosphere density changes. Solar flares are frequently accompanied by the expulsion of large volumes of plasma, known as coronal mass ejections (CMEs), which accelerate charged particles to high energies. When these solar energetic particles (SEPs) reach Earth, they cause radiation hazards to spacecraft, aircraft and humans. Extreme SEP events can produce isotopes, called cosmogenic isotopes, which form when high-energy particles interact with the Earth’s atmosphere. These isotopes are then recorded in natural archives, such as tree rings and ice cores. The total amount of energy released by each flare varies by many orders of magnitude, as determined by a complex interplay between the physical mechanisms of particle acceleration and plasma heating in the Sun’s
atmosphere.

Solar flares have been observed for less than two centuries. Although thousands of them have been detected and measured, only about a dozen are known to have exceeded a bolometric (integrated over all wavelengths) energy of 1032 erg. Among them was the Carrington Event on 1 September 1859, which was accompanied by a CME that had the strongest recorded impact on Earth. Modern estimates of the Carrington Event’s total bolometric energy are 4 × 1032 to 6 × 1032 erg.

It is unknown whether the Sun can unleash flares with even higher energies, often referred to as superflares, and if so, how frequently that could happen. The period of direct solar observations is too short to reach any firm conclusions. There are two indirect methods to investigate the potential for more intense flares on the Sun. One method uses extreme SEP events recorded in cosmogenic isotope data, which have been used to quantify the occurrence rate of strong CMEs reaching Earth over the past few millennia. There are five confirmed (and three candidate) extreme SEP events that are known to have occurred in the last 10,000 yr, implying a mean occurrence rate of ∼ 10−3 yr−1. However, the relationship between SEPs and flares is poorly understood, especially for the stronger events.

A second method is to study superflares on stars similar to the Sun. If the properties of the observed stars sufficiently match the Sun, the superflare occurrence rate on those stars can be used to estimate the rate on the Sun.

We found that Sun-like stars produce superflares with bolometric energies > 1034 erg roughly once per century. That is more than an order of magnitude more energetic than any solar flare recorded during the space age, about sixty years. Between 1996 and 2012 twelve solar flares had bolometric energies > 1032 erg, but none were > 1033 erg. The most powerful solar flare recorded occurred on 28 October 2003, with an estimated bolometric energy of 7 × 1032 erg, which exceeds estimates for the Carrington Event (4 × 1032 to 6 × 1032 erg).

We cannot exclude the possibility that there is an inherent difference between flaring and non-flaring stars that was not accounted for by our selection criteria. If so, the flaring stars in the Kepler observations would not be representative of the Sun. Approximately 30% of flaring stars are known to have a binary companion. Flares in those systems might originate on the companion star or be triggered by tidal interactions. If instead our sample of Sun-like stars is representative of the Sun’s future behavior, it is substantially more likely to produce a superflare than was previously thought.

More about the Carrington Event:
https://en.wikipedia.org/wiki/Carrington_Event

ChronoFlow: A Data-Driven Model for Gyrochronology
https://arxiv.org/abs/2412.12244

Gyrochronology is a technique for constraining stellar ages using rotation periods, which change over a star’s main sequence lifetime due to magnetic braking. This technique shows promise for main sequence FGKM stars, where other methods are imprecise. However, models have historically struggled to capture the observed rotational dispersion in stellar populations. To properly understand this complexity, we have assembled the largest standardized data catalog of rotators in open clusters to date, consisting of ~7,400 stars across 30 open clusters/associations spanning ages of 1.5 Myr to 4 Gyr.

Stars in open clusters are all about the same age, so this is highly useful in training models that use stellar rotation periods to determine stellar age.
https://en.wikipedia.org/wiki/Gyrochronology

On The Lunar Origin of Near-Earth Asteroid 2024 PT5
https://arxiv.org/abs/2412.10264

The Near-Earth Asteroid (NEA) 2024 PT5 is on an Earth-like orbit which remained in Earth’s immediate vicinity for several months at the end of 2024. PT5’s orbit is challenging to populate with asteroids originating from the Main Belt and is more commonly associated with rocket bodies mistakenly identified as natural objects or with debris ejected from impacts on the Moon. We obtained visible and near-infrared reflectance spectra of PT5 with the Lowell Discovery Telescope and NASA Infrared Telescope Facility on 2024 August 16. The combined reflectance spectrum matches lunar samples but does not match any known asteroid types—it is pyroxene-rich while asteroids of comparable spectral redness are olivine-rich. Moreover, the amount of solar radiation pressure observed on the PT5 trajectory is orders of magnitude lower than what would be expected for an artificial object. We therefore conclude that 2024 PT5 is ejecta from an impact on the Moon, thus making PT5 the second NEA suggested to be sourced from the surface of the Moon. While one object might be an outlier, two suggest that there is an underlying population to be characterized. Long-term predictions of the position of 2024 PT5 are challenging due to the slow Earth encounters characteristic of objects in these orbits. A population of near-Earth objects which are sourced by the Moon would be important to characterize for understanding how impacts work on our nearest neighbor and for identifying the source regions of asteroids and meteorites from this under-studied population of objects on very Earth-like orbits.

Perhaps the most significant conclusion to finding a second near-Earth object with an apparently Moon-like surface composition is the realization of lunar ejecta as a genuine population of objects. The Quasi-Satellite Kamo‘oalewa has a slightly redder spectrum than 2024 PT5, but the higher quality of our data at longer wavelengths (the Quasi-Satellite was significantly dimmer, so only photometry was obtained beyond ≈ 1.25μm) makes a discussion of how different the two spectra are only qualitative. At the very least, the two lunar NEOs do not look identical. Sharkey et al. (2021) argued that the red spectrum of Kamo‘oalewa was partially due to space weathering – an exposure time of a few million years was likely sufficient to explain its surface properties and was similar to its approximate dynamical lifetime and even the age of the crater that Jiao et al. (2024) suggested it came from, Giordano Bruno. If correct, perhaps 2024 PT5 has a somewhat younger surface than the larger Kamo‘oalewa. In any case, PT5 is smaller than Kamo‘oalewa and thus the craters that are energetic enough to produce an object its size are more common – a more recent ejection age, and thus a ‘younger’ surface might be preferred from that argument as well. (Granted, smaller fragments would be more common than larger ones in cratering events of any size as well.) Further work to study these two objects and to find more lunar-like NEOs will be needed to ascertain the origin of these differences and how they can be related to the circumstances of their creation. At any rate, the smaller size of PT5 means that we are approaching being able to study the impactors and outcomes from the kinds of small impacts seen regularly by the Lunar Reconaissance Orbiter.

For more information about 2024 PT5 and Kamo‘oalewa:
https://en.wikipedia.org/wiki/2024_PT5
https://en.wikipedia.org/wiki/469219_Kamo%CA%BBoalewa

Call to Protect the Dark and Quiet Sky from Harmful Interference by Satellite Constellations
https://arxiv.org/abs/2412.08244

The growing number of satellite constellations in low Earth orbit (LEO) enhances global communications and Earth observation, and support of space commerce is a high priority of many governments. At the same time, the proliferation of satellites in LEO has negative effects on astronomical observations and research, and the preservation of the dark and quiet sky. These satellite constellations reflect sunlight onto optical telescopes, and their radio emission impacts radio observatories, jeopardising our access to essential scientific discoveries through astronomy. The changing visual appearance of the sky also impacts our cultural heritage and environment. Both ground-based observatories and space-based telescopes in LEO are affected, and there are no places on Earth that can escape the effects of satellite constellations given their global nature. The minimally disturbed dark and radio-quiet sky1 is crucial for conducting fundamental research in astronomy and important public services such as planetary defence, technology development, and high-precision geolocation.

Some aspects of satellite deployment and operation are regulated by States and intergovernmental organisations. While regulatory agencies in some States have started to require operators to coordinate with their national astronomy agencies over impacts, mitigation of the impact of space objects on astronomical activities is not sufficiently regulated.

1We refer to the radio-quiet sky as simply the ‘quiet sky’

To address this issue, the CPS [International Astronomical Union (IAU) Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (CPS)] urges States and the international community to:

1) Safeguard access to the dark and quiet sky and prevent catastrophic
loss of high quality observations.

2) Increase financial support for astronomy to offset and compensate the impacts on observatory operations and implement mitigation measures at observatories and in software.

3) Encourage and support satellite operators and industry to collaborate with the astronomy community to develop, share and adopt best practices in interference mitigation, leading to widely adopted standards and guidelines.

4) Provide incentive measures for the space industry to develop the required technology to minimise negative impacts. Support the establishment of test labs for brightness and basic research into alternate less reflective materials
and reduction of unwanted radiation in the radio regime for spacecraft manufacturing.

5) In the longer term, establish regulations and conditions of authorization and supervision based on practical experience as well as the general provisions of international law and main principles of environmental law to codify industry best practices that mitigate the negative impacts on astronomical observations. Satellites in LEO should be designed and operated in ways that minimise adverse effects on astronomy and the dark and quiet sky.

6) Continue to support finding solutions to space sustainability issues, including the problem of increasing space debris leading to a brighter sky. Minimising the production of space debris will also benefit the field of astronomy and all sky observers worldwide.

The elephant in the room—not specifically mentioned in this report—is that countries and companies should be sharing satellite constellations as much as possible to minimize the number of satellite constellations in orbit. This is analogous to the co-location often required for terrestrial communication towers. Our current satellite constellation predicament illustrates yet another reason why we need a binding set of international laws that apply to all nations and are enforced by a global authority. The sooner we have this the better, as our cultural survival—if not our physical survival—may depend upon it.

A New Method to Derive an Empirical Lower Limit on the Mass Density of a UFO
https://arxiv.org/abs/2412.12142

I derive a lower limit on the mass of an Unidentified Flying Object (UFO) based on measurements of its speed and acceleration, as well as the infrared luminosity of the airglow around it. If the object’s radial velocity can be neglected, the mass limit is independent of distance. Measuring the distance and angular size of the object allows to infer its minimum mass density. The Galileo Project will be collecting the necessary data on millions of objects in the sky over the coming year.

Any object moving through air radiates excess heat in the form of infrared airglow luminosity, L. The airglow luminosity is a fraction of the total power dissipated by the object’s speed, v, times the frictional force of air acting on the object. The radiative efficiency depends on the specific shape of the object and the turbulence and thermodynamic conditions in the atmosphere around it. If the object accelerates, then this friction force must be smaller than the force provided by the engine which propels the object. The net force equals the object’s mass, M, times its acceleration, a.

In conclusion, one gets an unavoidable lower limit on the mass of an accelerating object. The object’s mass must be larger than the infrared luminosity from heated air around it, divided by the product of the object’s acceleration and speed.

This limit provides an elegant way to constrain the minimum mass of Unidentified Flying Objects (UFOs), also labeled as Unidentified Anomalous Phenomena (UAPs). To turn the inequality into an equality, one needs to know the detailed object shape and atmospheric conditions around the object.

The first Galileo Project Observatory at Harvard University collects data on ∼ 105 objects in the sky every month. A comprehensive description of its commissioning data on ∼ 5 × 105 objects was provided in a recent paper (Dominé et al. 2024). The data includes infrared images captured by an all-sky Dalek array of eight uncooled infrared cameras placed on half a sphere.

Within the coming month, the Galileo Project’s research team plans to employ multiple Daleks separated by a few miles, in order to measure distances to objects through the method of triangulation.

If the measured velocity and acceleration of a technological object are outside the flight characteristics and performance envelopes of drones or airplanes, then the object would be classified by the Galileo Project’s research team as an outlier. In such a case, it would be interesting to calculate the minimum mass density of the object. If the result exceeds normal solid densities, then the object would qualify as anomalous, a UAP. Infrared emission by the object would be a source of confusion, unless the object is resolved and the emission from it can be separated from the heated air around it.

All flying objects made by humans have a volume-averaged mass density ⟨ρ⟩ which is orders of magnitude below 22.6 g cm−3, the density of Osmium – which is the densest metal known on Earth. A UFO with a higher mass density than Osmium would have to carry exotic material, not found on Earth.

By summer 2025, there will be three Galileo Project observatories operating in three different states within the U.S. and collecting data on a few million objects per year. With new quantitative data on infrared luminosities, velocities and accelerations of technological objects, it would be possible to check whether there are any UFOs denser than Osmium.

I admire the author, Avi Loeb, Harvard astrophysics professor, for his creative approaches to interesting problems outside the mainstream that many of his colleagues tend to avoid. Lately, he’s been focusing a lot on technosignatures, and I imagine he has a keen interest in the recent spate of unexplained nighttime drone sightings in New Jersey and elsewhere. For more about Loeb and the Galileo Project:
https://en.wikipedia.org/wiki/Avi_Loeb
https://en.wikipedia.org/wiki/The_Galileo_Project

Beyond CCDs: Characterization of sCMOS detectors for optical astronomy
https://arxiv.org/abs/2409.16449

Modern scientific complementary metal-oxide semiconductor (sCMOS) detectors provide a highly competitive alternative to charge-coupled devices (CCDs), the latter of which have historically been dominant in optical imaging. sCMOS boast comparable performances to CCDs with faster frame rates, lower read noise, and a higher dynamic range. Furthermore, their lower production costs are shifting the industry to abandon CCD support and production in favour of CMOS, making their characterization urgent. In this work, we characterized a variety of high-end commercially available sCMOS detectors to gauge the state of this technology in the context of applications in optical astronomy. We evaluated a range of sCMOS detectors, including larger pixel models such as the Teledyne Prime 95B and the Andor Sona-11, which are similar to CCDs in pixel size and suitable for wide-field astronomy. Additionally, we assessed smaller pixel detectors like the Ximea xiJ and Andor Sona-6, which are better suited for deep-sky imaging. Furthermore, high-sensitivity quantitative sCMOS detectors such as the Hamamatsu Orca-Quest C15550-20UP, capable of resolving individual photoelectrons, were also tested. In-lab testing showed low levels of dark current, read noise, faulty pixels, and fixed pattern noise, as well as linearity levels above 98% across all detectors. The Orca-Quest had particularly low noise levels with a dark current of 0.0067±0.0003 e−/s (at −20∘C with air cooling) and a read noise of 0.37±0.09 e− using its standard readout mode. Our tests revealed that the latest generation of sCMOS detectors excels in optical imaging performance, offering a more accessible alternative to CCDs for future optical astronomy instruments.

The Hamamatsu Orca-Quest CP15550-20UP, simply called Orca-Quest, is advertised as being a quantitative CMOS detector with extremely low noise levels and photoelectron counting capabilities. It features a custom 9.4-megapixel sensor with 4.6 × 4.6 μm pixels. The Orca-Quest has two scan modes that were characterized: standard and ultra-quiet. The ultra-quiet mode has a much lower frame rate at 5 frames per second (fps) compared to the standard mode’s 120 fps, which allows for much lower read noise. Also characterized was the ‘photon number resolving’ readout mode which claims to report the integer number of incident photoelectrons based on a proprietary calibrated algorithm using the ultra-quiet scan. The Orca-Quest has a detector-imposed temperature lock at −20◦C when air-cooled. The standard and ultra-quiet modes are 16-bit, with a saturation limit of 65536 ADU while the photon number resolving mode has a saturation limit of only 200 ADU. The Orca-Quest boasts a peak quantum efficiency of 85%.

Unlike CCDs, which use a single global amplifier with a shift register, sCMOS pixels have individual readout electronics, requiring each pixel to be tested as an independent detector. Historically, this led to high fixed pattern noise in CMOS detectors, but we found negligible fixed pattern noise in almost all the detectors we analyzed pixel-wise.

Most Distant Human-Made Object

In 1895, Italian inventor and electrical engineer Guglielmo Marconi (1874-1937) produced the first human-made radio waves capable of traveling beyond the Earth, so radio evidence of the existence of human civilization has now traveled 128 light years from Earth. Assuming a stellar number density in the solar neighborhood of (7.99 ± 0.11) × 10−2 stars per cubic parsec1, Earth’s radio emissions have already reached about 20,000 star systems.

The most distant physical human-made object, however, is the Voyager 1 spacecraft, now over 160 AU from the solar system barycenter (SSB), a distance of almost 15 billion miles. That certainly sounds impressive by human standards, but that is only 0.0025 light years. As the distance of Voyager 1 from the solar system barycenter is constantly increasing, you’ll want to visit JPL Horizons to get up-to-date information using the settings below for your date range of interest. Delta gives the distance from the SSB to the Voyager 1 spacecraft in astronomical units (AU).

This still-functioning spacecraft that was launched on September 5, 1977, flew by Jupiter on March 5, 1979, and flew by Saturn on November 12, 1980, is now heading into interstellar space in the direction of the constellation Ophiuchus, the Serpent Bearer, near the Ophiuchus/Hercules border.

Given Voyager 1’s current distance (from Earth), a radio signal from Earth traveling at the speed of light would take 22 hours and 8 minutes to reach Voyager 1, and the response from Voyager 1 back to Earth another 22 hours and 8 minutes. So, when engineers send a command to Voyager 1, they won’t know for another 44 hours and 16 minutes (almost 2 days) whether Voyager 1 successfully executed the command. Patience is indeed a virtue!

Thanks to three onboard radioisotope thermoelectric generators (RTGs)2, Voyager 1 should be able to continue to operate in the bone-chilling cold of deep space until at least 2025.

In about 50,000 years, Voyager 1 will be at a distance comparable to the nearest stars.

1The Fifth Catalogue of Nearby Stars (CNS5)
Alex Golovin, Sabine Reffert, Andreas Just, Stefan Jordan, Akash Vani, Hartmut Jahreiß, A&A 670 A19 (2023), DOI: 10.1051/0004-6361/202244250

2At launch, the Voyager 1 RTGs contained a total of about 4.5 kg of plutonium-238, generating 390W of electricity.

Light Blue Blob in a Daytime Sky

Joan Oesper photographed this anomalous light blue patch on
April 13, 2023 at 1:04 p.m. CDT (1804 UT) from Alpine, TX

See the light blue blob in the photograph above? Even though it is partly cloudy, the light blue blob is decidedly different in color from the nearby patches of blue sky. Is this some unusual atmospheric phenomenon, or was there a daytime on orbit rocket burn (such as an apogee kick motor)? If the latter, I have not been able to find any evidence online of a rocket firing around 1804 UT on 13 Apr 2023.

A closeup of the light blue patch

Joan Oesper took this photo from the campus of Sul Ross State University in Alpine, TX at 1:04 p.m. CDT (1804 UT) on Thursday, April 13, 2023. The exact coordinates where the photograph was taken are 30° 21′ 54″ N, 103° 39′ 00″ W. She was facing an azimuth of approximately 161° (SSE) and the altitude of the blue blob was approximately 15° above the horizon.

Joan writes, “The people I saw it with said they’d been watching it and that it had moved eastward during the 5-10 minutes they were watching. It seemed to be behind the clouds.”

Has anyone seen something like this in the past? Was there an on-orbit daytime rocket firing at this time?

Quotable Arthur C. Clarke

Sir Arthur Charles Clarke (1917-2008)

Clarke’s Three Laws

  1. When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
  2. The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
  3. Any sufficiently advanced technology is indistinguishable from magic.

The greatest tragedy in mankind’s entire history may be the hijacking of morality by religion.

I don’t believe in God but I’m very interested in her.

The rash assertion that “God made man in His own image” is ticking like a time bomb at the foundation of many faiths, and as the hierarchy of the universe is disclosed to us, we may have to recognize this chilling truth: if there are any gods whose chief concern is man, they cannot be very important gods.

Science can destroy religion by ignoring it as well as by disproving its tenets. No one ever demonstrated, so far as I am aware, the non-existence of Zeus or Thor—but they have few followers now.

I would defend the liberty of consenting adult creationists to practice whatever intellectual perversions they like in the privacy of their own homes; but it is also necessary to protect the young and innocent.

I would like to assure my many Buddhist, Christian, Hindu, Jewish, and Muslim friends that I am sincerely happy that the religion which Chance has given you has contributed to your peace of mind (and often, as Western medical science now reluctantly admits, to your physical well-being). Perhaps it is better to be un-sane and happy, than sane and un-happy. But it is the best of all to be sane and happy. Whether our descendants can achieve that goal will be the greatest challenge of the future. Indeed, it may well decide whether we have any future.

There is the possibility that humankind can outgrown its infantile tendencies, as I suggested in Childhood’s End. But it is amazing how childishly gullible humans are. There are, for example, so many different religions—each of them claiming to have the truth, each saying that their truths are clearly superior to the truths of others—how can someone possibly take any of them seriously? I mean, that’s insane. Though I sometimes call myself a crypto-Buddhist, Buddhism is not a religion. Of those around at the moment, Islam is the only one that has any appeal to me. But, of course, Islam has been tainted by other influences. The Muslims are behaving like Christians, I’m afraid.

Sometimes I think we’re alone in the universe, and sometimes I think we’re not. In either case the idea is quite staggering.

Perhaps, as some wit remarked, the best proof that there is Intelligent Life in Outer Space is the fact it hasn’t come here. Well, it can’t hide forever—one day we will overhear it.

The fact that we have not yet found the slightest evidence for life—much less intelligence—beyond this Earth does not surprise or disappoint me in the least. Our technology must still be laughably primitive, we may be like jungle savages listening for the throbbing of tom-toms while the ether around them carries more words per second than they could utter in a lifetime.

The moon is the first milestone on the road to the stars.

We are just tenants on this world. We have just been given a new lease, and a warning from the landlord.

Human judges can show mercy. But against the laws of nature, there is no appeal.

This is the first age that’s ever paid much attention to the future, which is a little ironic since we may not have one.

As our own species is in the process of proving, one cannot have superior science and inferior morals. The combination is unstable and self-destroying.

Our age is in many ways unique, full of events and phenomena that never occurred before and can never happen again. They distort our thinking, making us believe that what is true now will be true forever, though perhaps on a larger scale.

It is not easy to see how the more extreme forms of nationalism can long survive when men have seen the Earth in its true perspective as a single small globe against the stars.

New ideas pass through three periods:

  1. It can’t be done.
  2. It probably can be done, but it’s not worth doing.
  3. I knew it was a good idea all along!

Politicians should read science fiction, not westerns and detective stories.

There is hopeful symbolism in the fact that flags do not wave in a vacuum.

The Information Age offers much to mankind, and I would like to think that we will rise to the challenges it presents. But it is vital to remember that information—in the sense of raw data—is not knowledge, that knowledge is not wisdom, and that wisdom is not foresight. But information is the first essential step to all of these.

Communication technologies are necessary, but not sufficient, for us humans to get along with each other. This is why we still have many disputes and conflicts in the world. Technology tools help us to gather and disseminate information, but we also need qualities like tolerance and compassion to achieve greater understanding between peoples and nations. I have great faith in optimism as a guiding principle, if only because it offers us the opportunity of creating a self-fulfilling prophecy. So I hope we’ve learnt something from the most barbaric century in history—the 20th. I would like to see us overcome our tribal divisions and begin to think and act as if we were one family. That would be real globalisation. [December 2007]

Mariner 9

Fifty years ago this day, Mariner 9 became the first spacecraft to orbit another planet. Mariner 9 arrived at Mars after a 167-day flight on November 14, 1971. When it arrived, a global dust storm was raging on the planet, so it had to wait out the storm before any useful pictures could be taken. During its orbital tour of duty, Mariner 9 returned 54 gigabits of information to eager scientists on Earth, including 7,329 images of the red planet and its moons.

Mariner 9 was powered by 14,742 solar cells on four solar panels. The solar panels generated 500W of power while the spacecraft orbited Mars. A 20 amp-hour nickel cadmium battery stored the energy produced by the solar panels. The onboard computer had just 2K of memory (long before the days of “bloatware”), and an onboard digital reel-to-reel tape recorder was used to store data for later radio broadcast back to Earth.

Mariner 9’s mission to Mars ended on October 27, 1972 when it ran out of nitrogen gas for the attitude control jets. Mariner 9 remains in orbit around Mars, and is expected to burn up in the Martian atmosphere no sooner than the year 2022.

Satellites and More – 2021 #1

Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but on October 4, 1957 another “species” of sky vermin made its debut: artificial satellites.  In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my 17 × 11 arcminute field of view.

I’ve put together a video montage of satellites I serendipitously recorded during the first half of 2021.  Many of the satellites move across the field as “dashes” because of the longer integration times I need to use for some of my asteroid occultation work. A table of these events is shown below the video. The range is the distance between observer and satellite at the time of observation. North is up and east is to the left.

North is up and east is to the left; field size 17′ x 11′

Interestingly, four of the satellites above (2, 9, 12 & 13) are in retrograde orbits, that is their orbital inclination is > 90˚ and their east-west component of motion is towards the west instead of the east. However, one of these retrograde satellites (#12) appears to be orbiting prograde. This is Japan’s GCOM W1 environmental satellite, which is in a sun-synchronous orbit. Now, if you look at the very next satellite in the list (#13) you’ll see that it has very similar orbital elements (retrograde, sun-synchronous), I observed it just 5 days later, and it appears to be orbiting retrograde as you would expect (unlike GCOM W1). This is NASA’s Aqua environmental satellite. GCOM W1 and Aqua have orbital inclinations of 98.2082˚ and 98.2090˚, respectively.

There is also a prograde-orbiting satellite (#5) that appears to be orbiting retrograde. This is OneWeb-0056, a broadband internet satellite that is part of the OneWeb constellation, a competitor to SpaceX’s Starlink satellites. Last summer, I saw this same behavior with OneWeb-0047 which has a very similar orbital inclination to OneWeb-0056 (87.5188˚ and 87.8802˚, respectively).

Apparently, satellites with orbital inclinations within a few degrees of 90˚ (polar orbit) can sometimes appear to move in the opposite sense than their orbital inclination would indicate, when seen from the ground. I suspect that it must have something to do with where the satellite is in the sky and the vector sum of the line-of-sight motion of the satellite and the Earth’s rotation, but I have not yet found an expert who can confirm this or provide another explanation.

Satellite #11 is faint and makes a brief appearance in the extreme lower right corner of the frame. If you don’t look there you’ll miss it!

There were two satellites I was unable to identify, shown in the video below. They are either classified satellites or, more likely, small pieces of space debris that only government agencies are keeping track of. Note that the first unidentifiable satellite was moving in a retrograde (westward) orbit. The second satellite could be CZ-3A satellite debris (2007-003Q), but I think it was moving too fast to be that satellite (range 3,018.9 km, perigee 511.7 km, apogee 37,523.8 km, period 671.13 minutes, inclination 24.9940˚, eccentricity 0.7287013).

Unidentifiable satellites

During this period, I recorded one geosynchronous satellite, JCSAT-3. It is no longer operational. Here is the video, followed by the satellite information, followed by the light curve. As you can see when you watch the video and look at the accompanying light curve, this satellite gradually got brighter as it crossed the tiny 17′ x 11′ field of view of the video camera. Amazing!

Geosynchronous satellite JCSAT-3 moves slowly across the field and slowly brightens
JCSAT-3 brightens as it crosses the field

Occasionally, I record other phenomena of interest. Meteors during this period are described here, and you will find a high energy particle that “zapped” the CCD chip in the middle of the following three consecutive video frames. The red circles identify a spot and a pair of spots located some distance away that “lit up” when the high energy particle hit the chip. Events like this are fairly common, but what’s unusual here is the wide separation of the two regions that lit up.

References
Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21

Satellites and More – 2020 #2

Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but on October 4, 1957 another “species” of sky vermin made its debut: artificial satellites.  In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my 17 × 11 arcminute field of view.

I’ve put together a video montage of satellites I serendipitously recorded during the second half of 2020.  Many of the satellites move across the field as “dashes” because of the longer integration times I need to use for some of my asteroid occultation work. A table of these events is shown below the video. The range is the distance between observer and satellite at the time of observation. North is up and east is to the left.

North is up and east is to the left; field size 17′ x 11′

Interestingly, two of the satellites above (7 & 22) are in retrograde orbits, that is their orbital inclination is > 90˚ and their east-west component of motion is towards the west instead of the east. However, one of the prograde-orbiting satellites (11) appears to be orbiting retrograde. It has an orbital inclination close to 90˚ (87.5˚), and must appear retrograde because of the vector sum of the line-of-sight motion of the satellite plus the Earth’s rotation, but I have not yet found an expert who can confirm this.

Satellite #12 has an interesting story. It is piece of debris from the Iridium 33 satellite after the 10 Feb 2009 collision between Iridium 33 and Cosmos 2251. A cautionary tale as now thousands of internet satellites are being launched into orbit.

Because of the long integration time, satellite #14 was only captured on a single frame, but the satellite trail clearly shows this piece of Fregat debris is tumbling and leading to rapid and no doubt periodic changes in brightness.

The satellite trail of #17 looks funky because wind was shaking the telescope as the satellite crossed the field.

There were four satellites I was unable to identify, shown in the video below. They are either classified satellites or, more likely, small pieces of space debris that only government agencies are keeping track of. Interestingly, three of the four unidentifiable satellites were moving in retrograde (westward) orbits.

Unidentifiable satellites

I recorded a non-operational geostationary satellite, Intelsat 5, now in a “graveyard” orbit, on 30 Aug 2020.

Intelsat 5

On 29 Nov 2020, I recorded a rapidly tumbling Briz-M rocket body. Below the video you’ll find the light curve showing the large amplitude of its reflected light variation.

Briz-M rocket body, rapidly tumbling
Briz-M rocket body, high-amplitude light curve

The NOAA-13 environmental satellite failed shortly after launch, and as you can see from the light curve below the video, it got dimmer as it crossed the field—probably indicating that this retrograde, non-operational satellite is slowly tumbling.

NOAA-13, in a retrograde orbit
NOAA-13 dimmed as it crossed the field

Occasionally, I record other phenomena of interest. Meteors during this period are described here, and you will find a couple of jet contrails in the video below.

References
Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21

Space Records

Russian cosmonaut Valeri Polyakov, M.D. (1942-) holds the record for the longest spaceflight duration. During 1994-1995, he spent 437.8 contiguous days in orbit, almost all of them aboard the Mir space station.

The largest number of people in space at the same time was thirteen, and this has happened four times.

The fastest humans have ever traveled (relative to Earth) occurred on May 26, 1969 when the Apollo 10 crew (Thomas Stafford, John Young, and Eugene Cernan) reached a speed of 24,791 mph—just 0.0037% the speed of light.

Both Jerry Ross and Franklin Chang Díaz hold the record for the most spaceflights. Both astronauts have gone into space seven times. Jerry Ross (STS-61-B, STS-27, STS-37, STS-55, STS-74, STS-88, STS-110) between November 26, 1985 and April 19, 2002 (Space Shuttle Atlantis: 5, Columbia: 1, Endeavour: 1), and Franklin Chang Díaz (STS-61-C, STS-34, STS-46, STS-60, STS-75, STS-91, STS-111) between January 12, 1986 and June 19, 2002 (Space Shuttle Columbia: 2, Atlantis: 2, Discovery: 2, Endeavour: 1). Both astronauts were mission specialists in the NASA Astronaut Group 9, announced May 29, 1980.

The farthest humans have ever been from Earth occurred at 0:21 UT on April 15, 1970 when the crippled Apollo 13 spacecraft (Jim Lovell, Fred Haise, and Jack Swigert) executed a free-return trajectory to Earth. They were furthest from Earth above the lunar farside, 158 miles above the surface and 248,655 miles from Earth.

The youngest person ever to fly in space was Gherman Titov who was 25 years old during his solo Vostok 2 spaceflight on August 6, 1961. He was the second person to orbit the Earth.

The oldest person ever to fly in space was John Glenn who was 77 years old during his second spaceflight aboard the Space Shuttle Discovery STS-95 from October 29, 1998 to November 7, 1998. He was the first American to orbit the Earth in 1962.

The longest spacewalk occurred on March 11, 2001 when James Voss and Susan Helms were outside the Space Shuttle Discovery (STS-102) and the International Space Station for 8 hours and 56 minutes.

The longest moonwalk occurred on December 12-13, 1972 when Apollo 17 astronauts Eugene Cernan and Harrison Schmitt spent 7 hours and 37 minutes outside the lunar module on their second of three lunar excursions. All were longer than 7 hours. This was the final Apollo mission, and Gene Cernan, who died in 2017, is still the last person to walk on the surface of the Moon.

Satellites and More – 2020 #1

Edmund Weiss (1837-1917) and many astronomers since have called asteroids “vermin of the sky”, but on October 4, 1957 another “species” of sky vermin made its debut: artificial satellites.  In the process of video recording stars for possible asteroid occultations, I frequently see satellites passing through my 17 × 11 arcminute field of view.

I’ve put together a video montage of satellites I serendipitously recorded during the first half of 2020.  Many of the satellites move across the field as “dashes” because of the longer integration times I need to use for some of my asteroid occultation work. A table of these events is shown below the video. The range is the distance between observer and satellite at the time of observation. North is up and east is to the left.

North is up and east is to the left; field size 17′ x 11′

Interestingly, three of the above satellites (7,9,18) are in retrograde orbits, that is their orbital inclination is > 90˚ and their east-west component of motion is towards the west instead of the east. However, I was surprised to find that two of the prograde orbiting satellites (5,6) appear to be orbiting retrograde! Both have orbital inclinations close to 90˚ (82.6˚ and 87.5˚, respectively), and both were in the western sky at northern declinations at the time of observation. But another satellite (8) with an orbital inclination of 82.5˚ at a southern declination in the southern sky at the time of observation exhibited the expected “barely” prograde motion. I suspect the ~0.5 km/s rotation of the Earth towards the east might have something to do with this “apparent retrograde” motion, but I was unable to find any reference that describes this situation.

Satellite #12 has an interesting story. It is the Inertial Upper Stage (IUS) used to launch USA-48 (Magnum), a classified DoD payload, from the Space Shuttle Discovery (STS-33).

In addition to these 18 satellites, I observed 7 geosynchronous satellites, shown below.

This non-operational Soviet communications satellite is a “tumbler”, meaning its changing orientation causes variation in its brightness, as shown below.

This non-operational communications satellite is also a tumbler, as seen in this light curve from a portion of the video.

SGDC-1 is a Brazilian geostationary communications satellite stationed over longitude 75˚ W, and in this video is followed by Star One C3 which will replace Brasilsat B3, also located over longitude 75˚ W.
Star One C3, a geostationary television satellite led by SGDC-1 and followed by GOES-16.
GOES-16, a geostationary weather satellite that is the primary weather satellite for the U.S., is stationed over longitude 75.2˚ W. Star One C3 precedes it in this video.
Intelsat 16 is a geostationary television satellite stationed over longitude 76˚ W currently.

There were four satellites I was unable to identify, shown in the video below. They were either classified satellites or, more likely, small pieces of space debris that only government agencies or contractors are keeping track of.

Unidentifiable satellites

Occasionally, I record other phenomena of interest. Meteors during this period are described here, and you will find a couple of other curiosities below.

An aircraft with flashing lights passed near the field containing UCAC4 376-101735 between 10:06:44 and 10:06:47 UT on 16 Apr 2020.
High energy particles zap the imaging chip from time to time, and here is one of the more interesting ones during the period, recorded on 9 May 2020 from 9:09:18 – 9:09:20 UT in the field of UCAC4 397-127754.

References
Hughes, D. W. & Marsden, B. G. 2007, J. Astron. Hist. Heritage, 10, 21

Luna 16: First Robotic Lunar Sample Return Mission

Fifty years ago this day, the Soviet Union’s Luna 16 robotic probe made a night landing in the Sea of Fertility. It drilled nearly 14 inches into the lunar regolith, collected 3.6 ounces of soil, and delivered its precious cargo to Earth four days later.

The astronauts on Apollo 11, 12, 14, 15, 16, and 17 between 1969 and 1972 brought back a total of 840 lbs of moon rocks and soil. Each successive Apollo mission brought back a larger amount of lunar material.

The Soviets brought back a total of 0.7 lbs of lunar soil through their robotic sample return missions Luna 16 (1970), Luna 20 (1972), and Luna 24 (1976).

So, excluding lunar meteorites that have befallen the Earth, a total of 840.7 lbs of lunar material has been brought to research laboratories here on Earth.

After a hiatus of over 44 years, China plans to launch two lunar sample return missions, Chang’e 5 in November 2020 and Chang’e 6 in 2023 or 2024. Chang’e 5 is expected to return at least 4.4 lbs of lunar material from nearly 7 ft. below the surface at its landing site in the Mons Rümker region of Oceanus Procellarum.

Chang’e is the Chinese goddess of the Moon, and is pronounced chong-EE.