The Overview · your week in space

From The Decisional Pass

Happy Fiestas Patrias to everyone in Chile, home to many of the world's biggest telescopes. This week Europe launched a satellite whose whole job is to watch plants do photosynthesis, Webb found brown dwarfs barely bigger than Jupiter, a telescope that launched two weeks ago saved enough fuel to double its life, and black holes of every size turned out to follow the same rule for when they start firing jets.

🌱 Europe launched a satellite to watch plants breathe

At 3:21 a.m. CEST on September 15, a Vega C lifted off from French Guiana on flight VV30 with two climate satellites. Sentinel-3C went first, about 1,143 kg, and FLEX, the Fluorescence Explorer, followed about an hour later, released from a dual-payload adapter. ESA's control center in Darmstadt picked up both.

FLEX is the one I can't stop thinking about. Plants give off a faint glow of fluorescence while they photosynthesize, far too dim to see, and FLEX is ESA's first satellite built specifically to measure it from orbit. That's a direct read on how hard vegetation is actually working, not just how green it looks. Sentinel-3C is the steady half of the pair: it takes over ocean, land, ice and atmosphere measurements from Sentinel-3A, which is past its 7.5-year design life. Eighth Vega C flight, second this year.

References: ESA (Sept. 15) · Spaceflight Now (Sept. 15)

🔭 Webb found the smallest brown dwarfs yet

On September 15, NASA and ESA released a big Webb panorama of IC 348, a star-forming cluster about 1,000 light-years away in Perseus. The team, led by Kevin Luhman at Penn State with ESA's Catarina Alves de Oliveira, found brown dwarfs as light as twice the mass of Jupiter, the least massive ones known. Webb's first look at the same cluster in 2022 bottomed out at three to four Jupiter masses.

Here's the bit that got me. One of those featherweights appears to have its own disk, and the smallest ones share a hydrocarbon signature nobody has identified yet. Objects that small forming the way stars do, some with their own disks, blur the line between a star and a planet in a way the formation models don't handle well.

References: NASA Science (Sept. 15) · ESA/Webb (Sept. 15)

⛽ Roman saved enough fuel to double its life

The Nancy Grace Roman Space Telescope was designed for 10 years of science. NASA said on September 14 it now has fuel for at least 22. Its first course correction burned about 40 pounds of propellant out of 441 budgeted, under 10 percent, which buys roughly four years on its own. Roman also launched lighter than the conservative budget, 8,056 kg against 9,800, and the extra fuel loaded before launch adds about four more. The team expects another four or so from the next correction and from settling in at L2 around early December.

This is my favorite kind of engineering news. Nobody found new money. The flight team just flew it precisely, and a flagship survey telescope picked up another decade.

References: NASA Science (Sept. 14)

🕳️ Black holes of every size start their jets at the same point

A paper out September 17 in Nature Astronomy, from Adelle Goodwin at Curtin University and Andrew Mummery at the Institute for Advanced Study, looked at black holes shredding stars that wander too close. Those events compress a feeding cycle that normally takes thousands of years into a few. Of 20 events, the team kept the 10 they could model cleanly, and found that supermassive black holes launch delayed jets once their feeding drops to about 2 percent of the Eddington limit.

That's the same threshold already known for black holes about 10 times the Sun's mass. One number across a range of millions in mass says jet launching is set by the physics of the inflow, not by how big the black hole is.

References: Phys.org (Sept. 17) · Nature Astronomy (Sept. 17)

🚀 China flew four rockets in 48 hours

Starting September 15, China launched four times in about two days from Jiuquan, Hainan and a platform at sea, opening with a Zhuque-2E carrying Qianfan broadband satellites. On the 16th, OrienSpace's Gravity-1 lifted off from the water off Shanghai with nine satellites, and Xinhua says it set Chinese sea-launch records for payload, over 3 tonnes, and insertion altitude, about 800 km. Spreading Qianfan across commercial rockets and sea platforms is how China plans to catch up on broadband constellations.

References: SpaceNews (Sept. 17) · Xinhua via GlobalSecurity (Sept. 16)

⚡ Quick hits

• 700 Falcons. A Falcon 9 flew the last three O3b mPOWER satellites for SES on September 13, the 700th Falcon launch: 687 Falcon 9s and 13 Falcon Heavies. Booster B1080 flew its 29th mission and landed. (Spaceflight Now, Sept. 13)
• Station traffic. Progress MS-35 launched from Baikonur on September 16 with about three tons of food, fuel and supplies, set to dock Saturday. Crew-13 has slipped to early October after a valve swap on its Dragon. (NASA, Sept. 16)
• A correction on Starship. Last week I said Flight 14 was no earlier than September 18. It hasn't flown. Local reporting in South Texas now puts it at September 28, pending regulatory approval, after a September 22 target also slipped. (KRGV, Sept. 17)

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