Issue No. 87


The Orbital Index

Issue No. 87 | Oct 21, 2020

🚀 🌍 🛰

Conjunction dysfunction. Last week, LeoLabs announced a potentially high-risk LEO conjunction between a decommissioned Soviet-era Parus navigation satellite and a Chinese CZ-4C upper stage with a collision probability of up to 20%. Luckily, they didn’t collide, likely missing each other by 25 m (± 18 m)—especially alarming given that the Soviet satellite has a 17 m gravity gradient boom. (On the other hand, US Space Command disagreed with the conjunction likelihood reported by LeoLabs, giving it a “nearly 0% probability of collision,” so this may not have been as close a call as reported.) Had they collided, orbital debris could have increased by 10-20%. Rocket upper stages present the largest risk for collisions, comprising 78% of the objects on a list of 50 most concerning space debris. Luckily, according to ESA’s just-released Annual Space Environment Report (pdf), in 2019, >70% of rocket bodies now comply with orbital debris guidelines, but this number was just ~20% in 2000, and a large number of elderly stages remain in orbit. Related: Last week, Peter Beck warned that Rocket Lab is already experiencing more difficult launch window selection due to the growing congestion in LEO, with launch vehicles having to “weave their way up in between these constellations.”


NASA announced 2020 Tipping Point awards. Around $370 million was awarded. The majority, $256 million, went to four companies—ULA, SpaceX, Lockheed Martin, and Eta Space—who are developing technologies for in-space cryogenic fuel management, an ability critical for using fuels prepared in-situ on the Moon and Mars, as well as for on-orbit refueling. Notably, SpaceX’s award uses Starship in a “large-scale flight demonstration to transfer 10 metric tons of cryogenic propellant, specifically liquid oxygen, between tanks on a Starship vehicle.” The remaining awards went to companies working on planetary landing, ISRU, power generation & storage, and communications—with Nokia winning $14.1 million “to deploy the first LTE/4G communications system in space.” Related: ULA’s Tory Bruno recently proposed a "Strategic Propellant Reserve" of orbital fuel depots that would incentivize companies to reuse upper stages and mine lunar water. Eric Berger discusses how fuel depots represent a directional change for NASA, politically threaten SLS, and enable a new paradigm for spaceflight.


Heat Islands and ECOSTRESS. Last weekend, Ben participated in a hackathon hosted by Earth Hacks, Urban Canopy, and JPL. The event focused on creating urban heat island maps using data from the ISS-mounted ECOSTRESS instrument (tutorial, for those of you following along at home)—heat islands are created by high population density, lack of vegetation, dark road and roof surfaces, as well as surfaces that are non-permeable. The ECOSTRESS mission provides the most detailed space-based temperature images to date, with a resolution of 70 m per pixel—it’s been hosted on the ISS since 2018 and is up for a mission extension to go beyond 2020. ECOSTRESS has recently been used for tracking forest fires along the US West Coast and was originally tasked with observing the thermal brightness of plants to understand their water consumption during diurnal, seasonal, and drought cycles. ECOSTRESS data has been upsampled using higher resolution multispectral data and machine learning techniques to generate temperature maps more detailed than current radiometers can capture (paper). For the hackathon, teams extracted data for a number of cities (San Diego, Chicago, Portland, Mumbai, and others) on hot days and identified hotspots, cool spots, and their respective potential causes. Here’s an in-progress world urban heat island map with multiple cities on it.


An upsampled heat map of Los Angeles during a heatwave, as captured by ECOSTRESS (credit: John Noble/JPL)

News in brief. OSIRIS-REx successfully booped the asteroid Bennu in its first sample acquisition attempt—results of the attempt will emerge over the next several days; an aging (but redundant) oxygen supply system on the ISS’s Russian Zvezda module failed and then was restored to operation—this is the same module with the slow air leak, which cosmonauts located using a teabag and attempted to patch on the 15th; seven countries (Australia, Canada, Italy, Japan, Luxembourg, UAE, UK) joined the US to sign the Artemis Accords (here’s a pdf) that dictate rules for peaceful exploration and mining of planetary bodies, sharing of science, and protection of heritage sites (like the Apollo landing sites)—notably, the UN has not been involved, and France, Germany, China, and Russia have not signed; a Soyuz MS-17 launched NASA’s Kate Rubins (likely the last NASA astronaut to ride on a Soyuz) and Roscosmos’ Sergey Ryzhikov and Sergey Kud-Sverchkov from Kazakhstan, and arrived safely at the ISS in a record breaking 3 hr 3 min flight from launch to docking (Scott Manley explains how 📺); BepiColombo slingshot past Venus 10,720 km above the surface, performing a number of observations that have a slight chance of phosphine confirmation—the simple amino acid glycine was also recently detected there (paper); and, SpaceX completed a nominal Starlink-13 launch (we’ve updated our coverage visualizer with the new TLEs), is targeting Starlink-14 for today (which will bring their active sat count to ~780), and successfully completed a static fire of Starship SN8 with three raptor engines for the first time, setting up a potential first flight in the next month.

A view of the underside of Starship SN8 with its three full-flow staged combustion cycle (video 📺) Raptor engines.


The ISS transiting Mars, by Tom Glenn.


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