Issue No. 174

The Orbital Index

Issue No. 174 | Jun 29, 2022

🚀 🌍 🛰

Two billion stars from GAIA. ESA’s Gaia mission recently released its third data dump containing details on almost two billion Milky Way stars: chemical composition, mass, temperature, and radial velocity. Most of these are derived from the release’s spectroscopy data. Radial velocity in particular is generated using Doppler Spectroscopy, measuring how a star’s light has been shifted toward either the red or blue ends of the visible spectrum based on whether it is moving away from or toward Earth. Somewhat unexpectedly, Gaia was also able to detect tiny changes to the shapes of thousands of stars that occured when their surfaces shifted suddenly—aptly named ‘starquakes’. This was not something Gaia was designed to do, and the thousands of these events were not predicted by current theory. Additionally, Gaia DR3 included the orbital determination of 154,741 solar system asteroids and the most extensive catalog of binary stars to date, as well as measurements of millions of galaxies and quasars beyond the Milky Way.

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Psyche delayed. Due to the late delivery of its flight software and compatibility issues with its testbed at JPL (resulting in insufficient time for testing), NASA’s Psyche mission will unfortunately not make its Aug-Oct launch window and can no longer rendezvous with Psyche in 2026. Launch windows exist in 2023 and 2024, but due to their less favorable orbital arrangements, Psyche wouldn’t reach its metal asteroid target until 2029 or 2030, respectively. NASA is evaluating options, and Psyche’s rideshare smallsat Janus will likely find a new launch partner (as will the mission’s ride-along free-floating high data rate laser transmitter). While we’re waiting to see what NASA decides for the mission, you can read lead PI Lindy Elkins-Tanton’s very-well-received recent book: A Portrait of the Scientist as a Young Woman.

NASA’s iSAT study. A couple years ago, NASA’s Astrophysics Division spent two years assessing the feasibility of assembling a large-aperture observatory in space. The In-Space Astronomical Telescope (iSAT) Assembly Design Study (pdf) concluded that In-Space Assembly (ISA) is the only option for building observatories with aperture diameters >15 m and would even be likely to be beneficial for smaller ones like the JWST (6.5 m aperture). Efforts like Northrop Grumman’s successful Mission Extension Vehicles, the upcoming DARPA RSGS mission, and NASA OSAM-1, along with the usage of Canadarm2 to install instruments with standardized interfaces on the outside of the ISS, all demonstrate the increasing maturity of robotic servicing and assembly. The iSAT study describes a telescope composed of modules with standardized interfaces, launched with a spacecraft bus that has attached Canadarm2-like robotic arms that can assemble and deploy modules delivered by space tug from multiple launches. The benefits over launching monolithic spacecraft with hundreds of single points of failure (cough JWST cough) are clear: the mission won’t be limited by a single launch vehicle’s lift ability or fairing size; the same inchworming robotic arm that does initial ISA can later perform repairs and upgrades, either with freshly delivered replacement modules or by debugging malfunctioning parts (see Mars Insight); the final deployed structure doesn’t need to be designed to handle the harsh launch environment; and, design and development will be faster without needing to design and test super reliable deployment mechanisms—if a part fails during orbital checkout, launch a replacement. The primary challenge is designing hardware that today’s limited-dexterity robotics can manipulate, and figuring out supervised autonomy with fallback telerobotics for bringing humans into the loop when needed. There are definitely challenges, but this feels like a feasible approach. If one could do it near a crewed station for infrequent debugging EVAs, even better.

Canadarm2-like robotic assembly of the iSAT model telescope’s backplane truss from modular elements.

News in brief. China launched their Kuaizhou-1A rocket successfully with the Tianxing-1 test satellite (of unknown purpose)—the Kuaizhou-1A had suffered a launch failure in December Lux Capital led a $10M investment in space tug startup Impulse Space (the startup, led by SpaceX founding engineer Tom Mueller, already raised $20M earlier this year) Lux Capital also recently led a $15M Series A in Epsilon3, manufacturing software startup (and one of our sponsors) Redwire sold an ISS-manufactured 2 g crystal of potassium dihydrogen phosphate, a material used to make high-energy lasers, to Ohio State University in what is claimed to be the “first time that a space-enabled materials product has been sold on Earth NASA selected three lunar surface, 40-kilowatt, 10-year-life nuclear reactor designs for further development A Chinese Long March-2D carrier rocket launched three (likely military) remote sensing satellites Iran performed a suborbital test of its Zuljanah satellite launch vehicle Viasat shareholders approved an acquisition of Inmarsat An Ariane 5 launched two GEO telecom sats A NASA suborbital sounding rocket with an x-ray payload to study Alpha Centauri launched from the new Arnhem Space Centre in Australia, in what is being claimed as the first commercial launch from the country Despite a hydrogen leak, the SLS will not have another wet dress rehearsal before launch sometime this fall, NASA thinks Artemis 1 is ready to go! CAPSTONE launched successfully (more on this next week) ● BepiColombo shot past Mercury for the second time, 200 km above the hellish planet’s surface—it enters orbit in 2025.

BepiColombo screams past Mercury 200 km above its surface.


  • Vast is building a commercial space station (with artificial gravity!) and is hiring for a wide variety of roles. (Andrew consults with Vast.)


A visualization of the velocity of 26 million Milky Way stars in three dimensions generated from Gaia DR3 data. It clearly shows the rotation of the galaxy via the blue/red shift of its stars.

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