The Orbital Index

Europa Clipper heads out. The 6-ton, $5B spacecraft, now with re-certified transistors, launches soon (initially planned for tomorrow, but now delayed due to Hurricane Milton). Clipper is headed to Jupiter and its mysterious icy moon Europa for arrival in April 2030. At 30 meters wide once its solar arrays are unfurled, Europa Clipper is NASA’s largest planetary exploration spacecraft ever. While originally congressionally mandated to fly on SLS, in 2020, lawmakers allowed the switch to the proven and far cheaper Falcon Heavy (even in fully expendable mode to handle Clipper’s high mass, and including add-on launch services, SpaceX received $178M for the launch, while a single SLS launch would cost likely more than $2.5B). Clipper’s nominal mission includes 49 passes by Europa, coming as close as 25 km above the surface, and through Jupiter’s harsh radiation belts. There was fear in May that some onboard rad-hard MOSFETS were not actually so rad-hard, but NASA has since tested spares and found them sufficient, based in part on the fact that the intense radiation will only come in bursts every 21 days during the spacecraft’s orbit, and the rest of the time the transistors can be slowly heated to allow them to anneal any radiation damage. Europa Clipper carries nine instruments to study Europa’s crust and its strongly suspected subsurface ocean, which may be 150 km deep. These include magnetometers, optical and thermal cameras, spectrographs, radio ranging systems for gravity measurement, ice-penetrating radar, MASPEX (which will study tenuous gasses around the moon), and SUDA (which will determine the source and spectral composition of dust particles as Clipper flies through suspected watery-plumes). If we get really lucky, maybe it’ll even detect life-like signatures. Hidden oceans are starting to look downright common in our solar system, with strong evidence for them on Ganymede, Callisto, and Enceladus, as well as some evidence for them on Titan, Mimas, and Pluto. But Europa is special because of its age (its ocean may have existed for 4.5 billion years) and its rocky and possibly radioisotope-rich mantle. We’ll know more in 2030!

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Good + Bad for Vulcan Centaur. Vulcan conducted its second certification flight last Friday. Originally scheduled to carry Dream Chaser to space for its first time on this flight, the launch went ahead even though Dream Chaser won’t be ready until sometime (hopefully early) next year. Flying a mass simulator instead of an active payload, the goal of this flight was reduced to solely obtaining national security certification. Unfortunately, shortly into the flight, one of the rocket’s two Northrop Grumman GEM 63XL strap-on boosters appeared to energetically lose its nozzle. The loss of a nozzle resulted in a thrust imbalance due to lower thrust on the side with the compromised booster. Vulcan’s two Blue Origin BE-4 engines performed commendably and were able to compensate for the anomaly and keep the rocket on a successful trajectory, with the powerful Centaur upper stage correcting for the earlier loss of performance and still delivering the payload to its target orbital insertion. BPS.space has a fun analysis video. The high-level outcome of the launch is a bit unclear: there was a failure, but the Vulcan Centaur itself performed admirably, even in the face of a semi-external anomaly, correcting for it and salvaging the mission. Given this, one could imagine national security clearance being granted for the core rocket. However, the SRBs are now very much in the spotlight and might be grounded until additional testing can be completed (although the FAA has said it won’t do a mishap investigation). This reality may delay the next 5-6 Vulcan launches since they all require SRBs (Vulcan can pack zero to six strap-on boosters).

TBIRD lasers down lots of data. Pew. Pew. NASA’s TBIRD cubesat mission, launched on Transporter 5 in 2022, is finally coming to an end. Originally planned for six months, the craft, which did not have moving mechanisms or a propulsion system, lasted for two years. Its precision pointing and tracking were accomplished with traditional attitude control and two-sided pointing (by controlling both craft and ground station orientation) as opposed to dedicated actuators, yet it was able to provide ~20 µrad tracking precision per axis. This allowed the craft to break a number of records (including some of its own multiple times over the course of the mission)—with the most important being the downlink of 4.8 terabytes of error-free data in one pass (~5 minutes) over Table Mountain Optical Ground Station 1 (which is also used for other laser comms missions, including DSOC on Psyche, cf. Issue № 328). Short-range laser downlinks like TBIRD’s can operate at very high bandwidth, in this case at a maximum of 200 gigabits per second. Distance is still a big factor in laser comms; Psyche’s DSOC will likely max out at ~2Mbps from 2.7AU.

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• “It takes 2 hours to orbit at the surface of any object made of rock.” 💫
• October is host to not one, but possibly two, comets that you might want to go outside and attempt to spot. C/2023 A3 is being joined by the recently spotted C/2024 S1. 
• The Moon is fractally cratered (here’s one with tardigrade for scale). Just try zooming in on ACT’s Lunar QuickMap to get a disconcerting sense of this.
• In fact, according to a new paper, the Moon’s very tenuous atmosphere (“exosphere”) is 70% due to all this impact vaporization of surface material by micrometeorites. The remaining 30% or so is from ion sputtering by the solar wind.
• Join the Exoasteroids citizen science project and peek into our solar system's distant future as you search for white dwarfs—remnants of Sun-like stars that have likely destroyed their inner planets and are now changing in brightness, possibly as they consume remnant asteroids.
• The Inouye Solar Telescope (which produces some stunning images) recently used its Cryogenic Near-Infrared Spectropolarimeter and coronagraph to perform the first mapping of the corona’s magnetic field, an accomplishment that will support our understanding of and ability to predict space weather.
• Eric Berger argues that Lunar Gateway should be canceled, along with SLS’s Block 1B upgrade, so that the Artemis program can focus on lunar surface activities, in part to better compete with China's rapidly advancing lunar program.
• Starship Flight 5 may launch as soon as Sunday, October 13th, pending regulatory approval. They’re hoping for a tower catch attempt of the returning Super Heavy booster. Excitement definitely seems guaranteed. 
• Last weekend, Ben got the chance to attend a small Star Party that included the unveiling of the latest large telescope in Ohio (not a traditional hotspot for celestial viewing). At slightly under 1 m in main mirror diameter, it is a beast of a telescope to be privately owned. Star Parties happen around the world and are a special kind of fun, attracting amateurs, professionals, and a lot of hardware. This party was hosted a few miles from the birthplace of George Ritchey, one of the most active large telescope makers of the early 1900s. Ritchey–Chrétien telescopes are still the predominant telescope design for large telescope optics, including well-known examples like Hubble and the Very Large Telescope. Ritchey’s last telescope was the 1 m telescope built for the US Naval Observatory in Flagstaff, AZ.