Video NASA's fourth release of data from its NEOWISE asteroid-hunter may well come as a relief, as it's again failed to spot a rock worthy of Bruce Willis' attention.
The new data dump, (downloadable here), brings the mission's total to 29,246 objects.
Those objects were observed in the four years since NASA mission scientists revived the "WISE" mission as the Near-Earth Orbit Wide-Field Infrared Survey Explorer. It's since made eight complete sky surveys.
That's harder than it sounds: the space telescope takes multiple images for each survey, to provide the time-series data vital to identifying moving objects.
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As its data release site explains: “NEOWISE scanned the sky nearly eight complete times during the first four years of survey operations, with six months separating survey passes. Twelve or more independent exposures are made on each point on the sky during each survey epoch.”
Last week's data release consolidates 2013 to 2017 data into a single file, to make it easier for researchers to query the whole data set at once.
The original WISE mission ended in 2011 after a two-year mission seeking extremely dim objects, when the solid hydrogen that cooled the optics to 7.6K depleted.
The video below animates all of NEOWISE's observations to date; watch at around the 25-second mark to 39 seconds, for a comet (yellow dot) practically skimming the Sun approaching from approximately the One O'clock direction.
It's still perfectly possible for a big rock to get past all the watchers, of course, as the 2013 impact over the Russian city of Chelyabinsk reminds us. ®