The Orbital Index is a curated newsletter about space and the space industry.

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The Orbital Index

Issue No. 92 | Nov 25, 2020

🚀 🌍 🛰

The end of the Arecibo Observatory. It looks like the world is losing Puerto Rico’s iconic and prolific 305-meter radio and radar observatory due to underfunded maintenance and a second cable break on Nov 7th. Critically, the second cable broke at ~60% of it’s rated minimum breaking strength (pdf), meaning that current structural models are wrong and assumptions about the underlying condition and strength of the remaining cables are strongly suspect. The cables were last inspected less than a year ago after a series of earthquakes occurred near the array, with no indications of issues at the time. Adding new cables to the 820 metric ton platform 150 m off the ground would require workers to be present on the platform, which could fall due to cascading cable failure at any time. This represents an unacceptable safety risk, and so the NSF has decided to decommission and demolish the radio installation. While no longer the largest radio telescope in the world (China’s FAST is 500 m wide), the Arecibo Observatory is by far the most powerful radar observatory, providing the highest sensitivity and transmitting power of any deep space radar. Among other things, this is important for precisely determining the orbits of potentially-dangerous near earth objects. Arecibo’s scientific contributions are too numerous to list, but a few include the radar determination of the rotational periods of Venus and Mercury, the first solid evidence of neutron stars, the first binary pulsar, the first millisecond pulsar, the first direct radar image of an asteroid, and the discovery of the first exoplanets. In 2006, the NSF cut Arecibo’s budget drastically, then again in 2017, from $12 million to $2 million (or 2.5% of a single F-35A fighter jet). As Scott Manley says in his analysis 📺, unfortunately the time to fix Arecibo was 10 years ago. 😭

The week in Rocketry 🚀

The first-stage of the ‘Return to Sender’ Electron booster floating in the Pacific.

News in brief. A 5-10 meter-wide meteor missed the Earth by only 400 km (2020 VT4), the altitude of the ISS—had it hit, it’d have been a once-a-decade-level light show, but probably not damaging; OneWeb emerged from bankruptcy and has a new CEO; Ukraine became the 9th nation to join the Artemis Accords; Raytheon is acquiring Blue Canyon Technologies; and, Virgin Galactic has delayed the upcoming SpaceShipTwo test flight due to surging COVID-19 cases.


Every cometary nuclei imaged by spacecraft and radar, to scale. Linked from Jatan’s “why explore asteroids, comets, and other small worlds.”