Issue No. 249

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The Orbital Index

Issue No. 249 | Dec 20, 2023

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ESA’s Ariel passes PDR. ESA’s Atmospheric Remote-sensing Infrared Exoplanet Large-survey space telescope (Ariel) recently passed its Preliminary Design Review, now moving into its early construction phase. Ariel is designed to survey the chemistry of at least 1,000 warm-to-hot exoplanet atmospheres, determining their compositions, temperatures, cloud coverages, and other characteristics. The 1-meter infrared and visible Cassegrain reflector telescope will analyze known transiting exoplanets (including those of TRAPPIST-1). It will use transmission spectroscopy (analyzing starlight passing through a transiting planet’s atmosphere), eclipse spectroscopy (analyzing thermal radiation and reflected light from a planet appearing and disappearing as it passes behind its star—pdf), and transit photometry (estimating an exoplanet’s orbit, size, and density by measuring the cadence and dimming of its passes in front of its star). Ariel is scheduled to launch on an Ariane 6 NET 2029 to Sun-Earth L2 and will have a nominal four-year mission, hopefully significantly expanding our knowledge of exoplanet diversity and giving us a sense of how common (or uncommon) places like our solar system are in the Milky Way. Related: a video about the above exoplanet detection methods.

A CAD rendering of Ariel. Its science instruments require active cooling to -220 °C while at L2, employing either a Joule-Thomson or Stirling cooler with neon as a working fluid.

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XPoSat is a go for LEO. The Indian X-ray Polarimeter Satellite (XPoSat), designed to study the dynamics of bright astronomical X-ray sources, is planned to launch in early January aboard an ISRO Polar Satellite Launch Vehicle. Developed by ISRO, U R Rao Satellite Centre, and the Raman Research Institute for about ₹600M ($72.2M), XPoSat hosts two scientific payloads, totaling 144 kg, attached to a modified ISRO Indian Mini Satellite (IMS-2) bus. The primary instrument is the Polarimeter Instrument in X-rays (POLIX) which will measure the degree and angle of polarization of X-ray photons in the 8-30 KeV range. Meanwhile, the second payload, X-ray Spectroscopy and Timing (XSPECT), will study photons from astronomical emissions in the 0.8-15 keV range. Data from these two instruments will help researchers gain a better understanding of the radiative and accretion physics of black holes, X-ray pulsars, neutron stars, active galactic nuclei, and magnetars. The mission will target 50 X-ray sources over a period of five years. Very long exposure times are needed for XPoSat to optimally observe an astronomical source of interest—persistent X-ray sources will require about a week, whereas X-ray transients will take a month of exposure. The spacecraft has three operating modes: in Observation Mode the payloads will collect data while the spacecraft rotates at 0.2 rpm around the payload viewing axis; in Sun Pointing Mode the solar panels will be positioned toward the Sun while sky background observations are made by POLIX; and, in the Earth Pointing Mode the X-band transmission antenna will be pointed to the ground station in Bengaluru for data downlink. It is expected that XPoSat’s findings will significantly contribute to the complementary research from NASA's Imaging X-ray Polarimetry Explorer (IXPE) satellite which launched about two years ago with three identical telescopes for observation in the 2-8 keV energy range.

XPoSat, shown in a stowed view with various components detailed. Credits:  ISRO

News in brief. Voyager 1 has stopped returning useful data to Earth—engineers are planning a patch, but debugging is hard with 45-hour round trip latency China launched their secretive likely-X-37B-like space plane for a third time, and a day later, launched a very large presumed geosynchronous, optical spy satelliteTrue Anomaly raised $100M for their agile space situational awareness satellites Relativity hot-fired the methane-fueled Aeon R engine for the first time—13 of these will power the Terran R’s first stage Networking startup Armada raised $55M to develop portable data centers that connect to Starlink The Polaris Dawn mission has been pushed to April 2024 due to the technical hurdles of designing a new EVA suit capable of a higher radiation environment and flying higher than previous Crew Dragon missions (targeting the highest ongoing crewed Earth orbit ever flown) SatVu’s HotSat-1 suffered a failure with their thermal camera, ending the mission Pakistan’s federal cabinet approved the country’s first national space policyNASA recently noted exceptional performance with two new EO missions: TEMPO that measures air pollution hourly as a hosted payload from GEO & SWOT that surveys surface water across the globe SpaceX hit a $180B valuationA French small rocket project, aptly-named “Baguette-One”, received more funding to continue developing a low-cost hybrid rocket engine NASA’s four Starling cubesats have maneuvered into their proper flight formation despite a propulsion leak on one craft OurSky raised $9.5M for a software platform for SSA data Rocket Lab’s Electron rocket returned to flight with the successful launch of an iQPS radar satellite, setting a new record of 10 launches this year for the company.

‘The Moon God Awakens’, Rocket Lab’s 10th Electron mission of the year.

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JWST recently captured Uranus in all its glory, including a seasonal north polar cloud cap, its dim inner and outer rings, and many of its 27 moons. Credits: NASA, ESA, CSA, STScI

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