Issue No. 40

Welcome to issue № 40 of The Orbital Index! This week our readership (that’s you!) hit 2,500 strong. For those that have recently joined us, a hearty welcome; and, for those that have been around a bit longer, thanks for sticking with us! As always, we welcome your feedback and content submissions.

The Orbital Index

Issue No. 40 | Nov 26, 2019

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Europa’s got water. Tantalizing (but not particularly surprising) news this week was the possible detection of water vapor above Europa’s surface (paper), supporting the existence of an ocean 20 km under the Jovian moon’s icy crust. This ocean would be kept liquid by gravitational tidal forces and might contain twice as much water as Earth’s oceans. Europa’s surface is enriched with energetic compounds like hydrogen peroxide which are synthesized by Jupiter’s radiation and could cycle into the ice to provide (hypothetical) extremophile life with food. NASA’s Europa Clipper mission is under active development (cf. Issue 27), and future missions may attempt to melt their way into the ocean and roll across the underside of the ice (video). Where else might life exist in our solar system? Saturn’s tiny 500 km wide moon Enceladus has deep southern fissures, called tiger stripes, that squirt water full of organic compounds into space from its own subsurface ocean, making it perhaps our most likely candidate at the moment—we mentioned last week that NASA is studying a mission to sample these plumes. Besides Europa and Enceladus, Mars is an obvious and often-discussed candidate. Mars was a wet world—possibly more habitable than Earth—when early life was evolving, and it’s even possible that terrestrial life comes from Mars. Mars 2020 will hunt for microscopic fossils in Jezero Crater. Elsewhere, Titan (recently mapped and with a planned visit from the nuclear-powered Dragonfly), Ganymede, Callisto, Ceres, Mimas, and even Neptune’s moon Triton may also have subsurface oceans that could make them life-habitable. Related: The Great Filter and those that worry that us finding simple extraterrestrial life would be very bad news (pdf).

Concern for mega-constellations’ impact on astronomy is growing. With Starlink now the largest communication constellation after two launches, but only 1% deployed (120/12,000 satellites), concern is building around its impact on astronomy. (See: an image showing the Starlink train affecting a DECam frame.) SpaceX has said that they will paint the bottoms of future Starlink satellites black to reduce reflectivity, but this will likely be insufficient to hide them from the most sensitive instruments. A recent study found that 90% of LSST exposures will “have a bright saturated trail across them.” SpaceX is seeking permission to launch 30,000 additional Starlink satellites, bringing the potential total to more than the number of stars visible to the naked eye. Constellations from OneWeb, Amazon, and others will only add more noise. The International Astronomical Union has expressed concern and called for collaboration between constellation builders and scientists, as well as regulatory investigation. However, we all know how well voluntary self-regulation of a Commons tends to go when there are billions of dollars to be made. While the potential impact of worldwide broadband delivered by LEO constellations is gargantuan, we hope we’re not witnessing the beginning of the end of ground-based astronomy.

The Starlink train over DECam on Cerro Tololo, the Andes, Chile.

Running out of fingers… might have to reuse some. Rocket Lab will launch its tenth Electron rocket this Wed/Thurs (to be streamed here). The rocket will be carrying six 5 cm PocketQube microsatellites from Alba Orbital as well as a “meteor” simulation cubesat from ALE (cf the previous item—paid meteor showers are probably not any good for astronomy either). The PocketQube sats attempt to deliver the experience of a 3U cubesat in a much smaller package. This sixth launch for Rocket Lab this year, named “Running out of Fingers,” will be the first launch with full telemetry and reuse systems added to Electron. The booster should orient itself using its new reaction control system and complete a controlled reentry. Rocket Lab’s mid-air catch maneuver will not be attempted on this flight.

News in brief. Four RS-25 engines, veterans of past Shuttle missions (video), have been installed on the SLS Core Stage; astronauts Luca Parmitano (ESA) & Andrew Morgan (NASA) performed a spacewalk to begin repairing the ISS’s Alpha Magnetic Spectrometer, a superconducting magnetic spectrometer that looks for antimatter and dark matter (and they also threw stuff into space); InSight’s mole is moving again; and, during a max-pressurization test at Boca Chica, SpaceX’s Starship Mk1 prototype experienced a nitrogen explosion, blowing the top bulkhead of the vehicle apart (videos)—not ideal, but it’s a manufacturing pathfinder, and this is why we test.

The JWST is really large and technically stunning (video). We hope its elaborate deployment process works as planned.

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