Space · Tuesday, 15 September 2026

01 Briefing what happened

Europe's Vega-C rocket launched two satellites together. One reads the faint glow of plants, and the other measures the air above them.

ESA's FLEX and the European Union's Sentinel-3C reached orbit from French Guiana on 15 September. The same week, new studies on dark energy and on a giant black-hole merger turned on what lies between a signal and the instrument that catches it.

about 1 km

between FLEX and Sentinel-3C as they circle Earth together, a few seconds apart

so the plant glow and the air above it are measured at almost the same moment [2][6]

300 m

the size of each square on FLEX's world maps of plant glow

measured from about 814 km up [7]

3.5 years

FLEX's planned working life

it will pass over the same spot every 27 days [2]

The lead story — what happened

Europe's Vega-C rocket lifted off from French Guiana at 01:21 GMT on 15 September, on a flight called VV30. [3][4]
It carried two satellites that watch Earth: ESA's FLEX and Sentinel-3C, part of the European Union's Copernicus programme. [1]
It was Vega-C's first launch of two satellites at once. They were stacked inside the nose cone with an adapter called Vespa. [4]
Sentinel-3C was released first and FLEX about an hour later. ESA's control centre in Germany then received a first signal from each. [1]
FLEX is ESA's first satellite built to measure photosynthesis from space. Photosynthesis is how plants turn sunlight and carbon dioxide into the energy they live on. [1]
Plants send back a tiny part of the sunlight they absorb as a faint red glow, far too weak for human eyes. [5]
That glow can change when a plant is short of water or attacked by pests, before its leaves visibly wilt. [5]
ESA's Simonetta Cheli said FLEX and Sentinel-3C will fly about 1 km and a few seconds apart. [2] The Sentinel-3 satellite beside FLEX measures clouds, haze, water vapour and ground temperature. [6]
Sentinel-3C is the third satellite of its kind. The first two, launched in 2016 and 2018, are still working. [3]
It measures oceans, land, ice and air, and its data feeds ocean and weather forecasts. [8] Eumetsat, Europe's weather-satellite agency, will run it with ESA. [1]
The Italian company Avio builds Vega-C and ran this launch itself. [9] It was only the second Vega-C flight Avio has managed without Arianespace, Europe's main launch company. [2][3]
Before this flight, Vega-C had flown seven times since July 2022, and six of those flights worked. [3] Its top stage uses an engine made in Ukraine. [2]

Who is involved

ESA

the European Space Agency; it built FLEX and leads the Vega-C rocket programme
Avio

an Italian rocket company; it builds Vega-C and ran this launch itself
Eumetsat

Europe's weather-satellite agency; it will run Sentinel-3C day to day with ESA
Simonetta Cheli

ESA's director of Earth observation; she explained why the two satellites fly together

How it unfolded

July 2022 Vega-C flies for the first time [3]
2016 and 2018 Sentinel-3A and Sentinel-3B launch, and both still work [3]
4 September ESA briefs reporters on FLEX and Sentinel-3C [6]
15 September, 01:21 GMT Vega-C flight VV30 lifts off from French Guiana [3][4]
About an hour later FLEX is released after Sentinel-3C, and both send first signals [1]
Coming days ESA checks the health of both satellites [1]

Where this points

Watch whether ESA's checks over the coming days find both satellites healthy and working as expected. [1]

What is pushing on the whole day

The bar and the word are our reading of how hard each one is pushing today. The arrow is where it is heading. The evidence is in the stories below.

Things in the way of a signal Building↑

FLEX flies beside a Sentinel-3 satellite that measures the clouds, haze and water vapour over the ground it reads. [5] A new study says a heavy object between Earth and a black-hole merger may have made the black holes look bigger. [12] Caltech astronomers used 114 radio bursts to measure gas that galaxies blow out, because that gas can look like dark energy. [13]

Old physics rules under test Building↑

A catalogue of almost 3,000 exploding stars adds to hints that dark energy, the push speeding up the universe's growth, is changing. [11] An Italian team says a record particle of light may have survived a trip of over two billion light-years if one of Einstein's rules breaks at very high energy. [14]

Satellites working for people on the ground Steady→

Sentinel-3C joins two older satellites whose data feeds ocean and weather forecasts. [8] A rescue system carried by 62 satellites has helped save more than 63,000 lives since 1982. [18] FLEX's glow readings can show plants under stress from drought before they wilt. [5]

The rest of the day

11 more stories on this beat.

Each with its own sources. None of these is a link to the story above.

02
Roman now has fuel for 22 years

NASA says its new Nancy Grace Roman Space Telescope has fuel for at least 22 years of science, more than double its 10-year plan. [10] Its first course-correction burn on 31 August used about 18 kg of fuel, against 200 kg set aside. [10] The telescope also launched lighter than budgeted, 8,056 kg instead of 9,800 kg, so the team filled its tanks. [10] A second, smaller burn is due later this month, and Roman should reach its working orbit around early December. [10]

Why it matters — Fuel is the main thing Roman uses up as it works. So the saved fuel could mean extra years of pictures after its 10-year design life. [10]
03
3,000 exploding stars hint dark energy changes

A team including Ryan Camilleri of the University of Queensland built a catalogue of almost 3,000 type Ia supernovas, which are exploding dead stars called white dwarfs. [11] These blasts all shine with nearly the same brightness, so their light shows how far away they are. [11] The team combined 30 years of observations from different telescopes, correcting for dust and for light bent on the way. [11] It found more evidence that dark energy, the unknown push speeding up the universe's growth, may change over time. [11]

Why it matters — The standard picture of the universe assumes dark energy never changes. [11] A separate survey called DESI found a similar hint in 2024, so two independent methods have now found hints that it changes. [11]
04
A giant black-hole merger may be magnified

In November 2023 the LIGO detectors, which sense ripples in space called gravitational waves, caught two black holes merging. [12] The signal, GW231123, seemed to come from black holes of 140 and 100 times the Sun's mass, which most models struggle to explain. [12] A study published on 25 August says a heavy object in between may have bent and magnified the ripples. [12] Allowing for that, the whole system comes out at about 140 Suns, not 240. [12]

Why it matters — If it holds, the black holes need no unusual explanation. [12] But the team cannot say what did the bending, and single objects that heavy should be very rare. [12]
05
Radio bursts weigh the gas galaxies blow out

Fast radio bursts are flashes of radio waves that last from a few thousandths of a second to a few seconds and come from billions of light-years away. [13] On the way to Earth they pass through gas, and denser gas spreads each signal out more. [13] A Caltech team led by Kritti Sharma used 114 bursts to measure how gas pushed out of galaxies smooths out the matter between them. [13] The paper appeared in the journal Nature Astronomy. [13]

Why it matters — That smoothing looks very like the effect of dark energy or of neutrinos, so it has to be measured before those can be. [13] A Caltech radio array due in 2029 is expected to find tens of thousands more bursts. [13]
06
A record particle of light and a rule of Einstein's

In October 2022 the brightest gamma-ray burst ever seen, called GRB 221009A, reached Earth from more than two billion light-years away. [14] A detector called Carpet, in Russia's Caucasus mountains, caught the highest-energy particle of light ever recorded from such a burst. [14] Known physics says faint leftover light from the Big Bang should have destroyed it on the way. [14] An Italian team says it may have survived by briefly turning into a very light, undetected particle, if one of Einstein's rules breaks at huge energies. [14]

Why it matters — The team notes the particle arrived about an hour after lower-energy light from the burst, as its idea predicts. [14] The paper has been accepted by the journal Physical Review Letters, but the particles it needs have never been detected. [14]
07
Venus may have destroyed its own moon

Venus and Mercury are the only planets in the solar system with no moon. [15] Stephen Kane of the University of California, Riverside simulated what would happen to a moon of Venus over billions of years. [15] In most runs the moon spiralled inward and was torn apart by the planet's gravity. [15] It survived only if early Venus spun fast, with a day shorter than about 12 hours, and the moon was no heavier than Earth's. [15]

Why it matters — Those conditions do not match what scientists think early Venus was like. [15] NASA's planned DAVINCI probe will measure the gases in Venus's air, where a lost moon might have left a chemical trace. [15]
08
NASA's watchdog on how the space station is supplied

NASA's Office of Inspector General, the agency's internal auditor, published an overview of its reports on 10 September. [16] It says both US cargo ships that supply the International Space Station, SpaceX's Cargo Dragon and Northrop Grumman's Cygnus, now launch on SpaceX's Falcon 9 rocket. [16] Boeing's Starliner capsule still has no certificate to carry astronauts, and its next flights are uncertain. [16] The office says it is now examining how NASA manages its cargo contracts. [16]

Why it matters — A June 2026 audit questioned $128 million in early payments to Boeing. [16] The station is due to be retired in 2031, so NASA has only a few years to get use out of Starliner. [16]
09
The US council studying UFOs met in private

In June the US government set up a science advisory council on UAP, the official name for UFOs. [17] Its chair, the Harvard astrophysicist Avi Loeb, told Space.com the council met privately on 31 August at the Office of the Director of National Intelligence. [17] He said he cannot disclose what was discussed. [17] A Gallup poll in July found that 49% of Americans think every UFO sighting has an ordinary, earthly explanation. [17]

Why it matters — Loeb said the US government is sincere about studying UAP by collecting scientific data. [17] Council member Ben Lamm, who runs the gene-editing company Colossal Biosciences, said findings would be shared openly. [17]
10
Rescue beacons carried by satellites

In May 2024 a fishing boat sank about 40 miles off the coast of Mississippi, and one of its crew switched on a personal locator beacon. [18] Its distress call went to SARSAT, a search-and-rescue system carried on satellites, which passes the location to the nearest ground station. [18] The crew was saved. [18] NASA's Goddard centre first developed the system's technology, and it began working in 1982. [18]

Why it matters — Today 62 satellites and 45 nations take part, and more than 63,000 lives have been saved. [18] It works far out at sea, where a phone has no signal. [18]
11
Soldering tested on the space station

On Monday NASA astronaut Anil Menon soldered parts onto a circuit board aboard the International Space Station, using a lead-free experiment called MIYOKA. [19] The samples will come back to Earth and be compared with identical ones soldered on the ground. [19] ESA astronaut Sophie Adenot tested a new European exercise machine, and two Russian crew members ran hearing and balance tests. [19] Commander Jessica Meir cleared storage space for the coming arrival of SpaceX's Crew-13. [19]

Why it matters — If electronics can be repaired in orbit, the station would rely less on costly supply flights. [19]
12
NASA's newest astronaut class is halfway

NASA's 10 astronaut candidates, introduced in September 2025, are about halfway through nearly two years of training. [20] This summer they studied rocks in New Mexico and Iceland, because future Moon crews will collect samples. [20] They also flew NASA's WB-57 high-altitude planes and T-38 jets, practised water survival and took Russian classes. [20] The class is due to graduate in 2027 and then wait for flight assignments. [20]

Why it matters — Its members could later work on the space station or fly on Artemis missions to the Moon. [20]

02 Lesson why it matters

To read a faint signal, first measure what it passed through

FLEX cannot read a plant's glow alone. A second satellite has to measure the clouds and haze above the same field at the same moment.

The twist

ESA put two satellites on one rocket because FLEX's reading of a plant's glow means little without Sentinel-3C's reading of the air above that plant. The second satellite is there to measure what is in the way.

How it works

A faint signal travels a long way to an instrument
On the way, air, gas, dust or a heavy object changes it
That change can look like the very thing scientists want to find
So the thing in the way gets measured on its own
Only then is what is left of the signal trusted

The same force, elsewhere today

Where this chain is also running, in today's other stories.

A giant black-hole merger may be magnified

A heavy object between Earth and the merger may have magnified the ripples, so the black holes looked like 240 Suns instead of about 140.
3,000 exploding stars hint dark energy changes

Before saying anything about dark energy, the team corrected each explosion's light for dust and for bending on its way to Earth.
Radio bursts weigh the gas galaxies blow out

Gas blown out of galaxies smooths matter in a way that looks like dark energy, so the Caltech team measured that gas first, using 114 bursts.

Where you've seen this

Kitchen scales

you set the scale to zero with the empty bowl on it, so the bowl is not counted as flour

Hearing tests

they happen in a quiet booth, so noise in the room is not counted as a sound the patient heard

Weather stations

thermometers sit in shaded white boxes, so sunshine on the glass is not read as warm air

The catch

A correction is only as good as the measurement of what was in the way. The black-hole team still cannot name the object that did the bending, and objects that heavy should be rare.

And the whole of it

A farmer who one day reads a FLEX map of stressed crops will see the plants, not the Sentinel-3C cloud readings that made the map usable. A weather forecast on a phone also starts from satellite readings that someone first corrected for the air between the satellite and the ground.

03 Truth what's really going on

What is really going on

Europe launched two satellites on one Vega-C rocket because FLEX, its new plant-glow satellite, needs Sentinel-3C's readings of the clouds and haze above the same fields. [2][5] This week's two biggest astronomy results, on dark energy and on the giant black-hole merger GW231123, also rest on corrections for what lay between the source and the instrument. [11][12]

Who gains

Avio, the Italian company that builds Vega-C — It ran this launch itself, only its second without Arianespace, and it was Vega-C's first flight carrying two satellites. [2][4]
Eumetsat, Europe's weather-satellite agency — Once testing ends it will run Sentinel-3C day to day and deliver its ocean data and its near-real-time air data. [1]
Astronomers who will use NASA's Roman telescope — A precise first burn and a lighter-than-planned launch left fuel for at least 22 years of possible science instead of 10. [10]
SpaceX — Both US cargo ships to the space station now launch on its Falcon 9 rocket, and NASA has paid to speed up SpaceX missions first planned for Boeing. [16]
Caltech's radio astronomers — Their study got encouraging results from only 114 bursts, and their own array, due in 2029, is expected to find tens of thousands. [13]

Who pays

Boeing — A June 2026 audit questioned $128 million in early payments to it, and missions first planned for Starliner went to SpaceX instead. [16]
People waiting to hear what the US UFO council found — Its first known meeting was private, and its chair says he cannot disclose what was discussed. [17]
Physicists whose standard picture treats dark energy as fixed — The 3,000-supernova catalogue adds a second, independent hint that dark energy changes, which that picture does not allow. [11]
Researchers who built theories for the heavy black holes in GW231123 — If the magnification study is right, the black holes were about 140 Suns together, not 240, and need no unusual explanation. [12]

What nobody knows yet

Open questions from across today’s stories — ours included.

01

Whether FLEX and Sentinel-3C are working properly.

Both sent a first signal, but ESA says checking their health and performance will take the coming days. [1]
02

What bent the ripples from the black-hole merger GW231123, if anything did.

The team's model needs an object of 190 to 850 times the Sun's mass, or a dense cluster of stars, and single objects that heavy should be very rare. [12]
03

Whether dark energy really changes over time.

Two separate methods show hints, not proof. The supernova catalogue is still growing, with more nearby explosions to come from a programme called DEBASS. [11]
04

How the record gamma-ray particle survived its trip.

The Italian team's answer needs particles nobody has detected and a break in one of Einstein's rules, and only future observations can test it. [14]
05

How much Vega-C can carry.

ESA's launch news gives 2,300 kg to low orbit, while its pre-launch picture page says up to 3,300 kg with no orbit named. [1][8] Spaceflight Now gives 2,300 kg to an orbit 700 km up. [2]
06

What the US council on UFOs discussed on 31 August.

Its chair, Avi Loeb, says he cannot disclose what was said at the private meeting. [17]
07

When Boeing's Starliner will carry astronauts again.

NASA's inspector general says its next flights remain uncertain, and it still has no certificate to fly crews. [16]
08

Whether Venus ever had a moon.

A moon lost billions of years ago leaves little direct trace, so the answer rests on simulations and on chemical clues a future probe might find. [15]

04 Hope carry this

FLEX and Sentinel-3C both reached orbit on 15 September, and each sent its first signal to ESA's control centre in Germany.

Also true today

A rescue system carried by 62 satellites, with 45 nations taking part, has helped save more than 63,000 lives since it began working in 1982.
NASA's Roman Space Telescope used less than a tenth of the fuel set aside for its first course correction. It now has enough fuel for at least 22 years of science.