Author: Robert Zimmerman

March 31, 2026 Quick space links

2:46 pm

Courtesy of BtB’s stringer Jay. This post is also an open thread. I welcome my readers to post any comments or additional links relating to any space issues, even if unrelated to the links below.

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Voyager-2 discovered Neptune to be a planet of quickly changing weather

10:53 am

Neptune's fast changing weather
Click for source.

Cool image time! When Voyager-2 flew past Uranus in 1986, the data showed the gas giant’s weather to be relatively sedate and quiet, with little changing during the fly-by. Scientists expected this: Uranus’s distance from the Sun meant it got little energy to fuel an active climate, with any activity produced by internal heating due to the gravitational pressure of its mass. And Uranus did not produce that much heat internally.

When Voyager-2 passed Neptune three year later, the scientists expected something similar, or even less, due to Neptune’s greater distance from the Sun. Instead, Voyager-2’s data showed Neptune’s weather patterns to be changing constantly and quickly, as illustrated by the three images of the Great Dark Spot to the right, the biggest storm on Neptune at that time and located in the planet’s southern mid-latitudes.

The bright cirrus-like clouds of Neptune change rapidly, often forming and dissipating over periods of several to tens of hours. In this sequence spanning two rotations of Neptune (about 36 hours) Voyager 2 observed cloud evolution in the region around the Great Dark Spot at an effective resolution of about 60 miles per pixel. The surprisingly rapid changes which occur over the 18 hours separating each panel shows that in this region Neptune’s weather is perhaps as dynamic and variable as that of the Earth. However, the scale is immense by our standards — the Earth and the [Great Dark Spot] are of similar size.

In Neptune’s frigid atmosphere, where temperatures are as low as 55 degrees Kelvin (360 F), the cirrus clouds are composed of frozen methane rather than Earth’s crystals of water ice.

Subsequent observations by the Hubble Space Telescope in 1994 found this Great Dark Spot was gone, replaced by a comparable storm in the northern hemisphere. Further Hubble observations found Neptune’s storms tend to last about two years, fading as they drifted towards the equator. Those observations however also detected storms drifting away from the equator. Other research suggested the storms might be influenced by the Sun’s sunspot cycle.

All of the data post-Voyager-2 remains very coarse and uncertain, as we are looking at Neptune at a great distance. Thus, no theory about what is happening carries much weight, especially because we do not know why Neptune produces so much more internal heat than Uranus, fueling this fast-changing weather. For example, Neptune gets 1/20th of the energy received by Jupiter, yet its atmosphere appears even more active and variable.

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India’s space agency requests proposals for building landing legs for its next new rocket

8:59 am

NGLV as proposed in November 2025
NGLV (the two rockets in the middle) as proposed
in November 2025. Click for bigger image.

India’s space agency ISRO has issued a request for bids from the country’s commercial aerospace sector to build landing legs for its next new rocket, dubbed the Next Generation Launch Vehicle (NGLV).

The tender, titled “Fabrication of Landing Leg Hardware with materials for Advanced Development Module for In-situ Reusable Technologies (Admire) VTVL (10 units)”, seeks industry participation in developing critical components for a vertical take-off, vertical landing (VTVL) test vehicle under the ADMIRE programme.

…According to ISRO’s tender documents, the selected vendor will be responsible for end-to-end development, including procurement of raw materials, manufacturing, quality control planning, and final delivery of landing leg hardware. The project has been structured into three distinct phases spanning approximately 12 months.

The NGLV rocket was first approved by the India government in September 2024. Since then ISRO has completed the preliminary design of its methane engine, but has also revised the rocket’s design twice, in October 2024 and again in November 2025. This new landing leg contract suggests the agency hopes to do some test hops of a first stage prototype a year from now.

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A 2nd Starlink satellite since December fails catastrophically

8:38 am

According to reports from two different companies (here and here) that monitor objects in orbit, a Starlink satellite broke apart for unknown reasons on March 29, 2026.

SpaceX yesterday confirmed the incident.

On Sunday, March 29, Starlink satellite 34343 experienced an anomaly on-orbit, resulting in loss of communications with the satellite at ~560 km above Earth. Latest analysis shows the event poses no new risk to the Space_Station, its crew, or to the upcoming launch of NASA’s Artemis II mission. We will continue to monitor the satellite along with any trackable debris and coordinate with NASA and the USSpaceForce.

This is the second time in just over three months that a Starlink satellite has failed suddenly. In mid-December a Starlink satellite began to tumble when fuel began venting from a tank. It burned up in the atmosphere a month later.

Considering that SpaceX has approximately ten thousand Starlinks in orbit, any failures should not be a surprise. You launch that many, some are going to fail. That the company has only had two such failures indicates instead SpaceX’s incredible quality control in manufacturing, as almost every satellite works as expected with no such failure.

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Countdown begins for the Artemis-2 mission around the Moon

11:57 pm

NASA this afternoon began the two-day long countdown leading up to the planned 6:24 pm (Eastern) launch of its Artemis-2 mission, sending three Americans and one Canadian around the Moon.

The onsite countdown clock started ticking down at 4:44 p.m. EDT to a targeted launch time of 6:24 p.m. on Wednesday, April 1. Artemis II is the first crewed launch of NASA’s SLS (Space Launch System) rocket and Orion spacecraft.

…NASA and weather officers with the U.S. Space Force’s Space Launch Delta 45 continue to pay close attention to weather conditions ahead of tanking operations. The weather forecast for launch day shows an 80% chance of favorable weather conditions with primary concerns being cloud coverage and the potential for high winds in the area. Teams will continue to monitor the weather in the coming days.

The ten-day mission will use the SLS rocket, which has only flown once previously, and has had repeated fueling issues prior to that 2022 launch as well as during dress rehearsal countdowns last month. It will also use an Orion capsule with a questionable heat shield and an untested life support system.

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March 30, 2026 Quick space links

2:45 pm

Courtesy of BtB’s stringer Jay. This post is also an open thread. I welcome my readers to post any comments or additional links relating to any space issues, even if unrelated to the links below.

3 comments

SpaceX launches first stage for record 34th time, passing shuttle Atlantis

2:25 pm

SpaceX today successfully launched another 29 Starlink satellites, its Falcon 9 rocket lifting off from Cape Canaveral Space Force Station in Florida.

The first stage (B1067) completed its 34th flight, landing on a drone ship in the Atlantic, only 32 days after its previous launch. With this flight, this stage passed the space shuttle Atlantis to hold second place in the rankings of the most reused launch vehicle.

39 Discovery space shuttle
34 Falcon 9 booster B1067
33 Atlantis space shuttle
32 Falcon 9 booster B1071
31 Falcon 9 booster B1063
30 Falcon 9 booster B1069
28 Columbia space shuttle
27 Falcon 9 booster B1077
27 Falcon 9 booster B1078

Sources here and here.

SpaceX continues to recycle its first stages in a month or less, so expect this booster to pass Discovery before the end of the year. We should also expect all the boosters in the list above to do the same by the end of next year, though it is possible some will be retired as SpaceX begins to transition from its Falcon 9 high launch rate to using Starship/Superheavy instead.

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Brownsville’s mayor: SpaceX has brought billions of dollars to the region

12:04 pm

According to Brownsville’s mayor, John Cowen, SpaceX has brought billions of dollars to the region as well as created tens of thousands of jobs, and should be unanimously hailed by everyone there.

“The aerospace giant has infused $13 billion into into the economy across Brownsville and South Texas. It has created 24,000 direct and indirect jobs across the region, with approximately 4,000 jobs on site today. It is projected that 4,000 more jobs are coming,” Cowen said.

Cowen made his remarks about SpaceX at his 2026 State of the City Address, held March 25 at Texas Southmost College’s Performing Arts Center.

“SpaceX has generated more than $305 million in tax revenue. It has managed business relationships with more than 350 suppliers, putting $147 million into the regional supply chain,” Cowen said.

None of this is a surprise, except to some local and national news outlets that like to act as PR departments for the fringe activist groups — Save RGV, the South Texas Environmental Justice Network and the fake Indian tribe dubbed the Carrizo/Comecrudo Nation of Texas — that have opposed SpaceX’s Boca Chica operations from day one, and have repeatedly gone to court to try to shut it down. Those news outlets always give these activists a big bullhorn to tout their position, even though they represent practically no one in the region and likely get their funding from leftist sources outside of Texas.

Hat tip to Robert Pratt of Pratt on Texas.

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Voyager-2’s view of clouds on top of clouds on Neptune

11:45 am

Neptune's upper clouds
Click for original image.

Time to continue our cool image tour this week of the Voyager-2 archive of Neptune, taken during the spacecraft’s August 25, 1989 close fly-by of the gas giant, zipping only 2,700 miles above the cloud-tops. This remains the only mission to visit Neptune so far.

The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken two hours before Voyager-2’s closest approach. From the caption:

These clouds were observed at a latitude of 29 degrees north near Neptune’s east terminator. The linear cloud forms are stretched approximately along lines of constant latitude and the sun is toward the lower [right]. The bright sides of the clouds which face the sun are brighter than the surrounding cloud deck because they are more directly exposed to the sun. Shadows can be seen on the side opposite the sun.

These shadows are less distinct at short wavelengths (violet filter) and more distinct at long wavelengths (orange filter). This can be understood if the underlying cloud deck on which the shadow is cast is at a relatively great depth, in which case scattering by molecules in the overlying atmosphere will diffuse light into the shadow. Because molecules scatter blue light much more efficiently than red light, the shadows will be darkest at the longest (reddest) wavelengths, and will appear blue under white light illumination.

The resolution of this image is 6.8 miles per pixel and the range is only 98,000 miles. The width of the cloud streaks range from 30 to 125 miles, and their shadow widths range from 18 to 30 miles. Cloud heights appear to be of the order of 31 miles.

Of all the high resolution images taken of Neptune by Voyager-2, this is the only one that clearly shows some dimensionality. Later photographs taken by Hubble and other ground- and space-based telescopes can only show global views that are far less sharp than the global views produced by Voyager-2.

This picture hints at Neptune’s very complex weather patterns, which has no well-defined surface and is made up mostly of gas and liquid. Though scientists have used Hubble to roughly track those weather patterns, they can only glean the most basic facts. For example, its fast-changing weather appears to be driven by high winds, thought to move as fast as 1,300 miles per hour. This fact however is woefully incomplete and very uncertain, as we have no way to track detailed weather patterns at multiple depths.

Our tour will continue tomorrow.

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A soft barred galaxy with an active nucleus

9:56 am

A barred galaxy with an active galactic nucleus
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken by the Hubble Space Telescope as part of two different surveys aimed at studying galaxies with what scientists call active galactic nuclei.

IC 486 lies right on the edge of the constellation Gemini (the Twins), around 380 million light-years from Earth. Classified as a barred spiral galaxy, it features a bright central bar-shaped structure from which its spiral arms unfurl, wrapping around the core in a smooth, almost ring-like pattern.

…At the galaxy’s center a noticeable white glow outshines the starlight around it. This is light given off by IC 486’s active galactic nucleus (AGN), powered by a supermassive black hole more than 100 million times the mass of the Sun. Every sufficiently large galaxy hosts a supermassive black hole at its center, but some of these black holes are particularly ravenous, marshaling vast amounts of gas and dust into swirling accretion discs from which they feed. The intense heat generated by the orbiting disc of material generates intense radiation up to and including X-rays, which can outshine the entire rest of the galaxy. In these cases, the galaxy is known as an active galaxy, with an AGN at its center.

For comparison, the relatively inactive supermassive black hole at the center of the Milky Way has a mass of about four million Suns, considerably smaller than IC 486’s. Why one is active and the other not however is not yet truly understood, though their different masses might provide part of the explanation.

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Two launches from China and SpaceX early today

9:42 am

Early this morning both SpaceX and China successfully launched rockets. First, SpaceX completed its sixteenth Transporter mission placing 119 payloads in orbit, its Falcon 9 rocket lifting off from Vandenberg Space Force Base in California.

The first stage completed its 12th flight, landing on a drone ship in the Pacific. A detailed description of the 119 payloads can be found here.

Next, China successfully completed the maiden launch of its Kinetica-2 rocket, lifting off from its Jiuquan spaceport in northwest China and placing three demonstration satellites into orbit. The rocket is built by the pseudo-company CAS Space, which is entirely owned by one of China’s government space agencies.

According to the developers, the rocket stands 53 meters tall, with a core stage diameter of 3.35 meters and a fairing 4.2 meters wide. At liftoff, it weighs 625 tons and produces 753 tons of thrust. It can deliver up to 12 tons to a 200 kilometers low Earth orbit or 8 tons to a 500 kilometers sun-synchronous orbit.

On this launch, the liquid-fueled core stage and two side boosters were expendable, and crashed somewhere in China. China will use this rocket to partly replace its older expendable Long March 2 and Long March 3 rockets that use very toxic hypergolic fuels, thus reducing the risk to its citizens somewhat from crashing lower stages. Eventually the plan is to make the core stage and boosters reusable, so that they no longer crash uncontrolled inside China.

The leaders in the 2026 launch race:

39 SpaceX
16 China
5 Rocket Lab
3 Russia

SpaceX continues to lead the entire world combined in total launches, as it did in both ’24 and ’25.

SpaceX has another Starlink launch scheduled for later today, using a first stage on a record 34th flight.

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Another rocket startup in India hopes to launch from its own spaceport

9:17 am

India's spaceports, active, under construction, or proposed
India’s spaceports, active, under construction, or proposed

A new rocket startup in India, dubbed Bharath Space Vehicle (BSV), is not only building a commercial rocket to launch smallsats, it hopes to establish its own private spaceport near the town of Kodinar in western India.

BSV has proposed a launch complex near Kodinar in Gujarat’s Gir Somnath district. Gujarat’s Science and Technology Minister Arjun Modhwadia told the state assembly that IN-SPACe has identified a suitable location between Diu and Kodinar for a satellite launch facility, comparable to Sriharikota.

The coastal location offers open sea access and favourable launch corridors for specialised satellite trajectories. Isro had earlier evaluated a Gujarat site for its SSLV launch complex before Kulasekarapattinam in Tamil Nadu was selected.

Sriharikota has been operated for decades by India’s space agency ISRO. Kulasekarapattinam is a new ISRO spaceport set to begin operations next year, focused on launching its Small Satellite Launch Vehicle (SSLV) for commercial missions. Hope Island is a proposed private and commercial spaceport, under study.

BSV’s rocket is called Agasthya-1 and will use liquid-fueled engines. It appears to be similar in design to SpaceX’s first rocket, the Falcon-1.

Though the company’s founders are all ISRO veterans who helped develop its rockets, its website makes no mention of a launch schedule. At present, India has two rocket startups, Skyroot and Agnikul, that appear close to their first orbital launch.

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China’s government strengthens its commitment to space

8:01 am

China's long term launch record
Taken from my 2025 year-end report on the state of
global launch industry.

In the Chinese government’s most recently announced five-year plan, it appears it has increased its commitment to its space program and its government-controlled commercial space sector.

Aviation and aerospace was elevated at the Two Sessions [conference earlier this month] to a ‘pillar industry’—a step up from its previous classification as an emerging sector. For the first time, the 15th 5-year plan (2026–30) explicitly sets the goal of building China into a space power by 2030.

The 5-year plan prioritizes reusable launch vehicles, large-scale satellite constellations, and the commercialization of space applications, with cost reduction cast as central to long-term viability. Satellite internet has been earmarked for rapid development as part of broader ambitions around integrated space-air-ground connectivity. A new ‘Space+’ framing suggests that satellite infrastructure is being treated as part of the broader industrial system, with growing interest in on-orbit computing rather than communications alone.

…But the sector still runs on patient state capital—a funding model that has enabled rapid scaling while deferring any serious test of commercial viability. No domestic launch provider has yet turned a profit, and closing the cost gap with SpaceX on reusable rockets remains the industry’s central challenge.

The report at the link is very detailed. Though it comes from a Chinese-based think tank that almost certainly gets funding and supervision from the Chinese communists, it is definitely worth reading. It notes the areas where China is doing well — its Beidou GPS-type constellation and its manned space program — as well as those areas it has come up short — re-usable rockets and its mega-satellite constellations.

Though the graph to the right illustrates the long-term growth of China as a space power, it has not yet been able to match the U.S. in these two areas, mostly because of SpaceX. Moreover, the inability of China’s pseudo-rocket companies to get its reusable rockets operational is hindering the ability of China’s pseudo-satellite companies to launch their satellites. In both cases this new five-year plan appears to be applying pressure on these pseudo-companies to get moving, or the government will take over.

I must repeat again that the Chinese government’s support for space is deep and widespread, strengthened by that government’s almost two-decade-long policy of using that program as a training ground for its political leaders. Many of its successful space industry managers have been promoted to higher political office, and thus wield great power in deciding policy. Their pro-space roots clearly influence that policy in favor of China’s space effort.

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Astronaut Mike Fincke finally reveals details of his medical emergency on ISS

9:33 am

Astronaut Mike Fincke, who had an undisclosed medical issue on ISS in January 2026 that forced the early return of his crew, has finally provided details of what happened.

Four-time space flier Mike Fincke said he was eating dinner on Jan. 7 after prepping for a spacewalk the next day when it happened. He couldn’t talk and remembers no pain, but his anxious crewmates jumped into action after seeing him in distress and requested help from flight surgeons on the ground. “It was completely out of the blue. It was just amazingly quick,” he said in an interview with The Associated Press from Houston’s Johnson Space Center.

Fincke, 59, a retired Air Force colonel, said the episode lasted roughly 20 minutes and he felt fine afterward. He said he still does. He never experienced anything like that before or since. Doctors have ruled out a heart attack and Fincke said he wasn’t choking, but everything else is still on the table and could be related to his 549 days of weightlessness. He was 5 ½ months into his latest space station stay when the problem struck like “a very, very fast lightning bolt.”

Fincke hopes he can fly in space again, but I doubt NASA would agree if the cause of this incident is not identified. His other option then would be to get hired by one of the commercial space station companies to fly to their stations, but even they might be reluctant to hire him.

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Rocket Lab launches GPS-type demo satellite for Europe

9:05 am

Rocket Lab this morning successfully placed a European Space Agency (ESA) smallsat into orbit, its Electron rocket lifting off from one of its two launchpads in New Zealand.

The smallsat, dubbed Celeste, is the first of two such demo satellites that ESA has contracted Rocket Lab to launch. They are designed to test a low Earth orbit constellation for providing global navigation and location information to users on the ground, similar to the U.S.’s GPS constellation. Celeste will work from low orbit with Europe’s medium orbit Galileo constellation, but being smaller will be cheaper and faster to build and launch.

The leaders in the 2026 launch race:

38 SpaceX
15 China
5 Rocket Lab
3 Russia

SpaceX continues to lead the entire world combined in total launches, as it did in both ’24 and ’25.

4 comments

March 27, 2026 Quick space links

3:01 pm

Courtesy of BtB’s stringer Jay. This post is also an open thread. I welcome my readers to post any comments or additional links relating to any space issues, even if unrelated to the links below.

14 comments

Neptune as seen by Voyager-2 in 1989, four days before closest approach

2:46 pm

Neptune as seen by Voyager-2 on approach
Click for original image.

Cool image time! In two earlier posts I highlighted the pictures taken by Voyager-2 of Neptune’s two largest moons, Triton and Proteus, when it made its close fly-by of Neptune in 1989. Other than a very distant low resolution picture of 105-mile-wide Nereid, Voyager-2 took no other good images of Neptune’s other known moons.

So today, let’s begin a tour of some of Voyager-2’s imagery of Neptune itself. The picture to the right, reduced slightly to post here, was taken on August 20, 1989 as the spacecraft was beginning its approach to Neptune. It shows the full daylight hemisphere of the gas giant. From the caption:

The images were taken at a range of 4.4 million miles from the planet, 4 days and 20 hours before closest approach. The picture shows the Great Dark Spot and its companion bright smudge; on the west limb the fast moving bright feature called Scooter and the little dark spot are visible. These clouds were seen to persist for as long as Voyager’s cameras could resolve them. North of these, a bright cloud band similar to the south polar streak may be seen.

Next week I will post some of the other good shots taken of Neptune, as well as one or two close-ups of Triton that need highlighting. Sadly, at that point we will have more or less reviewed most of the best data now available of this distant world. Astronomers have used the Hubble Space Telescope in subsequent years to attempt to track its weather patterns, but even Hubble really can’t provide enough resolution to really make that research substantive.

But stay tuned. The Voyager-2 images to come are worth viewing.

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China launches “test satellite”

9:23 am

China yesterday afternoon successfully placed what its state-run press merely described as “a test satellite”, its Long March 2C rocket lifting off from its Jiuquan spaceport in northwest China.

That state-run press also provided no information as to where the rocket’s lower stages, using very toxic hypergolic fuels, crashed inside China.

The leaders in the 2026 launch race:

38 SpaceX
15 China
4 Rocket Lab
3 Russia

SpaceX continues to lead the entire world combined in total launches, as it did in both ’24 and ’25.

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War Department conducts classified suborbital missile test from Cape Canaveral

9:16 am

The War Department yesterday launched an unidentified suborbital missile test from its Cape Canaveral Space Force Station in Florida, providing no public information about the rocket, the purpose of the launch, or who built it.

An unidentified missile launched and zoomed across the Atlantic Ocean Thursday, March 26, from Cape Canaveral Space Force Station, leaving a slim white contrail against the afternoon blue sky. None of the Space Coast’s major rocket-launch providers had missions scheduled on Thursday. The mysterious unannounced launch occurred at roughly 12:30 p.m.

The Pentagon did not respond to media requests for information.

The missile was likely a suborbital hypersonic test, but that is pure speculation. What makes it unusual is the lack of any information about launch provider. In recent years the military has relied entirely on the private sector to build its hypersonic test program. This launch suggests the War Department has moved from testing hypersonic components on private rockets, airplanes, and capsules to building and testing its own final hypersonic missile prototype.

This is also pure speculation. We will have to wait for some clarification from the Pentagon.

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Ispace to replace engine on its lunar lander, delaying its NASA mission to 2030

9:09 am

Ispace's old and new landers

The Japanese lunar lander startup Ispace has been forced to institute a major shake-up of its upgraded lunar lander design because a subcontractor’s engine did not meet the required specifications.

The engine, called Voidrunner and built by Agile Space Industries, was about to be installed in the lander for a 2027 launch of NASA lunar lander mission when a review found its performance to be unsatisfactory.

After closely monitoring the engine’s status and conducting careful review, Ispace has determined that a change in the development plan to incorporate a new alternative engine is necessary to ensure the successful execution of the lunar landing mission. The new engine, which will replace VoidRunner, has already been developed by the alternative supplier and has a proven track record of operation in past lunar missions.

The company has also decided to standardize its two lunar lander designs, one developed in Japan and the second in parallel by its American division. The new lander, dubbed Ultra, will use this new engine and fly all of Ispace’s subsequent missions. The image above shows the company’s original lander Hakuto-R on the left, compared to its new Ultra lander on the right.

This change will delay its planned NASA mission by three years, to 2030, though the company hopes it will not impact the schedule of two other lunar lander missions for Japan. Its new updated schedule, all using Ultra:

  • 2028: a Japanese mission funded by Japan’s Ministry of Economy, Trade and Industry
  • 2029: a Japanese mission funded by Japan’s Space Strategy Fund (designed at encouraging the private space sector
  • 2030: NASA’s mission, being built in partnership with the American company Draper

Ispace has also created a new lunar satellite program, to provide communications, location data, and satellite tracking from lunar orbit, with a goal of launching its first lunar orbiter by next year, and five by 2030.

As a lunar lander company Ispace has had a very mixed record. It has successfully flown two landers to lunar orbit and then down to the surface. Each however crashed, failing just prior to landing due to software issues. This new delay of its NASA mission is not going to please NASA administrator Jared Isaacman, who instead wants to speed up the agency’s lunar lander program, flying almost monthly beginning in 2030. It likely means Ispace is going to have problems winning any new NASA lander contracts, until it proves its new Ultra lander design.

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SpaceX launches another 25 Starlink satellites

10:02 pm

SpaceX this afternoon successfully placed another 25 Starlink satellites into orbit, its Falcon 9 rocket lifting off from Vandenberg Space Force Base in California.

The first stage completed its 23rd flight 39 days after its previous flight, landing on a drone ship in the Pacific.

The leaders in the 2026 launch race:

38 SpaceX
14 China
4 Rocket Lab
3 Russia

SpaceX continues to lead the entire world combined in total launches, as it did in both ’24 and ’25.

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Carl Perkins & Ringo Starr – Honey Don’t

6:01 pm

An evening pause: Performed live 1985.

Hat tip Judd Clark.

Readers: I am in need of evening pause suggestions. If you’ve sent me suggestions in the past you know the drill. More suggestions are welcome! If you haven’t and want to suggest something, say so in the comments below, but DON’T provide the link to your suggestion or mention it. I will contact you to send you the guidelines so you can send it to me to schedule.

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Proteus, Neptune’s second largest moon, discovered by Voyager-2 in 1989

3:02 pm

Proteus, Neptune's second largest moon
For original images go here and here.

Our tour continues of the only close visit to Neptune on August 25, 1989 by Voyager-2. The two pictures to the right were taken by the spacecraft during that fly-by of Neptune’s second largest moon, dubbed Proteus. Both pictures are shown as Voyager-2 took them.

The top picture was taken from a distance of about 540,000 miles, and has a resolution of about five miles per pixel.

The satellite has an average radius of about 120 miles and is uniformly dark with an albedo of about 6 percent. The irregular shape suggests that 1989N1 has been cold and rigid throughout its history and subject to significant impact cratering.

The bottom picture was taken from a distance of about 91,000 miles, and can resolve objects as small as 1.7 miles in size.

Hints of crater-like forms and groove-like lineations can be discerned. The apparent graininess of the image is caused by the short exposure necessary to avoid significant smear.

Proteus was not known prior to Voyager-2’s fly-by, because it orbits so close to Neptune (about 73,000 miles) that the ground-based telescopes of the time could not see it in the glare of the gas giant. It was discovered in early global pictures of Neptune as Voyager-2 approached.

While planetary scientists have made some educated guesses about the moon’s origin and geology based on these two images, they are simply guesses. These are the only detailed images we have of Proteus, and neither is particularly good.

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March 26, 2026 Quick space links

2:50 pm

Courtesy of BtB’s stringer Jay. This post is also an open thread. I welcome my readers to post any comments or additional links relating to any space issues, even if unrelated to the links below.

5 comments

Astronomers detect the first comet whose nucleus’ reversed its rotation

11:28 am

Astronomers using data collected by the orbiting Gehrels Swift and Hubble space telescopes now think the nucleus of a small comet reversed its rotation sometime in 2017, caused by the force of the material sublimated off its surface.

From the abstract of their paper [pdf]:

The rotations of cometary nuclei are known to change in response to outgassing torques. The nucleus of the Jupiter-family comet 41P/Tuttle–Giacobini–Kresak exhibited particularly dramatic rotational changes when near perihelion in 2017 April. Here, we use archival Hubble Space Telescope observations from 2017 December to study the postperihelion lightcurve of the nucleus and to assess the nucleus size.

From both Hubble photometry and nongravitational acceleration measurements, we find a diminutive nucleus with effective radius 500 ± 100 meters. Systematic optical variations are consistent with a two-peaked (i.e., rotationally symmetric) lightcurve with period 0.60 ± 0.01 days, substantially different from periods measured earlier in 2017. The spin of the nucleus likely reversed between perihelion in 2017 April and December as a result of the outgassing torque.

In plain English: the thrust of the material being thrown from the surface as the comet made its close approach to the Sun was sufficient to slow and then reverse the nucleus’s rotation. This process was helped by the relatively small size of the nucleus compared to the material being sublimated from it.

The data also suggests the nucleus was once much larger, and has been whittled down to its present small size as it made its multiple close fly-bys of the Sun during the past 1,500 years. Rather than break-up, as most comets do at some point as their nucleus gets smaller, this comet’s nucleus simply kept shrinking, to the point that the thrust of that material could change its rotation.

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The space station part of Isaacman’s new program is facing push back, from industry and Congress

10:37 am

The American space stations under construction
Four of the American space stations under development.
The fifth, Max Space, is a late comer and not shown.

At a hearing yesterday before the space subcommittee of the House Science, Space, and Technology Committee, both the trade organization representing the five commercial space station projects as well as some members of Congress expressed strong reservations about NASA’s new plan to build a core module as a basis for helping these companies develop their space stations.

Dave Cavossa, President of the Commercial Space Federation (CSF) that represents these companies, outlined in his statement [pdf] to the committee the industry’s dissatisfaction, not so much because of the specifics of NASA’s plan but because it follows other sudden changes last year by the previous NASA administrator Sean Duffy, and is still uncertain in its outline.

Given the delays and possible shifts in strategy, industry has been left to continue spending resources to develop private space stations without a full understanding of what NASA will require from a private station, how the agency will structure the rest of the procurement and program, and when industry may see a return on investment. This uncertainty challenges the public-private partnership business model and puts the agency at risk of deorbiting ISS before private stations are operational.

The trade group proposed that NASA stick with its previous plan to fund two or more station projects, dropping Isaacman’s core module proposal. It also wanted Congress give the agency the funds to do so.

Cavossa also strongly disputed NASA’s claim that the market at present doesn’t support these commercial stations.
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