Issue No. 104

The Orbital Index

Issue No. 104 | Feb 17, 2021

🚀 🌍 🛰

Tianwen takes another step. China’s first interplanetary mission successfully arrived at Mars last week, entering a highly elliptical 400 x 180,000 km orbit after a 15-minute deceleration burn. With this achievement, China became the sixth nation to orbit the Red Planet. Tianwen-1 (pronunciation guide) could become the first successful mission to deploy both an orbiter and rover from a single package, making it a very ambitious first solo deep-space mission for China. The orbiter will circle Mars until May, surveying the selected landing site in Utopia Planitia with as high as 50 cm/pixel optical imaging—this is the same region where Viking 2 landed and is thought to contain abundant buried ice. The solar-powered rover, similar in design to NASA’s Spirit and Opportunity rovers, but about a third larger at 240 kg, will be released for a retropropulsive landing once the site passes inspection. China is leaning heavily on its lunar robotic mission experience and has packed 13 scientific instruments into Tianwen-1. These surface and orbital instruments will study Martian morphology, regolith composition, ionosphere, magnetic field, and image the planet in high resolution. The orbiter and rover each have roles to play in every one of the mission’s primary science objectives, making it a unique look at orbiter- versus rover-based science (paper). The overarching focus is the history of water on Mars and its current presence as ice, both at the poles and in subsurface locations. Subsurface mapping will be conducted with regolith-penetrating radar from both the orbiter and rover, imaging up to 100 m below the surface and building on Yutu-2's success using the same technique on the Moon (the radar’s resolution will offer centimeter-level detail at up to 10 m depth, 1-meter detail at up to 100 m, and ice detection as deep as 1 km). With Tianwen's arrival, there are 10 missions currently operating at Mars—from ESA (Mars Express, ExoMars Trace Gas Orbiter), ISRO (Mars Orbiter Mission), NASA (Mars Odyssey, Mars Reconnaissance Orbiter, Curiosity, MAVEN, Insight), Roscosmos (ExoMars Trace Gas Orbiter in collaboration with ESA), U.A.E. (Hope), and now China.

Tianwen-1 took a picture of itself in deep space on its way to Mars with a deployable camera—which communicated with the main craft via wifi.

Seven minutes of terror. On Thursday, the largest and most ambitious of the 2020 Mars missions arrives. NASA’s Perseverance rover (and helicopter Ingenuity) will hit the Martian atmosphere traveling at 20,000 km/h and traverse the “seven minutes of terror” from interplanetary transfer to sitting alone in Jezero Crater at 3:55 pm EST—here’s an EDL (Entry, Descent, and Landing) trailer showing the complex progression which employs a supersonic parachute, autonomous guidance, and a rocket-powered sky crane. You can also watch an EDL visualization in your browser and read about how it will use Terrain Relative Navigation to find a safe landing spot. The landing show and virtual NASA Social start at 11:15 a.m. PST / 2:15 p.m. EST on this Thursday (the Empire State Building and Krispy Kreme will be lit for the event 🍩). Perseverance is phenomenally complex, its Sample Caching System alone contains 3,000+ parts and two robotic arms. We’re excited for all the sciencing this nuclear-powered, sample-drilling, laser-zapping behemoth can do when it joins its friends on the only planet (known) to be inhabited solely by robots. 🤞

Hope’s first image of Mars arrived this week, and it’s a lovely one.

Papers (about Mars, natch).

A sedimentary plain in Iceland may resemble the landscape near Gale Crater on Mars 3 billion years ago.

News in brief. Axiom Space raised $130 million—they are continuing to work on their ISS modules and have a private ISS mission that could launch as soon as January; a SpaceX Falcon 9 delivered 60 more Starlink satellites, but lost its 6x launched booster on landing (breaking their streak of 24 consecutive landings)—the next, and 20th, Starlink mission is planned for this coming Sunday; Lockheed Martin selected California-based ABL Space Systems to (attempt to) launch the first orbital rocket from the UK in 2022; NASA may buy one more Soyuz seat to the ISS for April; Russian Progress 76P MS-15 (intentionally) burned up after leaving the ISS; and, Turkish president Erdogan announced a 10-year space program, including lunar missions and the launch of a Turkish astronaut—the announcement was accompanied by the brief appearance of (soldiers standing around) a 3m high metal monolith near a UNESCO site. 🤷

A beautiful shot from orbit of Progress 76P MS-15 as it burned up in the atmosphere after leaving the ISS (photo by JAXA astronaut Soichi Noguchi).



A dust devil on Mars, caught by one of Curiosity’s navigation cameras on Aug. 9, 2020.

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