# Issue No. 136

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# The Orbital Index

Issue No. 136 | Sep 29, 2021

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 ¶Landsat 9. As Vandenberg’s 2,000th rocket to launch, Landsat 9 was carried to orbit by an Atlas V on Monday to replace the 22-year-old Landsat 7. The combined Landsat 8 + 9 revisit time (the period between imaging opportunities for any given location on the Earth) will remain 8 days, unchanged from that of Landsat 7 + 8. Landsat 9 carries two improved science instruments: OLI-2 for observing in visible, near-infrared, and shortwave-infrared light, and the Thermal Infrared Sensor 2 (TIRS-2) for observing in thermal infrared wavelengths (TIRS-2 will also correct a “stray light” issue in Landsat 9’s TIRS instrument). Landsat is the longest continually running Earth-observation program. Landsat data is free and you can even watch it come down in real-time. Also on board were some rideshare cubesats, including CU Boulder’s CUTE which will analyze the composition of exoplanet atmospheres based on transmission spectroscopy of a host star’s light as the exoplanet passes in front. Other rideshares are CuPID, a 6U cubesat that boasts the first wide field-of-view soft X-ray telescope on orbit and will measure x-rays emitted when solar wind plasma hits the Earth’s atmosphere, and Cesium 1 and 2, which will test phased array downlink and inter-satellite links for their customer communications experiment platform. (Here’s a 1/48th scale model of LandSat 9, if you’re into making paper models of nifty satellites for your desk.)
 Landsat 9 being prepared for encapsulation inside Atlas V’s fairings, with the rideshare ESPA ring at the bottom.
 ¶Etc.According to the (somewhat biased) ARK Invest research team, the cost of satellite bandwidth has dropped precipitously since 2004, with $/Gbps decreasing 7,500x from$300M/Gbps to $40K/Gbps. ARK is bullish on a future where Starlink deployed by Starship reduces this cost a further 40x down to the neighborhood of$1,000/Gbps. 🛰 📉 💰Jonathan McDowell’s Astronautical Glossary.If you’re a university student, you could enter the Over the Dusty Moon Challenge from the Colorado School of Mines to design and build a lunar regolith transport system for construction, mineral processing, and other ISRU activities.Also for students, apply for the Caltech Titan Sample Return Space Challenge, a 5-day international mission design challenge next March.The region around the ancient city of Tall el-Hammam, located in what is now Jordan, flourished for 3,000 years before suddenly becoming unoccupied around 3,600 years ago. A highly-publicized recent paper suggests that this event was caused by a Tunguska-scale meteoric airburst, killing about 8,000 people and possibly forming the “oral tradition that eventually became the written biblical account about the destruction of Sodom.” As evidence, they cite a transition to salty soils (as if sprayed with Dead Sea water), claims of spherules of shocked quartz, melted mudbrick fragments, glassified pottery, and other signs of destruction (“extreme disarticulation and skeletal fragmentation in nearby humans”). However, other researchers are highly skeptical of these claims, with Scott Manley summarizing and pointing out that some of the same authors published a different paper about a different nearby location also being destroyed by an airburst 10,000 years earlier—the odds are strongly against both being true.Scott also recently published a video about Meteor Crater in Arizona, possibly the best preserved meteorite impact crater on Earth. The crater was produced by a 50 m meteorite and yielded a 10-megaton impact, similar in energy to the Tunguska airburst. However, unlike the 1908 event, its iron-nickel makeup let it hang together until impacting the surface.Still speaking of impacts, 40 years ago, high concentrations of iridium at the 66 million years old K-Pg boundary (previously known as the K-T boundary) brought a team led by Luis Alvarez and his son to suggest that an impact event wiped out the dinosaurs (and 75% of all plant and animal species). It took 10 years to identify the crater, the Chicxulub impact formation in Mexico’s Yucatán Peninsula, roughly 150 km in diameter and 20-30 kilometers deep. This month marked 30 years since Hildebrand et al’s publication of that identification. 🦖 🦕 ☄️