NEOWISE: Surface Properties of 100+ Asteroids

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NEOWISE: Surface Properties of 100+ Asteroids

Post by bystander » Sat Jun 02, 2018 3:11 pm

NEOWISE Thermal Data Reveal Surface Properties of 100+ Asteroids
NASA | JPL-Caltech | NEOWISE | 2018 Jun 01
Nearly all asteroids are so far away and so small that the astronomical community only knows them as moving points of light. The rare exceptions are asteroids that have been visited by spacecraft, a small number of large asteroids resolved by NASA's Hubble Space Telescope or large ground-based telescopes, or those that have come close enough for radar imaging.

When seen by optical telescopes, these individual sources of reflected sunlight can provide some very valuable but also very basic information -- for example, the asteroid's orbit, a ballpark estimate of its size, sometimes an approximation of its shape, and perhaps an idea of its physical makeup. But to learn more about these elusive and important celestial objects requires a different type of instrument. An infrared sensor can, in the right circumstances, not only provide data on an asteroid's orbit and data that can be used to more accurately measure its size, but also chemical makeup and sometimes even its surface characteristics.

NASA's Near-Earth Object Wide-field Infrared Survey Explorer, or NEOWISE, spacecraft, in orbit around Earth, uses asteroid-hunting thermal sensors that allow an infrared view of asteroids without the obscuring effects of Earth's atmosphere. In a paper published recently in the journal Icarus, researchers led by Josef Hanuš, a scientist at the Astronomical Institute of Charles University, Prague, have made an in-depth analysis of more than 100 asteroids that have come under the temperature-sensing gaze of NEOWISE. This analysis tripled the number of asteroids which have undergone detailed "thermophysical" modeling of asteroid properties that vary with temperature. The results provide a more accurate glimpse into the surface properties of main belt asteroids and also reinforce the capabilities of spaceborne infrared observatories to accurately assess the sizes of asteroids. ...

Thermophysical Modeling of Main-Belt Asteroids from WISE Thermal Data - Josef Hanus et al
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Re: NEOWISE: Surface Properties of 100+ Asteroids

Post by neufer » Sat Jun 02, 2018 6:18 pm

  • Just sit right back and you'll hear a tale, a tale of a fateful trip,
    That started from this tropic port, aboard this tiny ship.
    The mate was a mighty sailin' man, the Skipper brave and sure.
    The space telescope set sail that day for a ten month tour.
    A ten month tour. wrote:
<<Wide-field Infrared Survey Explorer (WISE) is a NASA infrared-wavelength astronomical space telescope launched in December 2009 into the planned polar orbit at an altitude of 525 km above the Earth. WISE performed an all-sky astronomical survey with images in 3.4, 4.6, 12 and 22 μm wavelength range bands, over ten months using a 40 cm diameter infrared telescope in Earth orbit. By October 2010, over 33,500 new asteroids and comets were discovered, and over 154,000 Solar System objects were observed by WISE. While active it found dozens of previously unknown asteroids every day. In total, it captured more than 2.7 million images during its primary mission.

After its hydrogen coolant depleted the WISE group's bid for continued funding for an extended "warm mission" scored low by a NASA review board, in part because of a lack of outside groups publishing on WISE Data. Such a mission would have allowed use of the 3.4 and 4.6 micrometers detectors after the last of cryo-coolant had been exhausted, with the goal of completing a second sky survey to detect additional objects and obtain parallax data on putative brown dwarf stars.

In October 2010, NASA extended the mission by one month with a program called Near-Earth Object WISE (NEOWISE). Due to its success, the program was extended a further three months. The focus was to look for asteroids and comets close to Earth orbit, using the remaining post-cryogenic detection capability (two of four detectors on WISE work without cryogen). In February 2011, NASA announced that NEOWISE had discovered many new objects in the Solar System, including twenty comets. After completing a full scan of the asteroid belt for the NEOWISE mission, the spacecraft was put into hibernation on February 1, 2011. The spacecraft was briefly contacted to check its status on September 20, 2012.

On August 21, 2013, NASA announced it would recommission WISE to continue its search for near-Earth objects and potentially dangerous asteroids. It would additionally search for asteroids that a robotic spacecraft could intercept and redirect to orbit the Moon. The extended mission would be for three years at a cost of $5 million per year, and was brought about in part due to calls for NASA to step up asteroid detection after the Chelyabinsk meteor exploded over Russia in February 2013.
WISE was successfully taken out of hibernation in September 2013. With its coolant depleted, the spacecraft's temperature was reduced from 200 K —a relatively high temperature resulting from its hibernation—to an operating temperature of 75 K by having the telescope stare into deep space. Its instruments were then re-calibrated, and the first post-hibernation photograph was taken on December 19, 2013. The post-hibernation NEOWISE mission was anticipated to discover 150 previously unknown near-Earth objects and to learn more about the characteristics of 2,000 known asteroids. Few objects smaller than 100 m in diameter were detected by NEOWISE's automated detection software, known as the WISE Moving Object Processing Software (WMOPS), because it requires five or more detections to be reported. The average albedo of asteroids larger than 100 meters discovered by NEOWISE is 0.14.

As of May 2018, WISE/NEOWISE statistics lists a total of 290 near-Earth objects (NEOs). Of the 262 near-Earth asteroids (NEAs), 47 of them are considered potentially hazardous asteroids (PHAs), a subset of the much larger family of NEOs, but particularly more likely to hit Earth and cause significant destruction. NEOs can be divided into NECs (comets only) and NEAs (asteroids only), and further into subcategories such as Atira or Apohele asteroids, Aten asteroids, Apollo asteroids, Amor asteroids and the potentially hazardous asteroids (PHAs).>>
Art Neuendorffer