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You\u2019ve likely heard of the Breakthrough Starshot (BTS) initiative. BTS aims to send tiny gram-scale, light sail picospacecraft to our neighbour, Proxima Centauri B. In BTS\u2019s scheme, lasers would propel a whole fleet of tiny probes to the potentially water-rich exoplanet. <\/p>\n
Now, another company, Space Initiatives Inc., is tackling the idea. NASA has funded them so they can study the idea. What can we expect to learn from the effort?<\/p>\n
<\/p>\n Proxima b may be a close neighbour in planetary terms. But it\u2019s in a completely different solar system, about four light-years away. That means any probes sent there must travel at relativistic speeds if we want them to arrive in a reasonable amount of time. <\/p>\n That\u2019s why Space Initiatives Inc. proposes such tiny spacecraft. With their small masses, direct lasers can propel them to their destination. That means they must send a swarm of hundreds or even one thousand probes to get valuable scientific results. <\/p>\n This is much different than the architecture that missions usually conform to. Most missions are a single spacecraft, perhaps with a smaller attached probe like the Huygens probe attached to the Cassini spacecraft. How does using a swarm change the mission? What results can we expect?<\/p>\n \u201cWe anticipate our innovations would have a profound effect on space exploration.\u201d <\/p>\n Thomas Eubanks, Space Inititatives Inc. <\/cite><\/p><\/blockquote>\n<\/figure>\n A new presentation at the 55th Lunar and Planetary Science Conference (LPSC) in Texas examined the idea. It\u2019s titled \u201cSCIENTIFIC RETURN FROM IN SITU EXPLORATION OF THE PROXIMA B EXOPLANET.\u201d The lead author is T. Marshall Eubanks from Space Initiatives Inc., a start-up developing 50-gram femtosatellites that weigh less than 100 grams (3.5 oz.)<\/p>\n Tiny probes like these can only do flybys. They\u2019re too tiny and low-mass for anything else. When designing a mission like this, the first consideration is whether the probes will operate as a dispersed or coherent swarm. In a dispersed swarm, the probes reach their destination sequentially. In a coherent swarm, the probes are together when they do their flyby. Both architectures have their merits.<\/p>\n In either case, these tiny solar sail probes will be very thin. But thanks to technological advances, they can still gather high-resolution images by working together.<\/p>\n The image below shows 247 probes forming an array as they fly by Proxima b. Together, they have the light-collecting area of a three-meter telescope. This arrangement should enable sub-arc-second resolutions at optical wavelengths. Spectroscopy should be equally as fine. <\/p>\n \u201cWhile both erosion by the Interstellar Medium (ISM) and image smearing will degrade imaging, we anticipate these systems will enable sub-arcsecond resolution imaging and spectroscopy of the target planet,\u201d the authors write.<\/p>\n These tiny spacecraft could do some course correction, but not much. So, getting the navigation right is critical. Unfortunately, our data on Proxima b\u2019s orbit is not as well-understood as the planets in our own Solar System. It all comes down to ephemeris.<\/p>\n Ephemeris tables show the trajectory of planets and other objects in space. But in Proxima b\u2019s case, the ephemeris error is potentially quite large. <\/p>\n Added to that is the distance. If the probes can travel at 20% of light speed, reaching the planet will take over 21 years. The authors calculate that if they can restrict Proxima b\u2019s ephemeris error to 100,000 km and send 1,000 probes, at least one will come within 1,000 km of the planet. \u201cMeeting this ephemeris error goal will require improved astrometry of the Proxima system,\u201d the authors write.<\/p>\n \n\n