After nearly eight years, ESA and JAXA's BepiColombo spacecraft is finally nearing Mercury, as engineers begin the arrival sequence by jettisoning the power module that got it this far. The spacecraft stack separated from the Mercury Transfer Module (MTM) on September 3 at around 1400 CEST. After a tense few minutes, controllers confirmed that a preliminary Doppler signal had been detected, indicating that the MTM had separated successfully; by 1552 CEST, it was confirmed that signals had been picked up, indicating that all had gone to plan. The solar panels of the Mercury Planetary Orbiter (MPO) were charging the spacecraft's batteries. The next stage involves dropping into orbit around Mercury on November 21. Then the Mercury Magnetospheric Orbiter (MMO) – aka Mio – will be released between December 9 and 10, and a week later MPO will start moving to its final orbit over 480 x 1500 km, with science commencing in April 2027. The arrival is a year later than planned. BepiColombo was supposed to have been orbiting Mercury in December 2025, but problems with the spacecraft's Solar Electric Power (SEP) system meant the trajectory had to be rethought, which extended the spacecraft's cruise. BepiColombo is no stranger to Mercury and has performed six flybys of the planet since 2021. It has also conducted flybys of Venus and Earth following its 2018 launch. The spacecraft is an impressive example of international cooperation. The MPO and MTM are ESA contributions, while the MMO comes from JAXA. ESA also provided the sunshield to protect the MMO during transit. This sunshield will be ejected after the MMO is released. The MPO is the big brother of the BepiColombo partnership, with a main body measuring 2.4 x 2.2 x 1.7 m and a mass of 1,230 kg (including an 85 kg science payload). JAXA's MMO is 1.8 m in diameter and 1.1 m high, and weighs 255 kg (45 kg of which is the science payload). While MPO is 3-axis stabilized and nadir-pointing, MMO will be spin-stabilized at 15 rpm, with its spin axis 90 degrees to the Sun. The goal of the mission is a study of Mercury, "from the structure and dynamics of its magnetosphere and how it interacts with the solar wind, to the properties of its large iron core and the origin of its magnetic field." The initial mission at Mercury is planned for one Earth year (approximately four Mercury years), although it could be extended by another Earth year. ®

The Titan dune field where NASA's Dragonfly rotorcraft will land in 2034 has a name: Ahmakiq Undae. The International Astronomical Union (IAU) approved the name, and NASA announced it in an update as the spacecraft's 2028 launch edges closer. It is scheduled to arrive at Saturn's moon Titan in late 2034. Dragonfly's fabrication began in late 2024 and was completed about a year later. Most recently, engineers fitted the probe's wiring harness, which, according to NASA, includes an estimated 17,315 feet of conductor wire and 374 connectors, and weighs about 100 pounds. The harness is accompanied by a battery weighing in at almost 300 pounds. The nuclear-powered Dragonfly is an impressive piece of hardware. The fuselage is almost 13 feet long, and the arms will hold eight sets of rotors. The probe has landing skids and a cap on the end for its power source. The harness fitting means other Dragonfly components can be added, including its avionics and science instruments. During May and June, the rotorcraft was put through vibration testing, including suspending the fuselage on bungee cords to see how it behaves in the air, and a sealing test where engineers checked how well the structure keeps the environment out – Titan's atmosphere is, after all, dense, cold, and about 1.5 times the pressure of Earth's. Dragonfly isn't the first visitor to Titan - the European Space Agency (ESA) landed the Huygens probe there in 2005. However, while Huygens was a static probe that lasted just over an hour on the surface, Dragonfly is planned to spend at least 3.3 years exploring the moon's environment. According to NASA, the probe will explore "diverse environments from organic dunes to deposits associated with an impact crater – Selk Crater – where liquid water and complex organic materials key to life once existed together." The probe is effectively a flying laboratory and must withstand temperatures as low as minus 290 degrees Fahrenheit (minus 179 degrees Celsius) and potentially liquid methane rain. It also requires a heat shield to protect the spacecraft during its descent through Titan's dense atmosphere. Once on Titan, the plan is for the vehicle to fly to multiple locations during its mission. Installing the wiring harness (something familiar to anyone who has battled wiring looms on automobiles) and naming the landing zone are milestones on Dragonfly's journey to launch. Next will be connecting the wiring to science instruments as they are delivered, along with other flight components. In 2024, Dragonfly's total lifecycle cost was $3.35 billion - approximately twice the original estimate - and the mission was more than two years late, with the COVID-19 pandemic, supply-chain issues, and additional design work pushing up costs. The mission is currently scheduled to launch no earlier than July 2028 on a SpaceX Falcon Heavy rocket. ®

NASA's Neil Gehrels Swift Observatory may now be beyond rescue, but the team behind the spacecraft has reactivated its instruments to eke out a final few months of science data before it reenters Earth's atmosphere. The Ultraviolet/Optical and X-ray telescopes were reactivated last week, and the team hopes to return the Burst Alert Telescope to data collection during September. The former two telescopes were turned off in February to minimize drag and buy time for the reboost effort. The latter was halted in April to reduce power consumption and allow Swift's solar arrays to be positioned to further cut down on atmospheric drag. The reboost mission failed after control problems with the Katalyst Space LINK spacecraft ruled out an attempt to capture and rescue the Swift observatory. LINK is currently raising its orbit, and there are plans to begin phasing relative to Swift, but there won't be any grappling. The upshot is that Swift remains set to reenter the Earth's atmosphere in the coming months, perhaps as soon as October. Perhaps a bit later. Whatever the case, mission managers have decided that the potential science return is worth sacrificing a few weeks or months of orbital lifetime. Swift has spent more than two decades studying the cosmos and remains operational, but lacks the capability to boost itself to a higher orbit. Recent solar activity magnified the effects of drag on the spacecraft, and a high-risk rescue mission was launched a few months ago in an effort to prolong Swift's orbital life. According to NASA, switching to low-drag operations kept Swift above the critical 185-mile (300-kilometer) threshold until October; below that altitude, the descent rate would accelerate and rescue would no longer be feasible. "With the resumption of science observations, the team anticipates Swift will reach that milestone sometime in the next one to two months," said NASA. ®

The European Space Agency's Cluster quartet is preparing for its final bow after Samba reentered Earth's atmosphere, with Tango due to follow tonight. Samba lost contact at 21:26 UTC on August 31 and reentered at 21:39:38 UTC. Tango is expected to follow at 21:30:31 UTC tonight. The other two satellites, Rumba and Salsa, reentered in 2025 and 2024, respectively. The final reentries close the book on a prodigiously long-lived quartet that exceeded even optimistic expectations, thanks in no small part to the ingenuity of engineers on the ground. Cluster II launched in 2000 aboard two Soyuz rockets from the Baikonur Cosmodrome. It replaced the original quartet, which was destroyed during the maiden flight of Ariane 5 in 1996, drawing on spare hardware and work already completed for the doomed spacecraft. The four satellites were launched on a two-year mission to study the structure of Earth's magnetosphere in three dimensions. The spacecraft were designed to last for five years, and their mission was repeatedly extended. Why terminate a set of functional spacecraft when the science data is still rolling in? After about a decade, however, the batteries that powered the spacecraft while they passed through Earth's shadow failed. From an engineering perspective, each satellite effectively died whenever it entered an eclipse. "The first time it happened, this was a rather uncontrolled shutdown... the spacecraft were not designed to be switched off," recalled spacecraft operations manager Bruno Sousa in a 2020 interview with The Register. And yet the spacecraft survived and restarted. Engineers devised a workaround to bring the spacecraft back to life in a controlled fashion. More hardware failures occurred, and again, engineers devised ways to keep the mission going. The mission finally ended in 2024, when controllers halted science observations and began the quartet's disposal campaign. Earlier orbital adjustments sent the satellites toward targeted reentries over remote stretches of ocean, beginning with Salsa and culminating with Tango tonight. The mission had one final gift to offer. "When a spacecraft reenters the atmosphere, it experiences extreme forces," noted Stijn Lemmens, senior space debris mitigation analyst at ESA. "Temperatures soar, materials melt and vaporize, and the spacecraft gradually breaks apart. But how exactly?" If only there were some spacecraft to observe as they made a controlled entry into the Earth's atmosphere. Tango is expected to be destroyed tonight, completing the disposal of a quartet that survived far longer than its designers intended. Sousa's words to The Register in 2020 remain an apt epitaph for the engineers who kept Cluster alive: "Never give up. Never surrender." ®