NASA's WISE Surveyor

[neufer]

NASA's WISE Surveyor Sets Out to Illuminate Secrets of the Sky
By Katherine Noyes TechNewsWorld 12/14/09 1:19 PM PT

<<Shooting sky pictures every 11 seconds during an expected productive life span of about 10 months, the highly sensitive WISE infrared space telescope will gather more data than astronomers have ever had before about what's out there. "What you expect is the unexpected," said Neville Woolf, a professor of astronomy at the University of Arizona.

Early Monday morning, NASA launched a spacecraft that will map the entire sky in infrared light with more sensitivity and resolution than has ever been possible before. A Delta II rocket carrying NASA's new Wide-field Infrared Survey Explorer, or WISE, launched from Vandenberg Air Force Base in California at 6:09 a.m. PST Monday and deposited the instrument into a polar orbit 326 miles above Earth. "WISE thundered overhead, lighting up the pre-dawn skies," said William Irace, the mission's project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "All systems are looking good, and we are on our way to seeing the entire infrared sky better than ever before."


The space telescope is on a nine-month mission to record the infrared colors of the whole sky in more detail than was provided by the last infrared sky survey, which was performed 26 years ago. It will first scan the whole sky, and then it will scan one-half of the sky a second time before its mission ends.

Almost everything in the universe glows with infrared light, allowing WISE to catalog millions of images of a variety of astronomical objects, such as near-Earth asteroids, newborn stars, planet-forming disks and distant galaxies. The mission is expected to uncover objects never seen before, including cool stars known as "brown dwarfs," the universe's most luminous galaxies, and some of the darkest near-Earth asteroids and comets.

By measuring the infrared light emitted by asteroids and comets, for example, astronomers will get the first good estimate of the size distribution of the asteroid population. That, in turn, will indicate approximately how often Earth can expect an encounter with a potentially hazardous asteroid.
Insight Into Galactic Origins

Hundreds of millions of objects will ultimately be included in the WISE atlas, NASA said, providing astronomers and other space missions with a longlasting infrared road map that will help answer fundamental questions about the origins of planets, stars and galaxies.

The most interesting WISE finds will lay the groundwork for follow-up studies with other missions, such as NASA's Spitzer Space Telescope, the Herschel Space Observatory, NASA's Hubble Space Telescope, NASA's upcoming SOFIA airborne telescope and NASA's upcoming James Webb Space Telescope. Powerful ground-based telescopes will also follow up on WISE discoveries, NASA said.

"This will help us learn a lot about the heavens out there that we haven't seen before," Paul Czysz, professor emeritus of aerospace engineering at St. Louis University, told TechNewsWorld. It's not just WISE's use of infrared that will distinguish the insights it can provide, but also its wide field, Czysz noted. "It's not like the Hubble, where you can look at a precise star," he explained. Rather, "this can integrate a very large area, so you get to see a large section of the sky."

The WISE spacecraft is about the height and weight of a big polar bear, only wider. Its sensitivity, however, is hundreds of times greater than that of its predecessor -- the Infrared Astronomical Satellite -- which operated in 1983. Its sensitive infrared telescope and detectors are kept chilled inside a Thermos-like tank of solid hydrogen, called a "cryostat." This prevents WISE from picking up the heat, or infrared, signature of its own instrument. The solid hydrogen is expected to last about 10 months and will keep the WISE telescope a frigid minus-429 degrees Fahrenheit.

On its current mission, the craft will circle Earth via the poles about 15 times a day. A scan mirror within the WISE instrument, meanwhile, will stabilize the line of sight so that snapshots can be taken every 11 seconds over the entire sky. Each position on the sky will be imaged a minimum of eight times, and some areas near the poles will be imaged more than 1,000 times.

After a one-month checkout period, the infrared surveyor will spend six months mapping the whole sky. It will then begin a second scan to uncover even more objects and to look for any changes in the sky that might have occurred since the first survey.
'Expect the Unexpected'

"It's hard to tell what we might find," Czysz said. "We have some pictures in infrared, but this will look at wavelengths we've never seen before," he added. "We'll be learning about things that we've never seen."

Indeed, "this is very exciting," Neville Woolf, a professor of astronomy at the University of Arizona, told TechNewsWorld. WISE "has a much higher sensitivity than we've had before," Woolf added. "What you expect is the unexpected." >>

[harry]

G'day Neufer

Thanks mate, must read later

Merry Xmas

Darn got to go.

[neufer]

NASA's Wise Eye Spies First Glimpse of the Starry Sky; Infrared All-Sky Surveying Telescope Sends Back First Images from Space

WASHINGTON -- NASA's Wide-field Infrared Survey Explorer, or WISE, has captured its first look at the starry sky that it will soon begin surveying in infrared light. Launched on Dec. 14, WISE will scan the entire sky for millions of hidden objects, including asteroids, "failed" stars and powerful galaxies. WISE data will serve as navigation charts for other missions such as NASA's Hubble and Spitzer Space Telescopes, pointing them to the most interesting targets WISE finds.

A new WISE infrared image was taken shortly after the space telescope's cover was removed, exposing the instrument's detectors to starlight for the first time. The picture shows 3,000 stars in the Carina constellation:



The image covers a patch of sky about three times larger than the full moon. The patch was selected because it does not contain any unusually bright objects, which could damage instrument detectors if observed for too long. The picture was taken while the spacecraft was staring at a fixed patch of sky and is being used to calibrate the spacecraft's pointing system.

When the WISE survey begins, the spacecraft will scan the sky continuously as it circles the globe, while an internal scan mirror counteracts its motion. This allows WISE to take "freeze-frame" snapshots every 11 seconds, resulting in millions of images of the entire sky. "Right now, we are busy matching the rate of the scan mirror to the rate of the spacecraft, so we will capture sharp pictures as our telescope sweeps across the sky," said William Irace, the mission's project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

To sense the infrared glow of stars and galaxies, the WISE spacecraft cannot give off any detectable infrared light of its own. This is accomplished by chilling the telescope and detectors to ultra-cold temperatures. The coldest of WISE's detectors will operate at less than 8 Kelvin.

The first sky survey will be complete in six months, followed by a second scan of one-half of the sky lasting three months. The WISE mission ends when the frozen hydrogen that keeps the instrument cold evaporates away, an event expected to occur in October 2010. Preliminary survey images are expected to be released six months later, in April 2011, with the final atlas and catalog coming after another 11 months in March 2012. Selected images will be released to the public beginning in February 2010.>>

[neufer]

<<WISE is similar to past all-sky survey missions like COBE (the Cosmic Background Explorer, whose DIRBE instrument imaged the whole sky in near-infrared wavelengths) and IRAS (the Infrared Astronomical Satellite, which imaged the whole sky in mid-infrared wavelengths). However, WISE has hundreds of times the sensitivity of IRAS, and a whopping 500,000 ties the sensitivity of COBE DIRBE. The combination of WISE's great sensitivity, the choice of infrared wavelengths, and the fact that they obtain overlapping coverage of the same spot in the sky eight times in quick succession means that the mission will be able to detect hundreds of thousands of asteroids and measure their diameters very accurately, much more accurately than you get from optical observations; they should also perform the first complete survey of solitary brown dwarfs in the region of space near our Sun. In fact, if there are stray Jupiters or even Neptunes wandering around particularly nearby, WISE will find them.

WISE will be in a polar orbit, rotating once per orbit so that its telescope always points away from Earth. So on each orbit it maps a complete north-to-south strip across the sky at two longitudes -- one longitude running from north to south and then the longitude 180 degrees across from that as it returns from south to north. Thus it will take six months to produce the all-sky map. There are a few wiggles as it has to avoid looking at the Moon, but they'll compensate by adjusting the angle of the telescope slightly to the east or west of the Moon and will still manage to achieve complete coverage.

The images on each orbit overlap significantly, so that each spot in the sky gets imaged eight times on successive orbits. The images will be run through an automated process that identifies all the point light sources and compares them to existing maps of the sky, including the asteroid database maintained by Ted Bowell. There will be some point sources in each image that are unknown. The automated process will look at the overlapping coverage of these point sources and try to identify "tracklets" -- sets of observations of objects that appear to move between successive frames. There may be a role in here for humans -- members of the public -- to look at the automatically identified tracklets and see if they appear to be real or just fortuitous alignments of cosmic ray hits. Good-looking tracklets will be submitted to the Minor Planet Center, with the hopes that professional and amateur astronomers will perform followup observations to get longer observational arcs and thus better orbits. The objects are mostly going to be very faint -- magnitude 22, give or take a couple -- so relatively big scopes will be required.

WISE will be able to do more than just detect the asteroids, however. For most of them -- the ones for which they can get good orbits, giving the distance from the asteroid to the Sun -- it will also be able to calculate diameters, fairly accurately, using the "radiometric technique" for determining the diameters of asteroids. I'm accustomed to the highly uncertain diameter estimates that astronomers arrive at from optical observation. They're uncertain because they depend on albedo, that is, how much sunlight the surface of the asteroid reflects, and the albedoes of asteroids are generally small numbers (that is, asteroids are dark) but they can range over more than an order of magnitude. Wright explained to me that the thermal emission of an asteroid is basically all the solar energy input minus the sunlight that gets reflected away. So it's sensitive to "1 minus albedo," not the albedo itself. So this technique actually benefits from the low albedo of asteroids -- very little sunlight gets reflected away, so the thermal emission gives you a very good estimate of the diameter, and is fairly insensitive to inaccuracy in albedo estimate.

They should detect hundreds of thousands of asteroids, most of them main-belt asteroids. They should detect all of them larger than two or three kilometers in diameter, and possibly as small as 1 kilometer when they start doing tricky things like summing frames. That could be as many as 700,000 asteroids. Wright told me that there's 100 times as many main-belt asteroids as near-Earth asteroids, but any way you look at it that's still a lot of near-Earth asteroids that they should find. They'll do a particularly good job of locating and tracking asteroids observed at high latitude relative to the ecliptic, because their polar orbit means there's a lot of overlap at high latitude. Objects observed at high ecliptic latitude are mostly near-Earth objects.

I asked about the four infrared wavelengths they'll be using, and why they were chosen. Here's the deal:

* Band 1 - 3.4 microns -- is a "big broad filter" intended to see "light from stars and things made from stars," that is, galaxies.
* Band 2 - 4.6 microns -- "brown dwarfs radiate there." So it's thermal radiation from things that are colder than stars but which do have internal heat sources.
* Band 3 - 12 microns -- is where they'll see thermal radiation from asteroids.
* Band 4 - 22 microns -- is where they'll see "really cold stuff" like dust in star-forming regions.

Moving on to the brown dwarf detections, I asked how they came up with the numbers of brown dwarfs that they expect to find. Wright told me that the DIRBE instrument on COBE was really, really insensitive, but a consequence of that was that unlike most other infrared instruments it could look directly at Jupiter without saturating. Using the DIRBE measurements of Jupiter's infrared radiation, they determined that WISE would be able to detect another Jupiter, if there was one, out to one light year, which is quite far but still within our Sun's zone of gravitational control. An object with two to three times Jupiter's mass -- a lightweight brown dwarf -- should be observable at a distance of two or three parsecs (seven to ten light years).

On top of that, Wright has done some observational work on a small patch of sky with the Spitzer space telescope. Using a wavelength similar to WISE's Band 2, Wright and his coworkers detected 18 brown dwarfs in their one Spitzer observation. Now, Spitzer is a much much more powerful telescope than WISE is, but WISE's all-sky map will observe 4,000 times as much area as the one Spitzer observation. Assuming the Spitzer patch of sky is representative and accounting for its greater sensitivity, Wright calculated that WISE should find 700 cold brown dwarfs in its all-sky survey.

There's a few ways to determine the distance to these brown dwarfs. One way is to get another wavelength, most likely an optical wavelength through a larger telescope like Keck II or Hubble. Another is simple parallax observations -- these things are so close that their positions relative to background stars will shift as Earth orbits the Sun. Wright said there should be 100 brown dwarfs closer than 6 parsecs away, which is comparable to the number of stars known to be closer than 6 parsecs away. In other words, WISE will double the density of the objects we know to exist in our local neighborhood. It could even detect some really small objects (small, that is, compared to stars) if they are close enough: it could find a Neptune, if one existed, out to 700 AU.

How about Kuiper belt objects? Unfortunately, anything that doesn't have its own internal heat source will be too cold for WISE to detect. The objects need to be 70 to 100 Kelvin to be detectable; even another Earth, if there was such a body in the Kuiper belt, would be a frigid 35 Kelvin, too cold to spot.

I asked if there were any other neat things WISE can do within the solar system, and Wright told me that WISE should see comet trails -- thermal radiation from the cold dust left behind in the orbits of comets, the same stuff that's responsible for annual meteor showers like the Perseids and Leonids. Even IRAS saw this, so the more-sensitive WISE should see a lot of them. It may see trails along orbits of dead comets -- things that look like asteroids because they've had too many trips close to the Sun, turning things that we once called asteroids into comets.>>

[neufer]

WISE bags its first near-Earth object, 2010 AB78
By Emily Lakdawalla | Jan. 22, 2010

<<When an astronomer first notices a previously undiscovered object moving against the sky, they send their observations to the International Astronomical Union's Minor Planet Center (MPC), located at Harvard. If the wanderer is a possible near-Earth object, its positional information is posted to the MPC's NEO Confirmation Page so that other astronomers can attempt to find the object to confirm if it, in fact, exists, and if so, to note its current position. Near-Earth objects move very rapidly against background stars, so they have to be "recovered" in this way very soon after their discovery, or they quickly become too faint to be seen again. After there are enough measurements to provide a long enough observational arc, the MPC can derive the newly observed object's orbit, which makes it possible to predict future appearances. At this point the MPC gives the object a name: the year of its discovery, followed by a code that indicates when in the year the object was discovered.

The Wide-field Infrared Survey Explorer (WISE) just took its lens cap off on December 29, and posted its "first light" image on January 6. Now, just two weeks later, WISE has bagged its first near-Earth object. The object was discovered on January 12,observed again by WISE a day later, and then followed up on by Mauna Kea on January 18 and 19, which allowed the MPC to issue a "Minor Planet Electronic Circular" or MPEC naming the newly discovered object 2010 AB78.

2010 AB78 is not a particularly close near-Earth object; the closest its orbit will get it to Earth is within 0.2 astronomical units, or 30 million kilometers. But this is just the first of a great many asteroids and near-Earth objects that we can expect WISE to discover. There's already another WISE observation looking for followup on the NEO Confirmation Page, dating to January 14. WISE is expected to discover thousands of near-Earth objects during its mission -- this is just the start!>>

[bystander]

WISE has found its first comet, P/2010 B2 (WISE)
The Planetary Society Blog - 2010 Feb 08

Having discovered its first asteroid on January 12, Wide-field Infrared Survey Explorer (WISE) has now officially discovered its first comet, P/2010 B2 (WISE). The comet was first observed by WISE on January 22, and has since been followed up on by Mauna Kea, Spacewatch, and by Robert Holmes, a two-time winner of a Planetary Society Shoemaker NEO Grant.

Here's the Minor Planet Electronic Circular officially naming P/2010 B2 (WISE). Congratulations to all involved!

[neufer]

WISE bags its first near-Earth object, 2010 AB78
By Emily Lakdawalla | Jan. 22, 2010

WISE's first near-Earth asteroid, 2010 AB78

2010 AB78 is the first of what may be hundreds or even thousands of asteroids to be discovered by the Wide-Field Survey Explorer, or WISE. It is the red dot in the middle of this star field. It is roughly one kilometer (0.6 miles) in diameter, and was about 158 million kilometers (98 million miles) away from Earth when it was discovered. The image shows three infrared wavelengths, with red representing the longest wavelength of 12 microns, and green and blue showing 4.6- and 3.4-micron light, respectively. The asteroid appears redder than the rest of the background stars because it is cooler and emits most of its light at longer infrared wavelengths. In visible light, this space rock is very faint, around magnitude, 22, so is difficult to see. Credit: NASA / JPL>>

[neufer]

WISE has found its first comet, P/2010 B2 (WISE)

WISE Spies Its First Comet
by Nancy Atkinson February 11th, 2010


The red smudge at the center of this picture is the first comet discovered by
NASA's Wide-Field Infrared Survey Explorer, or WISE. Image credit: NASA/JPL-Caltech/UCLA

The Wide-field Infrared Survey Explorer or WISE is living up to expectations, as it now has discovered its first comet, shortly after finding its first asteroid. The spacecraft, just launched on Dec. 14, 2009 and first spotted the comet on January 22, 2010. WISE is expected to find millions of other objects during its ongoing survey of the whole sky in infrared light. Officially named "P/2010 B2 (WISE)," the comet is a dusty mass of ice more than 2 kilometers (1.2 miles) in diameter. Comet WISE takes 4.7 years to circle the sun, with its farthest point being about 4 astronomical units away, and its closest point being 1.6 astronomical units (near the orbit of Mars). Right now, the comet is heading away from the sun and is about 175 million kilometers (109 million miles) from Earth.


Animation of WISE Comet discovery W007s0z. Confirmation observation by ARO at magnitude 19.7 with observation from ARO found at MPEC 2010-C23. ARO was the first ground base observation of the WISE comet discovery. Credit: Robert Holmes/ARO

Comet and asteroid hunter Robert Holmes [not British amateur astronomer Edwin Holmes of Holmes comet fame] made the first ground-based confirmation of WISE's comet discovery, with his home-built 0.81-meter telescope. Many large observatories attempted to confirm this discovery more than 7 days earlier including the Faulkes 2.0m telescope in Hawaii, without success. And due to poor weather, Holmes had to wait several days to get a look at the WISE comet himself.>>

<<Main-belt comets are bodies orbiting within the main asteroid belt which have shown cometary activity during part of their orbit. Unlike most comets, which spend most of their orbit at Jupiter-like or greater distances from the Sun, main-belt comets follow near-circular orbits within the asteroid belt that are undistinguishable from the orbits of many standard asteroids. While quite a few short period comets have semimajor axes well within Jupiter's orbit, main-belt comets differ in having small eccentricities and inclinations just like main-belt asteroids. The three known main-belt comets all orbit within the outer part of the main belt.

It is not known how an outer solar system body like the other comets could have made its way into a low-eccentricity orbit typical of the asteroid belt, which is only weakly perturbed by the planets. Hence, it is assumed that unlike other comets, the main-belt comets are simply icy asteroids, which formed in an inner solar system orbit close to their present positions, and that many outer asteroids may be icy. Main belt comets display a cometary dust tail only for a part of their orbit near perihelion. The activity persists for a month or several out of each 5-6 year orbit, and is presumably due to ice being uncovered by minor impacts.

It has been hypothesised that Main-belt comets / icy asteroids may have been the source of Earth's water, since the deuterium-hydrogen ratio of the Earth's oceans is too low for classical comets to have been the principal source.

Presently there are [six] identified Main-belt comet members:

* 133P/Elst-Pizarro
* 176P/LINEAR
* P/2005 U1 (Read)
* P/2008 R1 (Garradd)
* P/2010 A2 (LINEAR)
* P/2010 B2 (WISE)

[boonnie]

What is the importance of NASA finding a planet circling around the star Fomalhaut? On November 13, 2008, NASA announced that the Hubble Space Telescope has taken a snapshot of a planet circling the star Fomalhaut. Obviously, this is the first planet other than our own that we know of orbits a base star. Other than this, why was this such a significant discovery?

[Chris Peterson]

What is the importance of NASA finding a planet circling around the star Fomalhaut? On November 13, 2008, NASA announced that the Hubble Space Telescope has taken a snapshot of a planet circling the star Fomalhaut. Obviously, this is the first planet other than our own that we know of orbits a base star. Other than this, why was this such a significant discovery?

Does there need to be an "other than this"? By itself, the discovery seems very significant. At the least, it demonstrates that imaging an extrasolar planet is possible, and is a step towards obtaining spectra for such planets, which is how we will (or will not) detect planets that harbor life.