Issue No. 120


The Orbital Index

Issue No. 120 | Jun 9, 2021

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Two Discovery-class missions are headed for Venus. NASA, making good on ex-administrator Bridenstine’s recommendation to send spacecraft back to our closest neighbor, announced funding for (a somewhat unexpected) two missions to Venus—its first missions dedicated to the planet in 30+ years. VERITAS and DAVINCI+ will journey to Venus circa 2028-2030 where they will spend multiple years studying its atmosphere, mapping its surface, and increasing our understanding of how exoplanets form and develop (video). DAVINCI+ will perform two fly-bys culminating in a planetary probe descending through the thick, inhospitable atmosphere to capture data and high-resolution images on its way to the surface of the Alpha Regio highlands. DAVINCI’s carrier craft will observe the Venusian atmosphere with a four-camera array, and drop its probe during the second fly-by to make a descent to the surface where it could land intact and function for up to 17 minutes. The probe, equipped with a Mass Spectrometer, a Tunable Laser Spectrometer, a descent imager, and a suite of environmental sensors (these will provide a descent profile for use as a baseline for the mission’s atmospheric science), borrows heavily from the success of Mars Science Lab’s instruments. On its dive down to the surface, it will test the atmosphere for the presence of Phosphine. The mission will host the Compact Ultraviolet to Visible Imaging Spectrometer (CUVIS) technology demonstration which may help understand why clouds on Venus absorb an unexpectedly large amount of UV. Meanwhile, VERITAS will orbit Venus using SAR to map the surface down to 2 mm resolution using interferometry (additionally generating a height map) to detect any tectonic activity and study the geologic history of a planet that developed very differently than Earth. VERITAS will also map the planet’s surface emissivity, and has been tuned to analyze surface elements despite their average temperature of 460° C. VERITAS will carry the Deep Space Atomic Clock 2 demonstration, which will eventually help spacecraft navigate autonomously in deep space. Both missions intend to use Doppler analysis to measure the planet’s gravitational characteristics, a staple of NASA’s deep space missions. Related: NASA did not pick the missions proposed to go to Triton and Io. Like DAVINCI, the Io mission may be improved and resubmitted in the next round of Discovery-class proposals. However, a low energy transfer window to Triton will not occur again for another 13 years, so the TRIDENT mission proposal is likely on hold for the time being.




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Gravitational Waves. Humanity’s first detection of a gravitational wave was on Sept 14th, 2015 by a pair of LIGO detectors in Washington state and Louisiana. That event, once again proving Einstein’s general theory of relativity correct, was the echo of two black holes merging and converting ~3 solar masses worth of matter into pure energy in the form of ripples in spacetime itself. “The total power output of gravitational waves during the brief collision was 50 times greater than all of the power put out by all of the stars in the universe put together.” Then, in Aug 2017, both LIGO and Virgo (in Italy) observed the ripples from a pair of neutron stars merging in time to give telescopes all over the world the chance to observe the event across the electromagnetic spectrum. The LIGO and Virgo observatories are currently undergoing upgrades for another observation run starting in June 2022, but in the meantime, they have released a catalog of the 50 gravitational wave events seen so far—here’s a tool to explore and visualize that dataset. Meanwhile, the NANOGrav project, which has spent over a decade using pulsars as a precise timing signal to try to detect incredibly small changes in the position of the Earth due to passing gravitational waves, has found early non-conclusive evidence (paper) of a very low frequency (e.g., nanohertz) Gravitational wave background. Related: Gravitational wave detectors are true wonders of engineering at the edges of quantum mechanics: “at its most sensitive state, LIGO will be able to detect a change in distance between its mirrors 1/10,000th the width of a proton! This is equivalent to measuring the distance to the nearest star (some 4.2 light-years away) to an accuracy smaller than the width of a human hair.” 


From xkcd.

News in brief. China’s Tianzhou-2 cargo craft brought supplies and fuel to the soon-to-be-crewed Tianhe; a small piece of space debris damaged Canadarm2 on the ISS, leaving a 5 mm hole in its thermal blanket and puncturing the internal boom, but the robotic arm remains functional; Launcher raised $11 million of Series-A funding—they are targeting a first launch of their small satellite "Launcher Light" vehicle in 2024; LeoLabs raised a $65M Series B for their space situational awareness radar network; a Cargo Dragon carried experiments and a set of Redwire rollup solar panels to the ISS on a brand new Falcon 9 booster, the first new booster in 20 launches; a Falcon 9 launched a SiriusXM SXM-8 satellite; Astra announced the acquisition of electric propulsion startup Apollo Fusion using funds from its upcoming SPAC reverse-IPO; New Zealand became the eleventh country to sign onto the Artemis Accords; Cosmonauts began the process of decommissioning the Russian Pirs module early Wednesday; and, Jeff Bezos will ride to suborbital space on the first crewed flight of New Shepard.
An old favorite: Hubble’s 2004 image of the stunning Messier 104, or Sombrero galaxy, 50,000 light-years across and 30 million light-years away. Here’s the full-res version for your desktop wallpaper.

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